AUTOCOMMIT mode is now an available backend GUC variable; setting it

to false provides more SQL-spec-compliant behavior than we had before.
I am not sure that setting it false is actually a good idea yet; there
is a lot of client-side code that will probably be broken by turning
autocommit off.  But it's a start.

Loosely based on a patch by David Van Wie.

Author: tglsfdc

doc/src/sgml/release.sgml

@@ -1,5 +1,5 @@
 <!--
-$Header: /cvsroot/pgsql/doc/src/sgml/release.sgml,v 1.155 2002/08/30 00:28:40 tgl Exp $
+$Header: /cvsroot/pgsql/doc/src/sgml/release.sgml,v 1.156 2002/08/30 22:18:05 tgl Exp $
 -->
 
 <appendix id="release">
@@ -24,6 +24,7 @@ CDATA means the content is "SGML-free", so you can write without
 worries about funny characters.
 -->
 <literallayout><![CDATA[
+No-autocommit mode is available (set autocommit to off)
 Substantial improvements in functionality for functions returning sets
 Client libraries older than 6.3 no longer supported (version 0 protocol removed)
 PREPARE statement allows caching query plans for interactive statements

doc/src/sgml/runtime.sgml

@@ -1,5 +1,5 @@
 <!--
-$Header: /cvsroot/pgsql/doc/src/sgml/runtime.sgml,v 1.130 2002/08/30 16:50:49 momjian Exp $
+$Header: /cvsroot/pgsql/doc/src/sgml/runtime.sgml,v 1.131 2002/08/30 22:18:05 tgl Exp $
 -->
 
 <Chapter Id="runtime">
@@ -1135,6 +1135,29 @@ env PGOPTIONS='-c geqo=off' psql
 
    <para>
     <variablelist>
+     <varlistentry>
+      <term><varname>AUTOCOMMIT</varname> (<type>bool</type>)</term>
+      <indexterm><primary>autocommit</></>
+      <listitem>
+       <para>
+        If set to true, <productname>PostgreSQL</productname> will
+	automatically do a <command>COMMIT</> after each successful command
+	that is not inside an explicit transaction block (that is, unless a
+	<command>BEGIN</> with no matching <command>COMMIT</> has been
+	given).
+	If set to false, <productname>PostgreSQL</productname> will commit
+	the effects of commands only on receiving an explicit
+	<command>COMMIT</> command.  This mode can also be thought of as
+	implicitly issuing <command>BEGIN</> whenever a command is received
+	and <productname>PostgreSQL</productname> is not already inside
+	a transaction block.
+	The default is true, for compatibility with historical
+	<productname>PostgreSQL</productname> behavior.  But for maximum
+	compatibility with the SQL specification, set it to false.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry>
       <term><varname>AUSTRALIAN_TIMEZONES</varname> (<type>bool</type>)</term>
       <indexterm><primary>Australian time zones</></>

src/backend/access/transam/xact.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/access/transam/xact.c,v 1.130 2002/08/06 02:36:33 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/access/transam/xact.c,v 1.131 2002/08/30 22:18:05 tgl Exp $
  *
  * NOTES
  *		Transaction aborts can now occur two ways:
@@ -220,10 +220,15 @@ TransactionState CurrentTransactionState = &CurrentTransactionStateData;
 int			DefaultXactIsoLevel = XACT_READ_COMMITTED;
 int			XactIsoLevel;
 
+bool		autocommit = true;
+
 int			CommitDelay = 0;	/* precommit delay in microseconds */
 int			CommitSiblings = 5; /* number of concurrent xacts needed to
 								 * sleep */
 
+
+static bool suppressChain = false;
+
 static void (*_RollbackFunc) (void *) = NULL;
 static void *_RollbackData = NULL;
 
@@ -1149,13 +1154,24 @@ CleanupTransaction(void)
 
 /* --------------------------------
  *		StartTransactionCommand
+ *
+ * preventChain, if true, forces autocommit behavior at the next
+ * CommitTransactionCommand call.
  * --------------------------------
  */
 void
-StartTransactionCommand(void)
+StartTransactionCommand(bool preventChain)
 {
 	TransactionState s = CurrentTransactionState;
 
+	/*
+	 * Remember if caller wants to prevent autocommit-off chaining.
+	 * This is only allowed if not already in a transaction block.
+	 */
+	suppressChain = preventChain;
+	if (preventChain && s->blockState != TBLOCK_DEFAULT)
+		elog(ERROR, "StartTransactionCommand: can't prevent chain");
+
 	switch (s->blockState)
 	{
 			/*
@@ -1231,21 +1247,41 @@ StartTransactionCommand(void)
 
 /* --------------------------------
  *		CommitTransactionCommand
+ *
+ * forceCommit = true forces autocommit behavior even when autocommit is off.
  * --------------------------------
  */
 void
-CommitTransactionCommand(void)
+CommitTransactionCommand(bool forceCommit)
 {
 	TransactionState s = CurrentTransactionState;
 
 	switch (s->blockState)
 	{
 			/*
-			 * if we aren't in a transaction block, we just do our usual
-			 * transaction commit
+			 * If we aren't in a transaction block, and we are doing
+			 * autocommit, just do our usual transaction commit.  But
+			 * if we aren't doing autocommit, start a transaction block
+			 * automatically by switching to INPROGRESS state.  (We handle
+			 * this choice here, and not earlier, so that an explicit BEGIN
+			 * issued in autocommit-off mode won't issue strange warnings.)
+			 *
+			 * Autocommit mode is forced by either a true forceCommit parameter
+			 * to me, or a true preventChain parameter to the preceding
+			 * StartTransactionCommand call.  This is needed so that commands
+			 * like VACUUM can ensure that the right things happen.
 			 */
 		case TBLOCK_DEFAULT:
-			CommitTransaction();
+			if (autocommit || forceCommit || suppressChain)
+				CommitTransaction();
+			else
+			{
+				BeginTransactionBlock();
+				Assert(s->blockState == TBLOCK_INPROGRESS);
+				/* This code must match the TBLOCK_INPROGRESS case below: */
+				CommandCounterIncrement();
+				MemoryContextResetAndDeleteChildren(TransactionCommandContext);
+			}
 			break;
 
 			/*
@@ -1406,7 +1442,10 @@ BeginTransactionBlock(void)
 	s->blockState = TBLOCK_BEGIN;
 
 	/*
-	 * do begin processing
+	 * do begin processing.  NOTE: if you put anything here, check that
+	 * it behaves properly in both autocommit-on and autocommit-off modes.
+	 * In the latter case we will already have done some work in the new
+	 * transaction.
 	 */
 
 	/*

src/backend/bootstrap/bootparse.y

@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/bootstrap/bootparse.y,v 1.50 2002/07/20 05:16:56 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/bootstrap/bootparse.y,v 1.51 2002/08/30 22:18:05 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -55,15 +55,15 @@
 static void
 do_start()
 {
-	StartTransactionCommand();
+	StartTransactionCommand(true);
 	elog(DEBUG3, "start transaction");
 }
 
 
 static void
 do_end()
 {
-	CommitTransactionCommand();
+	CommitTransactionCommand(true);
 	elog(DEBUG3, "commit transaction");
 	if (isatty(0))
 	{

src/backend/bootstrap/bootstrap.c

@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/bootstrap/bootstrap.c,v 1.138 2002/08/17 15:12:06 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/bootstrap/bootstrap.c,v 1.139 2002/08/30 22:18:05 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -448,7 +448,7 @@ BootstrapMain(int argc, char *argv[])
 	SetProcessingMode(BootstrapProcessing);
 
 	/* clean up processing */
-	StartTransactionCommand();
+	StartTransactionCommand(true);
 	cleanup();
 
 	/* not reached, here to make compiler happy */
@@ -821,7 +821,7 @@ cleanup()
 	}
 	if (boot_reldesc != NULL)
 		closerel(NULL);
-	CommitTransactionCommand();
+	CommitTransactionCommand(true);
 	proc_exit(Warnings);
 }
 

src/backend/catalog/namespace.c

@@ -13,7 +13,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/catalog/namespace.c,v 1.32 2002/08/29 00:17:02 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/catalog/namespace.c,v 1.33 2002/08/30 22:18:05 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1610,11 +1610,11 @@ RemoveTempRelationsCallback(void)
 	{
 		/* Need to ensure we have a usable transaction. */
 		AbortOutOfAnyTransaction();
-		StartTransactionCommand();
+		StartTransactionCommand(true);
 
 		RemoveTempRelations(myTempNamespace);
 
-		CommitTransactionCommand();
+		CommitTransactionCommand(true);
 	}
 }
 

src/backend/commands/async.c

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/commands/async.c,v 1.88 2002/08/05 03:29:16 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/async.c,v 1.89 2002/08/30 22:18:05 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -400,9 +400,9 @@ Async_UnlistenOnExit(void)
 	 */
 	AbortOutOfAnyTransaction();
 	/* Now we can do the unlisten */
-	StartTransactionCommand();
+	StartTransactionCommand(true);
 	Async_UnlistenAll();
-	CommitTransactionCommand();
+	CommitTransactionCommand(true);
 }
 
 /*
@@ -749,7 +749,7 @@ ProcessIncomingNotify(void)
 
 	notifyInterruptOccurred = 0;
 
-	StartTransactionCommand();
+	StartTransactionCommand(true);
 
 	lRel = heap_openr(ListenerRelationName, AccessExclusiveLock);
 	tdesc = RelationGetDescr(lRel);
@@ -803,7 +803,7 @@ ProcessIncomingNotify(void)
 	 */
 	heap_close(lRel, NoLock);
 
-	CommitTransactionCommand();
+	CommitTransactionCommand(true);
 
 	/*
 	 * Must flush the notify messages to ensure frontend gets them

src/backend/commands/indexcmds.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/commands/indexcmds.c,v 1.85 2002/08/29 15:56:20 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/indexcmds.c,v 1.86 2002/08/30 22:18:05 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -735,15 +735,16 @@ ReindexDatabase(const char *dbname, bool force, bool all)
 	heap_close(relationRelation, AccessShareLock);
 
 	/* Now reindex each rel in a separate transaction */
-	CommitTransactionCommand();
+	CommitTransactionCommand(true);
 	for (i = 0; i < relcnt; i++)
 	{
-		StartTransactionCommand();
+		StartTransactionCommand(true);
 		if (reindex_relation(relids[i], force))
 			elog(NOTICE, "relation %u was reindexed", relids[i]);
-		CommitTransactionCommand();
+		CommitTransactionCommand(true);
 	}
-	StartTransactionCommand();
+	/* Tell xact.c not to chain the upcoming commit */
+	StartTransactionCommand(true);
 
 	MemoryContextDelete(private_context);
 }