Several changes here, not very related but touching some of the same files.

* Buffer refcount cleanup (per my "progress report" to pghackers, 9/22).
* Add links to backend PROC structs to sinval's array of per-backend info,
and use these links for routines that need to check the state of all
backends (rather than the slow, complicated search of the ShmemIndex
hashtable that was used before).  Add databaseOID to PROC structs.
* Use this to implement an interlock that prevents DESTROY DATABASE of
a database containing running backends.  (It's a little tricky to prevent
a concurrently-starting backend from getting in there, since the new
backend is not able to lock anything at the time it tries to look up
its database in pg_database.  My solution is to recheck that the DB is
OK at the end of InitPostgres.  It may not be a 100% solution, but it's
a lot better than no interlock at all...)
* In ALTER TABLE RENAME, flush buffers for the relation before doing the
rename of the physical files, to ensure we don't get failures later from
mdblindwrt().
* Update TRUNCATE patch so that it actually compiles against current
sources :-(.
You should do "make clean all" after pulling these changes.

1 files changed, 70 insertions, 21 deletions

diff --git a/src/backend/commands/rename.c b/src/backend/commands/rename.c
index 3a822bd4e49..0a72ba497ec 100644
--- a/src/backend/commands/rename.c
+++ b/src/backend/commands/rename.c
@@ -7,12 +7,14 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/commands/Attic/rename.c,v 1.33 1999/09/18 19:06:40 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/Attic/rename.c,v 1.34 1999/09/24 00:24:17 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
 #include "postgres.h"
 
+#include <errno.h>
+
 #include "access/heapam.h"
 #include "catalog/catname.h"
 #include "utils/syscache.h"
@@ -21,6 +23,7 @@
 #include "catalog/catalog.h"
 #include "commands/rename.h"
 #include "miscadmin.h"
+#include "storage/smgr.h"
 #include "optimizer/prep.h"
 #include "utils/acl.h"
 
@@ -166,19 +169,6 @@ renameatt(char *relname,
 
 /*
  *		renamerel		- change the name of a relation
- *
- *		Relname attribute is changed in relation catalog.
- *		No record of the previous relname is kept (correct?).
- *
- *		scan relation catalog
- *				for name conflict
- *				for original relation (if not arg)
- *		modify relname in relation tuple
- *		insert modified relation in relation catalog
- *		delete original relation from relation catalog
- *
- *		XXX Will currently lose track of a relation if it is unable to
- *				properly replace the new relation tuple.
  */
 void
 renamerel(char *oldrelname, char *newrelname)
@@ -206,8 +196,55 @@ renamerel(char *oldrelname, char *newrelname)
 	 * until end of transaction.
 	 */
 	targetrelation = heap_openr(oldrelname, AccessExclusiveLock);
-	heap_close(targetrelation, NoLock);	/* close rel but keep lock! */
 
+	/* ----------------
+	 *	RENAME TABLE within a transaction block is dangerous, because
+	 *	if the transaction is later rolled back we have no way to
+	 *	undo the rename of the relation's physical file.  For now, allow it
+	 *	but emit a warning message.
+	 *	Someday we might want to consider postponing the physical rename
+	 *	until transaction commit, but that's a lot of work...
+	 *	The only case that actually works right is for relations created
+	 *	in the current transaction, since the post-abort state would be that
+	 *	they don't exist anyway.  So, no warning in that case.
+	 * ----------------
+	 */
+	if (IsTransactionBlock() && ! targetrelation->rd_myxactonly)
+		elog(NOTICE, "Caution: RENAME TABLE cannot be rolled back, so don't abort now");
+
+	/*
+	 * Flush all blocks of the relation out of the buffer pool.  We need this
+	 * because the blocks are marked with the relation's name as well as OID.
+	 * If some backend tries to write a dirty buffer with mdblindwrt after
+	 * we've renamed the physical file, we'll be in big trouble.
+	 *
+	 * Since we hold the exclusive lock on the relation, we don't have to
+	 * worry about more blocks being read in while we finish the rename.
+	 */
+	if (FlushRelationBuffers(targetrelation, (BlockNumber) 0, true) < 0)
+		elog(ERROR, "renamerel: unable to flush relation from buffer pool");
+
+	/*
+	 * Make sure smgr and lower levels close the relation's files.
+	 * (Next access to rel will reopen them.)
+	 *
+	 * Note: we rely on shared cache invalidation message to make other
+	 * backends close and re-open the files.
+	 */
+	smgrclose(DEFAULT_SMGR, targetrelation);
+
+	/*
+	 * Close rel, but keep exclusive lock!
+	 *
+	 * Note: we don't do anything about updating the relcache entry;
+	 * we assume it will be flushed by shared cache invalidate.
+	 * XXX is this good enough?  What if relation is myxactonly?
+	 */
+	heap_close(targetrelation, NoLock);
+
+	/*
+	 * Find relation's pg_class tuple, and make sure newrelname isn't in use.
+	 */
 	relrelation = heap_openr(RelationRelationName, RowExclusiveLock);
 
 	oldreltup = SearchSysCacheTupleCopy(RELNAME,
@@ -220,14 +257,17 @@ renamerel(char *oldrelname, char *newrelname)
 		elog(ERROR, "renamerel: relation \"%s\" exists", newrelname);
 
 	/*
-	 * XXX need to close relation and flush dirty buffers here!
+	 * Perform physical rename of files.  If this fails, we haven't yet
+	 * done anything irreversible.
+	 *
+	 * XXX smgr.c ought to provide an interface for this; doing it
+	 * directly is bletcherous.
 	 */
-
-	/* rename the path first, so if this fails the rename's not done */
 	strcpy(oldpath, relpath(oldrelname));
 	strcpy(newpath, relpath(newrelname));
 	if (rename(oldpath, newpath) < 0)
-		elog(ERROR, "renamerel: unable to rename file: %s", oldpath);
+		elog(ERROR, "renamerel: unable to rename %s to %s: %m",
+			 oldpath, newpath);
 
 	/* rename additional segments of relation, too */
 	for (i = 1;; i++)
@@ -235,13 +275,22 @@ renamerel(char *oldrelname, char *newrelname)
 		sprintf(toldpath, "%s.%d", oldpath, i);
 		sprintf(tnewpath, "%s.%d", newpath, i);
 		if (rename(toldpath, tnewpath) < 0)
-			break;
+		{
+			/* expected case is that there's not another segment file */
+			if (errno == ENOENT)
+				break;
+			/* otherwise we're up the creek... */
+			elog(ERROR, "renamerel: unable to rename %s to %s: %m",
+				 toldpath, tnewpath);
+		}
 	}
 
+	/*
+	 * Update pg_class tuple with new relname.
+	 */
 	StrNCpy((((Form_pg_class) GETSTRUCT(oldreltup))->relname.data),
 			newrelname, NAMEDATALEN);
 
-	/* insert fixed rel tuple */
 	heap_replace(relrelation, &oldreltup->t_self, oldreltup, NULL);
 
 	/* keep the system catalog indices current */