New Event Trigger: table_rewrite

Started by Dimitri Fontaineabout 11 years ago19 messages

dimitri@2ndQuadrant.fr

about 11 years ago

1 attachment(s)

Hi fellow hackers,

Please find attached to this email a patch to implement a new Event
Trigger, fired on the the "table_rewrite" event. As attached, it's meant
as a discussion enabler and only supports ALTER TABLE (and maybe not in
all forms of it). It will need to grow support for VACUUM FULL and
CLUSTER and more before getting commited.

Also, I'd like to work on the AccessExclusiveLock Event Trigger next,
but wanted this one, more simple, to get acceptance as the way to
approach adding events that are not DDL centric.

This time it's not about which command is running, it's about what the
command is doing.

src/backend/commands/event_trigger.c | 92 ++++++++++++++++++++-
src/backend/commands/tablecmds.c | 35 +++++++-
src/backend/utils/cache/evtcache.c | 2 +
src/include/commands/event_trigger.h | 1 +
src/include/utils/evtcache.h | 3 +-
src/test/regress/expected/event_trigger.out | 18 ++++
src/test/regress/sql/event_trigger.sql | 21 +++++
7 files changed, 166 insertions(+), 6 deletions(-)

Regards,
--
Dimitri Fontaine 06 63 07 10 78
http://2ndQuadrant.fr PostgreSQL : Expertise, Formation et Support

Attachments:

table_rewrite.0.patchtext/x-patchDownload

diff --git a/src/backend/commands/event_trigger.c b/src/backend/commands/event_trigger.c
index 1b8c94b..9314da9 100644
--- a/src/backend/commands/event_trigger.c
+++ b/src/backend/commands/event_trigger.c
@@ -119,11 +119,14 @@ static void AlterEventTriggerOwner_internal(Relation rel,
 								HeapTuple tup,
 								Oid newOwnerId);
 static event_trigger_command_tag_check_result check_ddl_tag(const char *tag);
+static event_trigger_command_tag_check_result check_table_rewrite_ddl_tag(
+	const char *tag);
 static void error_duplicate_filter_variable(const char *defname);
 static Datum filter_list_to_array(List *filterlist);
 static Oid insert_event_trigger_tuple(char *trigname, char *eventname,
 						   Oid evtOwner, Oid funcoid, List *tags);
 static void validate_ddl_tags(const char *filtervar, List *taglist);
+static void validate_table_rewrite_tags(const char *filtervar, List *taglist);
 static void EventTriggerInvoke(List *fn_oid_list, EventTriggerData *trigdata);
 
 /*
@@ -154,7 +157,8 @@ CreateEventTrigger(CreateEventTrigStmt *stmt)
 	/* Validate event name. */
 	if (strcmp(stmt->eventname, "ddl_command_start") != 0 &&
 		strcmp(stmt->eventname, "ddl_command_end") != 0 &&
-		strcmp(stmt->eventname, "sql_drop") != 0)
+		strcmp(stmt->eventname, "sql_drop") != 0 &&
+		strcmp(stmt->eventname, "table_rewrite") != 0)
 		ereport(ERROR,
 				(errcode(ERRCODE_SYNTAX_ERROR),
 				 errmsg("unrecognized event name \"%s\"",
@@ -183,6 +187,9 @@ CreateEventTrigger(CreateEventTrigStmt *stmt)
 		 strcmp(stmt->eventname, "sql_drop") == 0)
 		&& tags != NULL)
 		validate_ddl_tags("tag", tags);
+	else if (strcmp(stmt->eventname, "table_rewrite") == 0
+			 && tags != NULL)
+		validate_table_rewrite_tags("tag", tags);
 
 	/*
 	 * Give user a nice error message if an event trigger of the same name
@@ -281,6 +288,40 @@ check_ddl_tag(const char *tag)
 }
 
 /*
+ * Validate DDL command tags.
+ */
+static void
+validate_table_rewrite_tags(const char *filtervar, List *taglist)
+{
+	ListCell   *lc;
+
+	foreach(lc, taglist)
+	{
+		const char *tag = strVal(lfirst(lc));
+		event_trigger_command_tag_check_result result;
+
+		result = check_table_rewrite_ddl_tag(tag);
+		if (result == EVENT_TRIGGER_COMMAND_TAG_NOT_SUPPORTED)
+			ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+			/* translator: %s represents an SQL statement name */
+					 errmsg("event triggers are not supported for %s",
+							tag)));
+	}
+}
+
+static event_trigger_command_tag_check_result
+check_table_rewrite_ddl_tag(const char *tag)
+{
+	if (pg_strcasecmp(tag, "ALTER TABLE") == 0 ||
+		pg_strcasecmp(tag, "CLUSTER") == 0 ||
+		pg_strcasecmp(tag, "VACUUM") == 0)
+		return EVENT_TRIGGER_COMMAND_TAG_OK;
+
+	return EVENT_TRIGGER_COMMAND_TAG_NOT_SUPPORTED;
+}
+
+/*
  * Complain about a duplicate filter variable.
  */
 static void
@@ -838,6 +879,55 @@ EventTriggerSQLDrop(Node *parsetree)
 	list_free(runlist);
 }
 
+
+/*
+ * Fire table_rewrite triggers.
+ */
+void
+EventTriggerTableRewrite(Node *parsetree)
+{
+	List	   *runlist;
+	EventTriggerData trigdata;
+
+	/*
+	 * Event Triggers are completely disabled in standalone mode.  There are
+	 * (at least) two reasons for this:
+	 *
+	 * 1. A sufficiently broken event trigger might not only render the
+	 * database unusable, but prevent disabling itself to fix the situation.
+	 * In this scenario, restarting in standalone mode provides an escape
+	 * hatch.
+	 *
+	 * 2. BuildEventTriggerCache relies on systable_beginscan_ordered, and
+	 * therefore will malfunction if pg_event_trigger's indexes are damaged.
+	 * To allow recovery from a damaged index, we need some operating mode
+	 * wherein event triggers are disabled.  (Or we could implement
+	 * heapscan-and-sort logic for that case, but having disaster recovery
+	 * scenarios depend on code that's otherwise untested isn't appetizing.)
+	 */
+	if (!IsUnderPostmaster)
+		return;
+
+	runlist = EventTriggerCommonSetup(parsetree,
+									  EVT_TableRewrite,
+									  "table_rewrite",
+									  &trigdata);
+	if (runlist == NIL)
+		return;
+
+	/* Run the triggers. */
+	EventTriggerInvoke(runlist, &trigdata);
+
+	/* Cleanup. */
+	list_free(runlist);
+
+	/*
+	 * Make sure anything the event triggers did will be visible to the main
+	 * command.
+	 */
+	CommandCounterIncrement();
+}
+
 /*
  * Invoke each event trigger in a list of event triggers.
  */
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index ecdff1e..a381c33 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -46,6 +46,7 @@
 #include "commands/cluster.h"
 #include "commands/comment.h"
 #include "commands/defrem.h"
+#include "commands/event_trigger.h"
 #include "commands/policy.h"
 #include "commands/sequence.h"
 #include "commands/tablecmds.h"
@@ -303,7 +304,8 @@ static void validateForeignKeyConstraint(char *conname,
 static void createForeignKeyTriggers(Relation rel, Oid refRelOid,
 						 Constraint *fkconstraint,
 						 Oid constraintOid, Oid indexOid);
-static void ATController(Relation rel, List *cmds, bool recurse, LOCKMODE lockmode);
+static void ATController(AlterTableStmt *parsetree,
+						 Relation rel, List *cmds, bool recurse, LOCKMODE lockmode);
 static void ATPrepCmd(List **wqueue, Relation rel, AlterTableCmd *cmd,
 		  bool recurse, bool recursing, LOCKMODE lockmode);
 static void ATRewriteCatalogs(List **wqueue, LOCKMODE lockmode);
@@ -2723,7 +2725,8 @@ AlterTable(Oid relid, LOCKMODE lockmode, AlterTableStmt *stmt)
 
 	CheckTableNotInUse(rel, "ALTER TABLE");
 
-	ATController(rel, stmt->cmds, interpretInhOption(stmt->relation->inhOpt),
+	ATController(stmt,
+				 rel, stmt->cmds, interpretInhOption(stmt->relation->inhOpt),
 				 lockmode);
 }
 
@@ -2746,7 +2749,7 @@ AlterTableInternal(Oid relid, List *cmds, bool recurse)
 
 	rel = relation_open(relid, lockmode);
 
-	ATController(rel, cmds, recurse, lockmode);
+	ATController(NULL, rel, cmds, recurse, lockmode);
 }
 
 /*
@@ -3015,10 +3018,12 @@ AlterTableGetLockLevel(List *cmds)
 }
 
 static void
-ATController(Relation rel, List *cmds, bool recurse, LOCKMODE lockmode)
+ATController(AlterTableStmt *parsetree,
+			 Relation rel, List *cmds, bool recurse, LOCKMODE lockmode)
 {
 	List	   *wqueue = NIL;
 	ListCell   *lcmd;
+	ListCell   *ltab;
 
 	/* Phase 1: preliminary examination of commands, create work queue */
 	foreach(lcmd, cmds)
@@ -3031,6 +3036,28 @@ ATController(Relation rel, List *cmds, bool recurse, LOCKMODE lockmode)
 	/* Close the relation, but keep lock until commit */
 	relation_close(rel, NoLock);
 
+	/*
+	 * If a rewrite is needed, fire off an Event Trigger now.
+	 *
+	 * We don't support Event Trigger for nested commands anywhere, here
+	 * included, and parstree is given NULL when comming from
+	 * AlterTableInternal.
+	 */
+	if (parsetree)
+	{
+		foreach(ltab, wqueue)
+		{
+			AlteredTableInfo *tab = (AlteredTableInfo *) lfirst(ltab);
+
+			if (tab->rewrite)
+			{
+				/* we don't have no parsetree to provide for here. */
+				EventTriggerTableRewrite(parsetree);
+				break;
+			}
+		}
+	}
+
 	/* Phase 2: update system catalogs */
 	ATRewriteCatalogs(&wqueue, lockmode);
 
diff --git a/src/backend/utils/cache/evtcache.c b/src/backend/utils/cache/evtcache.c
index ae71bd6..b9d442c 100644
--- a/src/backend/utils/cache/evtcache.c
+++ b/src/backend/utils/cache/evtcache.c
@@ -169,6 +169,8 @@ BuildEventTriggerCache(void)
 			event = EVT_DDLCommandEnd;
 		else if (strcmp(evtevent, "sql_drop") == 0)
 			event = EVT_SQLDrop;
+		else if (strcmp(evtevent, "table_rewrite") == 0)
+			event = EVT_TableRewrite;
 		else
 			continue;
 
diff --git a/src/include/commands/event_trigger.h b/src/include/commands/event_trigger.h
index 0233f4c..d7e2958 100644
--- a/src/include/commands/event_trigger.h
+++ b/src/include/commands/event_trigger.h
@@ -46,6 +46,7 @@ extern bool EventTriggerSupportsObjectClass(ObjectClass objclass);
 extern void EventTriggerDDLCommandStart(Node *parsetree);
 extern void EventTriggerDDLCommandEnd(Node *parsetree);
 extern void EventTriggerSQLDrop(Node *parsetree);
+extern void EventTriggerTableRewrite(Node *parsetree);
 
 extern bool EventTriggerBeginCompleteQuery(void);
 extern void EventTriggerEndCompleteQuery(void);
diff --git a/src/include/utils/evtcache.h b/src/include/utils/evtcache.h
index c4c284f..4bbd80a 100644
--- a/src/include/utils/evtcache.h
+++ b/src/include/utils/evtcache.h
@@ -20,7 +20,8 @@ typedef enum
 {
 	EVT_DDLCommandStart,
 	EVT_DDLCommandEnd,
-	EVT_SQLDrop
+	EVT_SQLDrop,
+	EVT_TableRewrite
 } EventTriggerEvent;
 
 typedef struct
diff --git a/src/test/regress/expected/event_trigger.out b/src/test/regress/expected/event_trigger.out
index d4723b2..ec80170 100644
--- a/src/test/regress/expected/event_trigger.out
+++ b/src/test/regress/expected/event_trigger.out
@@ -294,3 +294,21 @@ SELECT * FROM dropped_objects WHERE type = 'schema';
 DROP ROLE regression_bob;
 DROP EVENT TRIGGER regress_event_trigger_drop_objects;
 DROP EVENT TRIGGER undroppable;
+-- test Table Rewrite Event Trigger
+CREATE OR REPLACE FUNCTION test_evtrig_no_rewrite() RETURNS event_trigger
+LANGUAGE plpgsql AS $$
+BEGIN
+  RAISE EXCEPTION 'I''m sorry Sir, No Rewrite Allowed.';
+END;
+$$;
+create event trigger no_rewrite_allowed on table_rewrite
+  execute procedure test_evtrig_no_rewrite();
+create table rewriteme (foo float);
+insert into rewriteme
+     select x * 1.001 from generate_series(1, 500) as t(x);
+alter table rewriteme alter column foo type numeric;
+ERROR:  I'm sorry Sir, No Rewrite Allowed.
+alter table rewriteme add column baz int default 0;
+drop table rewriteme;
+drop event trigger no_rewrite_allowed;
+drop function test_evtrig_no_rewrite();
diff --git a/src/test/regress/sql/event_trigger.sql b/src/test/regress/sql/event_trigger.sql
index 11d2ce5..90b3d7e 100644
--- a/src/test/regress/sql/event_trigger.sql
+++ b/src/test/regress/sql/event_trigger.sql
@@ -206,3 +206,24 @@ DROP ROLE regression_bob;
 
 DROP EVENT TRIGGER regress_event_trigger_drop_objects;
 DROP EVENT TRIGGER undroppable;
+
+-- test Table Rewrite Event Trigger
+CREATE OR REPLACE FUNCTION test_evtrig_no_rewrite() RETURNS event_trigger
+LANGUAGE plpgsql AS $$
+BEGIN
+  RAISE EXCEPTION 'I''m sorry Sir, No Rewrite Allowed.';
+END;
+$$;
+
+create event trigger no_rewrite_allowed on table_rewrite
+  execute procedure test_evtrig_no_rewrite();
+
+create table rewriteme (foo float);
+insert into rewriteme
+     select x * 1.001 from generate_series(1, 500) as t(x);
+alter table rewriteme alter column foo type numeric;
+alter table rewriteme add column baz int default 0;
+
+drop table rewriteme;
+drop event trigger no_rewrite_allowed;
+drop function test_evtrig_no_rewrite();

Dimitri Fontaine

dimitri@2ndQuadrant.fr

about 11 years ago

In reply to: Dimitri Fontaine (#1)

1 attachment(s)

Re: New Event Trigger: table_rewrite

Dimitri Fontaine <dimitri@2ndQuadrant.fr> writes:

Please find attached to this email a patch to implement a new Event
Trigger, fired on the the "table_rewrite" event. As attached, it's meant
as a discussion enabler and only supports ALTER TABLE (and maybe not in
all forms of it). It will need to grow support for VACUUM FULL and
CLUSTER and more before getting commited.

And here's already a new version of it, including support for ALTER
TABLE, VACUUM and CLUSTER commands, and documentation.

Still is a small patch:

doc/src/sgml/event-trigger.sgml | 106 ++++++++++++++++++++
src/backend/commands/cluster.c | 14 ++-
src/backend/commands/event_trigger.c | 106 +++++++++++++++++++-
src/backend/commands/tablecmds.c | 53 ++++++++--
src/backend/commands/vacuum.c | 3 +-
src/backend/utils/cache/evtcache.c | 2 +
src/include/commands/cluster.h | 4 +-
src/include/commands/event_trigger.h | 1 +
src/include/utils/evtcache.h | 3 +-
src/test/regress/expected/event_trigger.out | 23 +++++
src/test/regress/sql/event_trigger.sql | 24 +++++
11 files changed, 322 insertions(+), 17 deletions(-)

--
Dimitri Fontaine 06 63 07 10 78
http://2ndQuadrant.fr PostgreSQL : Expertise, Formation et Support

Attachments:

table_rewrite.1.patchtext/x-patchDownload

diff --git a/doc/src/sgml/event-trigger.sgml b/doc/src/sgml/event-trigger.sgml
index 6f71a27..08ae838 100644
--- a/doc/src/sgml/event-trigger.sgml
+++ b/doc/src/sgml/event-trigger.sgml
@@ -65,6 +65,12 @@
    </para>
 
    <para>
+    The <literal>table_rewrite</> event occurs just before a table is going to
+    get rewritten by the commands <literal>ALTER TABLE</literal>,
+    <literal>CLUSTER</literal> or <literal>VACUUM</literal>.
+   </para>
+
+   <para>
      Event triggers (like other functions) cannot be executed in an aborted
      transaction.  Thus, if a DDL command fails with an error, any associated
      <literal>ddl_command_end</> triggers will not be executed.  Conversely,
@@ -120,6 +126,7 @@
         <entry><literal>ddl_command_start</literal></entry>
         <entry><literal>ddl_command_end</literal></entry>
         <entry><literal>sql_drop</literal></entry>
+        <entry><literal>table_rewrite</literal></entry>
        </row>
       </thead>
       <tbody>
@@ -128,510 +135,609 @@
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER COLLATION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER CONVERSION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER DOMAIN</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER EXTENSION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER FOREIGN DATA WRAPPER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER FOREIGN TABLE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER FUNCTION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER LANGUAGE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER OPERATOR</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER OPERATOR CLASS</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER OPERATOR FAMILY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER POLICY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER SCHEMA</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER SEQUENCE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER SERVER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER TABLE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>X</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER TEXT SEARCH CONFIGURATION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER TEXT SEARCH DICTIONARY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER TEXT SEARCH PARSER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER TEXT SEARCH TEMPLATE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER TRIGGER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER TYPE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER USER MAPPING</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER VIEW</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
+       </row>
+       <row>
+        <entry align="left"><literal>CLUSTER</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>X</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE AGGREGATE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE CAST</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE COLLATION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE CONVERSION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE DOMAIN</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE EXTENSION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE FOREIGN DATA WRAPPER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE FOREIGN TABLE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE FUNCTION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE INDEX</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE LANGUAGE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE OPERATOR</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE OPERATOR CLASS</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE OPERATOR FAMILY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE POLICY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE RULE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE SCHEMA</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE SEQUENCE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE SERVER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE TABLE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE TABLE AS</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE TEXT SEARCH CONFIGURATION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE TEXT SEARCH DICTIONARY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE TEXT SEARCH PARSER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE TEXT SEARCH TEMPLATE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE TRIGGER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE TYPE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE USER MAPPING</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE VIEW</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP AGGREGATE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP CAST</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP COLLATION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP CONVERSION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP DOMAIN</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP EXTENSION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP FOREIGN DATA WRAPPER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP FOREIGN TABLE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP FUNCTION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP INDEX</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP LANGUAGE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP OPERATOR</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP OPERATOR CLASS</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP OPERATOR FAMILY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP OWNED</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP POLICY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP RULE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP SCHEMA</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP SEQUENCE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP SERVER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP TABLE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP TEXT SEARCH CONFIGURATION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP TEXT SEARCH DICTIONARY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP TEXT SEARCH PARSER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP TEXT SEARCH TEMPLATE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP TRIGGER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP TYPE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP USER MAPPING</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP VIEW</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>IMPORT FOREIGN SCHEMA</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>SELECT INTO</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
+       </row>
+       <row>
+        <entry align="left"><literal>VACUUM</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>X</literal></entry>
        </row>
       </tbody>
      </tgroup>
diff --git a/src/backend/commands/cluster.c b/src/backend/commands/cluster.c
index ff80b09..fcf11ef 100644
--- a/src/backend/commands/cluster.c
+++ b/src/backend/commands/cluster.c
@@ -31,6 +31,7 @@
 #include "catalog/objectaccess.h"
 #include "catalog/toasting.h"
 #include "commands/cluster.h"
+#include "commands/event_trigger.h"
 #include "commands/tablecmds.h"
 #include "commands/vacuum.h"
 #include "miscadmin.h"
@@ -175,7 +176,7 @@ cluster(ClusterStmt *stmt, bool isTopLevel)
 		heap_close(rel, NoLock);
 
 		/* Do the job. */
-		cluster_rel(tableOid, indexOid, false, stmt->verbose);
+		cluster_rel((Node *)stmt, tableOid, indexOid, false, stmt->verbose);
 	}
 	else
 	{
@@ -225,7 +226,8 @@ cluster(ClusterStmt *stmt, bool isTopLevel)
 			/* functions in indexes may want a snapshot set */
 			PushActiveSnapshot(GetTransactionSnapshot());
 			/* Do the job. */
-			cluster_rel(rvtc->tableOid, rvtc->indexOid, true, stmt->verbose);
+			cluster_rel((Node *)stmt,
+						rvtc->tableOid, rvtc->indexOid, true, stmt->verbose);
 			PopActiveSnapshot();
 			CommitTransactionCommand();
 		}
@@ -256,7 +258,8 @@ cluster(ClusterStmt *stmt, bool isTopLevel)
  * and error messages should refer to the operation as VACUUM not CLUSTER.
  */
 void
-cluster_rel(Oid tableOid, Oid indexOid, bool recheck, bool verbose)
+cluster_rel(Node *parsetree,
+			Oid tableOid, Oid indexOid, bool recheck, bool verbose)
 {
 	Relation	OldHeap;
 
@@ -264,6 +267,11 @@ cluster_rel(Oid tableOid, Oid indexOid, bool recheck, bool verbose)
 	CHECK_FOR_INTERRUPTS();
 
 	/*
+	 * Fire off an Event Trigger now, before actually rewriting the table.
+	 */
+	EventTriggerTableRewrite((Node *)parsetree);
+
+	/*
 	 * We grab exclusive access to the target rel and index for the duration
 	 * of the transaction.  (This is redundant for the single-transaction
 	 * case, since cluster() already did it.)  The index lock is taken inside
diff --git a/src/backend/commands/event_trigger.c b/src/backend/commands/event_trigger.c
index 1b8c94b..8bf2d28 100644
--- a/src/backend/commands/event_trigger.c
+++ b/src/backend/commands/event_trigger.c
@@ -119,11 +119,14 @@ static void AlterEventTriggerOwner_internal(Relation rel,
 								HeapTuple tup,
 								Oid newOwnerId);
 static event_trigger_command_tag_check_result check_ddl_tag(const char *tag);
+static event_trigger_command_tag_check_result check_table_rewrite_ddl_tag(
+	const char *tag);
 static void error_duplicate_filter_variable(const char *defname);
 static Datum filter_list_to_array(List *filterlist);
 static Oid insert_event_trigger_tuple(char *trigname, char *eventname,
 						   Oid evtOwner, Oid funcoid, List *tags);
 static void validate_ddl_tags(const char *filtervar, List *taglist);
+static void validate_table_rewrite_tags(const char *filtervar, List *taglist);
 static void EventTriggerInvoke(List *fn_oid_list, EventTriggerData *trigdata);
 
 /*
@@ -154,7 +157,8 @@ CreateEventTrigger(CreateEventTrigStmt *stmt)
 	/* Validate event name. */
 	if (strcmp(stmt->eventname, "ddl_command_start") != 0 &&
 		strcmp(stmt->eventname, "ddl_command_end") != 0 &&
-		strcmp(stmt->eventname, "sql_drop") != 0)
+		strcmp(stmt->eventname, "sql_drop") != 0 &&
+		strcmp(stmt->eventname, "table_rewrite") != 0)
 		ereport(ERROR,
 				(errcode(ERRCODE_SYNTAX_ERROR),
 				 errmsg("unrecognized event name \"%s\"",
@@ -183,6 +187,9 @@ CreateEventTrigger(CreateEventTrigStmt *stmt)
 		 strcmp(stmt->eventname, "sql_drop") == 0)
 		&& tags != NULL)
 		validate_ddl_tags("tag", tags);
+	else if (strcmp(stmt->eventname, "table_rewrite") == 0
+			 && tags != NULL)
+		validate_table_rewrite_tags("tag", tags);
 
 	/*
 	 * Give user a nice error message if an event trigger of the same name
@@ -281,6 +288,40 @@ check_ddl_tag(const char *tag)
 }
 
 /*
+ * Validate DDL command tags.
+ */
+static void
+validate_table_rewrite_tags(const char *filtervar, List *taglist)
+{
+	ListCell   *lc;
+
+	foreach(lc, taglist)
+	{
+		const char *tag = strVal(lfirst(lc));
+		event_trigger_command_tag_check_result result;
+
+		result = check_table_rewrite_ddl_tag(tag);
+		if (result == EVENT_TRIGGER_COMMAND_TAG_NOT_SUPPORTED)
+			ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+			/* translator: %s represents an SQL statement name */
+					 errmsg("event triggers are not supported for %s",
+							tag)));
+	}
+}
+
+static event_trigger_command_tag_check_result
+check_table_rewrite_ddl_tag(const char *tag)
+{
+	if (pg_strcasecmp(tag, "ALTER TABLE") == 0 ||
+		pg_strcasecmp(tag, "CLUSTER") == 0 ||
+		pg_strcasecmp(tag, "VACUUM") == 0)
+		return EVENT_TRIGGER_COMMAND_TAG_OK;
+
+	return EVENT_TRIGGER_COMMAND_TAG_NOT_SUPPORTED;
+}
+
+/*
  * Complain about a duplicate filter variable.
  */
 static void
@@ -641,8 +682,18 @@ EventTriggerCommonSetup(Node *parsetree,
 		const char *dbgtag;
 
 		dbgtag = CreateCommandTag(parsetree);
-		if (check_ddl_tag(dbgtag) != EVENT_TRIGGER_COMMAND_TAG_OK)
-			elog(ERROR, "unexpected command tag \"%s\"", dbgtag);
+		if (event == EVT_DDLCommandStart ||
+			event == EVT_DDLCommandEnd   ||
+			event == EVT_SQLDrop)
+		{
+			if (check_ddl_tag(dbgtag) != EVENT_TRIGGER_COMMAND_TAG_OK)
+				elog(ERROR, "unexpected command tag \"%s\"", dbgtag);
+		}
+		else if (event == EVT_TableRewrite)
+		{
+			if(check_table_rewrite_ddl_tag(dbgtag) != EVENT_TRIGGER_COMMAND_TAG_OK)
+				elog(ERROR, "unexpected command tag \"%s\"", dbgtag);
+		}
 	}
 #endif
 
@@ -838,6 +889,55 @@ EventTriggerSQLDrop(Node *parsetree)
 	list_free(runlist);
 }
 
+
+/*
+ * Fire table_rewrite triggers.
+ */
+void
+EventTriggerTableRewrite(Node *parsetree)
+{
+	List	   *runlist;
+	EventTriggerData trigdata;
+
+	/*
+	 * Event Triggers are completely disabled in standalone mode.  There are
+	 * (at least) two reasons for this:
+	 *
+	 * 1. A sufficiently broken event trigger might not only render the
+	 * database unusable, but prevent disabling itself to fix the situation.
+	 * In this scenario, restarting in standalone mode provides an escape
+	 * hatch.
+	 *
+	 * 2. BuildEventTriggerCache relies on systable_beginscan_ordered, and
+	 * therefore will malfunction if pg_event_trigger's indexes are damaged.
+	 * To allow recovery from a damaged index, we need some operating mode
+	 * wherein event triggers are disabled.  (Or we could implement
+	 * heapscan-and-sort logic for that case, but having disaster recovery
+	 * scenarios depend on code that's otherwise untested isn't appetizing.)
+	 */
+	if (!IsUnderPostmaster)
+		return;
+
+	runlist = EventTriggerCommonSetup(parsetree,
+									  EVT_TableRewrite,
+									  "table_rewrite",
+									  &trigdata);
+	if (runlist == NIL)
+		return;
+
+	/* Run the triggers. */
+	EventTriggerInvoke(runlist, &trigdata);
+
+	/* Cleanup. */
+	list_free(runlist);
+
+	/*
+	 * Make sure anything the event triggers did will be visible to the main
+	 * command.
+	 */
+	CommandCounterIncrement();
+}
+
 /*
  * Invoke each event trigger in a list of event triggers.
  */
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index ecdff1e..ccc144c 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -46,6 +46,7 @@
 #include "commands/cluster.h"
 #include "commands/comment.h"
 #include "commands/defrem.h"
+#include "commands/event_trigger.h"
 #include "commands/policy.h"
 #include "commands/sequence.h"
 #include "commands/tablecmds.h"
@@ -303,13 +304,15 @@ static void validateForeignKeyConstraint(char *conname,
 static void createForeignKeyTriggers(Relation rel, Oid refRelOid,
 						 Constraint *fkconstraint,
 						 Oid constraintOid, Oid indexOid);
-static void ATController(Relation rel, List *cmds, bool recurse, LOCKMODE lockmode);
+static void ATController(AlterTableStmt *parsetree,
+						 Relation rel, List *cmds, bool recurse, LOCKMODE lockmode);
 static void ATPrepCmd(List **wqueue, Relation rel, AlterTableCmd *cmd,
 		  bool recurse, bool recursing, LOCKMODE lockmode);
 static void ATRewriteCatalogs(List **wqueue, LOCKMODE lockmode);
 static void ATExecCmd(List **wqueue, AlteredTableInfo *tab, Relation rel,
 		  AlterTableCmd *cmd, LOCKMODE lockmode);
-static void ATRewriteTables(List **wqueue, LOCKMODE lockmode);
+static void ATRewriteTables(AlterTableStmt *parsetree,
+							List **wqueue, LOCKMODE lockmode);
 static void ATRewriteTable(AlteredTableInfo *tab, Oid OIDNewHeap, LOCKMODE lockmode);
 static AlteredTableInfo *ATGetQueueEntry(List **wqueue, Relation rel);
 static void ATSimplePermissions(Relation rel, int allowed_targets);
@@ -2723,7 +2726,8 @@ AlterTable(Oid relid, LOCKMODE lockmode, AlterTableStmt *stmt)
 
 	CheckTableNotInUse(rel, "ALTER TABLE");
 
-	ATController(rel, stmt->cmds, interpretInhOption(stmt->relation->inhOpt),
+	ATController(stmt,
+				 rel, stmt->cmds, interpretInhOption(stmt->relation->inhOpt),
 				 lockmode);
 }
 
@@ -2746,7 +2750,7 @@ AlterTableInternal(Oid relid, List *cmds, bool recurse)
 
 	rel = relation_open(relid, lockmode);
 
-	ATController(rel, cmds, recurse, lockmode);
+	ATController(NULL, rel, cmds, recurse, lockmode);
 }
 
 /*
@@ -3015,7 +3019,8 @@ AlterTableGetLockLevel(List *cmds)
 }
 
 static void
-ATController(Relation rel, List *cmds, bool recurse, LOCKMODE lockmode)
+ATController(AlterTableStmt *parsetree,
+			 Relation rel, List *cmds, bool recurse, LOCKMODE lockmode)
 {
 	List	   *wqueue = NIL;
 	ListCell   *lcmd;
@@ -3035,7 +3040,7 @@ ATController(Relation rel, List *cmds, bool recurse, LOCKMODE lockmode)
 	ATRewriteCatalogs(&wqueue, lockmode);
 
 	/* Phase 3: scan/rewrite tables as needed */
-	ATRewriteTables(&wqueue, lockmode);
+	ATRewriteTables(parsetree, &wqueue, lockmode);
 }
 
 /*
@@ -3606,8 +3611,9 @@ ATExecCmd(List **wqueue, AlteredTableInfo *tab, Relation rel,
  * ATRewriteTables: ALTER TABLE phase 3
  */
 static void
-ATRewriteTables(List **wqueue, LOCKMODE lockmode)
+ATRewriteTables(AlterTableStmt *parsetree, List **wqueue, LOCKMODE lockmode)
 {
+	bool        evt_table_rewrite_fired = false;
 	ListCell   *ltab;
 
 	/* Go through each table that needs to be checked or rewritten */
@@ -3727,6 +3733,22 @@ ATRewriteTables(List **wqueue, LOCKMODE lockmode)
 									   lockmode);
 
 			/*
+			 * Fire off an Event Trigger now, before actually rewriting the
+			 * table.
+			 *
+			 * We don't support Event Trigger for nested commands anywhere,
+			 * here included, and parstree is given NULL when comming from
+			 * AlterTableInternal.
+			 *
+			 * And fire it only once.
+			 */
+			if (parsetree && !evt_table_rewrite_fired)
+			{
+				EventTriggerTableRewrite((Node *)parsetree);
+				evt_table_rewrite_fired = true;
+			}
+
+			/*
 			 * Copy the heap data into the new table with the desired
 			 * modifications, and test the current data within the table
 			 * against new constraints generated by ALTER TABLE commands.
@@ -3764,7 +3786,24 @@ ATRewriteTables(List **wqueue, LOCKMODE lockmode)
 			 * generated by ALTER TABLE commands, but don't rebuild data.
 			 */
 			if (tab->constraints != NIL || tab->new_notnull)
+			{
+				/*
+				 * Fire off an Event Trigger now, before actually rewriting the
+				 * table.
+				 *
+				 * We don't support Event Trigger for nested commands anywhere,
+				 * here included, and parstree is given NULL when comming from
+				 * AlterTableInternal.
+				 *
+				 * And fire it only once.
+				 */
+				if (parsetree && !evt_table_rewrite_fired)
+				{
+					EventTriggerTableRewrite((Node *)parsetree);
+					evt_table_rewrite_fired = true;
+				}
 				ATRewriteTable(tab, InvalidOid, lockmode);
+			}
 
 			/*
 			 * If we had SET TABLESPACE but no reason to reconstruct tuples,
diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c
index e5fefa3..779ceb8 100644
--- a/src/backend/commands/vacuum.c
+++ b/src/backend/commands/vacuum.c
@@ -1278,7 +1278,8 @@ vacuum_rel(Oid relid, VacuumStmt *vacstmt, bool do_toast, bool for_wraparound)
 		onerel = NULL;
 
 		/* VACUUM FULL is now a variant of CLUSTER; see cluster.c */
-		cluster_rel(relid, InvalidOid, false,
+		cluster_rel((Node *)vacstmt,
+					relid, InvalidOid, false,
 					(vacstmt->options & VACOPT_VERBOSE) != 0);
 	}
 	else
diff --git a/src/backend/utils/cache/evtcache.c b/src/backend/utils/cache/evtcache.c
index ae71bd6..b9d442c 100644
--- a/src/backend/utils/cache/evtcache.c
+++ b/src/backend/utils/cache/evtcache.c
@@ -169,6 +169,8 @@ BuildEventTriggerCache(void)
 			event = EVT_DDLCommandEnd;
 		else if (strcmp(evtevent, "sql_drop") == 0)
 			event = EVT_SQLDrop;
+		else if (strcmp(evtevent, "table_rewrite") == 0)
+			event = EVT_TableRewrite;
 		else
 			continue;
 
diff --git a/src/include/commands/cluster.h b/src/include/commands/cluster.h
index f7730a9..80b7433 100644
--- a/src/include/commands/cluster.h
+++ b/src/include/commands/cluster.h
@@ -19,8 +19,8 @@
 
 
 extern void cluster(ClusterStmt *stmt, bool isTopLevel);
-extern void cluster_rel(Oid tableOid, Oid indexOid, bool recheck,
-			bool verbose);
+extern void cluster_rel(Node *parsetree,
+						Oid tableOid, Oid indexOid, bool recheck, bool verbose);
 extern void check_index_is_clusterable(Relation OldHeap, Oid indexOid,
 						   bool recheck, LOCKMODE lockmode);
 extern void mark_index_clustered(Relation rel, Oid indexOid, bool is_internal);
diff --git a/src/include/commands/event_trigger.h b/src/include/commands/event_trigger.h
index 0233f4c..d7e2958 100644
--- a/src/include/commands/event_trigger.h
+++ b/src/include/commands/event_trigger.h
@@ -46,6 +46,7 @@ extern bool EventTriggerSupportsObjectClass(ObjectClass objclass);
 extern void EventTriggerDDLCommandStart(Node *parsetree);
 extern void EventTriggerDDLCommandEnd(Node *parsetree);
 extern void EventTriggerSQLDrop(Node *parsetree);
+extern void EventTriggerTableRewrite(Node *parsetree);
 
 extern bool EventTriggerBeginCompleteQuery(void);
 extern void EventTriggerEndCompleteQuery(void);
diff --git a/src/include/utils/evtcache.h b/src/include/utils/evtcache.h
index c4c284f..4bbd80a 100644
--- a/src/include/utils/evtcache.h
+++ b/src/include/utils/evtcache.h
@@ -20,7 +20,8 @@ typedef enum
 {
 	EVT_DDLCommandStart,
 	EVT_DDLCommandEnd,
-	EVT_SQLDrop
+	EVT_SQLDrop,
+	EVT_TableRewrite
 } EventTriggerEvent;
 
 typedef struct
diff --git a/src/test/regress/expected/event_trigger.out b/src/test/regress/expected/event_trigger.out
index d4723b2..5b08bd8 100644
--- a/src/test/regress/expected/event_trigger.out
+++ b/src/test/regress/expected/event_trigger.out
@@ -294,3 +294,26 @@ SELECT * FROM dropped_objects WHERE type = 'schema';
 DROP ROLE regression_bob;
 DROP EVENT TRIGGER regress_event_trigger_drop_objects;
 DROP EVENT TRIGGER undroppable;
+-- test Table Rewrite Event Trigger
+CREATE OR REPLACE FUNCTION test_evtrig_no_rewrite() RETURNS event_trigger
+LANGUAGE plpgsql AS $$
+BEGIN
+  RAISE EXCEPTION 'I''m sorry Sir, No Rewrite Allowed.';
+END;
+$$;
+create event trigger no_rewrite_allowed on table_rewrite
+  execute procedure test_evtrig_no_rewrite();
+create table rewriteme (id serial primary key, foo float);
+insert into rewriteme
+     select x * 1.001 from generate_series(1, 500) as t(x);
+alter table rewriteme alter column foo type numeric;
+ERROR:  I'm sorry Sir, No Rewrite Allowed.
+alter table rewriteme add column baz int default 0;
+ERROR:  I'm sorry Sir, No Rewrite Allowed.
+cluster rewriteme using rewriteme_pkey;
+ERROR:  I'm sorry Sir, No Rewrite Allowed.
+vacuum full rewriteme;
+ERROR:  I'm sorry Sir, No Rewrite Allowed.
+drop table rewriteme;
+drop event trigger no_rewrite_allowed;
+drop function test_evtrig_no_rewrite();
diff --git a/src/test/regress/sql/event_trigger.sql b/src/test/regress/sql/event_trigger.sql
index 11d2ce5..1fc244e 100644
--- a/src/test/regress/sql/event_trigger.sql
+++ b/src/test/regress/sql/event_trigger.sql
@@ -206,3 +206,27 @@ DROP ROLE regression_bob;
 
 DROP EVENT TRIGGER regress_event_trigger_drop_objects;
 DROP EVENT TRIGGER undroppable;
+
+-- test Table Rewrite Event Trigger
+CREATE OR REPLACE FUNCTION test_evtrig_no_rewrite() RETURNS event_trigger
+LANGUAGE plpgsql AS $$
+BEGIN
+  RAISE EXCEPTION 'I''m sorry Sir, No Rewrite Allowed.';
+END;
+$$;
+
+create event trigger no_rewrite_allowed on table_rewrite
+  execute procedure test_evtrig_no_rewrite();
+
+create table rewriteme (id serial primary key, foo float);
+insert into rewriteme
+     select x * 1.001 from generate_series(1, 500) as t(x);
+alter table rewriteme alter column foo type numeric;
+alter table rewriteme add column baz int default 0;
+
+cluster rewriteme using rewriteme_pkey;
+vacuum full rewriteme;
+
+drop table rewriteme;
+drop event trigger no_rewrite_allowed;
+drop function test_evtrig_no_rewrite();

Simon Riggs

simon@2ndQuadrant.com

about 11 years ago

In reply to: Dimitri Fontaine (#2)

Re: New Event Trigger: table_rewrite

On 16 October 2014 10:18, Dimitri Fontaine <dimitri@2ndquadrant.fr> wrote:

Dimitri Fontaine <dimitri@2ndQuadrant.fr> writes:

Please find attached to this email a patch to implement a new Event
Trigger, fired on the the "table_rewrite" event. As attached, it's meant
as a discussion enabler and only supports ALTER TABLE (and maybe not in
all forms of it). It will need to grow support for VACUUM FULL and
CLUSTER and more before getting commited.

And here's already a new version of it, including support for ALTER
TABLE, VACUUM and CLUSTER commands, and documentation.

The patch itself looks fine overall. Docs look in place, tests OK.

API changes may need more thought. I'm not sure myself, they just look
fairly quick.

It would be more useful to work on the applications of this....

1. INSERT into a table
* Action start time
* Schema
* Tablename
* Number of blocks in table
which would then allow you to do these things run an assessment report
showing which tables would be rewritten.

2. Get access to number of blocks, so you could limit rewrites only to
smaller tables by putting a block limit in place.

3. It might be even cooler to contemplate having pg_stat_activity
publish an estimated end time.
We'd probably need some kind of time_per_block parameter for each
tablespace so we can estimate the time.

Doing 1 and 2 at least would make this a good feature. We can do a
later patch for 3, or similar, once this is accepted.

--
Simon Riggs http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services

--
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
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Dimitri Fontaine

dimitri@2ndQuadrant.fr

about 11 years ago

In reply to: Simon Riggs (#3)

1 attachment(s)

Re: New Event Trigger: table_rewrite

Simon Riggs <simon@2ndQuadrant.com> writes:

It would be more useful to work on the applications of this....

1. INSERT into a table
* Action start time
* Schema
* Tablename
* Number of blocks in table
which would then allow you to do these things run an assessment report
showing which tables would be rewritten.

That should be done by the user, from within his Event Trigger code. For
that to be possible, the previous patch was missing a way to expose the
OID of the table being rewritten, I've now added support for that.

2. Get access to number of blocks, so you could limit rewrites only to
smaller tables by putting a block limit in place.

Also, I did expand the docs to fully cover your practical use case of a
table_rewrite Event Trigger implementing such a table rewrite policy.

3. It might be even cooler to contemplate having pg_stat_activity
publish an estimated end time.
We'd probably need some kind of time_per_block parameter for each
tablespace so we can estimate the time.

That feels like another patch entirely.

Regards,
--
Dimitri Fontaine 06 63 07 10 78
http://2ndQuadrant.fr PostgreSQL : Expertise, Formation et Support

Attachments:

table_rewrite.2.patchtext/x-patchDownload

diff --git a/doc/src/sgml/event-trigger.sgml b/doc/src/sgml/event-trigger.sgml
index 6f71a27..7eb3225 100644
--- a/doc/src/sgml/event-trigger.sgml
+++ b/doc/src/sgml/event-trigger.sgml
@@ -65,6 +65,12 @@
    </para>
 
    <para>
+    The <literal>table_rewrite</> event occurs just before a table is going to
+    get rewritten by the commands <literal>ALTER TABLE</literal>,
+    <literal>CLUSTER</literal> or <literal>VACUUM</literal>.
+   </para>
+
+   <para>
      Event triggers (like other functions) cannot be executed in an aborted
      transaction.  Thus, if a DDL command fails with an error, any associated
      <literal>ddl_command_end</> triggers will not be executed.  Conversely,
@@ -120,518 +126,625 @@
         <entry><literal>ddl_command_start</literal></entry>
         <entry><literal>ddl_command_end</literal></entry>
         <entry><literal>sql_drop</literal></entry>
+        <entry><literal>table_rewrite</literal></entry>
        </row>
       </thead>
       <tbody>
        <row>
+        <entry align="left"><literal>ANALYZE</literal></entry>
+        <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
+       </row>
+       <row>
         <entry align="left"><literal>ALTER AGGREGATE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER COLLATION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER CONVERSION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER DOMAIN</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER EXTENSION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER FOREIGN DATA WRAPPER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER FOREIGN TABLE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER FUNCTION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER LANGUAGE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER OPERATOR</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER OPERATOR CLASS</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER OPERATOR FAMILY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER POLICY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER SCHEMA</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER SEQUENCE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER SERVER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER TABLE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>X</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER TEXT SEARCH CONFIGURATION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER TEXT SEARCH DICTIONARY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER TEXT SEARCH PARSER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER TEXT SEARCH TEMPLATE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER TRIGGER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER TYPE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER USER MAPPING</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER VIEW</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
+       </row>
+       <row>
+        <entry align="left"><literal>CLUSTER</literal></entry>
+        <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>X</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE AGGREGATE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE CAST</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE COLLATION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE CONVERSION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE DOMAIN</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE EXTENSION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE FOREIGN DATA WRAPPER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE FOREIGN TABLE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE FUNCTION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE INDEX</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE LANGUAGE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE OPERATOR</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE OPERATOR CLASS</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE OPERATOR FAMILY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE POLICY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE RULE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE SCHEMA</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE SEQUENCE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE SERVER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE TABLE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE TABLE AS</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE TEXT SEARCH CONFIGURATION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE TEXT SEARCH DICTIONARY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE TEXT SEARCH PARSER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE TEXT SEARCH TEMPLATE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE TRIGGER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE TYPE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE USER MAPPING</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE VIEW</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP AGGREGATE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP CAST</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP COLLATION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP CONVERSION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP DOMAIN</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP EXTENSION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP FOREIGN DATA WRAPPER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP FOREIGN TABLE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP FUNCTION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP INDEX</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP LANGUAGE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP OPERATOR</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP OPERATOR CLASS</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP OPERATOR FAMILY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP OWNED</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP POLICY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP RULE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP SCHEMA</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP SEQUENCE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP SERVER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP TABLE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP TEXT SEARCH CONFIGURATION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP TEXT SEARCH DICTIONARY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP TEXT SEARCH PARSER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP TEXT SEARCH TEMPLATE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP TRIGGER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP TYPE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP USER MAPPING</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP VIEW</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>IMPORT FOREIGN SCHEMA</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>SELECT INTO</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
+       </row>
+       <row>
+        <entry align="left"><literal>VACUUM</literal></entry>
+        <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>X</literal></entry>
        </row>
       </tbody>
      </tgroup>
@@ -843,4 +956,58 @@ COMMIT;
     event triggers.)
    </para>
   </sect1>
+
+  <sect1 id="event-trigger-table-rewrite-example">
+   <title>A Table Rewrite Event Trigger Example</title>
+
+   <para>
+    Thanks to the <literal>table_rewrite</> event, it is possible to implement
+    a table rewriting policy only allowing the rewrite in maintenance windows.
+   </para>
+
+   <para>
+    Here's an example implementing such a policy.
+<programlisting>
+create or replace function no_rewrite()
+ returns event_trigger
+ language plpgsql as
+$$
+---
+--- Implement local Table Rewriting policy:
+---   public.foo is not allowed rewriting, ever
+---   other tables are only allowed rewriting between 1am and 6am
+---   unless they have more than 100 blocks
+---
+declare
+  table_oid oid := pg_event_trigger_table_rewrite_oid();
+  current_hour integer := extract('hour' from current_time);
+  pages integer;
+  max_pages integer := 100;
+begin
+  if pg_event_trigger_table_rewrite_oid() = 'public.foo'::regclass
+  then
+        raise exception 'you''re not allowed to rewrite the table %',
+                        table_oid::regclass;
+  end if;
+
+  select into pages relpages from pg_class where oid = table_oid;
+  if pages > max_pages
+  then
+        raise exception 'rewrites only allowed for table with less than % pages',
+                        max_pages;
+  end if;
+
+  if not current_hour between 1 and 6
+  then
+        raise exception 'rewrites only allowed between 1am and 6am';
+  end if;
+end;
+$$;
+
+create event trigger no_rewrite_allowed
+                  on table_rewrite
+   execute procedure no_rewrite();
+</programlisting>
+   </para>
+ </sect1>
 </chapter>
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 7e5bcd9..24bf78c 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -17540,16 +17540,20 @@ FOR EACH ROW EXECUTE PROCEDURE suppress_redundant_updates_trigger();
   <sect1 id="functions-event-triggers">
    <title>Event Trigger Functions</title>
 
+   <para>
+    Currently <productname>PostgreSQL</> provides two built-in event trigger
+    helper function, <function>pg_event_trigger_dropped_objects</>
+    and <function>pg_event_trigger_table_rewrite_oid</>.
+   </para>
+
+  <sect2 id="pg-event-trigger-dropped-objects">
+   <title>Processing objects dropped by a DDL command.</title>
+
    <indexterm>
      <primary>pg_event_trigger_dropped_objects</primary>
    </indexterm>
 
    <para>
-    Currently <productname>PostgreSQL</> provides one built-in event trigger
-    helper function, <function>pg_event_trigger_dropped_objects</>.
-   </para>
-
-   <para>
     <function>pg_event_trigger_dropped_objects</> returns a list of all objects
     dropped by the command in whose <literal>sql_drop</> event it is called.
     If called in any other context,
@@ -17647,6 +17651,68 @@ CREATE EVENT TRIGGER test_event_trigger_for_drops
        For more information about event triggers,
        see <xref linkend="event-triggers">.
     </para>
+  </sect2>
+
+  <sect2 id="pg-event-trigger-table-rewrite-oid">
+   <title>Handling a Table Rewrite Event</title>
+
+   <indexterm>
+     <primary>pg_event_trigger_table_rewrite_oid</primary>
+   </indexterm>
+
+   <para>
+    <function>pg_event_trigger_table_rewrite_oid</> returns
+    the <literal>OID</> of the table that is going to be rewritten on-disk by
+    the current DDL command. If called in any other context,
+    <function>pg_event_trigger_table_rewrite_oid</> raises an error.
+    <function>pg_event_trigger_table_rewrite_oid</> returns the following
+    columns:
+
+    <informaltable>
+     <tgroup cols="3">
+      <thead>
+       <row>
+        <entry>Name</entry>
+        <entry>Type</entry>
+        <entry>Description</entry>
+       </row>
+      </thead>
+
+      <tbody>
+       <row>
+        <entry><literal>oid</literal></entry>
+        <entry><type>Oid</type></entry>
+        <entry>OID of the pg_class entry for the table.</entry>
+       </row>
+      </tbody>
+     </tgroup>
+    </informaltable>
+   </para>
+
+   <para>
+    The <function>pg_event_trigger_table_rewrite_oid</> function can be used
+    in an event trigger like this:
+<programlisting>
+create function test_event_trigger_table_rewrite_oid()
+ returns event_trigger
+ language plpgsql as
+$$
+begin
+  raise notice 'rewriting table %', pg_event_trigger_table_rewrite_oid()::regclass;
+end;
+$$;
+
+create event trigger test_table_rewrite_oid
+                  on table_rewrite
+   execute procedure test_event_trigger_table_rewrite_oid();
+</programlisting>
+    </para>
+
+     <para>
+       For more information about event triggers,
+       see <xref linkend="event-triggers">.
+    </para>
+  </sect2>
   </sect1>
 
 </chapter>
diff --git a/src/backend/commands/cluster.c b/src/backend/commands/cluster.c
index ff80b09..64d1312 100644
--- a/src/backend/commands/cluster.c
+++ b/src/backend/commands/cluster.c
@@ -31,6 +31,7 @@
 #include "catalog/objectaccess.h"
 #include "catalog/toasting.h"
 #include "commands/cluster.h"
+#include "commands/event_trigger.h"
 #include "commands/tablecmds.h"
 #include "commands/vacuum.h"
 #include "miscadmin.h"
@@ -175,7 +176,7 @@ cluster(ClusterStmt *stmt, bool isTopLevel)
 		heap_close(rel, NoLock);
 
 		/* Do the job. */
-		cluster_rel(tableOid, indexOid, false, stmt->verbose);
+		cluster_rel((Node *)stmt, tableOid, indexOid, false, stmt->verbose);
 	}
 	else
 	{
@@ -225,7 +226,8 @@ cluster(ClusterStmt *stmt, bool isTopLevel)
 			/* functions in indexes may want a snapshot set */
 			PushActiveSnapshot(GetTransactionSnapshot());
 			/* Do the job. */
-			cluster_rel(rvtc->tableOid, rvtc->indexOid, true, stmt->verbose);
+			cluster_rel((Node *)stmt,
+						rvtc->tableOid, rvtc->indexOid, true, stmt->verbose);
 			PopActiveSnapshot();
 			CommitTransactionCommand();
 		}
@@ -256,7 +258,8 @@ cluster(ClusterStmt *stmt, bool isTopLevel)
  * and error messages should refer to the operation as VACUUM not CLUSTER.
  */
 void
-cluster_rel(Oid tableOid, Oid indexOid, bool recheck, bool verbose)
+cluster_rel(Node *parsetree,
+			Oid tableOid, Oid indexOid, bool recheck, bool verbose)
 {
 	Relation	OldHeap;
 
@@ -264,6 +267,11 @@ cluster_rel(Oid tableOid, Oid indexOid, bool recheck, bool verbose)
 	CHECK_FOR_INTERRUPTS();
 
 	/*
+	 * Fire off an Event Trigger now, before actually rewriting the table.
+	 */
+	EventTriggerTableRewrite((Node *)parsetree, tableOid);
+
+	/*
 	 * We grab exclusive access to the target rel and index for the duration
 	 * of the transaction.  (This is redundant for the single-transaction
 	 * case, since cluster() already did it.)  The index lock is taken inside
diff --git a/src/backend/commands/event_trigger.c b/src/backend/commands/event_trigger.c
index 1b8c94b..d9fcc8a 100644
--- a/src/backend/commands/event_trigger.c
+++ b/src/backend/commands/event_trigger.c
@@ -42,11 +42,15 @@
 #include "utils/syscache.h"
 #include "tcop/utility.h"
 
-
+/*
+ * Data Structure for sql_drop and table_rewrite Event Trigger support.
+ */
 typedef struct EventTriggerQueryState
 {
 	slist_head	SQLDropList;
 	bool		in_sql_drop;
+	bool		in_table_rewrite;
+	Oid			tableOid;
 	MemoryContext cxt;
 	struct EventTriggerQueryState *previous;
 } EventTriggerQueryState;
@@ -119,11 +123,14 @@ static void AlterEventTriggerOwner_internal(Relation rel,
 								HeapTuple tup,
 								Oid newOwnerId);
 static event_trigger_command_tag_check_result check_ddl_tag(const char *tag);
+static event_trigger_command_tag_check_result check_table_rewrite_ddl_tag(
+	const char *tag);
 static void error_duplicate_filter_variable(const char *defname);
 static Datum filter_list_to_array(List *filterlist);
 static Oid insert_event_trigger_tuple(char *trigname, char *eventname,
 						   Oid evtOwner, Oid funcoid, List *tags);
 static void validate_ddl_tags(const char *filtervar, List *taglist);
+static void validate_table_rewrite_tags(const char *filtervar, List *taglist);
 static void EventTriggerInvoke(List *fn_oid_list, EventTriggerData *trigdata);
 
 /*
@@ -154,7 +161,8 @@ CreateEventTrigger(CreateEventTrigStmt *stmt)
 	/* Validate event name. */
 	if (strcmp(stmt->eventname, "ddl_command_start") != 0 &&
 		strcmp(stmt->eventname, "ddl_command_end") != 0 &&
-		strcmp(stmt->eventname, "sql_drop") != 0)
+		strcmp(stmt->eventname, "sql_drop") != 0 &&
+		strcmp(stmt->eventname, "table_rewrite") != 0)
 		ereport(ERROR,
 				(errcode(ERRCODE_SYNTAX_ERROR),
 				 errmsg("unrecognized event name \"%s\"",
@@ -183,6 +191,9 @@ CreateEventTrigger(CreateEventTrigStmt *stmt)
 		 strcmp(stmt->eventname, "sql_drop") == 0)
 		&& tags != NULL)
 		validate_ddl_tags("tag", tags);
+	else if (strcmp(stmt->eventname, "table_rewrite") == 0
+			 && tags != NULL)
+		validate_table_rewrite_tags("tag", tags);
 
 	/*
 	 * Give user a nice error message if an event trigger of the same name
@@ -257,6 +268,7 @@ check_ddl_tag(const char *tag)
 
 	/*
 	 * Otherwise, command should be CREATE, ALTER, or DROP.
+	 * Or one of ANALYZE, CLUSTER, VACUUM.
 	 */
 	if (pg_strncasecmp(tag, "CREATE ", 7) == 0)
 		obtypename = tag + 7;
@@ -264,6 +276,10 @@ check_ddl_tag(const char *tag)
 		obtypename = tag + 6;
 	else if (pg_strncasecmp(tag, "DROP ", 5) == 0)
 		obtypename = tag + 5;
+	else if (pg_strncasecmp(tag, "ANALYZE", 7) == 0 ||
+			 pg_strncasecmp(tag, "CLUSTER", 7) == 0 ||
+			 pg_strncasecmp(tag, "VACUUM", 6) == 0)
+		return EVENT_TRIGGER_COMMAND_TAG_OK;
 	else
 		return EVENT_TRIGGER_COMMAND_TAG_NOT_RECOGNIZED;
 
@@ -281,6 +297,41 @@ check_ddl_tag(const char *tag)
 }
 
 /*
+ * Validate DDL command tags.
+ */
+static void
+validate_table_rewrite_tags(const char *filtervar, List *taglist)
+{
+	ListCell   *lc;
+
+	foreach(lc, taglist)
+	{
+		const char *tag = strVal(lfirst(lc));
+		event_trigger_command_tag_check_result result;
+
+		result = check_table_rewrite_ddl_tag(tag);
+		if (result == EVENT_TRIGGER_COMMAND_TAG_NOT_SUPPORTED)
+			ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+			/* translator: %s represents an SQL statement name */
+					 errmsg("event triggers are not supported for %s",
+							tag)));
+	}
+}
+
+static event_trigger_command_tag_check_result
+check_table_rewrite_ddl_tag(const char *tag)
+{
+	if (pg_strcasecmp(tag, "ALTER TABLE") == 0 ||
+		pg_strcasecmp(tag, "CLUSTER") == 0 ||
+		pg_strcasecmp(tag, "VACUUM") == 0 ||
+		pg_strcasecmp(tag, "ANALYZE") == 0 )
+		return EVENT_TRIGGER_COMMAND_TAG_OK;
+
+	return EVENT_TRIGGER_COMMAND_TAG_NOT_SUPPORTED;
+}
+
+/*
  * Complain about a duplicate filter variable.
  */
 static void
@@ -641,8 +692,18 @@ EventTriggerCommonSetup(Node *parsetree,
 		const char *dbgtag;
 
 		dbgtag = CreateCommandTag(parsetree);
-		if (check_ddl_tag(dbgtag) != EVENT_TRIGGER_COMMAND_TAG_OK)
-			elog(ERROR, "unexpected command tag \"%s\"", dbgtag);
+		if (event == EVT_DDLCommandStart ||
+			event == EVT_DDLCommandEnd   ||
+			event == EVT_SQLDrop)
+		{
+			if (check_ddl_tag(dbgtag) != EVENT_TRIGGER_COMMAND_TAG_OK)
+				elog(ERROR, "unexpected command tag \"%s\"", dbgtag);
+		}
+		else if (event == EVT_TableRewrite)
+		{
+			if(check_table_rewrite_ddl_tag(dbgtag) != EVENT_TRIGGER_COMMAND_TAG_OK)
+				elog(ERROR, "unexpected command tag \"%s\"", dbgtag);
+		}
 	}
 #endif
 
@@ -838,6 +899,80 @@ EventTriggerSQLDrop(Node *parsetree)
 	list_free(runlist);
 }
 
+
+/*
+ * Fire table_rewrite triggers.
+ */
+void
+EventTriggerTableRewrite(Node *parsetree, Oid tableOid)
+{
+	List	   *runlist;
+	EventTriggerData trigdata;
+
+	elog(DEBUG1, "EventTriggerTableRewrite(%u)", tableOid);
+
+	/*
+	 * Event Triggers are completely disabled in standalone mode.  There are
+	 * (at least) two reasons for this:
+	 *
+	 * 1. A sufficiently broken event trigger might not only render the
+	 * database unusable, but prevent disabling itself to fix the situation.
+	 * In this scenario, restarting in standalone mode provides an escape
+	 * hatch.
+	 *
+	 * 2. BuildEventTriggerCache relies on systable_beginscan_ordered, and
+	 * therefore will malfunction if pg_event_trigger's indexes are damaged.
+	 * To allow recovery from a damaged index, we need some operating mode
+	 * wherein event triggers are disabled.  (Or we could implement
+	 * heapscan-and-sort logic for that case, but having disaster recovery
+	 * scenarios depend on code that's otherwise untested isn't appetizing.)
+	 */
+	if (!IsUnderPostmaster)
+		return;
+
+	runlist = EventTriggerCommonSetup(parsetree,
+									  EVT_TableRewrite,
+									  "table_rewrite",
+									  &trigdata);
+	if (runlist == NIL)
+		return;
+
+	/*
+	 * Make sure pg_event_trigger_table_rewrite_oid only works when running
+	 * these triggers.  Use PG_TRY to ensure in_table_rewrite is reset even when
+	 * one trigger fails.  (This is perhaps not necessary, as the currentState
+	 * variable will be removed shortly by our caller, but it seems better to
+	 * play safe.)
+	 */
+	currentEventTriggerState->in_table_rewrite = true;
+	currentEventTriggerState->tableOid = tableOid;
+
+	/* Run the triggers. */
+	PG_TRY();
+	{
+		EventTriggerInvoke(runlist, &trigdata);
+	}
+	PG_CATCH();
+	{
+		currentEventTriggerState->in_table_rewrite = false;
+		currentEventTriggerState->tableOid = InvalidOid;
+		PG_RE_THROW();
+	}
+	PG_END_TRY();
+
+	currentEventTriggerState->in_table_rewrite = false;
+	currentEventTriggerState->tableOid = InvalidOid;
+
+	/* Cleanup. */
+	list_free(runlist);
+
+	/*
+	 * Make sure anything the event triggers did will be visible to the main
+	 * command.
+	 */
+	CommandCounterIncrement();
+}
+
 /*
  * Invoke each event trigger in a list of event triggers.
  */
@@ -871,6 +1006,8 @@ EventTriggerInvoke(List *fn_oid_list, EventTriggerData *trigdata)
 		FunctionCallInfoData fcinfo;
 		PgStat_FunctionCallUsage fcusage;
 
+		elog(DEBUG1, "EventTriggerInvoke %u", fnoid);
+
 		/*
 		 * We want each event trigger to be able to see the results of the
 		 * previous event trigger's action.  Caller is responsible for any
@@ -1041,6 +1178,8 @@ EventTriggerBeginCompleteQuery(void)
 	state->cxt = cxt;
 	slist_init(&(state->SQLDropList));
 	state->in_sql_drop = false;
+	state->in_table_rewrite = false;
+	state->tableOid = InvalidOid;
 
 	state->previous = currentEventTriggerState;
 	currentEventTriggerState = state;
@@ -1080,8 +1219,9 @@ EventTriggerEndCompleteQuery(void)
 bool
 trackDroppedObjectsNeeded(void)
 {
-	/* true if any sql_drop event trigger exists */
-	return list_length(EventCacheLookup(EVT_SQLDrop)) > 0;
+	/* true if any sql_drop or table_rewrite event trigger exists */
+	return list_length(EventCacheLookup(EVT_SQLDrop)) > 0 ||
+		list_length(EventCacheLookup(EVT_TableRewrite)) > 0;
 }
 
 /*
@@ -1297,3 +1437,25 @@ pg_event_trigger_dropped_objects(PG_FUNCTION_ARGS)
 
 	return (Datum) 0;
 }
+
+/*
+ * pg_event_trigger_table_rewrite_oid
+ *
+ * Make the Oid of the table going to be rewritten available to the user
+ * function run by the Event Trigger.
+ */
+Datum
+pg_event_trigger_table_rewrite_oid(PG_FUNCTION_ARGS)
+{
+	/*
+	 * Protect this function from being called out of context
+	 */
+	if (!currentEventTriggerState ||
+		!currentEventTriggerState->in_table_rewrite)
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+		 errmsg("%s can only be called in a table_rewrite event trigger function",
+				"pg_event_trigger_table_rewrite_oid()")));
+
+	PG_RETURN_OID(currentEventTriggerState->tableOid);
+}
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index ecdff1e..7477dd0 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -46,6 +46,7 @@
 #include "commands/cluster.h"
 #include "commands/comment.h"
 #include "commands/defrem.h"
+#include "commands/event_trigger.h"
 #include "commands/policy.h"
 #include "commands/sequence.h"
 #include "commands/tablecmds.h"
@@ -303,13 +304,15 @@ static void validateForeignKeyConstraint(char *conname,
 static void createForeignKeyTriggers(Relation rel, Oid refRelOid,
 						 Constraint *fkconstraint,
 						 Oid constraintOid, Oid indexOid);
-static void ATController(Relation rel, List *cmds, bool recurse, LOCKMODE lockmode);
+static void ATController(AlterTableStmt *parsetree,
+						 Relation rel, List *cmds, bool recurse, LOCKMODE lockmode);
 static void ATPrepCmd(List **wqueue, Relation rel, AlterTableCmd *cmd,
 		  bool recurse, bool recursing, LOCKMODE lockmode);
 static void ATRewriteCatalogs(List **wqueue, LOCKMODE lockmode);
 static void ATExecCmd(List **wqueue, AlteredTableInfo *tab, Relation rel,
 		  AlterTableCmd *cmd, LOCKMODE lockmode);
-static void ATRewriteTables(List **wqueue, LOCKMODE lockmode);
+static void ATRewriteTables(AlterTableStmt *parsetree,
+							List **wqueue, LOCKMODE lockmode);
 static void ATRewriteTable(AlteredTableInfo *tab, Oid OIDNewHeap, LOCKMODE lockmode);
 static AlteredTableInfo *ATGetQueueEntry(List **wqueue, Relation rel);
 static void ATSimplePermissions(Relation rel, int allowed_targets);
@@ -2723,7 +2726,8 @@ AlterTable(Oid relid, LOCKMODE lockmode, AlterTableStmt *stmt)
 
 	CheckTableNotInUse(rel, "ALTER TABLE");
 
-	ATController(rel, stmt->cmds, interpretInhOption(stmt->relation->inhOpt),
+	ATController(stmt,
+				 rel, stmt->cmds, interpretInhOption(stmt->relation->inhOpt),
 				 lockmode);
 }
 
@@ -2746,7 +2750,7 @@ AlterTableInternal(Oid relid, List *cmds, bool recurse)
 
 	rel = relation_open(relid, lockmode);
 
-	ATController(rel, cmds, recurse, lockmode);
+	ATController(NULL, rel, cmds, recurse, lockmode);
 }
 
 /*
@@ -3015,7 +3019,8 @@ AlterTableGetLockLevel(List *cmds)
 }
 
 static void
-ATController(Relation rel, List *cmds, bool recurse, LOCKMODE lockmode)
+ATController(AlterTableStmt *parsetree,
+			 Relation rel, List *cmds, bool recurse, LOCKMODE lockmode)
 {
 	List	   *wqueue = NIL;
 	ListCell   *lcmd;
@@ -3035,7 +3040,7 @@ ATController(Relation rel, List *cmds, bool recurse, LOCKMODE lockmode)
 	ATRewriteCatalogs(&wqueue, lockmode);
 
 	/* Phase 3: scan/rewrite tables as needed */
-	ATRewriteTables(&wqueue, lockmode);
+	ATRewriteTables(parsetree, &wqueue, lockmode);
 }
 
 /*
@@ -3606,8 +3611,9 @@ ATExecCmd(List **wqueue, AlteredTableInfo *tab, Relation rel,
  * ATRewriteTables: ALTER TABLE phase 3
  */
 static void
-ATRewriteTables(List **wqueue, LOCKMODE lockmode)
+ATRewriteTables(AlterTableStmt *parsetree, List **wqueue, LOCKMODE lockmode)
 {
+	bool        evt_table_rewrite_fired = false;
 	ListCell   *ltab;
 
 	/* Go through each table that needs to be checked or rewritten */
@@ -3727,6 +3733,22 @@ ATRewriteTables(List **wqueue, LOCKMODE lockmode)
 									   lockmode);
 
 			/*
+			 * Fire off an Event Trigger now, before actually rewriting the
+			 * table.
+			 *
+			 * We don't support Event Trigger for nested commands anywhere,
+			 * here included, and parstree is given NULL when comming from
+			 * AlterTableInternal.
+			 *
+			 * And fire it only once.
+			 */
+			if (parsetree && !evt_table_rewrite_fired)
+			{
+				EventTriggerTableRewrite((Node *)parsetree, tab->relid);
+				evt_table_rewrite_fired = true;
+			}
+
+			/*
 			 * Copy the heap data into the new table with the desired
 			 * modifications, and test the current data within the table
 			 * against new constraints generated by ALTER TABLE commands.
@@ -3764,7 +3786,24 @@ ATRewriteTables(List **wqueue, LOCKMODE lockmode)
 			 * generated by ALTER TABLE commands, but don't rebuild data.
 			 */
 			if (tab->constraints != NIL || tab->new_notnull)
+			{
+				/*
+				 * Fire off an Event Trigger now, before actually rewriting the
+				 * table.
+				 *
+				 * We don't support Event Trigger for nested commands anywhere,
+				 * here included, and parstree is given NULL when comming from
+				 * AlterTableInternal.
+				 *
+				 * And fire it only once.
+				 */
+				if (parsetree && !evt_table_rewrite_fired)
+				{
+					EventTriggerTableRewrite((Node *)parsetree, tab->relid);
+					evt_table_rewrite_fired = true;
+				}
 				ATRewriteTable(tab, InvalidOid, lockmode);
+			}
 
 			/*
 			 * If we had SET TABLESPACE but no reason to reconstruct tuples,
diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c
index e5fefa3..779ceb8 100644
--- a/src/backend/commands/vacuum.c
+++ b/src/backend/commands/vacuum.c
@@ -1278,7 +1278,8 @@ vacuum_rel(Oid relid, VacuumStmt *vacstmt, bool do_toast, bool for_wraparound)
 		onerel = NULL;
 
 		/* VACUUM FULL is now a variant of CLUSTER; see cluster.c */
-		cluster_rel(relid, InvalidOid, false,
+		cluster_rel((Node *)vacstmt,
+					relid, InvalidOid, false,
 					(vacstmt->options & VACOPT_VERBOSE) != 0);
 	}
 	else
diff --git a/src/backend/tcop/utility.c b/src/backend/tcop/utility.c
index 4a2a339..cb9a0ba 100644
--- a/src/backend/tcop/utility.c
+++ b/src/backend/tcop/utility.c
@@ -626,23 +626,6 @@ standard_ProcessUtility(Node *parsetree,
 			}
 			break;
 
-		case T_ClusterStmt:
-			/* we choose to allow this during "read only" transactions */
-			PreventCommandDuringRecovery("CLUSTER");
-			cluster((ClusterStmt *) parsetree, isTopLevel);
-			break;
-
-		case T_VacuumStmt:
-			{
-				VacuumStmt *stmt = (VacuumStmt *) parsetree;
-
-				/* we choose to allow this during "read only" transactions */
-				PreventCommandDuringRecovery((stmt->options & VACOPT_VACUUM) ?
-											 "VACUUM" : "ANALYZE");
-				vacuum(stmt, InvalidOid, true, NULL, false, isTopLevel);
-			}
-			break;
-
 		case T_ExplainStmt:
 			ExplainQuery((ExplainStmt *) parsetree, queryString, params, dest);
 			break;
@@ -953,6 +936,25 @@ ProcessUtilitySlow(Node *parsetree,
 				}
 				break;
 
+			case T_ClusterStmt:
+				{
+					/* we choose to allow this during "read only" transactions */
+					PreventCommandDuringRecovery("CLUSTER");
+					cluster((ClusterStmt *) parsetree, isTopLevel);
+				}
+				break;
+
+			case T_VacuumStmt:
+				{
+					VacuumStmt *stmt = (VacuumStmt *) parsetree;
+
+					/* we choose to allow this during "read only" transactions */
+					PreventCommandDuringRecovery((stmt->options & VACOPT_VACUUM) ?
+												 "VACUUM" : "ANALYZE");
+					vacuum(stmt, InvalidOid, true, NULL, false, isTopLevel);
+				}
+				break;
+
 			case T_AlterTableStmt:
 				{
 					AlterTableStmt *atstmt = (AlterTableStmt *) parsetree;
diff --git a/src/backend/utils/cache/evtcache.c b/src/backend/utils/cache/evtcache.c
index ae71bd6..b9d442c 100644
--- a/src/backend/utils/cache/evtcache.c
+++ b/src/backend/utils/cache/evtcache.c
@@ -169,6 +169,8 @@ BuildEventTriggerCache(void)
 			event = EVT_DDLCommandEnd;
 		else if (strcmp(evtevent, "sql_drop") == 0)
 			event = EVT_SQLDrop;
+		else if (strcmp(evtevent, "table_rewrite") == 0)
+			event = EVT_TableRewrite;
 		else
 			continue;
 
diff --git a/src/include/catalog/pg_proc.h b/src/include/catalog/pg_proc.h
index 4736532..b1e0372 100644
--- a/src/include/catalog/pg_proc.h
+++ b/src/include/catalog/pg_proc.h
@@ -4990,6 +4990,8 @@ DESCR("peek at binary changes from replication slot");
 /* event triggers */
 DATA(insert OID = 3566 (  pg_event_trigger_dropped_objects		PGNSP PGUID 12 10 100 0 0 f f f f t t s 0 0 2249 "" "{26,26,23,25,25,25,25}" "{o,o,o,o,o,o,o}" "{classid, objid, objsubid, object_type, schema_name, object_name, object_identity}" _null_ pg_event_trigger_dropped_objects _null_ _null_ _null_ ));
 DESCR("list objects dropped by the current command");
+DATA(insert OID = 4566 (  pg_event_trigger_table_rewrite_oid	PGNSP PGUID 12 10 100 0 0 f f f f t t s 0 0 26 "" "{26}" "{o}" "{oid}" _null_ pg_event_trigger_table_rewrite_oid _null_ _null_ _null_ ));
+DESCR("return Oid of the table getting rewritten");
 
 /* generic transition functions for ordered-set aggregates */
 DATA(insert OID = 3970 ( ordered_set_transition			PGNSP PGUID 12 1 0 0 0 f f f f f f i 2 0 2281 "2281 2276" _null_ _null_ _null_ _null_ ordered_set_transition _null_ _null_ _null_ ));
diff --git a/src/include/commands/cluster.h b/src/include/commands/cluster.h
index f7730a9..80b7433 100644
--- a/src/include/commands/cluster.h
+++ b/src/include/commands/cluster.h
@@ -19,8 +19,8 @@
 
 
 extern void cluster(ClusterStmt *stmt, bool isTopLevel);
-extern void cluster_rel(Oid tableOid, Oid indexOid, bool recheck,
-			bool verbose);
+extern void cluster_rel(Node *parsetree,
+						Oid tableOid, Oid indexOid, bool recheck, bool verbose);
 extern void check_index_is_clusterable(Relation OldHeap, Oid indexOid,
 						   bool recheck, LOCKMODE lockmode);
 extern void mark_index_clustered(Relation rel, Oid indexOid, bool is_internal);
diff --git a/src/include/commands/event_trigger.h b/src/include/commands/event_trigger.h
index 0233f4c..5080f4f 100644
--- a/src/include/commands/event_trigger.h
+++ b/src/include/commands/event_trigger.h
@@ -46,6 +46,7 @@ extern bool EventTriggerSupportsObjectClass(ObjectClass objclass);
 extern void EventTriggerDDLCommandStart(Node *parsetree);
 extern void EventTriggerDDLCommandEnd(Node *parsetree);
 extern void EventTriggerSQLDrop(Node *parsetree);
+extern void EventTriggerTableRewrite(Node *parsetree, Oid tableOid);
 
 extern bool EventTriggerBeginCompleteQuery(void);
 extern void EventTriggerEndCompleteQuery(void);
diff --git a/src/include/utils/builtins.h b/src/include/utils/builtins.h
index fb1b4a4..02b581d 100644
--- a/src/include/utils/builtins.h
+++ b/src/include/utils/builtins.h
@@ -1189,6 +1189,7 @@ extern Datum unique_key_recheck(PG_FUNCTION_ARGS);
 
 /* commands/event_trigger.c */
 extern Datum pg_event_trigger_dropped_objects(PG_FUNCTION_ARGS);
+extern Datum pg_event_trigger_table_rewrite_oid(PG_FUNCTION_ARGS);
 
 /* commands/extension.c */
 extern Datum pg_available_extensions(PG_FUNCTION_ARGS);
diff --git a/src/include/utils/evtcache.h b/src/include/utils/evtcache.h
index c4c284f..4bbd80a 100644
--- a/src/include/utils/evtcache.h
+++ b/src/include/utils/evtcache.h
@@ -20,7 +20,8 @@ typedef enum
 {
 	EVT_DDLCommandStart,
 	EVT_DDLCommandEnd,
-	EVT_SQLDrop
+	EVT_SQLDrop,
+	EVT_TableRewrite
 } EventTriggerEvent;
 
 typedef struct
diff --git a/src/test/regress/expected/event_trigger.out b/src/test/regress/expected/event_trigger.out
index d4723b2..5b08bd8 100644
--- a/src/test/regress/expected/event_trigger.out
+++ b/src/test/regress/expected/event_trigger.out
@@ -294,3 +294,26 @@ SELECT * FROM dropped_objects WHERE type = 'schema';
 DROP ROLE regression_bob;
 DROP EVENT TRIGGER regress_event_trigger_drop_objects;
 DROP EVENT TRIGGER undroppable;
+-- test Table Rewrite Event Trigger
+CREATE OR REPLACE FUNCTION test_evtrig_no_rewrite() RETURNS event_trigger
+LANGUAGE plpgsql AS $$
+BEGIN
+  RAISE EXCEPTION 'I''m sorry Sir, No Rewrite Allowed.';
+END;
+$$;
+create event trigger no_rewrite_allowed on table_rewrite
+  execute procedure test_evtrig_no_rewrite();
+create table rewriteme (id serial primary key, foo float);
+insert into rewriteme
+     select x * 1.001 from generate_series(1, 500) as t(x);
+alter table rewriteme alter column foo type numeric;
+ERROR:  I'm sorry Sir, No Rewrite Allowed.
+alter table rewriteme add column baz int default 0;
+ERROR:  I'm sorry Sir, No Rewrite Allowed.
+cluster rewriteme using rewriteme_pkey;
+ERROR:  I'm sorry Sir, No Rewrite Allowed.
+vacuum full rewriteme;
+ERROR:  I'm sorry Sir, No Rewrite Allowed.
+drop table rewriteme;
+drop event trigger no_rewrite_allowed;
+drop function test_evtrig_no_rewrite();
diff --git a/src/test/regress/sql/event_trigger.sql b/src/test/regress/sql/event_trigger.sql
index 11d2ce5..1fc244e 100644
--- a/src/test/regress/sql/event_trigger.sql
+++ b/src/test/regress/sql/event_trigger.sql
@@ -206,3 +206,27 @@ DROP ROLE regression_bob;
 
 DROP EVENT TRIGGER regress_event_trigger_drop_objects;
 DROP EVENT TRIGGER undroppable;
+
+-- test Table Rewrite Event Trigger
+CREATE OR REPLACE FUNCTION test_evtrig_no_rewrite() RETURNS event_trigger
+LANGUAGE plpgsql AS $$
+BEGIN
+  RAISE EXCEPTION 'I''m sorry Sir, No Rewrite Allowed.';
+END;
+$$;
+
+create event trigger no_rewrite_allowed on table_rewrite
+  execute procedure test_evtrig_no_rewrite();
+
+create table rewriteme (id serial primary key, foo float);
+insert into rewriteme
+     select x * 1.001 from generate_series(1, 500) as t(x);
+alter table rewriteme alter column foo type numeric;
+alter table rewriteme add column baz int default 0;
+
+cluster rewriteme using rewriteme_pkey;
+vacuum full rewriteme;
+
+drop table rewriteme;
+drop event trigger no_rewrite_allowed;
+drop function test_evtrig_no_rewrite();

Simon Riggs

simon@2ndQuadrant.com

about 11 years ago

In reply to: Dimitri Fontaine (#4)

Re: New Event Trigger: table_rewrite

On 7 November 2014 12:35, Dimitri Fontaine <dimitri@2ndquadrant.fr> wrote:

Simon Riggs <simon@2ndQuadrant.com> writes:

It would be more useful to work on the applications of this....

1. INSERT into a table
* Action start time
* Schema
* Tablename
* Number of blocks in table
which would then allow you to do these things run an assessment report
showing which tables would be rewritten.

That should be done by the user, from within his Event Trigger code. For
that to be possible, the previous patch was missing a way to expose the
OID of the table being rewritten, I've now added support for that.

2. Get access to number of blocks, so you could limit rewrites only to
smaller tables by putting a block limit in place.

Also, I did expand the docs to fully cover your practical use case of a
table_rewrite Event Trigger implementing such a table rewrite policy.

That looks complete, very useful and well documented.

I'm looking to commit this tomorrow.

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Michael Paquier

michael.paquier@gmail.com

about 11 years ago

In reply to: Simon Riggs (#5)

Re: New Event Trigger: table_rewrite

On Sun, Nov 16, 2014 at 8:57 AM, Simon Riggs <simon@2ndquadrant.com> wrote:

On 7 November 2014 12:35, Dimitri Fontaine <dimitri@2ndquadrant.fr> wrote:

Simon Riggs <simon@2ndQuadrant.com> writes:

It would be more useful to work on the applications of this....

1. INSERT into a table
* Action start time
* Schema
* Tablename
* Number of blocks in table
which would then allow you to do these things run an assessment report
showing which tables would be rewritten.

That should be done by the user, from within his Event Trigger code. For
that to be possible, the previous patch was missing a way to expose the
OID of the table being rewritten, I've now added support for that.

2. Get access to number of blocks, so you could limit rewrites only to
smaller tables by putting a block limit in place.

Also, I did expand the docs to fully cover your practical use case of a
table_rewrite Event Trigger implementing such a table rewrite policy.

That looks complete, very useful and well documented.

I'm looking to commit this tomorrow.

Patch applies, with many hunks though. Patch and documentation compile
without warnings, passing make check-world.

Some comments:
1) This patch is authorizing VACUUM and CLUSTER to use the event
triggers ddl_command_start and ddl_command_end, but aren't those
commands actually not DDLs but control commands?
2) The documentation of src/sgml/event-trigger.sgml can be improved,
particularly I think that the example function should use a maximum of
upper-case letters for reserved keywords, and also this bit:
you're not allowed to rewrite the table foo
should be rewritten to something like that:
Rewrite of table foo not allowed
3) A typo, missing a plural:
provides two built-in event trigger helper functionS
4) pg_event_trigger_table_rewrite_oid is able to return only one OID,
which is the one of the table being rewritten, and it is limited to
one OID because VACUUM, CLUSTER and ALTER TABLE can only run on one
object at the same time in a single transaction. What about thinking
that we may have in the future multiple objects rewritten in a single
transaction, hence multiple OIDs could be fetched?
5) parsetree is passed to cluster_rel only for
EventTriggerTableRewrite. I am not sure if there are any extension
using cluster_rel as is but wouldn't it make more sense to call
EventTriggerTableRewrite before the calls to cluster_rel instead? ISTM
that this patch is breaking cluster_rel way of doing things.
6) in_table_rewrite seems unnecessary.
 typedef struct EventTriggerQueryState
 {
        slist_head      SQLDropList;
        bool            in_sql_drop;
+       bool            in_table_rewrite;
+       Oid                     tableOid;
We could simplify that by renaming tableOid to rewriteTableOid or
rewriteObjOid and check if its value is InvalidOid to determine if the
event table_rewrite is in use or not. Each code path setting those
variables sets them all the time similarly:
+       state->in_table_rewrite = false;
+       state->tableOid = InvalidOid;
And if tableOid is InvaliOid, in_table_rewrite is false. If it is a
valid Oid, in_table_rewrite is set to true.
7) table_rewrite is kicked in ALTER TABLE only when ATRewriteTables is
used. The list of commands that actually go through this code path
should be clarified in the documentation IMO to help the user
apprehend this function.

Note that this patch has been submitted but there have been no real
discussion around it.. This seems a bit too fast to commit it, no?
Regards,
--
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Simon Riggs

simon@2ndQuadrant.com

about 11 years ago

In reply to: Michael Paquier (#6)

Re: New Event Trigger: table_rewrite

On 16 November 2014 06:59, Michael Paquier <michael.paquier@gmail.com> wrote:

Note that this patch has been submitted but there have been no real
discussion around it.. This seems a bit too fast to commit it, no?

Committing uncontentious patches at the end of the commitfest seems normal, no?

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Simon Riggs

simon@2ndQuadrant.com

about 11 years ago

In reply to: Michael Paquier (#6)

Re: New Event Trigger: table_rewrite

On 16 November 2014 06:59, Michael Paquier <michael.paquier@gmail.com> wrote:

1) This patch is authorizing VACUUM and CLUSTER to use the event
triggers ddl_command_start and ddl_command_end, but aren't those
commands actually not DDLs but control commands?

I could go either way on that. I'm happy to remove those from this commit.

2) The documentation of src/sgml/event-trigger.sgml can be improved,
particularly I think that the example function should use a maximum of
upper-case letters for reserved keywords, and also this bit:
you're not allowed to rewrite the table foo
should be rewritten to something like that:
Rewrite of table foo not allowed
3) A typo, missing a plural:
provides two built-in event trigger helper functionS

I thought the documentation was very good, in comparison to most other
feature submissions. Given that this is one of the areas I moan about
a lot, that says something.

4) pg_event_trigger_table_rewrite_oid is able to return only one OID,
which is the one of the table being rewritten, and it is limited to
one OID because VACUUM, CLUSTER and ALTER TABLE can only run on one
object at the same time in a single transaction. What about thinking
that we may have in the future multiple objects rewritten in a single
transaction, hence multiple OIDs could be fetched?

Why would this API support something which the normal trigger API
doesn't, just in case we support a feature that hadn't ever been
proposed or discussed? Why can't such a change wait until that feature
arrives?

5) parsetree is passed to cluster_rel only for
EventTriggerTableRewrite. I am not sure if there are any extension
using cluster_rel as is but wouldn't it make more sense to call
EventTriggerTableRewrite before the calls to cluster_rel instead? ISTM
that this patch is breaking cluster_rel way of doing things.

I will remove the call to CLUSTER and VACUUM as proposed above.

6) in_table_rewrite seems unnecessary.
typedef struct EventTriggerQueryState
{
slist_head      SQLDropList;
bool            in_sql_drop;
+       bool            in_table_rewrite;
+       Oid                     tableOid;
We could simplify that by renaming tableOid to rewriteTableOid or
rewriteObjOid and check if its value is InvalidOid to determine if the
event table_rewrite is in use or not. Each code path setting those
variables sets them all the time similarly:
+       state->in_table_rewrite = false;
+       state->tableOid = InvalidOid;
And if tableOid is InvaliOid, in_table_rewrite is false. If it is a
valid Oid, in_table_rewrite is set to true.

Well, that seems a minor change. I'm happy to accept the original
coding, but also happy to receive suggested changes.

7) table_rewrite is kicked in ALTER TABLE only when ATRewriteTables is
used. The list of commands that actually go through this code path
should be clarified in the documentation IMO to help the user
apprehend this function.

That is somewhat orthogonal to the patch. The rules for rewriting are
quite complex, which is why this is needed and why documentation isn't
really the answer. Separate doc patch on that would be welcome.

--
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PostgreSQL Development, 24x7 Support, Training & Services

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Robert Haas

robertmhaas@gmail.com

about 11 years ago

In reply to: Simon Riggs (#8)

Re: New Event Trigger: table_rewrite

On Sun, Nov 16, 2014 at 5:51 AM, Simon Riggs <simon@2ndquadrant.com> wrote:

On 16 November 2014 06:59, Michael Paquier <michael.paquier@gmail.com> wrote:

1) This patch is authorizing VACUUM and CLUSTER to use the event
triggers ddl_command_start and ddl_command_end, but aren't those
commands actually not DDLs but control commands?

I could go either way on that. I'm happy to remove those from this commit.

Yeah, this patch definitely shouldn't change the set of commands to
which existing event triggers apply as a side-effect. There's no
reason new DDL commands need to apply to the same set of operations as
existing DDL commands, but the existing ones shouldn't be changed
without specific discussion and agreement.

It seems pretty weird, also, that the event trigger will fire after
we've taken AccessExclusiveLock when you cluster a particular
relation, and before we've taken AccessExclusiveLock when you cluster
database-wide. That's more or less an implementation artifact of the
current code that we're exposing to the use for, really, no good
reason.

--
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EnterpriseDB: http://www.enterprisedb.com
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#10

Dimitri Fontaine

dimitri@2ndQuadrant.fr

about 11 years ago

In reply to: Michael Paquier (#6)

1 attachment(s)

Re: New Event Trigger: table_rewrite

Hi,

Michael Paquier <michael.paquier@gmail.com> writes:

1) This patch is authorizing VACUUM and CLUSTER to use the event
triggers ddl_command_start and ddl_command_end, but aren't those
commands actually not DDLs but control commands?

Reverted in the attached version 3 of the patch.

6) in_table_rewrite seems unnecessary.

Removed in the attached version 3 of the patch.

On Sun, Nov 16, 2014 at 5:51 AM, Simon Riggs <simon@2ndquadrant.com> wrote:

4) pg_event_trigger_table_rewrite_oid is able to return only one OID,
which is the one of the table being rewritten, and it is limited to
one OID because VACUUM, CLUSTER and ALTER TABLE can only run on one
object at the same time in a single transaction. What about thinking
that we may have in the future multiple objects rewritten in a single
transaction, hence multiple OIDs could be fetched?

Why would this API support something which the normal trigger API
doesn't, just in case we support a feature that hadn't ever been
proposed or discussed? Why can't such a change wait until that feature
arrives?

Agreed, unchanged in the attached.

Robert Haas <robertmhaas@gmail.com> writes:

It seems pretty weird, also, that the event trigger will fire after
we've taken AccessExclusiveLock when you cluster a particular
relation, and before we've taken AccessExclusiveLock when you cluster
database-wide. That's more or less an implementation artifact of the
current code that we're exposing to the use for, really, no good
reason.

In the CLUSTER implementation we have only one call site for invoking
the Event Trigger, in cluster_rel(). While it's true that in the single
relation case, the relation is opened in cluster() then cluster_rel() is
called, the opening is done with NoLock in cluster():

rel = heap_open(tableOid, NoLock);

My understanding is that the relation locking only happens in
cluster_rel() at this line:

OldHeap = try_relation_open(tableOid, AccessExclusiveLock);

Please help me through the cluster locking strategy here, I feel like
I'm missing something obvious, as my conclusion from re-reading the code
in lights of your comment is that your comment is not accurate with
respect to the current state of the code.

Regards,
--
Dimitri Fontaine
http://2ndQuadrant.fr PostgreSQL : Expertise, Formation et Support

Attachments:

table_rewrite.3.patchtext/x-patchDownload

diff --git a/doc/src/sgml/event-trigger.sgml b/doc/src/sgml/event-trigger.sgml
index 6f71a27..704a377 100644
--- a/doc/src/sgml/event-trigger.sgml
+++ b/doc/src/sgml/event-trigger.sgml
@@ -65,6 +65,12 @@
    </para>
 
    <para>
+    The <literal>table_rewrite</> event occurs just before a table is going to
+    get rewritten by the commands <literal>ALTER TABLE</literal>,
+    <literal>CLUSTER</literal> or <literal>VACUUM</literal>.
+   </para>
+
+   <para>
      Event triggers (like other functions) cannot be executed in an aborted
      transaction.  Thus, if a DDL command fails with an error, any associated
      <literal>ddl_command_end</> triggers will not be executed.  Conversely,
@@ -120,518 +126,625 @@
         <entry><literal>ddl_command_start</literal></entry>
         <entry><literal>ddl_command_end</literal></entry>
         <entry><literal>sql_drop</literal></entry>
+        <entry><literal>table_rewrite</literal></entry>
        </row>
       </thead>
       <tbody>
        <row>
+        <entry align="left"><literal>ANALYZE</literal></entry>
+        <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
+       </row>
+       <row>
         <entry align="left"><literal>ALTER AGGREGATE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER COLLATION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER CONVERSION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER DOMAIN</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER EXTENSION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER FOREIGN DATA WRAPPER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER FOREIGN TABLE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER FUNCTION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER LANGUAGE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER OPERATOR</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER OPERATOR CLASS</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER OPERATOR FAMILY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER POLICY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER SCHEMA</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER SEQUENCE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER SERVER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER TABLE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>X</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER TEXT SEARCH CONFIGURATION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER TEXT SEARCH DICTIONARY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER TEXT SEARCH PARSER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER TEXT SEARCH TEMPLATE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER TRIGGER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER TYPE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER USER MAPPING</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER VIEW</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
+       </row>
+       <row>
+        <entry align="left"><literal>CLUSTER</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>X</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE AGGREGATE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE CAST</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE COLLATION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE CONVERSION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE DOMAIN</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE EXTENSION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE FOREIGN DATA WRAPPER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE FOREIGN TABLE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE FUNCTION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE INDEX</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE LANGUAGE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE OPERATOR</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE OPERATOR CLASS</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE OPERATOR FAMILY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE POLICY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE RULE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE SCHEMA</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE SEQUENCE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE SERVER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE TABLE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE TABLE AS</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE TEXT SEARCH CONFIGURATION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE TEXT SEARCH DICTIONARY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE TEXT SEARCH PARSER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE TEXT SEARCH TEMPLATE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE TRIGGER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE TYPE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE USER MAPPING</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE VIEW</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP AGGREGATE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP CAST</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP COLLATION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP CONVERSION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP DOMAIN</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP EXTENSION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP FOREIGN DATA WRAPPER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP FOREIGN TABLE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP FUNCTION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP INDEX</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP LANGUAGE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP OPERATOR</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP OPERATOR CLASS</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP OPERATOR FAMILY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP OWNED</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP POLICY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP RULE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP SCHEMA</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP SEQUENCE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP SERVER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP TABLE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP TEXT SEARCH CONFIGURATION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP TEXT SEARCH DICTIONARY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP TEXT SEARCH PARSER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP TEXT SEARCH TEMPLATE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP TRIGGER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP TYPE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP USER MAPPING</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP VIEW</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>IMPORT FOREIGN SCHEMA</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>SELECT INTO</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
+       </row>
+       <row>
+        <entry align="left"><literal>VACUUM</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>X</literal></entry>
        </row>
       </tbody>
      </tgroup>
@@ -843,4 +956,58 @@ COMMIT;
     event triggers.)
    </para>
   </sect1>
+
+  <sect1 id="event-trigger-table-rewrite-example">
+   <title>A Table Rewrite Event Trigger Example</title>
+
+   <para>
+    Thanks to the <literal>table_rewrite</> event, it is possible to implement
+    a table rewriting policy only allowing the rewrite in maintenance windows.
+   </para>
+
+   <para>
+    Here's an example implementing such a policy.
+<programlisting>
+create or replace function no_rewrite()
+ returns event_trigger
+ language plpgsql as
+$$
+---
+--- Implement local Table Rewriting policy:
+---   public.foo is not allowed rewriting, ever
+---   other tables are only allowed rewriting between 1am and 6am
+---   unless they have more than 100 blocks
+---
+declare
+  table_oid oid := pg_event_trigger_table_rewrite_oid();
+  current_hour integer := extract('hour' from current_time);
+  pages integer;
+  max_pages integer := 100;
+begin
+  if pg_event_trigger_table_rewrite_oid() = 'public.foo'::regclass
+  then
+        raise exception 'you''re not allowed to rewrite the table %',
+                        table_oid::regclass;
+  end if;
+
+  select into pages relpages from pg_class where oid = table_oid;
+  if pages > max_pages
+  then
+        raise exception 'rewrites only allowed for table with less than % pages',
+                        max_pages;
+  end if;
+
+  if not current_hour between 1 and 6
+  then
+        raise exception 'rewrites only allowed between 1am and 6am';
+  end if;
+end;
+$$;
+
+create event trigger no_rewrite_allowed
+                  on table_rewrite
+   execute procedure no_rewrite();
+</programlisting>
+   </para>
+ </sect1>
 </chapter>
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 7e5bcd9..24bf78c 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -17540,16 +17540,20 @@ FOR EACH ROW EXECUTE PROCEDURE suppress_redundant_updates_trigger();
   <sect1 id="functions-event-triggers">
    <title>Event Trigger Functions</title>
 
+   <para>
+    Currently <productname>PostgreSQL</> provides two built-in event trigger
+    helper function, <function>pg_event_trigger_dropped_objects</>
+    and <function>pg_event_trigger_table_rewrite_oid</>.
+   </para>
+
+  <sect2 id="pg-event-trigger-dropped-objects">
+   <title>Processing objects dropped by a DDL command.</title>
+
    <indexterm>
      <primary>pg_event_trigger_dropped_objects</primary>
    </indexterm>
 
    <para>
-    Currently <productname>PostgreSQL</> provides one built-in event trigger
-    helper function, <function>pg_event_trigger_dropped_objects</>.
-   </para>
-
-   <para>
     <function>pg_event_trigger_dropped_objects</> returns a list of all objects
     dropped by the command in whose <literal>sql_drop</> event it is called.
     If called in any other context,
@@ -17647,6 +17651,68 @@ CREATE EVENT TRIGGER test_event_trigger_for_drops
        For more information about event triggers,
        see <xref linkend="event-triggers">.
     </para>
+  </sect2>
+
+  <sect2 id="pg-event-trigger-table-rewrite-oid">
+   <title>Handling a Table Rewrite Event</title>
+
+   <indexterm>
+     <primary>pg_event_trigger_table_rewrite_oid</primary>
+   </indexterm>
+
+   <para>
+    <function>pg_event_trigger_table_rewrite_oid</> returns
+    the <literal>OID</> of the table that is going to be rewritten on-disk by
+    the current DDL command. If called in any other context,
+    <function>pg_event_trigger_table_rewrite_oid</> raises an error.
+    <function>pg_event_trigger_table_rewrite_oid</> returns the following
+    columns:
+
+    <informaltable>
+     <tgroup cols="3">
+      <thead>
+       <row>
+        <entry>Name</entry>
+        <entry>Type</entry>
+        <entry>Description</entry>
+       </row>
+      </thead>
+
+      <tbody>
+       <row>
+        <entry><literal>oid</literal></entry>
+        <entry><type>Oid</type></entry>
+        <entry>OID of the pg_class entry for the table.</entry>
+       </row>
+      </tbody>
+     </tgroup>
+    </informaltable>
+   </para>
+
+   <para>
+    The <function>pg_event_trigger_table_rewrite_oid</> function can be used
+    in an event trigger like this:
+<programlisting>
+create function test_event_trigger_table_rewrite_oid()
+ returns event_trigger
+ language plpgsql as
+$$
+begin
+  raise notice 'rewriting table %', pg_event_trigger_table_rewrite_oid()::regclass;
+end;
+$$;
+
+create event trigger test_table_rewrite_oid
+                  on table_rewrite
+   execute procedure test_event_trigger_table_rewrite_oid();
+</programlisting>
+    </para>
+
+     <para>
+       For more information about event triggers,
+       see <xref linkend="event-triggers">.
+    </para>
+  </sect2>
   </sect1>
 
 </chapter>
diff --git a/src/backend/commands/cluster.c b/src/backend/commands/cluster.c
index ff80b09..64d1312 100644
--- a/src/backend/commands/cluster.c
+++ b/src/backend/commands/cluster.c
@@ -31,6 +31,7 @@
 #include "catalog/objectaccess.h"
 #include "catalog/toasting.h"
 #include "commands/cluster.h"
+#include "commands/event_trigger.h"
 #include "commands/tablecmds.h"
 #include "commands/vacuum.h"
 #include "miscadmin.h"
@@ -175,7 +176,7 @@ cluster(ClusterStmt *stmt, bool isTopLevel)
 		heap_close(rel, NoLock);
 
 		/* Do the job. */
-		cluster_rel(tableOid, indexOid, false, stmt->verbose);
+		cluster_rel((Node *)stmt, tableOid, indexOid, false, stmt->verbose);
 	}
 	else
 	{
@@ -225,7 +226,8 @@ cluster(ClusterStmt *stmt, bool isTopLevel)
 			/* functions in indexes may want a snapshot set */
 			PushActiveSnapshot(GetTransactionSnapshot());
 			/* Do the job. */
-			cluster_rel(rvtc->tableOid, rvtc->indexOid, true, stmt->verbose);
+			cluster_rel((Node *)stmt,
+						rvtc->tableOid, rvtc->indexOid, true, stmt->verbose);
 			PopActiveSnapshot();
 			CommitTransactionCommand();
 		}
@@ -256,7 +258,8 @@ cluster(ClusterStmt *stmt, bool isTopLevel)
  * and error messages should refer to the operation as VACUUM not CLUSTER.
  */
 void
-cluster_rel(Oid tableOid, Oid indexOid, bool recheck, bool verbose)
+cluster_rel(Node *parsetree,
+			Oid tableOid, Oid indexOid, bool recheck, bool verbose)
 {
 	Relation	OldHeap;
 
@@ -264,6 +267,11 @@ cluster_rel(Oid tableOid, Oid indexOid, bool recheck, bool verbose)
 	CHECK_FOR_INTERRUPTS();
 
 	/*
+	 * Fire off an Event Trigger now, before actually rewriting the table.
+	 */
+	EventTriggerTableRewrite((Node *)parsetree, tableOid);
+
+	/*
 	 * We grab exclusive access to the target rel and index for the duration
 	 * of the transaction.  (This is redundant for the single-transaction
 	 * case, since cluster() already did it.)  The index lock is taken inside
diff --git a/src/backend/commands/event_trigger.c b/src/backend/commands/event_trigger.c
index 1b8c94b..5d132df 100644
--- a/src/backend/commands/event_trigger.c
+++ b/src/backend/commands/event_trigger.c
@@ -42,11 +42,14 @@
 #include "utils/syscache.h"
 #include "tcop/utility.h"
 
-
+/*
+ * Data Structure for sql_drop and table_rewrite Event Trigger support.
+ */
 typedef struct EventTriggerQueryState
 {
 	slist_head	SQLDropList;
 	bool		in_sql_drop;
+	Oid			table_rewrite_oid;
 	MemoryContext cxt;
 	struct EventTriggerQueryState *previous;
 } EventTriggerQueryState;
@@ -119,11 +122,14 @@ static void AlterEventTriggerOwner_internal(Relation rel,
 								HeapTuple tup,
 								Oid newOwnerId);
 static event_trigger_command_tag_check_result check_ddl_tag(const char *tag);
+static event_trigger_command_tag_check_result check_table_rewrite_ddl_tag(
+	const char *tag);
 static void error_duplicate_filter_variable(const char *defname);
 static Datum filter_list_to_array(List *filterlist);
 static Oid insert_event_trigger_tuple(char *trigname, char *eventname,
 						   Oid evtOwner, Oid funcoid, List *tags);
 static void validate_ddl_tags(const char *filtervar, List *taglist);
+static void validate_table_rewrite_tags(const char *filtervar, List *taglist);
 static void EventTriggerInvoke(List *fn_oid_list, EventTriggerData *trigdata);
 
 /*
@@ -154,7 +160,8 @@ CreateEventTrigger(CreateEventTrigStmt *stmt)
 	/* Validate event name. */
 	if (strcmp(stmt->eventname, "ddl_command_start") != 0 &&
 		strcmp(stmt->eventname, "ddl_command_end") != 0 &&
-		strcmp(stmt->eventname, "sql_drop") != 0)
+		strcmp(stmt->eventname, "sql_drop") != 0 &&
+		strcmp(stmt->eventname, "table_rewrite") != 0)
 		ereport(ERROR,
 				(errcode(ERRCODE_SYNTAX_ERROR),
 				 errmsg("unrecognized event name \"%s\"",
@@ -183,6 +190,9 @@ CreateEventTrigger(CreateEventTrigStmt *stmt)
 		 strcmp(stmt->eventname, "sql_drop") == 0)
 		&& tags != NULL)
 		validate_ddl_tags("tag", tags);
+	else if (strcmp(stmt->eventname, "table_rewrite") == 0
+			 && tags != NULL)
+		validate_table_rewrite_tags("tag", tags);
 
 	/*
 	 * Give user a nice error message if an event trigger of the same name
@@ -257,6 +267,7 @@ check_ddl_tag(const char *tag)
 
 	/*
 	 * Otherwise, command should be CREATE, ALTER, or DROP.
+	 * Or one of ANALYZE, CLUSTER, VACUUM.
 	 */
 	if (pg_strncasecmp(tag, "CREATE ", 7) == 0)
 		obtypename = tag + 7;
@@ -264,6 +275,10 @@ check_ddl_tag(const char *tag)
 		obtypename = tag + 6;
 	else if (pg_strncasecmp(tag, "DROP ", 5) == 0)
 		obtypename = tag + 5;
+	else if (pg_strncasecmp(tag, "ANALYZE", 7) == 0 ||
+			 pg_strncasecmp(tag, "CLUSTER", 7) == 0 ||
+			 pg_strncasecmp(tag, "VACUUM", 6) == 0)
+		return EVENT_TRIGGER_COMMAND_TAG_OK;
 	else
 		return EVENT_TRIGGER_COMMAND_TAG_NOT_RECOGNIZED;
 
@@ -281,6 +296,41 @@ check_ddl_tag(const char *tag)
 }
 
 /*
+ * Validate DDL command tags.
+ */
+static void
+validate_table_rewrite_tags(const char *filtervar, List *taglist)
+{
+	ListCell   *lc;
+
+	foreach(lc, taglist)
+	{
+		const char *tag = strVal(lfirst(lc));
+		event_trigger_command_tag_check_result result;
+
+		result = check_table_rewrite_ddl_tag(tag);
+		if (result == EVENT_TRIGGER_COMMAND_TAG_NOT_SUPPORTED)
+			ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+			/* translator: %s represents an SQL statement name */
+					 errmsg("event triggers are not supported for %s",
+							tag)));
+	}
+}
+
+static event_trigger_command_tag_check_result
+check_table_rewrite_ddl_tag(const char *tag)
+{
+	if (pg_strcasecmp(tag, "ALTER TABLE") == 0 ||
+		pg_strcasecmp(tag, "CLUSTER") == 0 ||
+		pg_strcasecmp(tag, "VACUUM") == 0 ||
+		pg_strcasecmp(tag, "ANALYZE") == 0 )
+		return EVENT_TRIGGER_COMMAND_TAG_OK;
+
+	return EVENT_TRIGGER_COMMAND_TAG_NOT_SUPPORTED;
+}
+
+/*
  * Complain about a duplicate filter variable.
  */
 static void
@@ -641,8 +691,18 @@ EventTriggerCommonSetup(Node *parsetree,
 		const char *dbgtag;
 
 		dbgtag = CreateCommandTag(parsetree);
-		if (check_ddl_tag(dbgtag) != EVENT_TRIGGER_COMMAND_TAG_OK)
-			elog(ERROR, "unexpected command tag \"%s\"", dbgtag);
+		if (event == EVT_DDLCommandStart ||
+			event == EVT_DDLCommandEnd   ||
+			event == EVT_SQLDrop)
+		{
+			if (check_ddl_tag(dbgtag) != EVENT_TRIGGER_COMMAND_TAG_OK)
+				elog(ERROR, "unexpected command tag \"%s\"", dbgtag);
+		}
+		else if (event == EVT_TableRewrite)
+		{
+			if(check_table_rewrite_ddl_tag(dbgtag) != EVENT_TRIGGER_COMMAND_TAG_OK)
+				elog(ERROR, "unexpected command tag \"%s\"", dbgtag);
+		}
 	}
 #endif
 
@@ -838,6 +898,77 @@ EventTriggerSQLDrop(Node *parsetree)
 	list_free(runlist);
 }
 
+
+/*
+ * Fire table_rewrite triggers.
+ */
+void
+EventTriggerTableRewrite(Node *parsetree, Oid tableOid)
+{
+	List	   *runlist;
+	EventTriggerData trigdata;
+
+	elog(DEBUG1, "EventTriggerTableRewrite(%u)", tableOid);
+
+	/*
+	 * Event Triggers are completely disabled in standalone mode.  There are
+	 * (at least) two reasons for this:
+	 *
+	 * 1. A sufficiently broken event trigger might not only render the
+	 * database unusable, but prevent disabling itself to fix the situation.
+	 * In this scenario, restarting in standalone mode provides an escape
+	 * hatch.
+	 *
+	 * 2. BuildEventTriggerCache relies on systable_beginscan_ordered, and
+	 * therefore will malfunction if pg_event_trigger's indexes are damaged.
+	 * To allow recovery from a damaged index, we need some operating mode
+	 * wherein event triggers are disabled.  (Or we could implement
+	 * heapscan-and-sort logic for that case, but having disaster recovery
+	 * scenarios depend on code that's otherwise untested isn't appetizing.)
+	 */
+	if (!IsUnderPostmaster)
+		return;
+
+	runlist = EventTriggerCommonSetup(parsetree,
+									  EVT_TableRewrite,
+									  "table_rewrite",
+									  &trigdata);
+	if (runlist == NIL)
+		return;
+
+	/*
+	 * Make sure pg_event_trigger_table_rewrite_oid only works when running
+	 * these triggers. Use PG_TRY to ensure table_rewrite_oid is reset even
+	 * when one trigger fails. (This is perhaps not necessary, as the
+	 * currentState variable will be removed shortly by our caller, but it
+	 * seems better to play safe.)
+	 */
+	currentEventTriggerState->table_rewrite_oid = tableOid;
+
+	/* Run the triggers. */
+	PG_TRY();
+	{
+		EventTriggerInvoke(runlist, &trigdata);
+	}
+	PG_CATCH();
+	{
+		currentEventTriggerState->table_rewrite_oid = InvalidOid;
+		PG_RE_THROW();
+	}
+	PG_END_TRY();
+
+	currentEventTriggerState->table_rewrite_oid = InvalidOid;
+
+	/* Cleanup. */
+	list_free(runlist);
+
+	/*
+	 * Make sure anything the event triggers did will be visible to the main
+	 * command.
+	 */
+	CommandCounterIncrement();
+}
+
 /*
  * Invoke each event trigger in a list of event triggers.
  */
@@ -871,6 +1002,8 @@ EventTriggerInvoke(List *fn_oid_list, EventTriggerData *trigdata)
 		FunctionCallInfoData fcinfo;
 		PgStat_FunctionCallUsage fcusage;
 
+		elog(DEBUG1, "EventTriggerInvoke %u", fnoid);
+
 		/*
 		 * We want each event trigger to be able to see the results of the
 		 * previous event trigger's action.  Caller is responsible for any
@@ -1026,8 +1159,9 @@ EventTriggerBeginCompleteQuery(void)
 	MemoryContext cxt;
 
 	/*
-	 * Currently, sql_drop events are the only reason to have event trigger
-	 * state at all; so if there are none, don't install one.
+	 * Currently, sql_drop and table_rewrite events are the only reason to
+	 * have event trigger state at all; so if there are none, don't install
+	 * one.
 	 */
 	if (!trackDroppedObjectsNeeded())
 		return false;
@@ -1041,6 +1175,7 @@ EventTriggerBeginCompleteQuery(void)
 	state->cxt = cxt;
 	slist_init(&(state->SQLDropList));
 	state->in_sql_drop = false;
+	state->table_rewrite_oid = InvalidOid;
 
 	state->previous = currentEventTriggerState;
 	currentEventTriggerState = state;
@@ -1080,8 +1215,9 @@ EventTriggerEndCompleteQuery(void)
 bool
 trackDroppedObjectsNeeded(void)
 {
-	/* true if any sql_drop event trigger exists */
-	return list_length(EventCacheLookup(EVT_SQLDrop)) > 0;
+	/* true if any sql_drop or table_rewrite event trigger exists */
+	return list_length(EventCacheLookup(EVT_SQLDrop)) > 0 ||
+		list_length(EventCacheLookup(EVT_TableRewrite)) > 0;
 }
 
 /*
@@ -1297,3 +1433,25 @@ pg_event_trigger_dropped_objects(PG_FUNCTION_ARGS)
 
 	return (Datum) 0;
 }
+
+/*
+ * pg_event_trigger_table_rewrite_oid
+ *
+ * Make the Oid of the table going to be rewritten available to the user
+ * function run by the Event Trigger.
+ */
+Datum
+pg_event_trigger_table_rewrite_oid(PG_FUNCTION_ARGS)
+{
+	/*
+	 * Protect this function from being called out of context
+	 */
+	if (!currentEventTriggerState ||
+		currentEventTriggerState->table_rewrite_oid != InvalidOid)
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+		 errmsg("%s can only be called in a table_rewrite event trigger function",
+				"pg_event_trigger_table_rewrite_oid()")));
+
+	PG_RETURN_OID(currentEventTriggerState->table_rewrite_oid);
+}
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index ecdff1e..7477dd0 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -46,6 +46,7 @@
 #include "commands/cluster.h"
 #include "commands/comment.h"
 #include "commands/defrem.h"
+#include "commands/event_trigger.h"
 #include "commands/policy.h"
 #include "commands/sequence.h"
 #include "commands/tablecmds.h"
@@ -303,13 +304,15 @@ static void validateForeignKeyConstraint(char *conname,
 static void createForeignKeyTriggers(Relation rel, Oid refRelOid,
 						 Constraint *fkconstraint,
 						 Oid constraintOid, Oid indexOid);
-static void ATController(Relation rel, List *cmds, bool recurse, LOCKMODE lockmode);
+static void ATController(AlterTableStmt *parsetree,
+						 Relation rel, List *cmds, bool recurse, LOCKMODE lockmode);
 static void ATPrepCmd(List **wqueue, Relation rel, AlterTableCmd *cmd,
 		  bool recurse, bool recursing, LOCKMODE lockmode);
 static void ATRewriteCatalogs(List **wqueue, LOCKMODE lockmode);
 static void ATExecCmd(List **wqueue, AlteredTableInfo *tab, Relation rel,
 		  AlterTableCmd *cmd, LOCKMODE lockmode);
-static void ATRewriteTables(List **wqueue, LOCKMODE lockmode);
+static void ATRewriteTables(AlterTableStmt *parsetree,
+							List **wqueue, LOCKMODE lockmode);
 static void ATRewriteTable(AlteredTableInfo *tab, Oid OIDNewHeap, LOCKMODE lockmode);
 static AlteredTableInfo *ATGetQueueEntry(List **wqueue, Relation rel);
 static void ATSimplePermissions(Relation rel, int allowed_targets);
@@ -2723,7 +2726,8 @@ AlterTable(Oid relid, LOCKMODE lockmode, AlterTableStmt *stmt)
 
 	CheckTableNotInUse(rel, "ALTER TABLE");
 
-	ATController(rel, stmt->cmds, interpretInhOption(stmt->relation->inhOpt),
+	ATController(stmt,
+				 rel, stmt->cmds, interpretInhOption(stmt->relation->inhOpt),
 				 lockmode);
 }
 
@@ -2746,7 +2750,7 @@ AlterTableInternal(Oid relid, List *cmds, bool recurse)
 
 	rel = relation_open(relid, lockmode);
 
-	ATController(rel, cmds, recurse, lockmode);
+	ATController(NULL, rel, cmds, recurse, lockmode);
 }
 
 /*
@@ -3015,7 +3019,8 @@ AlterTableGetLockLevel(List *cmds)
 }
 
 static void
-ATController(Relation rel, List *cmds, bool recurse, LOCKMODE lockmode)
+ATController(AlterTableStmt *parsetree,
+			 Relation rel, List *cmds, bool recurse, LOCKMODE lockmode)
 {
 	List	   *wqueue = NIL;
 	ListCell   *lcmd;
@@ -3035,7 +3040,7 @@ ATController(Relation rel, List *cmds, bool recurse, LOCKMODE lockmode)
 	ATRewriteCatalogs(&wqueue, lockmode);
 
 	/* Phase 3: scan/rewrite tables as needed */
-	ATRewriteTables(&wqueue, lockmode);
+	ATRewriteTables(parsetree, &wqueue, lockmode);
 }
 
 /*
@@ -3606,8 +3611,9 @@ ATExecCmd(List **wqueue, AlteredTableInfo *tab, Relation rel,
  * ATRewriteTables: ALTER TABLE phase 3
  */
 static void
-ATRewriteTables(List **wqueue, LOCKMODE lockmode)
+ATRewriteTables(AlterTableStmt *parsetree, List **wqueue, LOCKMODE lockmode)
 {
+	bool        evt_table_rewrite_fired = false;
 	ListCell   *ltab;
 
 	/* Go through each table that needs to be checked or rewritten */
@@ -3727,6 +3733,22 @@ ATRewriteTables(List **wqueue, LOCKMODE lockmode)
 									   lockmode);
 
 			/*
+			 * Fire off an Event Trigger now, before actually rewriting the
+			 * table.
+			 *
+			 * We don't support Event Trigger for nested commands anywhere,
+			 * here included, and parstree is given NULL when comming from
+			 * AlterTableInternal.
+			 *
+			 * And fire it only once.
+			 */
+			if (parsetree && !evt_table_rewrite_fired)
+			{
+				EventTriggerTableRewrite((Node *)parsetree, tab->relid);
+				evt_table_rewrite_fired = true;
+			}
+
+			/*
 			 * Copy the heap data into the new table with the desired
 			 * modifications, and test the current data within the table
 			 * against new constraints generated by ALTER TABLE commands.
@@ -3764,7 +3786,24 @@ ATRewriteTables(List **wqueue, LOCKMODE lockmode)
 			 * generated by ALTER TABLE commands, but don't rebuild data.
 			 */
 			if (tab->constraints != NIL || tab->new_notnull)
+			{
+				/*
+				 * Fire off an Event Trigger now, before actually rewriting the
+				 * table.
+				 *
+				 * We don't support Event Trigger for nested commands anywhere,
+				 * here included, and parstree is given NULL when comming from
+				 * AlterTableInternal.
+				 *
+				 * And fire it only once.
+				 */
+				if (parsetree && !evt_table_rewrite_fired)
+				{
+					EventTriggerTableRewrite((Node *)parsetree, tab->relid);
+					evt_table_rewrite_fired = true;
+				}
 				ATRewriteTable(tab, InvalidOid, lockmode);
+			}
 
 			/*
 			 * If we had SET TABLESPACE but no reason to reconstruct tuples,
diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c
index e5fefa3..779ceb8 100644
--- a/src/backend/commands/vacuum.c
+++ b/src/backend/commands/vacuum.c
@@ -1278,7 +1278,8 @@ vacuum_rel(Oid relid, VacuumStmt *vacstmt, bool do_toast, bool for_wraparound)
 		onerel = NULL;
 
 		/* VACUUM FULL is now a variant of CLUSTER; see cluster.c */
-		cluster_rel(relid, InvalidOid, false,
+		cluster_rel((Node *)vacstmt,
+					relid, InvalidOid, false,
 					(vacstmt->options & VACOPT_VERBOSE) != 0);
 	}
 	else
diff --git a/src/backend/tcop/utility.c b/src/backend/tcop/utility.c
index 4a2a339..c72bc72 100644
--- a/src/backend/tcop/utility.c
+++ b/src/backend/tcop/utility.c
@@ -626,23 +626,6 @@ standard_ProcessUtility(Node *parsetree,
 			}
 			break;
 
-		case T_ClusterStmt:
-			/* we choose to allow this during "read only" transactions */
-			PreventCommandDuringRecovery("CLUSTER");
-			cluster((ClusterStmt *) parsetree, isTopLevel);
-			break;
-
-		case T_VacuumStmt:
-			{
-				VacuumStmt *stmt = (VacuumStmt *) parsetree;
-
-				/* we choose to allow this during "read only" transactions */
-				PreventCommandDuringRecovery((stmt->options & VACOPT_VACUUM) ?
-											 "VACUUM" : "ANALYZE");
-				vacuum(stmt, InvalidOid, true, NULL, false, isTopLevel);
-			}
-			break;
-
 		case T_ExplainStmt:
 			ExplainQuery((ExplainStmt *) parsetree, queryString, params, dest);
 			break;
@@ -843,6 +826,74 @@ standard_ProcessUtility(Node *parsetree,
 }
 
 /*
+ * VACUUM and CLUSTER support the table_rewrite Event Trigger, but they are
+ * not covered by the ddl_command_{start|end} event triggers, so they need a
+ * special treatment here.
+ */
+static bool
+ProcessUtilityForTableRewriteSupportOnly(Node *parsetree,
+										 const char *queryString,
+										 ProcessUtilityContext context,
+										 ParamListInfo params,
+										 DestReceiver *dest,
+										 char *completionTag,
+										 bool isTopLevel,
+										 bool needCleanup)
+{
+	bool done = false;
+
+	PG_TRY();
+	{
+		switch (nodeTag(parsetree))
+		{
+			case T_ClusterStmt:
+				{
+					/* we choose to allow this during "read only" transactions */
+					PreventCommandDuringRecovery("CLUSTER");
+					cluster((ClusterStmt *) parsetree, isTopLevel);
+
+					done = true;
+				}
+				break;
+
+			case T_VacuumStmt:
+				{
+					VacuumStmt *stmt = (VacuumStmt *) parsetree;
+					/* we choose to allow this during "read only" transactions */
+					PreventCommandDuringRecovery((stmt->options & VACOPT_VACUUM) ?
+												 "VACUUM" : "ANALYZE");
+					vacuum(stmt, InvalidOid, true, NULL, false, isTopLevel);
+
+					done = true;
+				}
+				break;
+
+			default:
+				{
+					/*
+					 * make compiler happy about all those enumeration value we
+					 * are not handling on purpose.
+					 */
+					(void) 0;
+				}
+				break;
+		}
+	}
+	PG_CATCH();
+	{
+		if (done && needCleanup)
+			EventTriggerEndCompleteQuery();
+		PG_RE_THROW();
+	}
+	PG_END_TRY();
+
+	if (done && needCleanup)
+		EventTriggerEndCompleteQuery();
+
+	return done;
+}
+
+/*
  * The "Slow" variant of ProcessUtility should only receive statements
  * supported by the event triggers facility.  Therefore, we always
  * perform the trigger support calls if the context allows it.
@@ -862,6 +913,21 @@ ProcessUtilitySlow(Node *parsetree,
 	/* All event trigger calls are done only when isCompleteQuery is true */
 	needCleanup = isCompleteQuery && EventTriggerBeginCompleteQuery();
 
+	/*
+	 * Take care of commands with support for table_rewrite but no support for
+	 * ddl_command_start and ddl_command_end Event Trigger support, currently
+	 * only CLUSTER and VACUUM.
+	 */
+	if (ProcessUtilityForTableRewriteSupportOnly(parsetree,
+												 queryString,
+												 context,
+												 params,
+												 dest,
+												 completionTag,
+												 isTopLevel,
+												 needCleanup))
+		return;
+
 	/* PG_TRY block is to ensure we call EventTriggerEndCompleteQuery */
 	PG_TRY();
 	{
diff --git a/src/backend/utils/cache/evtcache.c b/src/backend/utils/cache/evtcache.c
index ae71bd6..b9d442c 100644
--- a/src/backend/utils/cache/evtcache.c
+++ b/src/backend/utils/cache/evtcache.c
@@ -169,6 +169,8 @@ BuildEventTriggerCache(void)
 			event = EVT_DDLCommandEnd;
 		else if (strcmp(evtevent, "sql_drop") == 0)
 			event = EVT_SQLDrop;
+		else if (strcmp(evtevent, "table_rewrite") == 0)
+			event = EVT_TableRewrite;
 		else
 			continue;
 
diff --git a/src/include/catalog/pg_proc.h b/src/include/catalog/pg_proc.h
index 4736532..b1e0372 100644
--- a/src/include/catalog/pg_proc.h
+++ b/src/include/catalog/pg_proc.h
@@ -4990,6 +4990,8 @@ DESCR("peek at binary changes from replication slot");
 /* event triggers */
 DATA(insert OID = 3566 (  pg_event_trigger_dropped_objects		PGNSP PGUID 12 10 100 0 0 f f f f t t s 0 0 2249 "" "{26,26,23,25,25,25,25}" "{o,o,o,o,o,o,o}" "{classid, objid, objsubid, object_type, schema_name, object_name, object_identity}" _null_ pg_event_trigger_dropped_objects _null_ _null_ _null_ ));
 DESCR("list objects dropped by the current command");
+DATA(insert OID = 4566 (  pg_event_trigger_table_rewrite_oid	PGNSP PGUID 12 10 100 0 0 f f f f t t s 0 0 26 "" "{26}" "{o}" "{oid}" _null_ pg_event_trigger_table_rewrite_oid _null_ _null_ _null_ ));
+DESCR("return Oid of the table getting rewritten");
 
 /* generic transition functions for ordered-set aggregates */
 DATA(insert OID = 3970 ( ordered_set_transition			PGNSP PGUID 12 1 0 0 0 f f f f f f i 2 0 2281 "2281 2276" _null_ _null_ _null_ _null_ ordered_set_transition _null_ _null_ _null_ ));
diff --git a/src/include/commands/cluster.h b/src/include/commands/cluster.h
index f7730a9..80b7433 100644
--- a/src/include/commands/cluster.h
+++ b/src/include/commands/cluster.h
@@ -19,8 +19,8 @@
 
 
 extern void cluster(ClusterStmt *stmt, bool isTopLevel);
-extern void cluster_rel(Oid tableOid, Oid indexOid, bool recheck,
-			bool verbose);
+extern void cluster_rel(Node *parsetree,
+						Oid tableOid, Oid indexOid, bool recheck, bool verbose);
 extern void check_index_is_clusterable(Relation OldHeap, Oid indexOid,
 						   bool recheck, LOCKMODE lockmode);
 extern void mark_index_clustered(Relation rel, Oid indexOid, bool is_internal);
diff --git a/src/include/commands/event_trigger.h b/src/include/commands/event_trigger.h
index 0233f4c..5080f4f 100644
--- a/src/include/commands/event_trigger.h
+++ b/src/include/commands/event_trigger.h
@@ -46,6 +46,7 @@ extern bool EventTriggerSupportsObjectClass(ObjectClass objclass);
 extern void EventTriggerDDLCommandStart(Node *parsetree);
 extern void EventTriggerDDLCommandEnd(Node *parsetree);
 extern void EventTriggerSQLDrop(Node *parsetree);
+extern void EventTriggerTableRewrite(Node *parsetree, Oid tableOid);
 
 extern bool EventTriggerBeginCompleteQuery(void);
 extern void EventTriggerEndCompleteQuery(void);
diff --git a/src/include/utils/builtins.h b/src/include/utils/builtins.h
index fb1b4a4..02b581d 100644
--- a/src/include/utils/builtins.h
+++ b/src/include/utils/builtins.h
@@ -1189,6 +1189,7 @@ extern Datum unique_key_recheck(PG_FUNCTION_ARGS);
 
 /* commands/event_trigger.c */
 extern Datum pg_event_trigger_dropped_objects(PG_FUNCTION_ARGS);
+extern Datum pg_event_trigger_table_rewrite_oid(PG_FUNCTION_ARGS);
 
 /* commands/extension.c */
 extern Datum pg_available_extensions(PG_FUNCTION_ARGS);
diff --git a/src/include/utils/evtcache.h b/src/include/utils/evtcache.h
index c4c284f..4bbd80a 100644
--- a/src/include/utils/evtcache.h
+++ b/src/include/utils/evtcache.h
@@ -20,7 +20,8 @@ typedef enum
 {
 	EVT_DDLCommandStart,
 	EVT_DDLCommandEnd,
-	EVT_SQLDrop
+	EVT_SQLDrop,
+	EVT_TableRewrite
 } EventTriggerEvent;
 
 typedef struct
diff --git a/src/test/regress/expected/event_trigger.out b/src/test/regress/expected/event_trigger.out
index d4723b2..5b08bd8 100644
--- a/src/test/regress/expected/event_trigger.out
+++ b/src/test/regress/expected/event_trigger.out
@@ -294,3 +294,26 @@ SELECT * FROM dropped_objects WHERE type = 'schema';
 DROP ROLE regression_bob;
 DROP EVENT TRIGGER regress_event_trigger_drop_objects;
 DROP EVENT TRIGGER undroppable;
+-- test Table Rewrite Event Trigger
+CREATE OR REPLACE FUNCTION test_evtrig_no_rewrite() RETURNS event_trigger
+LANGUAGE plpgsql AS $$
+BEGIN
+  RAISE EXCEPTION 'I''m sorry Sir, No Rewrite Allowed.';
+END;
+$$;
+create event trigger no_rewrite_allowed on table_rewrite
+  execute procedure test_evtrig_no_rewrite();
+create table rewriteme (id serial primary key, foo float);
+insert into rewriteme
+     select x * 1.001 from generate_series(1, 500) as t(x);
+alter table rewriteme alter column foo type numeric;
+ERROR:  I'm sorry Sir, No Rewrite Allowed.
+alter table rewriteme add column baz int default 0;
+ERROR:  I'm sorry Sir, No Rewrite Allowed.
+cluster rewriteme using rewriteme_pkey;
+ERROR:  I'm sorry Sir, No Rewrite Allowed.
+vacuum full rewriteme;
+ERROR:  I'm sorry Sir, No Rewrite Allowed.
+drop table rewriteme;
+drop event trigger no_rewrite_allowed;
+drop function test_evtrig_no_rewrite();
diff --git a/src/test/regress/sql/event_trigger.sql b/src/test/regress/sql/event_trigger.sql
index 11d2ce5..1fc244e 100644
--- a/src/test/regress/sql/event_trigger.sql
+++ b/src/test/regress/sql/event_trigger.sql
@@ -206,3 +206,27 @@ DROP ROLE regression_bob;
 
 DROP EVENT TRIGGER regress_event_trigger_drop_objects;
 DROP EVENT TRIGGER undroppable;
+
+-- test Table Rewrite Event Trigger
+CREATE OR REPLACE FUNCTION test_evtrig_no_rewrite() RETURNS event_trigger
+LANGUAGE plpgsql AS $$
+BEGIN
+  RAISE EXCEPTION 'I''m sorry Sir, No Rewrite Allowed.';
+END;
+$$;
+
+create event trigger no_rewrite_allowed on table_rewrite
+  execute procedure test_evtrig_no_rewrite();
+
+create table rewriteme (id serial primary key, foo float);
+insert into rewriteme
+     select x * 1.001 from generate_series(1, 500) as t(x);
+alter table rewriteme alter column foo type numeric;
+alter table rewriteme add column baz int default 0;
+
+cluster rewriteme using rewriteme_pkey;
+vacuum full rewriteme;
+
+drop table rewriteme;
+drop event trigger no_rewrite_allowed;
+drop function test_evtrig_no_rewrite();

#11

Alvaro Herrera

alvherre@2ndquadrant.com

about 11 years ago

In reply to: Dimitri Fontaine (#10)

Re: New Event Trigger: table_rewrite

Dimitri Fontaine wrote:

In the CLUSTER implementation we have only one call site for invoking
the Event Trigger, in cluster_rel(). While it's true that in the single
relation case, the relation is opened in cluster() then cluster_rel() is
called, the opening is done with NoLock in cluster():

rel = heap_open(tableOid, NoLock);

My understanding is that the relation locking only happens in
cluster_rel() at this line:

OldHeap = try_relation_open(tableOid, AccessExclusiveLock);

Please help me through the cluster locking strategy here, I feel like
I'm missing something obvious, as my conclusion from re-reading the code
in lights of your comment is that your comment is not accurate with
respect to the current state of the code.

Almost the whole of that function is conditions to bail out clustering
the relation if things have changed since the relation list was
collected. It seems wrong to invoke the event trigger in all those
cases; it's going to fire spuriously. I think you should move the
invocation of the event trigger at the end, just before rebuild_relation
is called. Not sure where relative to the predicate lock stuff therein;
probably before, so that we avoid doing that dance if the event trigger
function decides to jump ship.

In ATRewriteTables, it seems wrong to call it after make_new_heap. If
the event trigger function aborts, we end up with useless work done
there; so I think it should be called before that. Also, why do you
have the evt_table_rewrite_fired stuff? I think you should fire one
event per table, no?

The second ATRewriteTable call in ATRewriteTables does not actually
rewrite the table; it only scans it to verify constraints. So I'm
thinking you shouldn't call this event trigger there. Or, if we decide
we want this, we probably also need something for the table scans in
ALTER DOMAIN too.

You still have the ANALYZE thing in docs, which now should be removed.

--
ï¿½lvaro Herrera http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services

--
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#12

Dimitri Fontaine

dimitri@2ndQuadrant.fr

about 11 years ago

In reply to: Alvaro Herrera (#11)

1 attachment(s)

Re: New Event Trigger: table_rewrite

Alvaro Herrera <alvherre@2ndquadrant.com> writes:

Almost the whole of that function is conditions to bail out clustering
the relation if things have changed since the relation list was
collected. It seems wrong to invoke the event trigger in all those
cases; it's going to fire spuriously. I think you should move the
invocation of the event trigger at the end, just before rebuild_relation
is called. Not sure where relative to the predicate lock stuff therein;
probably before, so that we avoid doing that dance if the event trigger
function decides to jump ship.

Actually when you do a CLUSTER or a VACUUM FULL you know that the
table is going to be rewritten on disk, because that's about the only
purpose of the command.

Given the complexity involved here, the new version of the patch
(attached) has removed support for those statements.

In ATRewriteTables, it seems wrong to call it after make_new_heap. If
the event trigger function aborts, we end up with useless work done
there; so I think it should be called before that. Also, why do you
have the evt_table_rewrite_fired stuff? I think you should fire one
event per table, no?

Fixed in the attached version of the patch.

The second ATRewriteTable call in ATRewriteTables does not actually
rewrite the table; it only scans it to verify constraints. So I'm
thinking you shouldn't call this event trigger there. Or, if we decide
we want this, we probably also need something for the table scans in
ALTER DOMAIN too.

Fixed in the attached version of the patch.

You still have the ANALYZE thing in docs, which now should be removed.

Fixed in the attached version of the patch.

--
Dimitri Fontaine 06 63 07 10 78
http://2ndQuadrant.fr PostgreSQL : Expertise, Formation et Support

Attachments:

table_rewrite.4.patchtext/x-patchDownload

diff --git a/doc/src/sgml/event-trigger.sgml b/doc/src/sgml/event-trigger.sgml
index 6f71a27..78ec27b 100644
--- a/doc/src/sgml/event-trigger.sgml
+++ b/doc/src/sgml/event-trigger.sgml
@@ -65,6 +65,16 @@
    </para>
 
    <para>
+    The <literal>table_rewrite</> event occurs just before a table is going to
+    get rewritten by the commands <literal>ALTER TABLE</literal>. While other
+    control statements are available to rewrite a table,
+    like <literal>CLUSTER</literal> and <literal>VACUUM</literal>,
+    the <literal>table_rewrite</> event is currently only triggered by
+    the <literal>ALTER TABLE</literal> command, which might or might not need
+    to rewrite the table.
+   </para>
+
+   <para>
      Event triggers (like other functions) cannot be executed in an aborted
      transaction.  Thus, if a DDL command fails with an error, any associated
      <literal>ddl_command_end</> triggers will not be executed.  Conversely,
@@ -120,6 +130,7 @@
         <entry><literal>ddl_command_start</literal></entry>
         <entry><literal>ddl_command_end</literal></entry>
         <entry><literal>sql_drop</literal></entry>
+        <entry><literal>table_rewrite</literal></entry>
        </row>
       </thead>
       <tbody>
@@ -128,510 +139,595 @@
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER COLLATION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER CONVERSION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER DOMAIN</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER EXTENSION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER FOREIGN DATA WRAPPER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER FOREIGN TABLE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER FUNCTION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER LANGUAGE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER OPERATOR</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER OPERATOR CLASS</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER OPERATOR FAMILY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER POLICY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER SCHEMA</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER SEQUENCE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER SERVER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER TABLE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>X</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER TEXT SEARCH CONFIGURATION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER TEXT SEARCH DICTIONARY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER TEXT SEARCH PARSER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER TEXT SEARCH TEMPLATE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER TRIGGER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER TYPE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER USER MAPPING</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER VIEW</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE AGGREGATE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE CAST</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE COLLATION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE CONVERSION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE DOMAIN</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE EXTENSION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE FOREIGN DATA WRAPPER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE FOREIGN TABLE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE FUNCTION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE INDEX</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE LANGUAGE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE OPERATOR</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE OPERATOR CLASS</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE OPERATOR FAMILY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE POLICY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE RULE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE SCHEMA</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE SEQUENCE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE SERVER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE TABLE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE TABLE AS</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE TEXT SEARCH CONFIGURATION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE TEXT SEARCH DICTIONARY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE TEXT SEARCH PARSER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE TEXT SEARCH TEMPLATE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE TRIGGER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE TYPE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE USER MAPPING</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE VIEW</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP AGGREGATE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP CAST</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP COLLATION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP CONVERSION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP DOMAIN</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP EXTENSION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP FOREIGN DATA WRAPPER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP FOREIGN TABLE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP FUNCTION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP INDEX</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP LANGUAGE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP OPERATOR</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP OPERATOR CLASS</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP OPERATOR FAMILY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP OWNED</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP POLICY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP RULE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP SCHEMA</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP SEQUENCE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP SERVER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP TABLE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP TEXT SEARCH CONFIGURATION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP TEXT SEARCH DICTIONARY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP TEXT SEARCH PARSER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP TEXT SEARCH TEMPLATE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP TRIGGER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP TYPE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP USER MAPPING</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP VIEW</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>IMPORT FOREIGN SCHEMA</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>SELECT INTO</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
       </tbody>
      </tgroup>
@@ -843,4 +939,58 @@ COMMIT;
     event triggers.)
    </para>
   </sect1>
+
+  <sect1 id="event-trigger-table-rewrite-example">
+   <title>A Table Rewrite Event Trigger Example</title>
+
+   <para>
+    Thanks to the <literal>table_rewrite</> event, it is possible to implement
+    a table rewriting policy only allowing the rewrite in maintenance windows.
+   </para>
+
+   <para>
+    Here's an example implementing such a policy.
+<programlisting>
+create or replace function no_rewrite()
+ returns event_trigger
+ language plpgsql as
+$$
+---
+--- Implement local Table Rewriting policy:
+---   public.foo is not allowed rewriting, ever
+---   other tables are only allowed rewriting between 1am and 6am
+---   unless they have more than 100 blocks
+---
+declare
+  table_oid oid := pg_event_trigger_table_rewrite_oid();
+  current_hour integer := extract('hour' from current_time);
+  pages integer;
+  max_pages integer := 100;
+begin
+  if pg_event_trigger_table_rewrite_oid() = 'public.foo'::regclass
+  then
+        raise exception 'you''re not allowed to rewrite the table %',
+                        table_oid::regclass;
+  end if;
+
+  select into pages relpages from pg_class where oid = table_oid;
+  if pages > max_pages
+  then
+        raise exception 'rewrites only allowed for table with less than % pages',
+                        max_pages;
+  end if;
+
+  if not current_hour between 1 and 6
+  then
+        raise exception 'rewrites only allowed between 1am and 6am';
+  end if;
+end;
+$$;
+
+create event trigger no_rewrite_allowed
+                  on table_rewrite
+   execute procedure no_rewrite();
+</programlisting>
+   </para>
+ </sect1>
 </chapter>
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 7e5bcd9..24bf78c 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -17540,16 +17540,20 @@ FOR EACH ROW EXECUTE PROCEDURE suppress_redundant_updates_trigger();
   <sect1 id="functions-event-triggers">
    <title>Event Trigger Functions</title>
 
+   <para>
+    Currently <productname>PostgreSQL</> provides two built-in event trigger
+    helper function, <function>pg_event_trigger_dropped_objects</>
+    and <function>pg_event_trigger_table_rewrite_oid</>.
+   </para>
+
+  <sect2 id="pg-event-trigger-dropped-objects">
+   <title>Processing objects dropped by a DDL command.</title>
+
    <indexterm>
      <primary>pg_event_trigger_dropped_objects</primary>
    </indexterm>
 
    <para>
-    Currently <productname>PostgreSQL</> provides one built-in event trigger
-    helper function, <function>pg_event_trigger_dropped_objects</>.
-   </para>
-
-   <para>
     <function>pg_event_trigger_dropped_objects</> returns a list of all objects
     dropped by the command in whose <literal>sql_drop</> event it is called.
     If called in any other context,
@@ -17647,6 +17651,68 @@ CREATE EVENT TRIGGER test_event_trigger_for_drops
        For more information about event triggers,
        see <xref linkend="event-triggers">.
     </para>
+  </sect2>
+
+  <sect2 id="pg-event-trigger-table-rewrite-oid">
+   <title>Handling a Table Rewrite Event</title>
+
+   <indexterm>
+     <primary>pg_event_trigger_table_rewrite_oid</primary>
+   </indexterm>
+
+   <para>
+    <function>pg_event_trigger_table_rewrite_oid</> returns
+    the <literal>OID</> of the table that is going to be rewritten on-disk by
+    the current DDL command. If called in any other context,
+    <function>pg_event_trigger_table_rewrite_oid</> raises an error.
+    <function>pg_event_trigger_table_rewrite_oid</> returns the following
+    columns:
+
+    <informaltable>
+     <tgroup cols="3">
+      <thead>
+       <row>
+        <entry>Name</entry>
+        <entry>Type</entry>
+        <entry>Description</entry>
+       </row>
+      </thead>
+
+      <tbody>
+       <row>
+        <entry><literal>oid</literal></entry>
+        <entry><type>Oid</type></entry>
+        <entry>OID of the pg_class entry for the table.</entry>
+       </row>
+      </tbody>
+     </tgroup>
+    </informaltable>
+   </para>
+
+   <para>
+    The <function>pg_event_trigger_table_rewrite_oid</> function can be used
+    in an event trigger like this:
+<programlisting>
+create function test_event_trigger_table_rewrite_oid()
+ returns event_trigger
+ language plpgsql as
+$$
+begin
+  raise notice 'rewriting table %', pg_event_trigger_table_rewrite_oid()::regclass;
+end;
+$$;
+
+create event trigger test_table_rewrite_oid
+                  on table_rewrite
+   execute procedure test_event_trigger_table_rewrite_oid();
+</programlisting>
+    </para>
+
+     <para>
+       For more information about event triggers,
+       see <xref linkend="event-triggers">.
+    </para>
+  </sect2>
   </sect1>
 
 </chapter>
diff --git a/src/backend/commands/event_trigger.c b/src/backend/commands/event_trigger.c
index 1b8c94b..7b24a74 100644
--- a/src/backend/commands/event_trigger.c
+++ b/src/backend/commands/event_trigger.c
@@ -42,11 +42,14 @@
 #include "utils/syscache.h"
 #include "tcop/utility.h"
 
-
+/*
+ * Data Structure for sql_drop and table_rewrite Event Trigger support.
+ */
 typedef struct EventTriggerQueryState
 {
 	slist_head	SQLDropList;
 	bool		in_sql_drop;
+	Oid			table_rewrite_oid;
 	MemoryContext cxt;
 	struct EventTriggerQueryState *previous;
 } EventTriggerQueryState;
@@ -119,11 +122,14 @@ static void AlterEventTriggerOwner_internal(Relation rel,
 								HeapTuple tup,
 								Oid newOwnerId);
 static event_trigger_command_tag_check_result check_ddl_tag(const char *tag);
+static event_trigger_command_tag_check_result check_table_rewrite_ddl_tag(
+	const char *tag);
 static void error_duplicate_filter_variable(const char *defname);
 static Datum filter_list_to_array(List *filterlist);
 static Oid insert_event_trigger_tuple(char *trigname, char *eventname,
 						   Oid evtOwner, Oid funcoid, List *tags);
 static void validate_ddl_tags(const char *filtervar, List *taglist);
+static void validate_table_rewrite_tags(const char *filtervar, List *taglist);
 static void EventTriggerInvoke(List *fn_oid_list, EventTriggerData *trigdata);
 
 /*
@@ -154,7 +160,8 @@ CreateEventTrigger(CreateEventTrigStmt *stmt)
 	/* Validate event name. */
 	if (strcmp(stmt->eventname, "ddl_command_start") != 0 &&
 		strcmp(stmt->eventname, "ddl_command_end") != 0 &&
-		strcmp(stmt->eventname, "sql_drop") != 0)
+		strcmp(stmt->eventname, "sql_drop") != 0 &&
+		strcmp(stmt->eventname, "table_rewrite") != 0)
 		ereport(ERROR,
 				(errcode(ERRCODE_SYNTAX_ERROR),
 				 errmsg("unrecognized event name \"%s\"",
@@ -183,6 +190,9 @@ CreateEventTrigger(CreateEventTrigStmt *stmt)
 		 strcmp(stmt->eventname, "sql_drop") == 0)
 		&& tags != NULL)
 		validate_ddl_tags("tag", tags);
+	else if (strcmp(stmt->eventname, "table_rewrite") == 0
+			 && tags != NULL)
+		validate_table_rewrite_tags("tag", tags);
 
 	/*
 	 * Give user a nice error message if an event trigger of the same name
@@ -257,6 +267,7 @@ check_ddl_tag(const char *tag)
 
 	/*
 	 * Otherwise, command should be CREATE, ALTER, or DROP.
+	 * Or one of ANALYZE, CLUSTER, VACUUM.
 	 */
 	if (pg_strncasecmp(tag, "CREATE ", 7) == 0)
 		obtypename = tag + 7;
@@ -264,6 +275,10 @@ check_ddl_tag(const char *tag)
 		obtypename = tag + 6;
 	else if (pg_strncasecmp(tag, "DROP ", 5) == 0)
 		obtypename = tag + 5;
+	else if (pg_strncasecmp(tag, "ANALYZE", 7) == 0 ||
+			 pg_strncasecmp(tag, "CLUSTER", 7) == 0 ||
+			 pg_strncasecmp(tag, "VACUUM", 6) == 0)
+		return EVENT_TRIGGER_COMMAND_TAG_OK;
 	else
 		return EVENT_TRIGGER_COMMAND_TAG_NOT_RECOGNIZED;
 
@@ -281,6 +296,41 @@ check_ddl_tag(const char *tag)
 }
 
 /*
+ * Validate DDL command tags.
+ */
+static void
+validate_table_rewrite_tags(const char *filtervar, List *taglist)
+{
+	ListCell   *lc;
+
+	foreach(lc, taglist)
+	{
+		const char *tag = strVal(lfirst(lc));
+		event_trigger_command_tag_check_result result;
+
+		result = check_table_rewrite_ddl_tag(tag);
+		if (result == EVENT_TRIGGER_COMMAND_TAG_NOT_SUPPORTED)
+			ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+			/* translator: %s represents an SQL statement name */
+					 errmsg("event triggers are not supported for %s",
+							tag)));
+	}
+}
+
+static event_trigger_command_tag_check_result
+check_table_rewrite_ddl_tag(const char *tag)
+{
+	if (pg_strcasecmp(tag, "ALTER TABLE") == 0 ||
+		pg_strcasecmp(tag, "CLUSTER") == 0 ||
+		pg_strcasecmp(tag, "VACUUM") == 0 ||
+		pg_strcasecmp(tag, "ANALYZE") == 0 )
+		return EVENT_TRIGGER_COMMAND_TAG_OK;
+
+	return EVENT_TRIGGER_COMMAND_TAG_NOT_SUPPORTED;
+}
+
+/*
  * Complain about a duplicate filter variable.
  */
 static void
@@ -641,8 +691,18 @@ EventTriggerCommonSetup(Node *parsetree,
 		const char *dbgtag;
 
 		dbgtag = CreateCommandTag(parsetree);
-		if (check_ddl_tag(dbgtag) != EVENT_TRIGGER_COMMAND_TAG_OK)
-			elog(ERROR, "unexpected command tag \"%s\"", dbgtag);
+		if (event == EVT_DDLCommandStart ||
+			event == EVT_DDLCommandEnd   ||
+			event == EVT_SQLDrop)
+		{
+			if (check_ddl_tag(dbgtag) != EVENT_TRIGGER_COMMAND_TAG_OK)
+				elog(ERROR, "unexpected command tag \"%s\"", dbgtag);
+		}
+		else if (event == EVT_TableRewrite)
+		{
+			if(check_table_rewrite_ddl_tag(dbgtag) != EVENT_TRIGGER_COMMAND_TAG_OK)
+				elog(ERROR, "unexpected command tag \"%s\"", dbgtag);
+		}
 	}
 #endif
 
@@ -838,6 +898,77 @@ EventTriggerSQLDrop(Node *parsetree)
 	list_free(runlist);
 }
 
+
+/*
+ * Fire table_rewrite triggers.
+ */
+void
+EventTriggerTableRewrite(Node *parsetree, Oid tableOid)
+{
+	List	   *runlist;
+	EventTriggerData trigdata;
+
+	elog(DEBUG1, "EventTriggerTableRewrite(%u)", tableOid);
+
+	/*
+	 * Event Triggers are completely disabled in standalone mode.  There are
+	 * (at least) two reasons for this:
+	 *
+	 * 1. A sufficiently broken event trigger might not only render the
+	 * database unusable, but prevent disabling itself to fix the situation.
+	 * In this scenario, restarting in standalone mode provides an escape
+	 * hatch.
+	 *
+	 * 2. BuildEventTriggerCache relies on systable_beginscan_ordered, and
+	 * therefore will malfunction if pg_event_trigger's indexes are damaged.
+	 * To allow recovery from a damaged index, we need some operating mode
+	 * wherein event triggers are disabled.  (Or we could implement
+	 * heapscan-and-sort logic for that case, but having disaster recovery
+	 * scenarios depend on code that's otherwise untested isn't appetizing.)
+	 */
+	if (!IsUnderPostmaster)
+		return;
+
+	runlist = EventTriggerCommonSetup(parsetree,
+									  EVT_TableRewrite,
+									  "table_rewrite",
+									  &trigdata);
+	if (runlist == NIL)
+		return;
+
+	/*
+	 * Make sure pg_event_trigger_table_rewrite_oid only works when running
+	 * these triggers. Use PG_TRY to ensure table_rewrite_oid is reset even
+	 * when one trigger fails. (This is perhaps not necessary, as the
+	 * currentState variable will be removed shortly by our caller, but it
+	 * seems better to play safe.)
+	 */
+	currentEventTriggerState->table_rewrite_oid = tableOid;
+
+	/* Run the triggers. */
+	PG_TRY();
+	{
+		EventTriggerInvoke(runlist, &trigdata);
+	}
+	PG_CATCH();
+	{
+		currentEventTriggerState->table_rewrite_oid = InvalidOid;
+		PG_RE_THROW();
+	}
+	PG_END_TRY();
+
+	currentEventTriggerState->table_rewrite_oid = InvalidOid;
+
+	/* Cleanup. */
+	list_free(runlist);
+
+	/*
+	 * Make sure anything the event triggers did will be visible to the main
+	 * command.
+	 */
+	CommandCounterIncrement();
+}
+
 /*
  * Invoke each event trigger in a list of event triggers.
  */
@@ -871,6 +1002,8 @@ EventTriggerInvoke(List *fn_oid_list, EventTriggerData *trigdata)
 		FunctionCallInfoData fcinfo;
 		PgStat_FunctionCallUsage fcusage;
 
+		elog(DEBUG1, "EventTriggerInvoke %u", fnoid);
+
 		/*
 		 * We want each event trigger to be able to see the results of the
 		 * previous event trigger's action.  Caller is responsible for any
@@ -1026,8 +1159,9 @@ EventTriggerBeginCompleteQuery(void)
 	MemoryContext cxt;
 
 	/*
-	 * Currently, sql_drop events are the only reason to have event trigger
-	 * state at all; so if there are none, don't install one.
+	 * Currently, sql_drop and table_rewrite events are the only reason to
+	 * have event trigger state at all; so if there are none, don't install
+	 * one.
 	 */
 	if (!trackDroppedObjectsNeeded())
 		return false;
@@ -1041,6 +1175,7 @@ EventTriggerBeginCompleteQuery(void)
 	state->cxt = cxt;
 	slist_init(&(state->SQLDropList));
 	state->in_sql_drop = false;
+	state->table_rewrite_oid = InvalidOid;
 
 	state->previous = currentEventTriggerState;
 	currentEventTriggerState = state;
@@ -1080,8 +1215,9 @@ EventTriggerEndCompleteQuery(void)
 bool
 trackDroppedObjectsNeeded(void)
 {
-	/* true if any sql_drop event trigger exists */
-	return list_length(EventCacheLookup(EVT_SQLDrop)) > 0;
+	/* true if any sql_drop or table_rewrite event trigger exists */
+	return list_length(EventCacheLookup(EVT_SQLDrop)) > 0 ||
+		list_length(EventCacheLookup(EVT_TableRewrite)) > 0;
 }
 
 /*
@@ -1297,3 +1433,25 @@ pg_event_trigger_dropped_objects(PG_FUNCTION_ARGS)
 
 	return (Datum) 0;
 }
+
+/*
+ * pg_event_trigger_table_rewrite_oid
+ *
+ * Make the Oid of the table going to be rewritten available to the user
+ * function run by the Event Trigger.
+ */
+Datum
+pg_event_trigger_table_rewrite_oid(PG_FUNCTION_ARGS)
+{
+	/*
+	 * Protect this function from being called out of context
+	 */
+	if (!currentEventTriggerState ||
+		currentEventTriggerState->table_rewrite_oid == InvalidOid)
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+		 errmsg("%s can only be called in a table_rewrite event trigger function",
+				"pg_event_trigger_table_rewrite_oid()")));
+
+	PG_RETURN_OID(currentEventTriggerState->table_rewrite_oid);
+}
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index ecdff1e..8c08f46 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -46,6 +46,7 @@
 #include "commands/cluster.h"
 #include "commands/comment.h"
 #include "commands/defrem.h"
+#include "commands/event_trigger.h"
 #include "commands/policy.h"
 #include "commands/sequence.h"
 #include "commands/tablecmds.h"
@@ -303,13 +304,15 @@ static void validateForeignKeyConstraint(char *conname,
 static void createForeignKeyTriggers(Relation rel, Oid refRelOid,
 						 Constraint *fkconstraint,
 						 Oid constraintOid, Oid indexOid);
-static void ATController(Relation rel, List *cmds, bool recurse, LOCKMODE lockmode);
+static void ATController(AlterTableStmt *parsetree,
+						 Relation rel, List *cmds, bool recurse, LOCKMODE lockmode);
 static void ATPrepCmd(List **wqueue, Relation rel, AlterTableCmd *cmd,
 		  bool recurse, bool recursing, LOCKMODE lockmode);
 static void ATRewriteCatalogs(List **wqueue, LOCKMODE lockmode);
 static void ATExecCmd(List **wqueue, AlteredTableInfo *tab, Relation rel,
 		  AlterTableCmd *cmd, LOCKMODE lockmode);
-static void ATRewriteTables(List **wqueue, LOCKMODE lockmode);
+static void ATRewriteTables(AlterTableStmt *parsetree,
+							List **wqueue, LOCKMODE lockmode);
 static void ATRewriteTable(AlteredTableInfo *tab, Oid OIDNewHeap, LOCKMODE lockmode);
 static AlteredTableInfo *ATGetQueueEntry(List **wqueue, Relation rel);
 static void ATSimplePermissions(Relation rel, int allowed_targets);
@@ -2723,7 +2726,8 @@ AlterTable(Oid relid, LOCKMODE lockmode, AlterTableStmt *stmt)
 
 	CheckTableNotInUse(rel, "ALTER TABLE");
 
-	ATController(rel, stmt->cmds, interpretInhOption(stmt->relation->inhOpt),
+	ATController(stmt,
+				 rel, stmt->cmds, interpretInhOption(stmt->relation->inhOpt),
 				 lockmode);
 }
 
@@ -2746,7 +2750,7 @@ AlterTableInternal(Oid relid, List *cmds, bool recurse)
 
 	rel = relation_open(relid, lockmode);
 
-	ATController(rel, cmds, recurse, lockmode);
+	ATController(NULL, rel, cmds, recurse, lockmode);
 }
 
 /*
@@ -3015,7 +3019,8 @@ AlterTableGetLockLevel(List *cmds)
 }
 
 static void
-ATController(Relation rel, List *cmds, bool recurse, LOCKMODE lockmode)
+ATController(AlterTableStmt *parsetree,
+			 Relation rel, List *cmds, bool recurse, LOCKMODE lockmode)
 {
 	List	   *wqueue = NIL;
 	ListCell   *lcmd;
@@ -3035,7 +3040,7 @@ ATController(Relation rel, List *cmds, bool recurse, LOCKMODE lockmode)
 	ATRewriteCatalogs(&wqueue, lockmode);
 
 	/* Phase 3: scan/rewrite tables as needed */
-	ATRewriteTables(&wqueue, lockmode);
+	ATRewriteTables(parsetree, &wqueue, lockmode);
 }
 
 /*
@@ -3606,7 +3611,7 @@ ATExecCmd(List **wqueue, AlteredTableInfo *tab, Relation rel,
  * ATRewriteTables: ALTER TABLE phase 3
  */
 static void
-ATRewriteTables(List **wqueue, LOCKMODE lockmode)
+ATRewriteTables(AlterTableStmt *parsetree, List **wqueue, LOCKMODE lockmode)
 {
 	ListCell   *ltab;
 
@@ -3709,6 +3714,19 @@ ATRewriteTables(List **wqueue, LOCKMODE lockmode)
 			heap_close(OldHeap, NoLock);
 
 			/*
+			 * Fire off an Event Trigger now, before actually rewriting the
+			 * table.
+			 *
+			 * We don't support Event Trigger for nested commands anywhere,
+			 * here included, and parstree is given NULL when comming from
+			 * AlterTableInternal.
+			 *
+			 * And fire it only once.
+			 */
+			if (parsetree)
+				EventTriggerTableRewrite((Node *)parsetree, tab->relid);
+
+			/*
 			 * Create transient table that will receive the modified data.
 			 *
 			 * Ensure it is marked correctly as logged or unlogged.  We have
diff --git a/src/backend/utils/cache/evtcache.c b/src/backend/utils/cache/evtcache.c
index ae71bd6..b9d442c 100644
--- a/src/backend/utils/cache/evtcache.c
+++ b/src/backend/utils/cache/evtcache.c
@@ -169,6 +169,8 @@ BuildEventTriggerCache(void)
 			event = EVT_DDLCommandEnd;
 		else if (strcmp(evtevent, "sql_drop") == 0)
 			event = EVT_SQLDrop;
+		else if (strcmp(evtevent, "table_rewrite") == 0)
+			event = EVT_TableRewrite;
 		else
 			continue;
 
diff --git a/src/include/catalog/pg_proc.h b/src/include/catalog/pg_proc.h
index 4736532..b1e0372 100644
--- a/src/include/catalog/pg_proc.h
+++ b/src/include/catalog/pg_proc.h
@@ -4990,6 +4990,8 @@ DESCR("peek at binary changes from replication slot");
 /* event triggers */
 DATA(insert OID = 3566 (  pg_event_trigger_dropped_objects		PGNSP PGUID 12 10 100 0 0 f f f f t t s 0 0 2249 "" "{26,26,23,25,25,25,25}" "{o,o,o,o,o,o,o}" "{classid, objid, objsubid, object_type, schema_name, object_name, object_identity}" _null_ pg_event_trigger_dropped_objects _null_ _null_ _null_ ));
 DESCR("list objects dropped by the current command");
+DATA(insert OID = 4566 (  pg_event_trigger_table_rewrite_oid	PGNSP PGUID 12 10 100 0 0 f f f f t t s 0 0 26 "" "{26}" "{o}" "{oid}" _null_ pg_event_trigger_table_rewrite_oid _null_ _null_ _null_ ));
+DESCR("return Oid of the table getting rewritten");
 
 /* generic transition functions for ordered-set aggregates */
 DATA(insert OID = 3970 ( ordered_set_transition			PGNSP PGUID 12 1 0 0 0 f f f f f f i 2 0 2281 "2281 2276" _null_ _null_ _null_ _null_ ordered_set_transition _null_ _null_ _null_ ));
diff --git a/src/include/commands/event_trigger.h b/src/include/commands/event_trigger.h
index 0233f4c..5080f4f 100644
--- a/src/include/commands/event_trigger.h
+++ b/src/include/commands/event_trigger.h
@@ -46,6 +46,7 @@ extern bool EventTriggerSupportsObjectClass(ObjectClass objclass);
 extern void EventTriggerDDLCommandStart(Node *parsetree);
 extern void EventTriggerDDLCommandEnd(Node *parsetree);
 extern void EventTriggerSQLDrop(Node *parsetree);
+extern void EventTriggerTableRewrite(Node *parsetree, Oid tableOid);
 
 extern bool EventTriggerBeginCompleteQuery(void);
 extern void EventTriggerEndCompleteQuery(void);
diff --git a/src/include/utils/builtins.h b/src/include/utils/builtins.h
index fb1b4a4..02b581d 100644
--- a/src/include/utils/builtins.h
+++ b/src/include/utils/builtins.h
@@ -1189,6 +1189,7 @@ extern Datum unique_key_recheck(PG_FUNCTION_ARGS);
 
 /* commands/event_trigger.c */
 extern Datum pg_event_trigger_dropped_objects(PG_FUNCTION_ARGS);
+extern Datum pg_event_trigger_table_rewrite_oid(PG_FUNCTION_ARGS);
 
 /* commands/extension.c */
 extern Datum pg_available_extensions(PG_FUNCTION_ARGS);
diff --git a/src/include/utils/evtcache.h b/src/include/utils/evtcache.h
index c4c284f..4bbd80a 100644
--- a/src/include/utils/evtcache.h
+++ b/src/include/utils/evtcache.h
@@ -20,7 +20,8 @@ typedef enum
 {
 	EVT_DDLCommandStart,
 	EVT_DDLCommandEnd,
-	EVT_SQLDrop
+	EVT_SQLDrop,
+	EVT_TableRewrite
 } EventTriggerEvent;
 
 typedef struct
diff --git a/src/test/regress/expected/event_trigger.out b/src/test/regress/expected/event_trigger.out
index d4723b2..dbbb05e 100644
--- a/src/test/regress/expected/event_trigger.out
+++ b/src/test/regress/expected/event_trigger.out
@@ -294,3 +294,40 @@ SELECT * FROM dropped_objects WHERE type = 'schema';
 DROP ROLE regression_bob;
 DROP EVENT TRIGGER regress_event_trigger_drop_objects;
 DROP EVENT TRIGGER undroppable;
+-- only allowed from within an event trigger function, should fail
+select pg_event_trigger_table_rewrite_oid();
+ERROR:  pg_event_trigger_table_rewrite_oid() can only be called in a table_rewrite event trigger function
+-- test Table Rewrite Event Trigger
+CREATE OR REPLACE FUNCTION test_evtrig_no_rewrite() RETURNS event_trigger
+LANGUAGE plpgsql AS $$
+BEGIN
+  RAISE EXCEPTION 'I''m sorry Sir, No Rewrite Allowed.';
+END;
+$$;
+create event trigger no_rewrite_allowed on table_rewrite
+  execute procedure test_evtrig_no_rewrite();
+create table rewriteme (id serial primary key, foo float);
+insert into rewriteme
+     select x * 1.001 from generate_series(1, 500) as t(x);
+alter table rewriteme alter column foo type numeric;
+ERROR:  I'm sorry Sir, No Rewrite Allowed.
+alter table rewriteme add column baz int default 0;
+ERROR:  I'm sorry Sir, No Rewrite Allowed.
+-- test with more than one reason to rewrite a single table
+CREATE OR REPLACE FUNCTION test_evtrig_no_rewrite() RETURNS event_trigger
+LANGUAGE plpgsql AS $$
+BEGIN
+  RAISE NOTICE 'Table ''%'' is being rewritten',
+               pg_event_trigger_table_rewrite_oid()::regclass;
+END;
+$$;
+alter table rewriteme
+ add column onemore int default 0,
+ add column another int default -1,
+ alter column foo type numeric(10,4);
+NOTICE:  Table 'rewriteme' is being rewritten
+-- shouldn't trigger a table_rewrite event
+alter table rewriteme alter column foo type numeric(12,4);
+drop table rewriteme;
+drop event trigger no_rewrite_allowed;
+drop function test_evtrig_no_rewrite();
diff --git a/src/test/regress/sql/event_trigger.sql b/src/test/regress/sql/event_trigger.sql
index 11d2ce5..5b452b0 100644
--- a/src/test/regress/sql/event_trigger.sql
+++ b/src/test/regress/sql/event_trigger.sql
@@ -206,3 +206,44 @@ DROP ROLE regression_bob;
 
 DROP EVENT TRIGGER regress_event_trigger_drop_objects;
 DROP EVENT TRIGGER undroppable;
+
+-- only allowed from within an event trigger function, should fail
+select pg_event_trigger_table_rewrite_oid();
+
+-- test Table Rewrite Event Trigger
+CREATE OR REPLACE FUNCTION test_evtrig_no_rewrite() RETURNS event_trigger
+LANGUAGE plpgsql AS $$
+BEGIN
+  RAISE EXCEPTION 'I''m sorry Sir, No Rewrite Allowed.';
+END;
+$$;
+
+create event trigger no_rewrite_allowed on table_rewrite
+  execute procedure test_evtrig_no_rewrite();
+
+create table rewriteme (id serial primary key, foo float);
+insert into rewriteme
+     select x * 1.001 from generate_series(1, 500) as t(x);
+alter table rewriteme alter column foo type numeric;
+alter table rewriteme add column baz int default 0;
+
+-- test with more than one reason to rewrite a single table
+CREATE OR REPLACE FUNCTION test_evtrig_no_rewrite() RETURNS event_trigger
+LANGUAGE plpgsql AS $$
+BEGIN
+  RAISE NOTICE 'Table ''%'' is being rewritten',
+               pg_event_trigger_table_rewrite_oid()::regclass;
+END;
+$$;
+
+alter table rewriteme
+ add column onemore int default 0,
+ add column another int default -1,
+ alter column foo type numeric(10,4);
+
+-- shouldn't trigger a table_rewrite event
+alter table rewriteme alter column foo type numeric(12,4);
+
+drop table rewriteme;
+drop event trigger no_rewrite_allowed;
+drop function test_evtrig_no_rewrite();

#13

Robert Haas

robertmhaas@gmail.com

about 11 years ago

In reply to: Dimitri Fontaine (#10)

Re: New Event Trigger: table_rewrite

On Tue, Nov 18, 2014 at 5:14 PM, Dimitri Fontaine
<dimitri@2ndquadrant.fr> wrote:

Robert Haas <robertmhaas@gmail.com> writes:

It seems pretty weird, also, that the event trigger will fire after
we've taken AccessExclusiveLock when you cluster a particular
relation, and before we've taken AccessExclusiveLock when you cluster
database-wide. That's more or less an implementation artifact of the
current code that we're exposing to the use for, really, no good
reason.

In the CLUSTER implementation we have only one call site for invoking
the Event Trigger, in cluster_rel(). While it's true that in the single
relation case, the relation is opened in cluster() then cluster_rel() is
called, the opening is done with NoLock in cluster():

rel = heap_open(tableOid, NoLock);

My understanding is that the relation locking only happens in
cluster_rel() at this line:

OldHeap = try_relation_open(tableOid, AccessExclusiveLock);

Please help me through the cluster locking strategy here, I feel like
I'm missing something obvious, as my conclusion from re-reading the code
in lights of your comment is that your comment is not accurate with
respect to the current state of the code.

Unless I'm missing something, when you cluster a particular relation,
cluster() does this:

/* Find and lock the table */
rel = heap_openrv(stmt->relation, AccessExclusiveLock);

I don't see the "rel = heap_open(tableOid, NoLock);" line you quoted anywhere.

--
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#14

Robert Haas

robertmhaas@gmail.com

about 11 years ago

In reply to: Alvaro Herrera (#11)

Re: New Event Trigger: table_rewrite

On Tue, Nov 18, 2014 at 5:34 PM, Alvaro Herrera
<alvherre@2ndquadrant.com> wrote:

Almost the whole of that function is conditions to bail out clustering
the relation if things have changed since the relation list was
collected. It seems wrong to invoke the event trigger in all those
cases; it's going to fire spuriously. I think you should move the
invocation of the event trigger at the end, just before rebuild_relation
is called. Not sure where relative to the predicate lock stuff therein;
probably before, so that we avoid doing that dance if the event trigger
function decides to jump ship.

I can see two problems with that:

1. What if the conditions aren't true any more after the event trigger
has run? Then it's unsafe.

2. If we do it that way, then we'll unnecessarily wait for a lock on
the relation even if the event trigger is just going to bail out.

--
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EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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#15

Robert Haas

robertmhaas@gmail.com

about 11 years ago

In reply to: Robert Haas (#13)

Re: New Event Trigger: table_rewrite

On Wed, Nov 19, 2014 at 1:01 PM, Robert Haas <robertmhaas@gmail.com> wrote:

On Tue, Nov 18, 2014 at 5:14 PM, Dimitri Fontaine
<dimitri@2ndquadrant.fr> wrote:

Robert Haas <robertmhaas@gmail.com> writes:

It seems pretty weird, also, that the event trigger will fire after
we've taken AccessExclusiveLock when you cluster a particular
relation, and before we've taken AccessExclusiveLock when you cluster
database-wide. That's more or less an implementation artifact of the
current code that we're exposing to the use for, really, no good
reason.

In the CLUSTER implementation we have only one call site for invoking
the Event Trigger, in cluster_rel(). While it's true that in the single
relation case, the relation is opened in cluster() then cluster_rel() is
called, the opening is done with NoLock in cluster():

rel = heap_open(tableOid, NoLock);

My understanding is that the relation locking only happens in
cluster_rel() at this line:

OldHeap = try_relation_open(tableOid, AccessExclusiveLock);

Please help me through the cluster locking strategy here, I feel like
I'm missing something obvious, as my conclusion from re-reading the code
in lights of your comment is that your comment is not accurate with
respect to the current state of the code.

Unless I'm missing something, when you cluster a particular relation,
cluster() does this:

/* Find and lock the table */
rel = heap_openrv(stmt->relation, AccessExclusiveLock);

I don't see the "rel = heap_open(tableOid, NoLock);" line you quoted anywhere.

...which is because I have the 9.1 branch checked out. Genius. But
what I said originally is still true, because the current code looks
like this:

/* Find, lock, and check permissions on the table */
tableOid = RangeVarGetRelidExtended(stmt->relation,

AccessExclusiveLock,

false, false,

RangeVarCallbackOwnsTable, NULL);
rel = heap_open(tableOid, NoLock);

It's true that the heap_open() is not acquiring any lock. But the
RangeVarGetRelidExtended() call right before it is.

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#16

Michael Paquier

michael.paquier@gmail.com

about 11 years ago

In reply to: Dimitri Fontaine (#12)

Re: New Event Trigger: table_rewrite

On Thu, Nov 20, 2014 at 2:57 AM, Dimitri Fontaine
<dimitri@2ndquadrant.fr> wrote:

Fixed in the attached version of the patch.

Thanks! Things are moving nicely for this patch. Patch compiles and
passes check-world. Some minor comments about the latest version:
1) Couldn't this paragraph be reworked?
    <para>
+    The <literal>table_rewrite</> event occurs just before a table is going to
+    get rewritten by the commands <literal>ALTER TABLE</literal>. While other
+    control statements are available to rewrite a table,
+    like <literal>CLUSTER</literal> and <literal>VACUUM</literal>,
+    the <literal>table_rewrite</> event is currently only triggered by
+    the <literal>ALTER TABLE</literal> command, which might or might not need
+    to rewrite the table.
+   </para>
CLUSTER and VACUUM are not part of the supported commands anymore, so
I think that we could replace that by the addition of a reference
number in the cell of ALTER TABLE for the event table_rewrite and
write at the bottom of the table a description of how this event
behaves with ALTER TABLE. Note as well that "might or might not" is
not really helpful for the user.
2) The examples of SQL queries provided are still in lower case in the
docs, that's contrary to the rest of the docs where upper case is used
for reserved keywords.
+   <para>
+    Here's an example implementing such a policy.
+<programlisting>
+create or replace function no_rewrite()
+ returns event_trigger
+ language plpgsql as
[...]
3) This reference can be completely removed:
        /*
         * Otherwise, command should be CREATE, ALTER, or DROP.
+        * Or one of ANALYZE, CLUSTER, VACUUM.
         */
4) In those places as well CLUSTER and VACUUM should be removed:
+       else if (pg_strncasecmp(tag, "ANALYZE", 7) == 0 ||
+                        pg_strncasecmp(tag, "CLUSTER", 7) == 0 ||
+                        pg_strncasecmp(tag, "VACUUM", 6) == 0)
+               return EVENT_TRIGGER_COMMAND_TAG_OK;
        else
And here:
+       if (pg_strcasecmp(tag, "ALTER TABLE") == 0 ||
+               pg_strcasecmp(tag, "CLUSTER") == 0 ||
+               pg_strcasecmp(tag, "VACUUM") == 0 ||
+               pg_strcasecmp(tag, "ANALYZE") == 0 )
+               return EVENT_TRIGGER_COMMAND_TAG_OK
I am noticing that the points raised by Alvaro previously are fixed.
Regards,
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#17

Alvaro Herrera

alvherre@2ndquadrant.com

about 11 years ago

In reply to: Michael Paquier (#16)

Re: New Event Trigger: table_rewrite

Michael Paquier wrote:

1) Couldn't this paragraph be reworked?
<para>
+    The <literal>table_rewrite</> event occurs just before a table is going to
+    get rewritten by the commands <literal>ALTER TABLE</literal>. While other
+    control statements are available to rewrite a table,
+    like <literal>CLUSTER</literal> and <literal>VACUUM</literal>,
+    the <literal>table_rewrite</> event is currently only triggered by
+    the <literal>ALTER TABLE</literal> command, which might or might not need
+    to rewrite the table.
+   </para>
CLUSTER and VACUUM are not part of the supported commands anymore, so
I think that we could replace that by the addition of a reference
number in the cell of ALTER TABLE for the event table_rewrite and
write at the bottom of the table a description of how this event
behaves with ALTER TABLE. Note as well that "might or might not" is
not really helpful for the user.

That's precisely why we have an event trigger here, I think --- for some
subcommands, it's not easy to determine whether a rewrite happens or
not. (I think SET TYPE is the one). I don't think we want to document
precisely under what condition a rewrite takes place.

2) The examples of SQL queries provided are still in lower case in the
docs, that's contrary to the rest of the docs where upper case is used
for reserved keywords.
+   <para>
+    Here's an example implementing such a policy.
+<programlisting>
+create or replace function no_rewrite()
+ returns event_trigger
+ language plpgsql as

Yes please. <nitpick> Another thing in that sample code is "not current_hour
between 1 and 6". That reads strange to me. It should be equally
correct to spell it as "current_hour not between 1 and 6", which seems
more natural. </>

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#18

Dimitri Fontaine

dimitri@2ndQuadrant.fr

about 11 years ago

In reply to: Alvaro Herrera (#17)

1 attachment(s)

Re: New Event Trigger: table_rewrite

Alvaro Herrera <alvherre@2ndquadrant.com> writes:

CLUSTER and VACUUM are not part of the supported commands anymore, so
I think that we could replace that by the addition of a reference
number in the cell of ALTER TABLE for the event table_rewrite and
write at the bottom of the table a description of how this event
behaves with ALTER TABLE. Note as well that "might or might not" is
not really helpful for the user.

That's precisely why we have an event trigger here, I think --- for some
subcommands, it's not easy to determine whether a rewrite happens or
not. (I think SET TYPE is the one). I don't think we want to document
precisely under what condition a rewrite takes place.

Yeah, the current documentation expands to the following sentence, as
browsed in

http://www.postgresql.org/docs/9.3/interactive/sql-altertable.html

As an exception, if the USING clause does not change the column
contents and the old type is either binary coercible to the new type
or an unconstrained domain over the new type, a table rewrite is not
needed, but any indexes on the affected columns must still be rebuilt.

I don't think that “might or might not” is less helpful in the context
of the Event Trigger, because the whole point is that the event is only
triggered in case of a rewrite. Of course we could cross link the two
paragraphs or something.

2) The examples of SQL queries provided are still in lower case in the
docs, that's contrary to the rest of the docs where upper case is used
for reserved keywords.

Right, being consistent trumps personal preferences, changed in the
attached.

Yes please. <nitpick> Another thing in that sample code is "not current_hour
between 1 and 6". That reads strange to me. It should be equally
correct to spell it as "current_hour not between 1 and 6", which seems
more natural. </>

True, fixed in the attached.

Regards,
--
Dimitri Fontaine
http://2ndQuadrant.fr PostgreSQL : Expertise, Formation et Support

Attachments:

table_rewrite.5.patchtext/x-patchDownload

diff --git a/doc/src/sgml/event-trigger.sgml b/doc/src/sgml/event-trigger.sgml
index 6f71a27..0a80993 100644
--- a/doc/src/sgml/event-trigger.sgml
+++ b/doc/src/sgml/event-trigger.sgml
@@ -65,6 +65,16 @@
    </para>
 
    <para>
+    The <literal>table_rewrite</> event occurs just before a table is going to
+    get rewritten by the commands <literal>ALTER TABLE</literal>. While other
+    control statements are available to rewrite a table,
+    like <literal>CLUSTER</literal> and <literal>VACUUM</literal>,
+    the <literal>table_rewrite</> event is currently only triggered by
+    the <literal>ALTER TABLE</literal> command, which might or might not need
+    to rewrite the table.
+   </para>
+
+   <para>
      Event triggers (like other functions) cannot be executed in an aborted
      transaction.  Thus, if a DDL command fails with an error, any associated
      <literal>ddl_command_end</> triggers will not be executed.  Conversely,
@@ -120,6 +130,7 @@
         <entry><literal>ddl_command_start</literal></entry>
         <entry><literal>ddl_command_end</literal></entry>
         <entry><literal>sql_drop</literal></entry>
+        <entry><literal>table_rewrite</literal></entry>
        </row>
       </thead>
       <tbody>
@@ -128,510 +139,595 @@
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER COLLATION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER CONVERSION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER DOMAIN</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER EXTENSION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER FOREIGN DATA WRAPPER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER FOREIGN TABLE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER FUNCTION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER LANGUAGE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER OPERATOR</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER OPERATOR CLASS</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER OPERATOR FAMILY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER POLICY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER SCHEMA</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER SEQUENCE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER SERVER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER TABLE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>X</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER TEXT SEARCH CONFIGURATION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER TEXT SEARCH DICTIONARY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER TEXT SEARCH PARSER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER TEXT SEARCH TEMPLATE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER TRIGGER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER TYPE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER USER MAPPING</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>ALTER VIEW</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE AGGREGATE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE CAST</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE COLLATION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE CONVERSION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE DOMAIN</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE EXTENSION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE FOREIGN DATA WRAPPER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE FOREIGN TABLE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE FUNCTION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE INDEX</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE LANGUAGE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE OPERATOR</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE OPERATOR CLASS</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE OPERATOR FAMILY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE POLICY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE RULE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE SCHEMA</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE SEQUENCE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE SERVER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE TABLE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE TABLE AS</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE TEXT SEARCH CONFIGURATION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE TEXT SEARCH DICTIONARY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE TEXT SEARCH PARSER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE TEXT SEARCH TEMPLATE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE TRIGGER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE TYPE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE USER MAPPING</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>CREATE VIEW</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP AGGREGATE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP CAST</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP COLLATION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP CONVERSION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP DOMAIN</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP EXTENSION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP FOREIGN DATA WRAPPER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP FOREIGN TABLE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP FUNCTION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP INDEX</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP LANGUAGE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP OPERATOR</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP OPERATOR CLASS</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP OPERATOR FAMILY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP OWNED</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP POLICY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP RULE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP SCHEMA</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP SEQUENCE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP SERVER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP TABLE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP TEXT SEARCH CONFIGURATION</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP TEXT SEARCH DICTIONARY</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP TEXT SEARCH PARSER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP TEXT SEARCH TEMPLATE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP TRIGGER</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP TYPE</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP USER MAPPING</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>DROP VIEW</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>IMPORT FOREIGN SCHEMA</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
        <row>
         <entry align="left"><literal>SELECT INTO</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>X</literal></entry>
         <entry align="center"><literal>-</literal></entry>
+        <entry align="center"><literal>-</literal></entry>
        </row>
       </tbody>
      </tgroup>
@@ -843,4 +939,58 @@ COMMIT;
     event triggers.)
    </para>
   </sect1>
+
+  <sect1 id="event-trigger-table-rewrite-example">
+   <title>A Table Rewrite Event Trigger Example</title>
+
+   <para>
+    Thanks to the <literal>table_rewrite</> event, it is possible to implement
+    a table rewriting policy only allowing the rewrite in maintenance windows.
+   </para>
+
+   <para>
+    Here's an example implementing such a policy.
+<programlisting>
+CREATE OR REPLACE FUNCTION no_rewrite()
+ RETURNS event_trigger
+ LANGUAGE plpgsql AS
+$$
+---
+--- Implement local Table Rewriting policy:
+---   public.foo is not allowed rewriting, ever
+---   other tables are only allowed rewriting between 1am and 6am
+---   unless they have more than 100 blocks
+---
+DECLARE
+  table_oid oid := pg_event_trigger_table_rewrite_oid();
+  current_hour integer := extract('hour' from current_time);
+  pages integer;
+  max_pages integer := 100;
+BEGIN
+  IF pg_event_trigger_table_rewrite_oid() = 'public.foo'::regclass
+  THEN
+        RAISE EXCEPTION 'you''re not allowed to rewrite the table %',
+                        table_oid::regclass;
+  END IF;
+
+  SELECT INTO pages relpages FROM pg_class WHERE oid = table_oid;
+  IF pages > max_pages
+  THEN
+        RAISE EXCEPTION 'rewrites only allowed for table with less than % pages',
+                        max_pages;
+  END IF;
+
+  IF current_hour NOT BETWEEN 1 AND 6
+  THEN
+        RAISE EXCEPTION 'rewrites only allowed between 1am and 6am';
+  END IF;
+END;
+$$;
+
+CREATE EVENT TRIGGER no_rewrite_allowed
+                  ON table_rewrite
+   EXECUTE PROCEDURE no_rewrite();
+</programlisting>
+   </para>
+ </sect1>
 </chapter>
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 7e5bcd9..abe92ad 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -17540,16 +17540,20 @@ FOR EACH ROW EXECUTE PROCEDURE suppress_redundant_updates_trigger();
   <sect1 id="functions-event-triggers">
    <title>Event Trigger Functions</title>
 
+   <para>
+    Currently <productname>PostgreSQL</> provides two built-in event trigger
+    helper function, <function>pg_event_trigger_dropped_objects</>
+    and <function>pg_event_trigger_table_rewrite_oid</>.
+   </para>
+
+  <sect2 id="pg-event-trigger-dropped-objects">
+   <title>Processing objects dropped by a DDL command.</title>
+
    <indexterm>
      <primary>pg_event_trigger_dropped_objects</primary>
    </indexterm>
 
    <para>
-    Currently <productname>PostgreSQL</> provides one built-in event trigger
-    helper function, <function>pg_event_trigger_dropped_objects</>.
-   </para>
-
-   <para>
     <function>pg_event_trigger_dropped_objects</> returns a list of all objects
     dropped by the command in whose <literal>sql_drop</> event it is called.
     If called in any other context,
@@ -17647,6 +17651,68 @@ CREATE EVENT TRIGGER test_event_trigger_for_drops
        For more information about event triggers,
        see <xref linkend="event-triggers">.
     </para>
+  </sect2>
+
+  <sect2 id="pg-event-trigger-table-rewrite-oid">
+   <title>Handling a Table Rewrite Event</title>
+
+   <indexterm>
+     <primary>pg_event_trigger_table_rewrite_oid</primary>
+   </indexterm>
+
+   <para>
+    <function>pg_event_trigger_table_rewrite_oid</> returns
+    the <literal>OID</> of the table that is going to be rewritten on-disk by
+    the current DDL command. If called in any other context,
+    <function>pg_event_trigger_table_rewrite_oid</> raises an error.
+    <function>pg_event_trigger_table_rewrite_oid</> returns the following
+    columns:
+
+    <informaltable>
+     <tgroup cols="3">
+      <thead>
+       <row>
+        <entry>Name</entry>
+        <entry>Type</entry>
+        <entry>Description</entry>
+       </row>
+      </thead>
+
+      <tbody>
+       <row>
+        <entry><literal>oid</literal></entry>
+        <entry><type>Oid</type></entry>
+        <entry>OID of the pg_class entry for the table.</entry>
+       </row>
+      </tbody>
+     </tgroup>
+    </informaltable>
+   </para>
+
+   <para>
+    The <function>pg_event_trigger_table_rewrite_oid</> function can be used
+    in an event trigger like this:
+<programlisting>
+CREATE FUNCTION test_event_trigger_table_rewrite_oid()
+ RETURNS event_trigger
+ LANGUAGE plpgsql AS
+$$
+BEGIN
+  RAISE NOTICE 'rewriting table %', pg_event_trigger_table_rewrite_oid()::regclass;
+END;
+$$;
+
+CREATE EVENT TRIGGER test_table_rewrite_oid
+                  ON table_rewrite
+   EXECUTE PROCEDURE test_event_trigger_table_rewrite_oid();
+</programlisting>
+    </para>
+
+     <para>
+       For more information about event triggers,
+       see <xref linkend="event-triggers">.
+    </para>
+  </sect2>
   </sect1>
 
 </chapter>
diff --git a/src/backend/commands/event_trigger.c b/src/backend/commands/event_trigger.c
index 1b8c94b..7b24a74 100644
--- a/src/backend/commands/event_trigger.c
+++ b/src/backend/commands/event_trigger.c
@@ -42,11 +42,14 @@
 #include "utils/syscache.h"
 #include "tcop/utility.h"
 
-
+/*
+ * Data Structure for sql_drop and table_rewrite Event Trigger support.
+ */
 typedef struct EventTriggerQueryState
 {
 	slist_head	SQLDropList;
 	bool		in_sql_drop;
+	Oid			table_rewrite_oid;
 	MemoryContext cxt;
 	struct EventTriggerQueryState *previous;
 } EventTriggerQueryState;
@@ -119,11 +122,14 @@ static void AlterEventTriggerOwner_internal(Relation rel,
 								HeapTuple tup,
 								Oid newOwnerId);
 static event_trigger_command_tag_check_result check_ddl_tag(const char *tag);
+static event_trigger_command_tag_check_result check_table_rewrite_ddl_tag(
+	const char *tag);
 static void error_duplicate_filter_variable(const char *defname);
 static Datum filter_list_to_array(List *filterlist);
 static Oid insert_event_trigger_tuple(char *trigname, char *eventname,
 						   Oid evtOwner, Oid funcoid, List *tags);
 static void validate_ddl_tags(const char *filtervar, List *taglist);
+static void validate_table_rewrite_tags(const char *filtervar, List *taglist);
 static void EventTriggerInvoke(List *fn_oid_list, EventTriggerData *trigdata);
 
 /*
@@ -154,7 +160,8 @@ CreateEventTrigger(CreateEventTrigStmt *stmt)
 	/* Validate event name. */
 	if (strcmp(stmt->eventname, "ddl_command_start") != 0 &&
 		strcmp(stmt->eventname, "ddl_command_end") != 0 &&
-		strcmp(stmt->eventname, "sql_drop") != 0)
+		strcmp(stmt->eventname, "sql_drop") != 0 &&
+		strcmp(stmt->eventname, "table_rewrite") != 0)
 		ereport(ERROR,
 				(errcode(ERRCODE_SYNTAX_ERROR),
 				 errmsg("unrecognized event name \"%s\"",
@@ -183,6 +190,9 @@ CreateEventTrigger(CreateEventTrigStmt *stmt)
 		 strcmp(stmt->eventname, "sql_drop") == 0)
 		&& tags != NULL)
 		validate_ddl_tags("tag", tags);
+	else if (strcmp(stmt->eventname, "table_rewrite") == 0
+			 && tags != NULL)
+		validate_table_rewrite_tags("tag", tags);
 
 	/*
 	 * Give user a nice error message if an event trigger of the same name
@@ -257,6 +267,7 @@ check_ddl_tag(const char *tag)
 
 	/*
 	 * Otherwise, command should be CREATE, ALTER, or DROP.
+	 * Or one of ANALYZE, CLUSTER, VACUUM.
 	 */
 	if (pg_strncasecmp(tag, "CREATE ", 7) == 0)
 		obtypename = tag + 7;
@@ -264,6 +275,10 @@ check_ddl_tag(const char *tag)
 		obtypename = tag + 6;
 	else if (pg_strncasecmp(tag, "DROP ", 5) == 0)
 		obtypename = tag + 5;
+	else if (pg_strncasecmp(tag, "ANALYZE", 7) == 0 ||
+			 pg_strncasecmp(tag, "CLUSTER", 7) == 0 ||
+			 pg_strncasecmp(tag, "VACUUM", 6) == 0)
+		return EVENT_TRIGGER_COMMAND_TAG_OK;
 	else
 		return EVENT_TRIGGER_COMMAND_TAG_NOT_RECOGNIZED;
 
@@ -281,6 +296,41 @@ check_ddl_tag(const char *tag)
 }
 
 /*
+ * Validate DDL command tags.
+ */
+static void
+validate_table_rewrite_tags(const char *filtervar, List *taglist)
+{
+	ListCell   *lc;
+
+	foreach(lc, taglist)
+	{
+		const char *tag = strVal(lfirst(lc));
+		event_trigger_command_tag_check_result result;
+
+		result = check_table_rewrite_ddl_tag(tag);
+		if (result == EVENT_TRIGGER_COMMAND_TAG_NOT_SUPPORTED)
+			ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+			/* translator: %s represents an SQL statement name */
+					 errmsg("event triggers are not supported for %s",
+							tag)));
+	}
+}
+
+static event_trigger_command_tag_check_result
+check_table_rewrite_ddl_tag(const char *tag)
+{
+	if (pg_strcasecmp(tag, "ALTER TABLE") == 0 ||
+		pg_strcasecmp(tag, "CLUSTER") == 0 ||
+		pg_strcasecmp(tag, "VACUUM") == 0 ||
+		pg_strcasecmp(tag, "ANALYZE") == 0 )
+		return EVENT_TRIGGER_COMMAND_TAG_OK;
+
+	return EVENT_TRIGGER_COMMAND_TAG_NOT_SUPPORTED;
+}
+
+/*
  * Complain about a duplicate filter variable.
  */
 static void
@@ -641,8 +691,18 @@ EventTriggerCommonSetup(Node *parsetree,
 		const char *dbgtag;
 
 		dbgtag = CreateCommandTag(parsetree);
-		if (check_ddl_tag(dbgtag) != EVENT_TRIGGER_COMMAND_TAG_OK)
-			elog(ERROR, "unexpected command tag \"%s\"", dbgtag);
+		if (event == EVT_DDLCommandStart ||
+			event == EVT_DDLCommandEnd   ||
+			event == EVT_SQLDrop)
+		{
+			if (check_ddl_tag(dbgtag) != EVENT_TRIGGER_COMMAND_TAG_OK)
+				elog(ERROR, "unexpected command tag \"%s\"", dbgtag);
+		}
+		else if (event == EVT_TableRewrite)
+		{
+			if(check_table_rewrite_ddl_tag(dbgtag) != EVENT_TRIGGER_COMMAND_TAG_OK)
+				elog(ERROR, "unexpected command tag \"%s\"", dbgtag);
+		}
 	}
 #endif
 
@@ -838,6 +898,77 @@ EventTriggerSQLDrop(Node *parsetree)
 	list_free(runlist);
 }
 
+
+/*
+ * Fire table_rewrite triggers.
+ */
+void
+EventTriggerTableRewrite(Node *parsetree, Oid tableOid)
+{
+	List	   *runlist;
+	EventTriggerData trigdata;
+
+	elog(DEBUG1, "EventTriggerTableRewrite(%u)", tableOid);
+
+	/*
+	 * Event Triggers are completely disabled in standalone mode.  There are
+	 * (at least) two reasons for this:
+	 *
+	 * 1. A sufficiently broken event trigger might not only render the
+	 * database unusable, but prevent disabling itself to fix the situation.
+	 * In this scenario, restarting in standalone mode provides an escape
+	 * hatch.
+	 *
+	 * 2. BuildEventTriggerCache relies on systable_beginscan_ordered, and
+	 * therefore will malfunction if pg_event_trigger's indexes are damaged.
+	 * To allow recovery from a damaged index, we need some operating mode
+	 * wherein event triggers are disabled.  (Or we could implement
+	 * heapscan-and-sort logic for that case, but having disaster recovery
+	 * scenarios depend on code that's otherwise untested isn't appetizing.)
+	 */
+	if (!IsUnderPostmaster)
+		return;
+
+	runlist = EventTriggerCommonSetup(parsetree,
+									  EVT_TableRewrite,
+									  "table_rewrite",
+									  &trigdata);
+	if (runlist == NIL)
+		return;
+
+	/*
+	 * Make sure pg_event_trigger_table_rewrite_oid only works when running
+	 * these triggers. Use PG_TRY to ensure table_rewrite_oid is reset even
+	 * when one trigger fails. (This is perhaps not necessary, as the
+	 * currentState variable will be removed shortly by our caller, but it
+	 * seems better to play safe.)
+	 */
+	currentEventTriggerState->table_rewrite_oid = tableOid;
+
+	/* Run the triggers. */
+	PG_TRY();
+	{
+		EventTriggerInvoke(runlist, &trigdata);
+	}
+	PG_CATCH();
+	{
+		currentEventTriggerState->table_rewrite_oid = InvalidOid;
+		PG_RE_THROW();
+	}
+	PG_END_TRY();
+
+	currentEventTriggerState->table_rewrite_oid = InvalidOid;
+
+	/* Cleanup. */
+	list_free(runlist);
+
+	/*
+	 * Make sure anything the event triggers did will be visible to the main
+	 * command.
+	 */
+	CommandCounterIncrement();
+}
+
 /*
  * Invoke each event trigger in a list of event triggers.
  */
@@ -871,6 +1002,8 @@ EventTriggerInvoke(List *fn_oid_list, EventTriggerData *trigdata)
 		FunctionCallInfoData fcinfo;
 		PgStat_FunctionCallUsage fcusage;
 
+		elog(DEBUG1, "EventTriggerInvoke %u", fnoid);
+
 		/*
 		 * We want each event trigger to be able to see the results of the
 		 * previous event trigger's action.  Caller is responsible for any
@@ -1026,8 +1159,9 @@ EventTriggerBeginCompleteQuery(void)
 	MemoryContext cxt;
 
 	/*
-	 * Currently, sql_drop events are the only reason to have event trigger
-	 * state at all; so if there are none, don't install one.
+	 * Currently, sql_drop and table_rewrite events are the only reason to
+	 * have event trigger state at all; so if there are none, don't install
+	 * one.
 	 */
 	if (!trackDroppedObjectsNeeded())
 		return false;
@@ -1041,6 +1175,7 @@ EventTriggerBeginCompleteQuery(void)
 	state->cxt = cxt;
 	slist_init(&(state->SQLDropList));
 	state->in_sql_drop = false;
+	state->table_rewrite_oid = InvalidOid;
 
 	state->previous = currentEventTriggerState;
 	currentEventTriggerState = state;
@@ -1080,8 +1215,9 @@ EventTriggerEndCompleteQuery(void)
 bool
 trackDroppedObjectsNeeded(void)
 {
-	/* true if any sql_drop event trigger exists */
-	return list_length(EventCacheLookup(EVT_SQLDrop)) > 0;
+	/* true if any sql_drop or table_rewrite event trigger exists */
+	return list_length(EventCacheLookup(EVT_SQLDrop)) > 0 ||
+		list_length(EventCacheLookup(EVT_TableRewrite)) > 0;
 }
 
 /*
@@ -1297,3 +1433,25 @@ pg_event_trigger_dropped_objects(PG_FUNCTION_ARGS)
 
 	return (Datum) 0;
 }
+
+/*
+ * pg_event_trigger_table_rewrite_oid
+ *
+ * Make the Oid of the table going to be rewritten available to the user
+ * function run by the Event Trigger.
+ */
+Datum
+pg_event_trigger_table_rewrite_oid(PG_FUNCTION_ARGS)
+{
+	/*
+	 * Protect this function from being called out of context
+	 */
+	if (!currentEventTriggerState ||
+		currentEventTriggerState->table_rewrite_oid == InvalidOid)
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+		 errmsg("%s can only be called in a table_rewrite event trigger function",
+				"pg_event_trigger_table_rewrite_oid()")));
+
+	PG_RETURN_OID(currentEventTriggerState->table_rewrite_oid);
+}
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index ecdff1e..8c08f46 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -46,6 +46,7 @@
 #include "commands/cluster.h"
 #include "commands/comment.h"
 #include "commands/defrem.h"
+#include "commands/event_trigger.h"
 #include "commands/policy.h"
 #include "commands/sequence.h"
 #include "commands/tablecmds.h"
@@ -303,13 +304,15 @@ static void validateForeignKeyConstraint(char *conname,
 static void createForeignKeyTriggers(Relation rel, Oid refRelOid,
 						 Constraint *fkconstraint,
 						 Oid constraintOid, Oid indexOid);
-static void ATController(Relation rel, List *cmds, bool recurse, LOCKMODE lockmode);
+static void ATController(AlterTableStmt *parsetree,
+						 Relation rel, List *cmds, bool recurse, LOCKMODE lockmode);
 static void ATPrepCmd(List **wqueue, Relation rel, AlterTableCmd *cmd,
 		  bool recurse, bool recursing, LOCKMODE lockmode);
 static void ATRewriteCatalogs(List **wqueue, LOCKMODE lockmode);
 static void ATExecCmd(List **wqueue, AlteredTableInfo *tab, Relation rel,
 		  AlterTableCmd *cmd, LOCKMODE lockmode);
-static void ATRewriteTables(List **wqueue, LOCKMODE lockmode);
+static void ATRewriteTables(AlterTableStmt *parsetree,
+							List **wqueue, LOCKMODE lockmode);
 static void ATRewriteTable(AlteredTableInfo *tab, Oid OIDNewHeap, LOCKMODE lockmode);
 static AlteredTableInfo *ATGetQueueEntry(List **wqueue, Relation rel);
 static void ATSimplePermissions(Relation rel, int allowed_targets);
@@ -2723,7 +2726,8 @@ AlterTable(Oid relid, LOCKMODE lockmode, AlterTableStmt *stmt)
 
 	CheckTableNotInUse(rel, "ALTER TABLE");
 
-	ATController(rel, stmt->cmds, interpretInhOption(stmt->relation->inhOpt),
+	ATController(stmt,
+				 rel, stmt->cmds, interpretInhOption(stmt->relation->inhOpt),
 				 lockmode);
 }
 
@@ -2746,7 +2750,7 @@ AlterTableInternal(Oid relid, List *cmds, bool recurse)
 
 	rel = relation_open(relid, lockmode);
 
-	ATController(rel, cmds, recurse, lockmode);
+	ATController(NULL, rel, cmds, recurse, lockmode);
 }
 
 /*
@@ -3015,7 +3019,8 @@ AlterTableGetLockLevel(List *cmds)
 }
 
 static void
-ATController(Relation rel, List *cmds, bool recurse, LOCKMODE lockmode)
+ATController(AlterTableStmt *parsetree,
+			 Relation rel, List *cmds, bool recurse, LOCKMODE lockmode)
 {
 	List	   *wqueue = NIL;
 	ListCell   *lcmd;
@@ -3035,7 +3040,7 @@ ATController(Relation rel, List *cmds, bool recurse, LOCKMODE lockmode)
 	ATRewriteCatalogs(&wqueue, lockmode);
 
 	/* Phase 3: scan/rewrite tables as needed */
-	ATRewriteTables(&wqueue, lockmode);
+	ATRewriteTables(parsetree, &wqueue, lockmode);
 }
 
 /*
@@ -3606,7 +3611,7 @@ ATExecCmd(List **wqueue, AlteredTableInfo *tab, Relation rel,
  * ATRewriteTables: ALTER TABLE phase 3
  */
 static void
-ATRewriteTables(List **wqueue, LOCKMODE lockmode)
+ATRewriteTables(AlterTableStmt *parsetree, List **wqueue, LOCKMODE lockmode)
 {
 	ListCell   *ltab;
 
@@ -3709,6 +3714,19 @@ ATRewriteTables(List **wqueue, LOCKMODE lockmode)
 			heap_close(OldHeap, NoLock);
 
 			/*
+			 * Fire off an Event Trigger now, before actually rewriting the
+			 * table.
+			 *
+			 * We don't support Event Trigger for nested commands anywhere,
+			 * here included, and parstree is given NULL when comming from
+			 * AlterTableInternal.
+			 *
+			 * And fire it only once.
+			 */
+			if (parsetree)
+				EventTriggerTableRewrite((Node *)parsetree, tab->relid);
+
+			/*
 			 * Create transient table that will receive the modified data.
 			 *
 			 * Ensure it is marked correctly as logged or unlogged.  We have
diff --git a/src/backend/utils/cache/evtcache.c b/src/backend/utils/cache/evtcache.c
index ae71bd6..b9d442c 100644
--- a/src/backend/utils/cache/evtcache.c
+++ b/src/backend/utils/cache/evtcache.c
@@ -169,6 +169,8 @@ BuildEventTriggerCache(void)
 			event = EVT_DDLCommandEnd;
 		else if (strcmp(evtevent, "sql_drop") == 0)
 			event = EVT_SQLDrop;
+		else if (strcmp(evtevent, "table_rewrite") == 0)
+			event = EVT_TableRewrite;
 		else
 			continue;
 
diff --git a/src/include/catalog/pg_proc.h b/src/include/catalog/pg_proc.h
index 4736532..b1e0372 100644
--- a/src/include/catalog/pg_proc.h
+++ b/src/include/catalog/pg_proc.h
@@ -4990,6 +4990,8 @@ DESCR("peek at binary changes from replication slot");
 /* event triggers */
 DATA(insert OID = 3566 (  pg_event_trigger_dropped_objects		PGNSP PGUID 12 10 100 0 0 f f f f t t s 0 0 2249 "" "{26,26,23,25,25,25,25}" "{o,o,o,o,o,o,o}" "{classid, objid, objsubid, object_type, schema_name, object_name, object_identity}" _null_ pg_event_trigger_dropped_objects _null_ _null_ _null_ ));
 DESCR("list objects dropped by the current command");
+DATA(insert OID = 4566 (  pg_event_trigger_table_rewrite_oid	PGNSP PGUID 12 10 100 0 0 f f f f t t s 0 0 26 "" "{26}" "{o}" "{oid}" _null_ pg_event_trigger_table_rewrite_oid _null_ _null_ _null_ ));
+DESCR("return Oid of the table getting rewritten");
 
 /* generic transition functions for ordered-set aggregates */
 DATA(insert OID = 3970 ( ordered_set_transition			PGNSP PGUID 12 1 0 0 0 f f f f f f i 2 0 2281 "2281 2276" _null_ _null_ _null_ _null_ ordered_set_transition _null_ _null_ _null_ ));
diff --git a/src/include/commands/event_trigger.h b/src/include/commands/event_trigger.h
index 0233f4c..5080f4f 100644
--- a/src/include/commands/event_trigger.h
+++ b/src/include/commands/event_trigger.h
@@ -46,6 +46,7 @@ extern bool EventTriggerSupportsObjectClass(ObjectClass objclass);
 extern void EventTriggerDDLCommandStart(Node *parsetree);
 extern void EventTriggerDDLCommandEnd(Node *parsetree);
 extern void EventTriggerSQLDrop(Node *parsetree);
+extern void EventTriggerTableRewrite(Node *parsetree, Oid tableOid);
 
 extern bool EventTriggerBeginCompleteQuery(void);
 extern void EventTriggerEndCompleteQuery(void);
diff --git a/src/include/utils/builtins.h b/src/include/utils/builtins.h
index fb1b4a4..02b581d 100644
--- a/src/include/utils/builtins.h
+++ b/src/include/utils/builtins.h
@@ -1189,6 +1189,7 @@ extern Datum unique_key_recheck(PG_FUNCTION_ARGS);
 
 /* commands/event_trigger.c */
 extern Datum pg_event_trigger_dropped_objects(PG_FUNCTION_ARGS);
+extern Datum pg_event_trigger_table_rewrite_oid(PG_FUNCTION_ARGS);
 
 /* commands/extension.c */
 extern Datum pg_available_extensions(PG_FUNCTION_ARGS);
diff --git a/src/include/utils/evtcache.h b/src/include/utils/evtcache.h
index c4c284f..4bbd80a 100644
--- a/src/include/utils/evtcache.h
+++ b/src/include/utils/evtcache.h
@@ -20,7 +20,8 @@ typedef enum
 {
 	EVT_DDLCommandStart,
 	EVT_DDLCommandEnd,
-	EVT_SQLDrop
+	EVT_SQLDrop,
+	EVT_TableRewrite
 } EventTriggerEvent;
 
 typedef struct
diff --git a/src/test/regress/expected/event_trigger.out b/src/test/regress/expected/event_trigger.out
index d4723b2..dbbb05e 100644
--- a/src/test/regress/expected/event_trigger.out
+++ b/src/test/regress/expected/event_trigger.out
@@ -294,3 +294,40 @@ SELECT * FROM dropped_objects WHERE type = 'schema';
 DROP ROLE regression_bob;
 DROP EVENT TRIGGER regress_event_trigger_drop_objects;
 DROP EVENT TRIGGER undroppable;
+-- only allowed from within an event trigger function, should fail
+select pg_event_trigger_table_rewrite_oid();
+ERROR:  pg_event_trigger_table_rewrite_oid() can only be called in a table_rewrite event trigger function
+-- test Table Rewrite Event Trigger
+CREATE OR REPLACE FUNCTION test_evtrig_no_rewrite() RETURNS event_trigger
+LANGUAGE plpgsql AS $$
+BEGIN
+  RAISE EXCEPTION 'I''m sorry Sir, No Rewrite Allowed.';
+END;
+$$;
+create event trigger no_rewrite_allowed on table_rewrite
+  execute procedure test_evtrig_no_rewrite();
+create table rewriteme (id serial primary key, foo float);
+insert into rewriteme
+     select x * 1.001 from generate_series(1, 500) as t(x);
+alter table rewriteme alter column foo type numeric;
+ERROR:  I'm sorry Sir, No Rewrite Allowed.
+alter table rewriteme add column baz int default 0;
+ERROR:  I'm sorry Sir, No Rewrite Allowed.
+-- test with more than one reason to rewrite a single table
+CREATE OR REPLACE FUNCTION test_evtrig_no_rewrite() RETURNS event_trigger
+LANGUAGE plpgsql AS $$
+BEGIN
+  RAISE NOTICE 'Table ''%'' is being rewritten',
+               pg_event_trigger_table_rewrite_oid()::regclass;
+END;
+$$;
+alter table rewriteme
+ add column onemore int default 0,
+ add column another int default -1,
+ alter column foo type numeric(10,4);
+NOTICE:  Table 'rewriteme' is being rewritten
+-- shouldn't trigger a table_rewrite event
+alter table rewriteme alter column foo type numeric(12,4);
+drop table rewriteme;
+drop event trigger no_rewrite_allowed;
+drop function test_evtrig_no_rewrite();
diff --git a/src/test/regress/sql/event_trigger.sql b/src/test/regress/sql/event_trigger.sql
index 11d2ce5..5b452b0 100644
--- a/src/test/regress/sql/event_trigger.sql
+++ b/src/test/regress/sql/event_trigger.sql
@@ -206,3 +206,44 @@ DROP ROLE regression_bob;
 
 DROP EVENT TRIGGER regress_event_trigger_drop_objects;
 DROP EVENT TRIGGER undroppable;
+
+-- only allowed from within an event trigger function, should fail
+select pg_event_trigger_table_rewrite_oid();
+
+-- test Table Rewrite Event Trigger
+CREATE OR REPLACE FUNCTION test_evtrig_no_rewrite() RETURNS event_trigger
+LANGUAGE plpgsql AS $$
+BEGIN
+  RAISE EXCEPTION 'I''m sorry Sir, No Rewrite Allowed.';
+END;
+$$;
+
+create event trigger no_rewrite_allowed on table_rewrite
+  execute procedure test_evtrig_no_rewrite();
+
+create table rewriteme (id serial primary key, foo float);
+insert into rewriteme
+     select x * 1.001 from generate_series(1, 500) as t(x);
+alter table rewriteme alter column foo type numeric;
+alter table rewriteme add column baz int default 0;
+
+-- test with more than one reason to rewrite a single table
+CREATE OR REPLACE FUNCTION test_evtrig_no_rewrite() RETURNS event_trigger
+LANGUAGE plpgsql AS $$
+BEGIN
+  RAISE NOTICE 'Table ''%'' is being rewritten',
+               pg_event_trigger_table_rewrite_oid()::regclass;
+END;
+$$;
+
+alter table rewriteme
+ add column onemore int default 0,
+ add column another int default -1,
+ alter column foo type numeric(10,4);
+
+-- shouldn't trigger a table_rewrite event
+alter table rewriteme alter column foo type numeric(12,4);
+
+drop table rewriteme;
+drop event trigger no_rewrite_allowed;
+drop function test_evtrig_no_rewrite();

#19

Michael Paquier

michael.paquier@gmail.com

about 11 years ago

In reply to: Dimitri Fontaine (#18)

1 attachment(s)

Re: New Event Trigger: table_rewrite

On Thu, Nov 20, 2014 at 10:37 PM, Dimitri Fontaine
<dimitri@2ndquadrant.fr> wrote:

Alvaro Herrera <alvherre@2ndquadrant.com> writes:

CLUSTER and VACUUM are not part of the supported commands anymore, so
I think that we could replace that by the addition of a reference
number in the cell of ALTER TABLE for the event table_rewrite and
write at the bottom of the table a description of how this event
behaves with ALTER TABLE. Note as well that "might or might not" is
not really helpful for the user.

That's precisely why we have an event trigger here, I think --- for some
subcommands, it's not easy to determine whether a rewrite happens or
not. (I think SET TYPE is the one). I don't think we want to document
precisely under what condition a rewrite takes place.

Yeah, the current documentation expands to the following sentence, as
browsed in

http://www.postgresql.org/docs/9.3/interactive/sql-altertable.html

As an exception, if the USING clause does not change the column
contents and the old type is either binary coercible to the new type
or an unconstrained domain over the new type, a table rewrite is not
needed, but any indexes on the affected columns must still be rebuilt.

I don't think that "might or might not" is less helpful in the context
of the Event Trigger, because the whole point is that the event is only
triggered in case of a rewrite. Of course we could cross link the two
paragraphs or something.

2) The examples of SQL queries provided are still in lower case in the
docs, that's contrary to the rest of the docs where upper case is used
for reserved keywords.

Right, being consistent trumps personal preferences, changed in the
attached.

Yes please. <nitpick> Another thing in that sample code is "not current_hour
between 1 and 6". That reads strange to me. It should be equally
correct to spell it as "current_hour not between 1 and 6", which seems
more natural. </>

True, fixed in the attached.

The status of this patch was not updated on the commit fest app, so I
lost track of it. Sorry for not answering earlier btw.

The following things to note about v5:
1) There are still mentions of VACUUM, ANALYZE and CLUSTER:
@@ -264,6 +275,10 @@ check_ddl_tag(const char *tag)
                obtypename = tag + 6;
        else if (pg_strncasecmp(tag, "DROP ", 5) == 0)
                obtypename = tag + 5;
+       else if (pg_strncasecmp(tag, "ANALYZE", 7) == 0 ||
+                        pg_strncasecmp(tag, "CLUSTER", 7) == 0 ||
+                        pg_strncasecmp(tag, "VACUUM", 6) == 0)
+               return EVENT_TRIGGER_COMMAND_TAG_OK;
2) There are a couple of typos and incorrect styling, like "if(". Nothing huge..
Cleanup is done in the attached.

In any case, all the issues mentioned seem to have been addressed, so
switching this patch to ready for committer.
Regards,
--
Michael

Attachments:

20141202_table_rewrite_v6.patchtext/x-diff; charset=US-ASCII; name=20141202_table_rewrite_v6.patchDownload

diff --git a/src/backend/commands/event_trigger.c b/src/backend/commands/event_trigger.c
index 6a3002f..17b0818 100644
--- a/src/backend/commands/event_trigger.c
+++ b/src/backend/commands/event_trigger.c
@@ -42,11 +42,14 @@
 #include "utils/syscache.h"
 #include "tcop/utility.h"
 
-
+/*
+ * Data Structure for sql_drop and table_rewrite Event Trigger support.
+ */
 typedef struct EventTriggerQueryState
 {
 	slist_head	SQLDropList;
 	bool		in_sql_drop;
+	Oid			table_rewrite_oid;
 	MemoryContext cxt;
 	struct EventTriggerQueryState *previous;
 } EventTriggerQueryState;
@@ -119,11 +122,14 @@ static void AlterEventTriggerOwner_internal(Relation rel,
 								HeapTuple tup,
 								Oid newOwnerId);
 static event_trigger_command_tag_check_result check_ddl_tag(const char *tag);
+static event_trigger_command_tag_check_result check_table_rewrite_ddl_tag(
+	const char *tag);
 static void error_duplicate_filter_variable(const char *defname);
 static Datum filter_list_to_array(List *filterlist);
 static Oid insert_event_trigger_tuple(char *trigname, char *eventname,
 						   Oid evtOwner, Oid funcoid, List *tags);
 static void validate_ddl_tags(const char *filtervar, List *taglist);
+static void validate_table_rewrite_tags(const char *filtervar, List *taglist);
 static void EventTriggerInvoke(List *fn_oid_list, EventTriggerData *trigdata);
 
 /*
@@ -154,7 +160,8 @@ CreateEventTrigger(CreateEventTrigStmt *stmt)
 	/* Validate event name. */
 	if (strcmp(stmt->eventname, "ddl_command_start") != 0 &&
 		strcmp(stmt->eventname, "ddl_command_end") != 0 &&
-		strcmp(stmt->eventname, "sql_drop") != 0)
+		strcmp(stmt->eventname, "sql_drop") != 0 &&
+		strcmp(stmt->eventname, "table_rewrite") != 0)
 		ereport(ERROR,
 				(errcode(ERRCODE_SYNTAX_ERROR),
 				 errmsg("unrecognized event name \"%s\"",
@@ -183,6 +190,9 @@ CreateEventTrigger(CreateEventTrigStmt *stmt)
 		 strcmp(stmt->eventname, "sql_drop") == 0)
 		&& tags != NULL)
 		validate_ddl_tags("tag", tags);
+	else if (strcmp(stmt->eventname, "table_rewrite") == 0
+			 && tags != NULL)
+		validate_table_rewrite_tags("tag", tags);
 
 	/*
 	 * Give user a nice error message if an event trigger of the same name
@@ -281,6 +291,38 @@ check_ddl_tag(const char *tag)
 }
 
 /*
+ * Validate DDL command tags for event table_rewrite.
+ */
+static void
+validate_table_rewrite_tags(const char *filtervar, List *taglist)
+{
+	ListCell   *lc;
+
+	foreach(lc, taglist)
+	{
+		const char *tag = strVal(lfirst(lc));
+		event_trigger_command_tag_check_result result;
+
+		result = check_table_rewrite_ddl_tag(tag);
+		if (result == EVENT_TRIGGER_COMMAND_TAG_NOT_SUPPORTED)
+			ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+			/* translator: %s represents an SQL statement name */
+					 errmsg("event triggers are not supported for %s",
+							tag)));
+	}
+}
+
+static event_trigger_command_tag_check_result
+check_table_rewrite_ddl_tag(const char *tag)
+{
+	if (pg_strcasecmp(tag, "ALTER TABLE") == 0)
+		return EVENT_TRIGGER_COMMAND_TAG_OK;
+
+	return EVENT_TRIGGER_COMMAND_TAG_NOT_SUPPORTED;
+}
+
+/*
  * Complain about a duplicate filter variable.
  */
 static void
@@ -641,8 +683,18 @@ EventTriggerCommonSetup(Node *parsetree,
 		const char *dbgtag;
 
 		dbgtag = CreateCommandTag(parsetree);
-		if (check_ddl_tag(dbgtag) != EVENT_TRIGGER_COMMAND_TAG_OK)
-			elog(ERROR, "unexpected command tag \"%s\"", dbgtag);
+		if (event == EVT_DDLCommandStart ||
+			event == EVT_DDLCommandEnd   ||
+			event == EVT_SQLDrop)
+		{
+			if (check_ddl_tag(dbgtag) != EVENT_TRIGGER_COMMAND_TAG_OK)
+				elog(ERROR, "unexpected command tag \"%s\"", dbgtag);
+		}
+		else if (event == EVT_TableRewrite)
+		{
+			if (check_table_rewrite_ddl_tag(dbgtag) != EVENT_TRIGGER_COMMAND_TAG_OK)
+				elog(ERROR, "unexpected command tag \"%s\"", dbgtag);
+		}
 	}
 #endif
 
@@ -838,6 +890,77 @@ EventTriggerSQLDrop(Node *parsetree)
 	list_free(runlist);
 }
 
+
+/*
+ * Fire table_rewrite triggers.
+ */
+void
+EventTriggerTableRewrite(Node *parsetree, Oid tableOid)
+{
+	List	   *runlist;
+	EventTriggerData trigdata;
+
+	elog(DEBUG1, "EventTriggerTableRewrite(%u)", tableOid);
+
+	/*
+	 * Event Triggers are completely disabled in standalone mode.  There are
+	 * (at least) two reasons for this:
+	 *
+	 * 1. A sufficiently broken event trigger might not only render the
+	 * database unusable, but prevent disabling itself to fix the situation.
+	 * In this scenario, restarting in standalone mode provides an escape
+	 * hatch.
+	 *
+	 * 2. BuildEventTriggerCache relies on systable_beginscan_ordered, and
+	 * therefore will malfunction if pg_event_trigger's indexes are damaged.
+	 * To allow recovery from a damaged index, we need some operating mode
+	 * wherein event triggers are disabled.  (Or we could implement
+	 * heapscan-and-sort logic for that case, but having disaster recovery
+	 * scenarios depend on code that's otherwise untested isn't appetizing.)
+	 */
+	if (!IsUnderPostmaster)
+		return;
+
+	runlist = EventTriggerCommonSetup(parsetree,
+									  EVT_TableRewrite,
+									  "table_rewrite",
+									  &trigdata);
+	if (runlist == NIL)
+		return;
+
+	/*
+	 * Make sure pg_event_trigger_table_rewrite_oid only works when running
+	 * these triggers. Use PG_TRY to ensure table_rewrite_oid is reset even
+	 * when one trigger fails. (This is perhaps not necessary, as the
+	 * currentState variable will be removed shortly by our caller, but it
+	 * seems better to play safe.)
+	 */
+	currentEventTriggerState->table_rewrite_oid = tableOid;
+
+	/* Run the triggers. */
+	PG_TRY();
+	{
+		EventTriggerInvoke(runlist, &trigdata);
+	}
+	PG_CATCH();
+	{
+		currentEventTriggerState->table_rewrite_oid = InvalidOid;
+		PG_RE_THROW();
+	}
+	PG_END_TRY();
+
+	currentEventTriggerState->table_rewrite_oid = InvalidOid;
+
+	/* Cleanup. */
+	list_free(runlist);
+
+	/*
+	 * Make sure anything the event triggers did will be visible to the main
+	 * command.
+	 */
+	CommandCounterIncrement();
+}
+
 /*
  * Invoke each event trigger in a list of event triggers.
  */
@@ -871,6 +994,8 @@ EventTriggerInvoke(List *fn_oid_list, EventTriggerData *trigdata)
 		FunctionCallInfoData fcinfo;
 		PgStat_FunctionCallUsage fcusage;
 
+		elog(DEBUG1, "EventTriggerInvoke %u", fnoid);
+
 		/*
 		 * We want each event trigger to be able to see the results of the
 		 * previous event trigger's action.  Caller is responsible for any
@@ -1026,8 +1151,9 @@ EventTriggerBeginCompleteQuery(void)
 	MemoryContext cxt;
 
 	/*
-	 * Currently, sql_drop events are the only reason to have event trigger
-	 * state at all; so if there are none, don't install one.
+	 * Currently, sql_drop and table_rewrite events are the only reason to
+	 * have event trigger state at all; so if there are none, don't install
+	 * one.
 	 */
 	if (!trackDroppedObjectsNeeded())
 		return false;
@@ -1041,6 +1167,7 @@ EventTriggerBeginCompleteQuery(void)
 	state->cxt = cxt;
 	slist_init(&(state->SQLDropList));
 	state->in_sql_drop = false;
+	state->table_rewrite_oid = InvalidOid;
 
 	state->previous = currentEventTriggerState;
 	currentEventTriggerState = state;
@@ -1080,8 +1207,9 @@ EventTriggerEndCompleteQuery(void)
 bool
 trackDroppedObjectsNeeded(void)
 {
-	/* true if any sql_drop event trigger exists */
-	return list_length(EventCacheLookup(EVT_SQLDrop)) > 0;
+	/* true if any sql_drop or table_rewrite event trigger exists */
+	return list_length(EventCacheLookup(EVT_SQLDrop)) > 0 ||
+		list_length(EventCacheLookup(EVT_TableRewrite)) > 0;
 }
 
 /*
@@ -1297,3 +1425,25 @@ pg_event_trigger_dropped_objects(PG_FUNCTION_ARGS)
 
 	return (Datum) 0;
 }
+
+/*
+ * pg_event_trigger_table_rewrite_oid
+ *
+ * Make the Oid of the table going to be rewritten available to the user
+ * function run by the Event Trigger.
+ */
+Datum
+pg_event_trigger_table_rewrite_oid(PG_FUNCTION_ARGS)
+{
+	/*
+	 * Protect this function from being called out of context
+	 */
+	if (!currentEventTriggerState ||
+		currentEventTriggerState->table_rewrite_oid == InvalidOid)
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+		 errmsg("%s can only be called in a table_rewrite event trigger function",
+				"pg_event_trigger_table_rewrite_oid()")));
+
+	PG_RETURN_OID(currentEventTriggerState->table_rewrite_oid);
+}
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 2333e1b..776ae78 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -46,6 +46,7 @@
 #include "commands/cluster.h"
 #include "commands/comment.h"
 #include "commands/defrem.h"
+#include "commands/event_trigger.h"
 #include "commands/policy.h"
 #include "commands/sequence.h"
 #include "commands/tablecmds.h"
@@ -303,13 +304,15 @@ static void validateForeignKeyConstraint(char *conname,
 static void createForeignKeyTriggers(Relation rel, Oid refRelOid,
 						 Constraint *fkconstraint,
 						 Oid constraintOid, Oid indexOid);
-static void ATController(Relation rel, List *cmds, bool recurse, LOCKMODE lockmode);
+static void ATController(AlterTableStmt *parsetree,
+						 Relation rel, List *cmds, bool recurse, LOCKMODE lockmode);
 static void ATPrepCmd(List **wqueue, Relation rel, AlterTableCmd *cmd,
 		  bool recurse, bool recursing, LOCKMODE lockmode);
 static void ATRewriteCatalogs(List **wqueue, LOCKMODE lockmode);
 static void ATExecCmd(List **wqueue, AlteredTableInfo *tab, Relation rel,
 		  AlterTableCmd *cmd, LOCKMODE lockmode);
-static void ATRewriteTables(List **wqueue, LOCKMODE lockmode);
+static void ATRewriteTables(AlterTableStmt *parsetree,
+							List **wqueue, LOCKMODE lockmode);
 static void ATRewriteTable(AlteredTableInfo *tab, Oid OIDNewHeap, LOCKMODE lockmode);
 static AlteredTableInfo *ATGetQueueEntry(List **wqueue, Relation rel);
 static void ATSimplePermissions(Relation rel, int allowed_targets);
@@ -2724,7 +2727,8 @@ AlterTable(Oid relid, LOCKMODE lockmode, AlterTableStmt *stmt)
 
 	CheckTableNotInUse(rel, "ALTER TABLE");
 
-	ATController(rel, stmt->cmds, interpretInhOption(stmt->relation->inhOpt),
+	ATController(stmt,
+				 rel, stmt->cmds, interpretInhOption(stmt->relation->inhOpt),
 				 lockmode);
 }
 
@@ -2747,7 +2751,7 @@ AlterTableInternal(Oid relid, List *cmds, bool recurse)
 
 	rel = relation_open(relid, lockmode);
 
-	ATController(rel, cmds, recurse, lockmode);
+	ATController(NULL, rel, cmds, recurse, lockmode);
 }
 
 /*
@@ -3016,7 +3020,8 @@ AlterTableGetLockLevel(List *cmds)
 }
 
 static void
-ATController(Relation rel, List *cmds, bool recurse, LOCKMODE lockmode)
+ATController(AlterTableStmt *parsetree,
+			 Relation rel, List *cmds, bool recurse, LOCKMODE lockmode)
 {
 	List	   *wqueue = NIL;
 	ListCell   *lcmd;
@@ -3036,7 +3041,7 @@ ATController(Relation rel, List *cmds, bool recurse, LOCKMODE lockmode)
 	ATRewriteCatalogs(&wqueue, lockmode);
 
 	/* Phase 3: scan/rewrite tables as needed */
-	ATRewriteTables(&wqueue, lockmode);
+	ATRewriteTables(parsetree, &wqueue, lockmode);
 }
 
 /*
@@ -3607,7 +3612,7 @@ ATExecCmd(List **wqueue, AlteredTableInfo *tab, Relation rel,
  * ATRewriteTables: ALTER TABLE phase 3
  */
 static void
-ATRewriteTables(List **wqueue, LOCKMODE lockmode)
+ATRewriteTables(AlterTableStmt *parsetree, List **wqueue, LOCKMODE lockmode)
 {
 	ListCell   *ltab;
 
@@ -3710,6 +3715,19 @@ ATRewriteTables(List **wqueue, LOCKMODE lockmode)
 			heap_close(OldHeap, NoLock);
 
 			/*
+			 * Fire off an Event Trigger now, before actually rewriting the
+			 * table.
+			 *
+			 * We don't support Event Trigger for nested commands anywhere,
+			 * here included, and parstree is given NULL when comming from
+			 * AlterTableInternal.
+			 *
+			 * And fire it only once.
+			 */
+			if (parsetree)
+				EventTriggerTableRewrite((Node *)parsetree, tab->relid);
+
+			/*
 			 * Create transient table that will receive the modified data.
 			 *
 			 * Ensure it is marked correctly as logged or unlogged.  We have
diff --git a/src/backend/utils/cache/evtcache.c b/src/backend/utils/cache/evtcache.c
index ae71bd6..b9d442c 100644
--- a/src/backend/utils/cache/evtcache.c
+++ b/src/backend/utils/cache/evtcache.c
@@ -169,6 +169,8 @@ BuildEventTriggerCache(void)
 			event = EVT_DDLCommandEnd;
 		else if (strcmp(evtevent, "sql_drop") == 0)
 			event = EVT_SQLDrop;
+		else if (strcmp(evtevent, "table_rewrite") == 0)
+			event = EVT_TableRewrite;
 		else
 			continue;
 
diff --git a/src/include/catalog/pg_proc.h b/src/include/catalog/pg_proc.h
index 56399ac..a3faf2c 100644
--- a/src/include/catalog/pg_proc.h
+++ b/src/include/catalog/pg_proc.h
@@ -5039,6 +5039,8 @@ DESCR("peek at binary changes from replication slot");
 /* event triggers */
 DATA(insert OID = 3566 (  pg_event_trigger_dropped_objects		PGNSP PGUID 12 10 100 0 0 f f f f t t s 0 0 2249 "" "{26,26,23,25,25,25,25}" "{o,o,o,o,o,o,o}" "{classid, objid, objsubid, object_type, schema_name, object_name, object_identity}" _null_ pg_event_trigger_dropped_objects _null_ _null_ _null_ ));
 DESCR("list objects dropped by the current command");
+DATA(insert OID = 4566 (  pg_event_trigger_table_rewrite_oid	PGNSP PGUID 12 10 100 0 0 f f f f t t s 0 0 26 "" "{26}" "{o}" "{oid}" _null_ pg_event_trigger_table_rewrite_oid _null_ _null_ _null_ ));
+DESCR("return Oid of the table getting rewritten");
 
 /* generic transition functions for ordered-set aggregates */
 DATA(insert OID = 3970 ( ordered_set_transition			PGNSP PGUID 12 1 0 0 0 f f f f f f i 2 0 2281 "2281 2276" _null_ _null_ _null_ _null_ ordered_set_transition _null_ _null_ _null_ ));
diff --git a/src/include/commands/event_trigger.h b/src/include/commands/event_trigger.h
index 0233f4c..5080f4f 100644
--- a/src/include/commands/event_trigger.h
+++ b/src/include/commands/event_trigger.h
@@ -46,6 +46,7 @@ extern bool EventTriggerSupportsObjectClass(ObjectClass objclass);
 extern void EventTriggerDDLCommandStart(Node *parsetree);
 extern void EventTriggerDDLCommandEnd(Node *parsetree);
 extern void EventTriggerSQLDrop(Node *parsetree);
+extern void EventTriggerTableRewrite(Node *parsetree, Oid tableOid);
 
 extern bool EventTriggerBeginCompleteQuery(void);
 extern void EventTriggerEndCompleteQuery(void);
diff --git a/src/include/utils/builtins.h b/src/include/utils/builtins.h
index 417fd17..ecc11cf 100644
--- a/src/include/utils/builtins.h
+++ b/src/include/utils/builtins.h
@@ -1196,6 +1196,7 @@ extern Datum unique_key_recheck(PG_FUNCTION_ARGS);
 
 /* commands/event_trigger.c */
 extern Datum pg_event_trigger_dropped_objects(PG_FUNCTION_ARGS);
+extern Datum pg_event_trigger_table_rewrite_oid(PG_FUNCTION_ARGS);
 
 /* commands/extension.c */
 extern Datum pg_available_extensions(PG_FUNCTION_ARGS);
diff --git a/src/include/utils/evtcache.h b/src/include/utils/evtcache.h
index c4c284f..4bbd80a 100644
--- a/src/include/utils/evtcache.h
+++ b/src/include/utils/evtcache.h
@@ -20,7 +20,8 @@ typedef enum
 {
 	EVT_DDLCommandStart,
 	EVT_DDLCommandEnd,
-	EVT_SQLDrop
+	EVT_SQLDrop,
+	EVT_TableRewrite
 } EventTriggerEvent;
 
 typedef struct
diff --git a/src/test/regress/expected/event_trigger.out b/src/test/regress/expected/event_trigger.out
index d4723b2..dbbb05e 100644
--- a/src/test/regress/expected/event_trigger.out
+++ b/src/test/regress/expected/event_trigger.out
@@ -294,3 +294,40 @@ SELECT * FROM dropped_objects WHERE type = 'schema';
 DROP ROLE regression_bob;
 DROP EVENT TRIGGER regress_event_trigger_drop_objects;
 DROP EVENT TRIGGER undroppable;
+-- only allowed from within an event trigger function, should fail
+select pg_event_trigger_table_rewrite_oid();
+ERROR:  pg_event_trigger_table_rewrite_oid() can only be called in a table_rewrite event trigger function
+-- test Table Rewrite Event Trigger
+CREATE OR REPLACE FUNCTION test_evtrig_no_rewrite() RETURNS event_trigger
+LANGUAGE plpgsql AS $$
+BEGIN
+  RAISE EXCEPTION 'I''m sorry Sir, No Rewrite Allowed.';
+END;
+$$;
+create event trigger no_rewrite_allowed on table_rewrite
+  execute procedure test_evtrig_no_rewrite();
+create table rewriteme (id serial primary key, foo float);
+insert into rewriteme
+     select x * 1.001 from generate_series(1, 500) as t(x);
+alter table rewriteme alter column foo type numeric;
+ERROR:  I'm sorry Sir, No Rewrite Allowed.
+alter table rewriteme add column baz int default 0;
+ERROR:  I'm sorry Sir, No Rewrite Allowed.
+-- test with more than one reason to rewrite a single table
+CREATE OR REPLACE FUNCTION test_evtrig_no_rewrite() RETURNS event_trigger
+LANGUAGE plpgsql AS $$
+BEGIN
+  RAISE NOTICE 'Table ''%'' is being rewritten',
+               pg_event_trigger_table_rewrite_oid()::regclass;
+END;
+$$;
+alter table rewriteme
+ add column onemore int default 0,
+ add column another int default -1,
+ alter column foo type numeric(10,4);
+NOTICE:  Table 'rewriteme' is being rewritten
+-- shouldn't trigger a table_rewrite event
+alter table rewriteme alter column foo type numeric(12,4);
+drop table rewriteme;
+drop event trigger no_rewrite_allowed;
+drop function test_evtrig_no_rewrite();
diff --git a/src/test/regress/sql/event_trigger.sql b/src/test/regress/sql/event_trigger.sql
index 11d2ce5..5b452b0 100644
--- a/src/test/regress/sql/event_trigger.sql
+++ b/src/test/regress/sql/event_trigger.sql
@@ -206,3 +206,44 @@ DROP ROLE regression_bob;
 
 DROP EVENT TRIGGER regress_event_trigger_drop_objects;
 DROP EVENT TRIGGER undroppable;
+
+-- only allowed from within an event trigger function, should fail
+select pg_event_trigger_table_rewrite_oid();
+
+-- test Table Rewrite Event Trigger
+CREATE OR REPLACE FUNCTION test_evtrig_no_rewrite() RETURNS event_trigger
+LANGUAGE plpgsql AS $$
+BEGIN
+  RAISE EXCEPTION 'I''m sorry Sir, No Rewrite Allowed.';
+END;
+$$;
+
+create event trigger no_rewrite_allowed on table_rewrite
+  execute procedure test_evtrig_no_rewrite();
+
+create table rewriteme (id serial primary key, foo float);
+insert into rewriteme
+     select x * 1.001 from generate_series(1, 500) as t(x);
+alter table rewriteme alter column foo type numeric;
+alter table rewriteme add column baz int default 0;
+
+-- test with more than one reason to rewrite a single table
+CREATE OR REPLACE FUNCTION test_evtrig_no_rewrite() RETURNS event_trigger
+LANGUAGE plpgsql AS $$
+BEGIN
+  RAISE NOTICE 'Table ''%'' is being rewritten',
+               pg_event_trigger_table_rewrite_oid()::regclass;
+END;
+$$;
+
+alter table rewriteme
+ add column onemore int default 0,
+ add column another int default -1,
+ alter column foo type numeric(10,4);
+
+-- shouldn't trigger a table_rewrite event
+alter table rewriteme alter column foo type numeric(12,4);
+
+drop table rewriteme;
+drop event trigger no_rewrite_allowed;
+drop function test_evtrig_no_rewrite();