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

This reverts commit cb2fd7eac285b1b0a24eeb2b8ed4456b66c5a09f.  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

2 files changed, 15 insertions, 50 deletions

diff --git a/src/include/utils/rel.h b/src/include/utils/rel.h
index f02d2b561b9..11a635964fd 100644
--- a/src/include/utils/rel.h
+++ b/src/include/utils/rel.h
@@ -66,43 +66,25 @@ typedef struct RelationData
 
 	/*----------
 	 * rd_createSubid is the ID of the highest subtransaction the rel has
-	 * survived into or zero if the rel or its rd_node was created before the
-	 * current top transaction.  (IndexStmt.oldNode leads to the case of a new
-	 * rel with an old rd_node.)  rd_firstRelfilenodeSubid is the ID of the
-	 * highest subtransaction an rd_node change has survived into or zero if
-	 * rd_node matches the value it had at the start of the current top
-	 * transaction.  (Rolling back the subtransaction that
-	 * rd_firstRelfilenodeSubid denotes would restore rd_node to the value it
-	 * had at the start of the current top transaction.  Rolling back any
-	 * lower subtransaction would not.)  Their accuracy is critical to
-	 * RelationNeedsWAL().
-	 *
-	 * rd_newRelfilenodeSubid is the ID of the highest subtransaction the
-	 * most-recent relfilenode change has survived into or zero if not changed
-	 * in the current transaction (or we have forgotten changing it).  This
-	 * field is accurate when non-zero, but it can be zero when a relation has
-	 * multiple new relfilenodes within a single transaction, with one of them
-	 * occurring in a subsequently aborted subtransaction, e.g.
+	 * survived into; or zero if the rel was not created in the current top
+	 * transaction.  This can be now be relied on, whereas previously it could
+	 * be "forgotten" in earlier releases. Likewise, rd_newRelfilenodeSubid is
+	 * the ID of the highest subtransaction the relfilenode change has
+	 * survived into, or zero if not changed in the current transaction (or we
+	 * have forgotten changing it). rd_newRelfilenodeSubid can be forgotten
+	 * when a relation has multiple new relfilenodes within a single
+	 * transaction, with one of them occurring in a subsequently aborted
+	 * subtransaction, e.g.
 	 *		BEGIN;
 	 *		TRUNCATE t;
 	 *		SAVEPOINT save;
 	 *		TRUNCATE t;
 	 *		ROLLBACK TO save;
 	 *		-- rd_newRelfilenodeSubid is now forgotten
-	 *
-	 * If every rd_*Subid field is zero, they are read-only outside
-	 * relcache.c.  Files that trigger rd_node changes by updating
-	 * pg_class.reltablespace and/or pg_class.relfilenode call
-	 * RelationAssumeNewRelfilenode() to update rd_*Subid.
-	 *
-	 * rd_droppedSubid is the ID of the highest subtransaction that a drop of
-	 * the rel has survived into.  In entries visible outside relcache.c, this
-	 * is always zero.
 	 */
 	SubTransactionId rd_createSubid;	/* rel was created in current xact */
-	SubTransactionId rd_newRelfilenodeSubid;	/* highest subxact changing
-												 * rd_node to current value */
-	/* see end for rd_firstRelfilenodeSubid and rd_droppedSubid */
+	SubTransactionId rd_newRelfilenodeSubid;	/* new relfilenode assigned in
+												 * current xact */
 
 	Form_pg_class rd_rel;		/* RELATION tuple */
 	TupleDesc	rd_att;			/* tuple descriptor */
@@ -215,10 +197,6 @@ typedef struct RelationData
 	/* placed here to avoid ABI break before v12: */
 	bool		rd_partcheckvalid;	/* true if list has been computed */
 	MemoryContext rd_partcheckcxt;	/* private cxt for rd_partcheck, if any */
-
-	SubTransactionId rd_firstRelfilenodeSubid;	/* highest subxact changing
-												 * rd_node to any value */
-	SubTransactionId rd_droppedSubid;	/* dropped with another Subid set */
 } RelationData;
 
 
@@ -538,16 +516,9 @@ typedef struct ViewOptions
 /*
  * RelationNeedsWAL
  *		True if relation needs WAL.
- *
- * Returns false if wal_level = minimal and this relation is created or
- * truncated in the current transaction.  See "Skipping WAL for New
- * RelFileNode" in src/backend/access/transam/README.
- */
-#define RelationNeedsWAL(relation)										\
-	((relation)->rd_rel->relpersistence == RELPERSISTENCE_PERMANENT &&	\
-	 (XLogIsNeeded() ||													\
-	  (relation->rd_createSubid == InvalidSubTransactionId &&			\
-	   relation->rd_firstRelfilenodeSubid == InvalidSubTransactionId)))
+ */
+#define RelationNeedsWAL(relation) \
+	((relation)->rd_rel->relpersistence == RELPERSISTENCE_PERMANENT)
 
 /*
  * RelationUsesLocalBuffers
diff --git a/src/include/utils/relcache.h b/src/include/utils/relcache.h
index 50005f91667..54394303a85 100644
--- a/src/include/utils/relcache.h
+++ b/src/include/utils/relcache.h
@@ -108,11 +108,10 @@ extern Relation RelationBuildLocalRelation(const char *relname,
 						   char relkind);
 
 /*
- * Routines to manage assignment of new relfilenode to a relation
+ * Routine to manage assignment of new relfilenode to a relation
  */
 extern void RelationSetNewRelfilenode(Relation relation, char persistence,
 						  TransactionId freezeXid, MultiXactId minmulti);
-extern void RelationAssumeNewRelfilenode(Relation relation);
 
 /*
  * Routines for flushing/rebuilding relcache entries in various scenarios
@@ -125,11 +124,6 @@ extern void RelationCacheInvalidate(void);
 
 extern void RelationCloseSmgrByOid(Oid relationId);
 
-#ifdef USE_ASSERT_CHECKING
-extern void AssertPendingSyncs_RelationCache(void);
-#else
-#define AssertPendingSyncs_RelationCache() do {} while (0)
-#endif
 extern void AtEOXact_RelationCache(bool isCommit);
 extern void AtEOSubXact_RelationCache(bool isCommit, SubTransactionId mySubid,
 						  SubTransactionId parentSubid);