diff --git a/doc/src/sgml/ref/copy.sgml b/doc/src/sgml/ref/copy.sgml index a73b022..3a0e521 100644 *** a/doc/src/sgml/ref/copy.sgml --- b/doc/src/sgml/ref/copy.sgml *************** COPY { ta *** 42,47 **** --- 42,48 ---- FORCE_QUOTE { ( column [, ...] ) | * } FORCE_NOT_NULL ( column [, ...] ) | ENCODING 'encoding_name' + SKIP_WAL *************** COPY { ta *** 293,298 **** --- 294,312 ---- for more details. + + + SKIP_WAL + + + Specifies that the writing of WAL should be skipped if possible. + WAL can be skipped if the table being copied into is empty and + if an exclusive lock can be obtained without waiting. If this + option is specified and WAL is skipped then the transaction will + hold an exclusive lock on the table being copied until the transaction + commits. + + diff --git a/src/backend/commands/copy.c b/src/backend/commands/copy.c index 528a3a1..bd81a4b 100644 *** a/src/backend/commands/copy.c --- b/src/backend/commands/copy.c *************** *** 29,34 **** --- 29,35 ---- #include "commands/defrem.h" #include "commands/trigger.h" #include "executor/executor.h" + #include "commands/tablecmds.h" #include "libpq/libpq.h" #include "libpq/pqformat.h" #include "mb/pg_wchar.h" *************** *** 37,42 **** --- 38,44 ---- #include "parser/parse_relation.h" #include "rewrite/rewriteHandler.h" #include "storage/fd.h" + #include "storage/lmgr.h" #include "tcop/tcopprot.h" #include "utils/acl.h" #include "utils/builtins.h" *************** typedef struct CopyStateData *** 120,125 **** --- 122,128 ---- bool *force_quote_flags; /* per-column CSV FQ flags */ List *force_notnull; /* list of column names */ bool *force_notnull_flags; /* per-column CSV FNN flags */ + bool skip_wal; /* skip WAL if able */ /* these are just for error messages, see CopyFromErrorCallback */ const char *cur_relname; /* table name for error messages */ *************** ProcessCopyOptions(CopyState cstate, *** 965,970 **** --- 968,978 ---- errmsg("argument to option \"%s\" must be a valid encoding name", defel->defname))); } + else if (strcmp(defel->defname,"skip_wal") == 0) + { + + cstate->skip_wal=true; + } else ereport(ERROR, (errcode(ERRCODE_SYNTAX_ERROR), *************** CopyFrom(CopyState cstate) *** 1910,1915 **** --- 1918,1957 ---- if (!XLogIsNeeded()) hi_options |= HEAP_INSERT_SKIP_WAL; } + + /* + * if SKIP_WAL was requested we try to avoid writing + * WAL if the table is 0 bytes on disk (empty) and + * that we can obtain an exclusive lock on it without blocking. + * + */ + if(cstate->skip_wal && !XLogIsNeeded() && + ConditionalLockRelationOid(cstate->rel->rd_id,AccessExclusiveLock)) + { + + Datum size = DirectFunctionCall2(pg_relation_size, + ObjectIdGetDatum(cstate->rel->rd_id), + PointerGetDatum(cstring_to_text("main"))); + if ( DatumGetInt64(size)==0) + { + /** + * The relation is empty + unused. + * truncate it so that if this transaction + * rollsback then the changes to the relation files + * will dissapear (the current relation files will + * remain untouched) + */ + truncate_relation(cstate->rel); + hi_options |= HEAP_INSERT_SKIP_FSM; + hi_options |= HEAP_INSERT_SKIP_WAL; + } + else + { + UnlockRelation(cstate->rel,AccessExclusiveLock); + } + + } + /* * We need a ResultRelInfo so we can use the regular executor's diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c index 4509cda..ff5bf8d 100644 *** a/src/backend/commands/tablecmds.c --- b/src/backend/commands/tablecmds.c *************** ExecuteTruncate(TruncateStmt *stmt) *** 1053,1095 **** } else { ! Oid heap_relid; ! Oid toast_relid; ! ! /* ! * This effectively deletes all rows in the table, and may be done ! * in a serializable transaction. In that case we must record a ! * rw-conflict in to this transaction from each transaction ! * holding a predicate lock on the table. ! */ ! CheckTableForSerializableConflictIn(rel); ! ! /* ! * Need the full transaction-safe pushups. ! * ! * Create a new empty storage file for the relation, and assign it ! * as the relfilenode value. The old storage file is scheduled for ! * deletion at commit. ! */ ! RelationSetNewRelfilenode(rel, RecentXmin); ! ! heap_relid = RelationGetRelid(rel); ! toast_relid = rel->rd_rel->reltoastrelid; ! ! /* ! * The same for the toast table, if any. ! */ ! if (OidIsValid(toast_relid)) ! { ! rel = relation_open(toast_relid, AccessExclusiveLock); ! RelationSetNewRelfilenode(rel, RecentXmin); ! heap_close(rel, NoLock); ! } ! ! /* ! * Reconstruct the indexes to match, and we're done. ! */ ! reindex_relation(heap_relid, REINDEX_REL_PROCESS_TOAST); } } --- 1053,1059 ---- } else { ! truncate_relation(rel); } } *************** AtEOSubXact_on_commit_actions(bool isCom *** 9752,9754 **** --- 9716,9759 ---- } } } + + void truncate_relation(Relation rel) + { + Oid heap_relid; + Oid toast_relid; + + /* + * This effectively deletes all rows in the table, and may be done + * in a serializable transaction. In that case we must record a + * rw-conflict in to this transaction from each transaction + * holding a predicate lock on the table. + */ + CheckTableForSerializableConflictIn(rel); + + /* + * Need the full transaction-safe pushups. + * + * Create a new empty storage file for the relation, and assign it + * as the relfilenode value. The old storage file is scheduled for + * deletion at commit. + */ + RelationSetNewRelfilenode(rel, RecentXmin); + + heap_relid = RelationGetRelid(rel); + toast_relid = rel->rd_rel->reltoastrelid; + + /* + * The same for the toast table, if any. + */ + if (OidIsValid(toast_relid)) + { + rel = relation_open(toast_relid, AccessExclusiveLock); + RelationSetNewRelfilenode(rel, RecentXmin); + heap_close(rel, NoLock); + } + + /* + * Reconstruct the indexes to match, and we're done. + */ + reindex_relation(heap_relid, REINDEX_REL_PROCESS_TOAST); + } diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y index e9f3896..354cc3f 100644 *** a/src/backend/parser/gram.y --- b/src/backend/parser/gram.y *************** static void processCASbits(int cas_bits, *** 553,560 **** SAVEPOINT SCHEMA SCROLL SEARCH SECOND_P SECURITY SELECT SEQUENCE SEQUENCES SERIALIZABLE SERVER SESSION SESSION_USER SET SETOF SHARE ! SHOW SIMILAR SIMPLE SMALLINT SOME STABLE STANDALONE_P START STATEMENT ! STATISTICS STDIN STDOUT STORAGE STRICT_P STRIP_P SUBSTRING SYMMETRIC SYSID SYSTEM_P TABLE TABLES TABLESPACE TEMP TEMPLATE TEMPORARY TEXT_P THEN TIME TIMESTAMP --- 553,560 ---- SAVEPOINT SCHEMA SCROLL SEARCH SECOND_P SECURITY SELECT SEQUENCE SEQUENCES SERIALIZABLE SERVER SESSION SESSION_USER SET SETOF SHARE ! SHOW SIMILAR SIMPLE SKIP_WAL SMALLINT SOME STABLE STANDALONE_P ! START STATEMENT STATISTICS STDIN STDOUT STORAGE STRICT_P STRIP_P SUBSTRING SYMMETRIC SYSID SYSTEM_P TABLE TABLES TABLESPACE TEMP TEMPLATE TEMPORARY TEXT_P THEN TIME TIMESTAMP *************** copy_opt_item: *** 2297,2302 **** --- 2297,2306 ---- { $$ = makeDefElem("encoding", (Node *)makeString($2)); } + | SKIP_WAL + { + $$ = makeDefElem("skip_wal", (Node *)makeString("skip_wal")); + } ; /* The following exist for backward compatibility with very old versions */ diff --git a/src/include/commands/tablecmds.h b/src/include/commands/tablecmds.h index 0e8bbe0..5627c70 100644 *** a/src/include/commands/tablecmds.h --- b/src/include/commands/tablecmds.h *************** extern void AtEOXact_on_commit_actions(b *** 71,75 **** extern void AtEOSubXact_on_commit_actions(bool isCommit, SubTransactionId mySubid, SubTransactionId parentSubid); ! #endif /* TABLECMDS_H */ --- 71,75 ---- extern void AtEOSubXact_on_commit_actions(bool isCommit, SubTransactionId mySubid, SubTransactionId parentSubid); ! extern void truncate_relation(Relation rel); #endif /* TABLECMDS_H */ diff --git a/src/test/regress/expected/copy2.out b/src/test/regress/expected/copy2.out index 8e2bc0c..d4915e7 100644 *** a/src/test/regress/expected/copy2.out --- b/src/test/regress/expected/copy2.out *************** a\. *** 239,244 **** --- 239,285 ---- \.b c\.d "\." + -- test SKIP_WAL option + BEGIN; + CREATE TABLE test_notemp ( + a int4); + COMMIT; + select pg_relation_size(oid) from pg_class where relname='test_notemp'; + pg_relation_size + ------------------ + 0 + (1 row) + + COPY test_notemp FROM stdin WITH (skip_wal); + COPY test_notemp FROM stdin WITH (skip_wal); + select pg_relation_size(oid) from pg_class where relname='test_notemp'; + pg_relation_size + ------------------ + 8192 + (1 row) + + truncate test_notemp; + BEGIN; + COPY test_notemp FROM stdin WITH (skip_wal); + ROLLBACK; + --expect size of 0 + select pg_relation_size(oid) from pg_class where relname='test_notemp'; + pg_relation_size + ------------------ + 0 + (1 row) + + BEGIN; + COPY test_notemp FROM stdin csv; + ROLLBACK; + --expect non-zero size + select pg_relation_size(oid) from pg_class where relname='test_notemp'; + pg_relation_size + ------------------ + 8192 + (1 row) + + DROP TABLE test_notemp; DROP TABLE x, y; DROP FUNCTION fn_x_before(); DROP FUNCTION fn_x_after(); diff --git a/src/test/regress/sql/copy2.sql b/src/test/regress/sql/copy2.sql index 6322c8f..e41a9d8 100644 *** a/src/test/regress/sql/copy2.sql --- b/src/test/regress/sql/copy2.sql *************** c\.d *** 164,169 **** --- 164,206 ---- COPY testeoc TO stdout CSV; + -- test SKIP_WAL option + + BEGIN; + CREATE TABLE test_notemp ( + a int4); + COMMIT; + select pg_relation_size(oid) from pg_class where relname='test_notemp'; + COPY test_notemp FROM stdin WITH (skip_wal); + 1 + 2 + \. + COPY test_notemp FROM stdin WITH (skip_wal); + 1 + 2 + \. + select pg_relation_size(oid) from pg_class where relname='test_notemp'; + truncate test_notemp; + BEGIN; + COPY test_notemp FROM stdin WITH (skip_wal); + 1 + 2 + \. + ROLLBACK; + --expect size of 0 + select pg_relation_size(oid) from pg_class where relname='test_notemp'; + + BEGIN; + COPY test_notemp FROM stdin csv; + 1 + 2 + \. + ROLLBACK; + --expect non-zero size + select pg_relation_size(oid) from pg_class where relname='test_notemp'; + DROP TABLE test_notemp; + + DROP TABLE x, y; DROP FUNCTION fn_x_before(); DROP FUNCTION fn_x_after();