Generalize concept of temporary relations to "relation persistence".

This commit replaces pg_class.relistemp with pg_class.relpersistence;
and also modifies the RangeVar node type to carry relpersistence rather
than istemp.  It also removes removes rd_istemp from RelationData and
instead performs the correct computation based on relpersistence.

For clarity, we add three new macros: RelationNeedsWAL(),
RelationUsesLocalBuffers(), and RelationUsesTempNamespace(), so that we
can clarify the purpose of each check that previous depended on
rd_istemp.

This is intended as infrastructure for the upcoming unlogged tables
patch, as well as for future possible work on global temporary tables.

1 files changed, 19 insertions, 9 deletions

diff --git a/src/backend/utils/adt/dbsize.c b/src/backend/utils/adt/dbsize.c
index f5250a263cd..e352cdafb3b 100644
--- a/src/backend/utils/adt/dbsize.c
+++ b/src/backend/utils/adt/dbsize.c
@@ -612,16 +612,26 @@ pg_relation_filepath(PG_FUNCTION_ARGS)
 		PG_RETURN_NULL();
 	}
 
-	/* If temporary, determine owning backend. */
-	if (!relform->relistemp)
-		backend = InvalidBackendId;
-	else if (isTempOrToastNamespace(relform->relnamespace))
-		backend = MyBackendId;
-	else
+	/* Determine owning backend. */
+	switch (relform->relpersistence)
 	{
-		/* Do it the hard way. */
-		backend = GetTempNamespaceBackendId(relform->relnamespace);
-		Assert(backend != InvalidBackendId);
+		case RELPERSISTENCE_PERMANENT:
+			backend = InvalidBackendId;
+			break;
+		case RELPERSISTENCE_TEMP:
+			if (isTempOrToastNamespace(relform->relnamespace))
+				backend = MyBackendId;
+			else
+			{
+				/* Do it the hard way. */
+				backend = GetTempNamespaceBackendId(relform->relnamespace);
+				Assert(backend != InvalidBackendId);
+			}
+			break;
+		default:
+			elog(ERROR, "invalid relpersistence: %c", relform->relpersistence);
+			backend = InvalidBackendId; 	/* placate compiler */
+			break;
 	}
 
 	ReleaseSysCache(tuple);