From: Alvaro Herrera <alvherre@alvh.no-ip.org>
Date: Thu, 17 Jul 2008 21:02:41 +0000 (+0000)
Subject: Avoid crashing when a table is deleted while we're on the process of checking
X-Git-Tag: REL8_3_4~33
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f1583ed591fb2f1eccce3d3dcd30a0a802543adc;p=thirdparty%2Fpostgresql.git

Avoid crashing when a table is deleted while we're on the process of checking
it.  This is a stripped down version of the patch applied to HEAD.

Per report from Tom Lane based on buildfarm evidence.
---

diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c
index 411c1cd4ebb..833e258c8eb 100644
--- a/src/backend/postmaster/autovacuum.c
+++ b/src/backend/postmaster/autovacuum.c
@@ -55,7 +55,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/postmaster/autovacuum.c,v 1.71.2.3 2008/03/14 23:49:33 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/postmaster/autovacuum.c,v 1.71.2.4 2008/07/17 21:02:41 alvherre Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -2098,13 +2098,16 @@ do_autovacuum(void)
 
 		/*
 		 * Save the relation name for a possible error message, to avoid a
-		 * catalog lookup in case of an error.	Note: they must live in a
-		 * long-lived memory context because we call vacuum and analyze in
-		 * different transactions.
+		 * catalog lookup in case of an error.  If any of these return NULL,
+		 * then the relation has been dropped since last we checked; skip it.
+		 * Note: they must live in a long-lived memory context because we call
+		 * vacuum and analyze in different transactions.
 		 */
 		datname = get_database_name(MyDatabaseId);
 		nspname = get_namespace_name(get_rel_namespace(tab->at_relid));
 		relname = get_rel_name(tab->at_relid);
+		if (!datname || !nspname || !relname)
+			goto deleted;
 
 		/*
 		 * We will abort vacuuming the current table if something errors out,
@@ -2158,11 +2161,15 @@ do_autovacuum(void)
 
 		/* the PGPROC flags are reset at the next end of transaction */
 
+deleted:
 		/* be tidy */
 		pfree(tab);
-		pfree(datname);
-		pfree(nspname);
-		pfree(relname);
+		if (datname)
+			pfree(datname);
+		if (nspname)
+			pfree(nspname);
+		if (relname)
+			pfree(relname);
 
 		/* remove my info from shared memory */
 		LWLockAcquire(AutovacuumLock, LW_EXCLUSIVE);