Revert "Skip WAL for new relfilenodes, under wal_level=minimal."

This reverts commit cb2fd7eac2.  Per
numerous buildfarm members, it was incompatible with parallel query, and
a test case assumed LP64.  Back-patch to 9.5 (all supported versions).

Discussion: https://postgr.es/m/20200321224920.GB1763544@rfd.leadboat.com

src/backend/commands/cluster.c

@@ -1111,25 +1111,6 @@ swap_relation_files(Oid r1, Oid r2, bool target_is_pg_class,
 		*mapped_tables++ = r2;
 	}
 
-	/*
-	 * Recognize that rel1's relfilenode (swapped from rel2) is new in this
-	 * subtransaction. The rel2 storage (swapped from rel1) may or may not be
-	 * new.
-	 */
-	{
-		Relation	rel1,
-					rel2;
-
-		rel1 = relation_open(r1, NoLock);
-		rel2 = relation_open(r2, NoLock);
-		rel2->rd_createSubid = rel1->rd_createSubid;
-		rel2->rd_newRelfilenodeSubid = rel1->rd_newRelfilenodeSubid;
-		rel2->rd_firstRelfilenodeSubid = rel1->rd_firstRelfilenodeSubid;
-		RelationAssumeNewRelfilenode(rel1);
-		relation_close(rel1, NoLock);
-		relation_close(rel2, NoLock);
-	}
-
 	/*
 	 * In the case of a shared catalog, these next few steps will only affect
 	 * our own database's pg_class row; but that's okay, because they are all

src/backend/commands/copy.c

@@ -2715,15 +2715,63 @@ CopyFrom(CopyState cstate)
 							RelationGetRelationName(cstate->rel))));
 	}
 
-	/*
-	 * If the target file is new-in-transaction, we assume that checking FSM
-	 * for free space is a waste of time.  This could possibly be wrong, but
-	 * it's unlikely.
+	/*----------
+	 * Check to see if we can avoid writing WAL
+	 *
+	 * If archive logging/streaming is not enabled *and* either
+	 *	- table was created in same transaction as this COPY
+	 *	- data is being written to relfilenode created in this transaction
+	 * then we can skip writing WAL.  It's safe because if the transaction
+	 * doesn't commit, we'll discard the table (or the new relfilenode file).
+	 * If it does commit, we'll have done the table_finish_bulk_insert() at
+	 * the bottom of this routine first.
+	 *
+	 * As mentioned in comments in utils/rel.h, the in-same-transaction test
+	 * is not always set correctly, since in rare cases rd_newRelfilenodeSubid
+	 * can be cleared before the end of the transaction. The exact case is
+	 * when a relation sets a new relfilenode twice in same transaction, yet
+	 * the second one fails in an aborted subtransaction, e.g.
+	 *
+	 * BEGIN;
+	 * TRUNCATE t;
+	 * SAVEPOINT save;
+	 * TRUNCATE t;
+	 * ROLLBACK TO save;
+	 * COPY ...
+	 *
+	 * Also, if the target file is new-in-transaction, we assume that checking
+	 * FSM for free space is a waste of time, even if we must use WAL because
+	 * of archiving.  This could possibly be wrong, but it's unlikely.
+	 *
+	 * The comments for table_tuple_insert and RelationGetBufferForTuple
+	 * specify that skipping WAL logging is only safe if we ensure that our
+	 * tuples do not go into pages containing tuples from any other
+	 * transactions --- but this must be the case if we have a new table or
+	 * new relfilenode, so we need no additional work to enforce that.
+	 *
+	 * We currently don't support this optimization if the COPY target is a
+	 * partitioned table as we currently only lazily initialize partition
+	 * information when routing the first tuple to the partition.  We cannot
+	 * know at this stage if we can perform this optimization.  It should be
+	 * possible to improve on this, but it does mean maintaining heap insert
+	 * option flags per partition and setting them when we first open the
+	 * partition.
+	 *
+	 * This optimization is not supported for relation types which do not
+	 * have any physical storage, with foreign tables and views using
+	 * INSTEAD OF triggers entering in this category.  Partitioned tables
+	 * are not supported as per the description above.
+	 *----------
 	 */
+	/* createSubid is creation check, newRelfilenodeSubid is truncation check */
 	if (RELKIND_HAS_STORAGE(cstate->rel->rd_rel->relkind) &&
 		(cstate->rel->rd_createSubid != InvalidSubTransactionId ||
-		 cstate->rel->rd_firstRelfilenodeSubid != InvalidSubTransactionId))
+		 cstate->rel->rd_newRelfilenodeSubid != InvalidSubTransactionId))
+	{
 		ti_options |= TABLE_INSERT_SKIP_FSM;
+		if (!XLogIsNeeded())
+			ti_options |= TABLE_INSERT_SKIP_WAL;
+	}
 
 	/*
 	 * Optimize if new relfilenode was created in this subxact or one of its

src/backend/commands/createas.c

@@ -553,13 +553,16 @@ intorel_startup(DestReceiver *self, int operation, TupleDesc typeinfo)
 	myState->rel = intoRelationDesc;
 	myState->reladdr = intoRelationAddr;
 	myState->output_cid = GetCurrentCommandId(true);
-	myState->ti_options = TABLE_INSERT_SKIP_FSM;
-	myState->bistate = GetBulkInsertState();
 
 	/*
-	 * Valid smgr_targblock implies something already wrote to the relation.
-	 * This may be harmless, but this function hasn't planned for it.
+	 * We can skip WAL-logging the insertions, unless PITR or streaming
+	 * replication is in use. We can skip the FSM in any case.
 	 */
+	myState->ti_options = TABLE_INSERT_SKIP_FSM |
+		(XLogIsNeeded() ? 0 : TABLE_INSERT_SKIP_WAL);
+	myState->bistate = GetBulkInsertState();
+
+	/* Not using WAL requires smgr_targblock be initially invalid */
 	Assert(RelationGetTargetBlock(intoRelationDesc) == InvalidBlockNumber);
 }
 

src/backend/commands/indexcmds.c

@@ -1195,8 +1195,6 @@ DefineIndex(Oid relationId,
 					childStmt->relation = NULL;
 					childStmt->indexOid = InvalidOid;
 					childStmt->oldNode = InvalidOid;
-					childStmt->oldCreateSubid = InvalidSubTransactionId;
-					childStmt->oldFirstRelfilenodeSubid = InvalidSubTransactionId;
 
 					/*
 					 * Adjust any Vars (both in expressions and in the index's

src/backend/commands/matview.c

@@ -457,13 +457,17 @@ transientrel_startup(DestReceiver *self, int operation, TupleDesc typeinfo)
 	 */
 	myState->transientrel = transientrel;
 	myState->output_cid = GetCurrentCommandId(true);
-	myState->ti_options = TABLE_INSERT_SKIP_FSM | TABLE_INSERT_FROZEN;
-	myState->bistate = GetBulkInsertState();
 
 	/*
-	 * Valid smgr_targblock implies something already wrote to the relation.
-	 * This may be harmless, but this function hasn't planned for it.
+	 * We can skip WAL-logging the insertions, unless PITR or streaming
+	 * replication is in use. We can skip the FSM in any case.
 	 */
+	myState->ti_options = TABLE_INSERT_SKIP_FSM | TABLE_INSERT_FROZEN;
+	if (!XLogIsNeeded())
+		myState->ti_options |= TABLE_INSERT_SKIP_WAL;
+	myState->bistate = GetBulkInsertState();
+
+	/* Not using WAL requires smgr_targblock be initially invalid */
 	Assert(RelationGetTargetBlock(transientrel) == InvalidBlockNumber);
 }
 

src/backend/commands/tablecmds.c

@@ -4785,14 +4785,19 @@ ATRewriteTable(AlteredTableInfo *tab, Oid OIDNewHeap, LOCKMODE lockmode)
 		newrel = NULL;
 
 	/*
-	 * Prepare a BulkInsertState and options for table_tuple_insert.  The FSM
-	 * is empty, so don't bother using it.
+	 * Prepare a BulkInsertState and options for table_tuple_insert. Because
+	 * we're building a new heap, we can skip WAL-logging and fsync it to disk
+	 * at the end instead (unless WAL-logging is required for archiving or
+	 * streaming replication). The FSM is empty too, so don't bother using it.
 	 */
 	if (newrel)
 	{
 		mycid = GetCurrentCommandId(true);
 		bistate = GetBulkInsertState();
+
 		ti_options = TABLE_INSERT_SKIP_FSM;
+		if (!XLogIsNeeded())
+			ti_options |= TABLE_INSERT_SKIP_WAL;
 	}
 	else
 	{
@@ -7300,19 +7305,14 @@ ATExecAddIndex(AlteredTableInfo *tab, Relation rel,
 
 	/*
 	 * If TryReuseIndex() stashed a relfilenode for us, we used it for the new
-	 * index instead of building from scratch.  Restore associated fields.
-	 * This may store InvalidSubTransactionId in both fields, in which case
-	 * relcache.c will assume it can rebuild the relcache entry.  Hence, do
-	 * this after the CCI that made catalog rows visible to any rebuild.  The
-	 * DROP of the old edition of this index will have scheduled the storage
-	 * for deletion at commit, so cancel that pending deletion.
+	 * index instead of building from scratch.  The DROP of the old edition of
+	 * this index will have scheduled the storage for deletion at commit, so
+	 * cancel that pending deletion.
 	 */
 	if (OidIsValid(stmt->oldNode))
 	{
 		Relation	irel = index_open(address.objectId, NoLock);
 
-		irel->rd_createSubid = stmt->oldCreateSubid;
-		irel->rd_firstRelfilenodeSubid = stmt->oldFirstRelfilenodeSubid;
 		RelationPreserveStorage(irel->rd_node, true);
 		index_close(irel, NoLock);
 	}
@@ -11619,11 +11619,7 @@ TryReuseIndex(Oid oldId, IndexStmt *stmt)
 
 		/* If it's a partitioned index, there is no storage to share. */
 		if (irel->rd_rel->relkind != RELKIND_PARTITIONED_INDEX)
-		{
 			stmt->oldNode = irel->rd_node.relNode;
-			stmt->oldCreateSubid = irel->rd_createSubid;
-			stmt->oldFirstRelfilenodeSubid = irel->rd_firstRelfilenodeSubid;
-		}
 		index_close(irel, NoLock);
 	}
 }
@@ -12557,8 +12553,6 @@ ATExecSetTableSpace(Oid tableOid, Oid newTableSpace, LOCKMODE lockmode)
 
 	table_close(pg_class, RowExclusiveLock);
 
-	RelationAssumeNewRelfilenode(rel);
-
 	relation_close(rel, NoLock);
 
 	/* Make sure the reltablespace change is visible */