From a1c4ae874bf156a05da436838d6b2b73f6621905 Mon Sep 17 00:00:00 2001
From: Ronan Dunklau <ronan.dunklau@aiven.io>
Date: Fri, 13 Aug 2021 15:03:32 +0200
Subject: [PATCH v4 3/4] Output error tags in CSV logs

---
 doc/src/sgml/config.sgml       |  4 +++-
 doc/src/sgml/file-fdw.sgml     |  1 +
 src/backend/utils/error/elog.c | 25 ++++++++++++++++++++++++-
 3 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index afbb6c35e3..4df79fcbcc 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -7372,7 +7372,8 @@ log_line_prefix = '%m [%p] %q%u@%d/%a '
         location of the error in the PostgreSQL source code
         (if <varname>log_error_verbosity</varname> is set to <literal>verbose</literal>),
         application name, backend type, process ID of parallel group leader,
-        and query id.
+        query id,
+        and optional tags added by the logger as JSON.
         Here is a sample table definition for storing CSV-format log output:
 
 <programlisting>
@@ -7404,6 +7405,7 @@ CREATE TABLE postgres_log
   backend_type text,
   leader_pid integer,
   query_id bigint,
+  tags jsonb,
   PRIMARY KEY (session_id, session_line_num)
 );
 </programlisting>
diff --git a/doc/src/sgml/file-fdw.sgml b/doc/src/sgml/file-fdw.sgml
index 5b98782064..ccb4e9d8dd 100644
--- a/doc/src/sgml/file-fdw.sgml
+++ b/doc/src/sgml/file-fdw.sgml
@@ -268,6 +268,7 @@ CREATE FOREIGN TABLE pglog (
   backend_type text,
   leader_pid integer,
   query_id bigint
+  tags jsonb,
 ) SERVER pglog
 OPTIONS ( filename 'log/pglog.csv', format 'csv' );
 </programlisting>
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index d43e1c2c31..1e6c7222c3 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -80,6 +80,7 @@
 #include "storage/proc.h"
 #include "tcop/tcopprot.h"
 #include "utils/guc.h"
+#include "utils/json.h"
 #include "utils/memutils.h"
 #include "utils/ps_status.h"
 
@@ -3013,10 +3014,32 @@ write_csvlog(ErrorData *edata)
 			appendStringInfo(&buf, "%d", leader->pid);
 	}
 	appendStringInfoChar(&buf, ',');
-
 	/* query id */
 	appendStringInfo(&buf, "%lld", (long long) pgstat_get_my_query_id());
+	appendStringInfoChar(&buf, ',');
+	if (edata->tags != NIL)
+	{
+		StringInfoData tagbuf;
+		ListCell   *lc;
+		bool		first = true;
 
+		initStringInfo(&tagbuf);
+		appendStringInfoChar(&tagbuf, '{');
+		foreach(lc, edata->tags)
+		{
+			ErrorTag   *etag = lfirst(lc);
+
+			if (!first)
+				appendStringInfoChar(&tagbuf, ',');
+			escape_json(&tagbuf, etag->tagname);
+			appendStringInfoChar(&tagbuf, ':');
+			escape_json(&tagbuf, etag->tagvalue);
+			first = false;
+		}
+		appendStringInfoChar(&tagbuf, '}');
+		appendCSVLiteral(&buf, tagbuf.data);
+		pfree(tagbuf.data);
+	}
 	appendStringInfoChar(&buf, '\n');
 
 	/* If in the syslogger process, try to write messages direct to file */
-- 
2.34.1