Global tables with local buffers

Author: knizhnik

src/backend/access/gist/gistutil.c

@@ -1028,7 +1028,8 @@ gistGetFakeLSN(Relation rel)
 {
 	static XLogRecPtr counter = FirstNormalUnloggedLSN;
 
-	if (rel->rd_rel->relpersistence == RELPERSISTENCE_TEMP)
+	if (rel->rd_rel->relpersistence == RELPERSISTENCE_TEMP ||
+		rel->rd_rel->relpersistence == RELPERSISTENCE_SESSION)
 	{
 		/*
 		 * Temporary relations are only accessible in our session, so a simple

src/backend/access/heap/heapam_handler.c

@@ -673,6 +673,7 @@ heapam_relation_copy_data(Relation rel, const RelFileNode *newrnode)
 			 * init fork of an unlogged relation.
 			 */
 			if (rel->rd_rel->relpersistence == RELPERSISTENCE_PERMANENT ||
+				rel->rd_rel->relpersistence == RELPERSISTENCE_SESSION ||
 				(rel->rd_rel->relpersistence == RELPERSISTENCE_UNLOGGED &&
 				 forkNum == INIT_FORKNUM))
 				log_smgrcreate(newrnode, forkNum);

src/backend/access/nbtree/nbtpage.c

@@ -763,7 +763,11 @@ _bt_getbuf(Relation rel, BlockNumber blkno, int access)
 		/* Read an existing block of the relation */
 		buf = ReadBuffer(rel, blkno);
 		LockBuffer(buf, access);
-		_bt_checkpage(rel, buf);
+		/* Session temporary relation may be not yet initialized for this backend. */
+		if (blkno == BTREE_METAPAGE && PageIsNew(BufferGetPage(buf)) && IsSessionRelationBackendId(rel->rd_backend))
+			_bt_initmetapage(BufferGetPage(buf), P_NONE, 0);
+		else
+			_bt_checkpage(rel, buf);
 	}
 	else
 	{

src/backend/catalog/catalog.c

@@ -409,6 +409,9 @@ GetNewRelFileNode(Oid reltablespace, Relation pg_class, char relpersistence)
 		case RELPERSISTENCE_TEMP:
 			backend = BackendIdForTempRelations();
 			break;
+		case RELPERSISTENCE_SESSION:
+			backend = BackendIdForSessionRelations();
+			break;
 		case RELPERSISTENCE_UNLOGGED:
 		case RELPERSISTENCE_PERMANENT:
 			backend = InvalidBackendId;

src/backend/catalog/index.c

@@ -3590,7 +3590,7 @@ reindex_relation(Oid relid, int flags, int options)
 		if (flags & REINDEX_REL_FORCE_INDEXES_UNLOGGED)
 			persistence = RELPERSISTENCE_UNLOGGED;
 		else if (flags & REINDEX_REL_FORCE_INDEXES_PERMANENT)
-			persistence = RELPERSISTENCE_PERMANENT;
+			persistence = rel->rd_rel->relpersistence == RELPERSISTENCE_SESSION ? RELPERSISTENCE_SESSION : RELPERSISTENCE_PERMANENT;
 		else
 			persistence = rel->rd_rel->relpersistence;
 

src/backend/catalog/storage.c

@@ -93,6 +93,10 @@ RelationCreateStorage(RelFileNode rnode, char relpersistence)
 			backend = InvalidBackendId;
 			needs_wal = false;
 			break;
+		case RELPERSISTENCE_SESSION:
+			backend = BackendIdForSessionRelations();
+			needs_wal = false;
+			break;
 		case RELPERSISTENCE_PERMANENT:
 			backend = InvalidBackendId;
 			needs_wal = true;

src/backend/commands/cluster.c

@@ -1400,7 +1400,7 @@ finish_heap_swap(Oid OIDOldHeap, Oid OIDNewHeap,
 	 */
 	if (newrelpersistence == RELPERSISTENCE_UNLOGGED)
 		reindex_flags |= REINDEX_REL_FORCE_INDEXES_UNLOGGED;
-	else if (newrelpersistence == RELPERSISTENCE_PERMANENT)
+	else if (newrelpersistence != RELPERSISTENCE_TEMP)
 		reindex_flags |= REINDEX_REL_FORCE_INDEXES_PERMANENT;
 
 	/* Report that we are now reindexing relations */

src/backend/commands/sequence.c

@@ -94,7 +94,7 @@ static HTAB *seqhashtab = NULL; /* hash table for SeqTable items */
  */
 static SeqTableData *last_used_seq = NULL;
 
-static void fill_seq_with_data(Relation rel, HeapTuple tuple);
+static void fill_seq_with_data(Relation rel, HeapTuple tuple, Buffer buf);
 static Relation lock_and_open_sequence(SeqTable seq);
 static void create_seq_hashtable(void);
 static void init_sequence(Oid relid, SeqTable *p_elm, Relation *p_rel);
@@ -222,7 +222,7 @@ DefineSequence(ParseState *pstate, CreateSeqStmt *seq)
 
 	/* now initialize the sequence's data */
 	tuple = heap_form_tuple(tupDesc, value, null);
-	fill_seq_with_data(rel, tuple);
+	fill_seq_with_data(rel, tuple, InvalidBuffer);
 
 	/* process OWNED BY if given */
 	if (owned_by)
@@ -327,7 +327,7 @@ ResetSequence(Oid seq_relid)
 	/*
 	 * Insert the modified tuple into the new storage file.
 	 */
-	fill_seq_with_data(seq_rel, tuple);
+	fill_seq_with_data(seq_rel, tuple, InvalidBuffer);
 
 	/* Clear local cache so that we don't think we have cached numbers */
 	/* Note that we do not change the currval() state */
@@ -340,18 +340,21 @@ ResetSequence(Oid seq_relid)
  * Initialize a sequence's relation with the specified tuple as content
  */
 static void
-fill_seq_with_data(Relation rel, HeapTuple tuple)
+fill_seq_with_data(Relation rel, HeapTuple tuple, Buffer buf)
 {
-	Buffer		buf;
 	Page		page;
 	sequence_magic *sm;
 	OffsetNumber offnum;
+	bool lockBuffer = false;
 
 	/* Initialize first page of relation with special magic number */
 
-	buf = ReadBuffer(rel, P_NEW);
-	Assert(BufferGetBlockNumber(buf) == 0);
-
+	if (buf == InvalidBuffer)
+	{
+		buf = ReadBuffer(rel, P_NEW);
+		Assert(BufferGetBlockNumber(buf) == 0);
+		lockBuffer = true;
+	}
 	page = BufferGetPage(buf);
 
 	PageInit(page, BufferGetPageSize(buf), sizeof(sequence_magic));
@@ -360,7 +363,8 @@ fill_seq_with_data(Relation rel, HeapTuple tuple)
 
 	/* Now insert sequence tuple */
 
-	LockBuffer(buf, BUFFER_LOCK_EXCLUSIVE);
+	if (lockBuffer)
+		LockBuffer(buf, BUFFER_LOCK_EXCLUSIVE);
 
 	/*
 	 * Since VACUUM does not process sequences, we have to force the tuple to
@@ -410,7 +414,8 @@ fill_seq_with_data(Relation rel, HeapTuple tuple)
 
 	END_CRIT_SECTION();
 
-	UnlockReleaseBuffer(buf);
+	if (lockBuffer)
+		UnlockReleaseBuffer(buf);
 }
 
 /*
@@ -502,7 +507,7 @@ AlterSequence(ParseState *pstate, AlterSeqStmt *stmt)
 		/*
 		 * Insert the modified tuple into the new storage file.
 		 */
-		fill_seq_with_data(seqrel, newdatatuple);
+		fill_seq_with_data(seqrel, newdatatuple, InvalidBuffer);
 	}
 
 	/* process OWNED BY if given */
@@ -1178,6 +1183,16 @@ read_seq_tuple(Relation rel, Buffer *buf, HeapTuple seqdatatuple)
 	LockBuffer(*buf, BUFFER_LOCK_EXCLUSIVE);
 
 	page = BufferGetPage(*buf);
+	if (rel->rd_rel->relpersistence == RELPERSISTENCE_SESSION && PageIsNew(page))
+	{
+		/* Initialize sequence for global temporary tables */
+		Datum		value[SEQ_COL_LASTCOL] = {0};
+		bool		null[SEQ_COL_LASTCOL] = {false};
+		value[SEQ_COL_LASTVAL-1] = Int64GetDatumFast(1); /* start sequence with 1 */
+		HeapTuple tuple = heap_form_tuple(RelationGetDescr(rel), value, null);
+		fill_seq_with_data(rel, tuple, *buf);
+	}
+
 	sm = (sequence_magic *) PageGetSpecialPointer(page);
 
 	if (sm->magic != SEQ_MAGIC)

src/backend/commands/tablecmds.c

@@ -586,7 +586,8 @@ DefineRelation(CreateStmt *stmt, char relkind, Oid ownerId,
 	 * Check consistency of arguments
 	 */
 	if (stmt->oncommit != ONCOMMIT_NOOP
-		&& stmt->relation->relpersistence != RELPERSISTENCE_TEMP)
+		&& stmt->relation->relpersistence != RELPERSISTENCE_TEMP
+		&& stmt->relation->relpersistence != RELPERSISTENCE_SESSION)
 		ereport(ERROR,
 				(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
 				 errmsg("ON COMMIT can only be used on temporary tables")));
@@ -7678,6 +7679,12 @@ ATAddForeignKeyConstraint(List **wqueue, AlteredTableInfo *tab, Relation rel,
 						(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
 						 errmsg("constraints on unlogged tables may reference only permanent or unlogged tables")));
 			break;
+		case RELPERSISTENCE_SESSION:
+			if (pkrel->rd_rel->relpersistence != RELPERSISTENCE_SESSION)
+				ereport(ERROR,
+						(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
+						 errmsg("constraints on session tables may reference only session tables")));
+			break;
 		case RELPERSISTENCE_TEMP:
 			if (pkrel->rd_rel->relpersistence != RELPERSISTENCE_TEMP)
 				ereport(ERROR,
@@ -14082,6 +14089,13 @@ ATPrepChangePersistence(Relation rel, bool toLogged)
 							RelationGetRelationName(rel)),
 					 errtable(rel)));
 			break;
+		case RELPERSISTENCE_SESSION:
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
+					 errmsg("cannot change logged status of session table \"%s\"",
+							RelationGetRelationName(rel)),
+					 errtable(rel)));
+			break;
 		case RELPERSISTENCE_PERMANENT:
 			if (toLogged)
 				/* nothing to do */
@@ -14569,14 +14583,7 @@ PreCommit_on_commit_actions(void)
 				/* Do nothing (there shouldn't be such entries, actually) */
 				break;
 			case ONCOMMIT_DELETE_ROWS:
-
-				/*
-				 * If this transaction hasn't accessed any temporary
-				 * relations, we can skip truncating ON COMMIT DELETE ROWS
-				 * tables, as they must still be empty.
-				 */
-				if ((MyXactFlags & XACT_FLAGS_ACCESSEDTEMPNAMESPACE))
-					oids_to_truncate = lappend_oid(oids_to_truncate, oc->relid);
+				oids_to_truncate = lappend_oid(oids_to_truncate, oc->relid);
 				break;
 			case ONCOMMIT_DROP:
 				oids_to_drop = lappend_oid(oids_to_drop, oc->relid);

src/backend/parser/gram.y

@@ -3265,20 +3265,11 @@ OptTemp:	TEMPORARY					{ $$ = RELPERSISTENCE_TEMP; }
 			| TEMP						{ $$ = RELPERSISTENCE_TEMP; }
 			| LOCAL TEMPORARY			{ $$ = RELPERSISTENCE_TEMP; }
 			| LOCAL TEMP				{ $$ = RELPERSISTENCE_TEMP; }
-			| GLOBAL TEMPORARY
-				{
-					ereport(WARNING,
-							(errmsg("GLOBAL is deprecated in temporary table creation"),
-							 parser_errposition(@1)));
-					$$ = RELPERSISTENCE_TEMP;
-				}
-			| GLOBAL TEMP
-				{
-					ereport(WARNING,
-							(errmsg("GLOBAL is deprecated in temporary table creation"),
-							 parser_errposition(@1)));
-					$$ = RELPERSISTENCE_TEMP;
-				}
+			| GLOBAL TEMPORARY          { $$ = RELPERSISTENCE_SESSION; }
+			| GLOBAL TEMP               { $$ = RELPERSISTENCE_SESSION; }
+			| SESSION                   { $$ = RELPERSISTENCE_SESSION; }
+			| SESSION TEMPORARY         { $$ = RELPERSISTENCE_SESSION; }
+			| SESSION TEMP              { $$ = RELPERSISTENCE_SESSION; }
 			| UNLOGGED					{ $$ = RELPERSISTENCE_UNLOGGED; }
 			| /*EMPTY*/					{ $$ = RELPERSISTENCE_PERMANENT; }
 		;

src/backend/parser/parse_utilcmd.c

@@ -436,6 +436,14 @@ generateSerialExtraStmts(CreateStmtContext *cxt, ColumnDef *column,
 	seqstmt->sequence = makeRangeVar(snamespace, sname, -1);
 	seqstmt->options = seqoptions;
 
+	/*
+	 * Why we should not always use persistence of parent table?
+	 * Although it is prohibited to have unlogged sequences,
+	 * unlogged tables with SERIAL fields are accepted!
+	 */
+	if (cxt->relation->relpersistence != RELPERSISTENCE_UNLOGGED)
+		seqstmt->sequence->relpersistence = cxt->relation->relpersistence;
+
 	/*
 	 * If a sequence data type was specified, add it to the options.  Prepend
 	 * to the list rather than append; in case a user supplied their own AS

src/backend/postmaster/autovacuum.c

@@ -2069,7 +2069,8 @@ do_autovacuum(void)
 		 * Check if it is a temp table (presumably, of some other backend's).
 		 * We cannot safely process other backends' temp tables.
 		 */
-		if (classForm->relpersistence == RELPERSISTENCE_TEMP)
+		if (classForm->relpersistence == RELPERSISTENCE_TEMP ||
+			classForm->relpersistence == RELPERSISTENCE_SESSION)
 		{
 			/*
 			 * We just ignore it if the owning backend is still active and
@@ -2154,7 +2155,8 @@ do_autovacuum(void)
 		/*
 		 * We cannot safely process other backends' temp tables, so skip 'em.
 		 */
-		if (classForm->relpersistence == RELPERSISTENCE_TEMP)
+		if (classForm->relpersistence == RELPERSISTENCE_TEMP ||
+			classForm->relpersistence == RELPERSISTENCE_SESSION)
 			continue;
 
 		relid = classForm->oid;