Clean up handling of XactReadOnly and RecoveryInProgress checks.

Add some checks that seem logically necessary, in particular let's make
real sure that HS slave sessions cannot create temp tables.  (If they did
they would think that temp tables belonging to the master's session with
the same BackendId were theirs.  We *must* not allow myTempNamespace to
become set in a slave session.)

Change setval() and nextval() so that they are only allowed on temp sequences
in a read-only transaction.  This seems consistent with what we allow for
table modifications in read-only transactions.  Since an HS slave can't have a
temp sequence, this also provides a nicer cure for the setval PANIC reported
by Erik Rijkers.

Make the error messages more uniform, and have them mention the specific
command being complained of.  This seems worth the trifling amount of extra
code, since people are likely to see such messages a lot more than before.

1 files changed, 9 insertions, 7 deletions

diff --git a/src/backend/commands/sequence.c b/src/backend/commands/sequence.c
index ffb7fcaba9d..fc2446997a7 100644
--- a/src/backend/commands/sequence.c
+++ b/src/backend/commands/sequence.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/sequence.c,v 1.167 2010/02/19 06:29:19 heikki Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/sequence.c,v 1.168 2010/02/20 21:24:02 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -459,9 +459,6 @@ nextval_internal(Oid relid)
 				rescnt = 0;
 	bool		logit = false;
 
-	/* nextval() writes to database and must be prevented during recovery */
-	PreventCommandDuringRecovery();
-
 	/* open and AccessShareLock sequence */
 	init_sequence(relid, &elm, &seqrel);
 
@@ -472,6 +469,10 @@ nextval_internal(Oid relid)
 				 errmsg("permission denied for sequence %s",
 						RelationGetRelationName(seqrel))));
 
+	/* read-only transactions may only modify temp sequences */
+	if (!seqrel->rd_islocaltemp)
+		PreventCommandIfReadOnly("nextval()");
+
 	if (elm->last != elm->cached)		/* some numbers were cached */
 	{
 		Assert(elm->last_valid);
@@ -736,9 +737,6 @@ do_setval(Oid relid, int64 next, bool iscalled)
 	Buffer		buf;
 	Form_pg_sequence seq;
 
-	/* setval() writes to database and must be prevented during recovery */
-	PreventCommandDuringRecovery();
-
 	/* open and AccessShareLock sequence */
 	init_sequence(relid, &elm, &seqrel);
 
@@ -748,6 +746,10 @@ do_setval(Oid relid, int64 next, bool iscalled)
 				 errmsg("permission denied for sequence %s",
 						RelationGetRelationName(seqrel))));
 
+	/* read-only transactions may only modify temp sequences */
+	if (!seqrel->rd_islocaltemp)
+		PreventCommandIfReadOnly("setval()");
+
 	/* lock page' buffer and read tuple */
 	seq = read_info(elm, seqrel, &buf);