Re: [PATCHES] patch for pg_autovacuum 8.0.x prevent segv for dropped tables
On Thu, Oct 20, 2005 at 12:30:27PM -0400, Tom Lane wrote: > "Matthew T. O'Connor" writes: > > Tom Lane wrote: > >> Surely this is completely broken? AFAICT you are testing the result > >> from a VACUUM or ANALYZE command, which is not going to return any > >> tuples. > > > Upon further inspection, I think you are right. I would think that > > instead of checking the query result with PQntuples, it should probably > > be checked with |PQresultStatus. > > ISTM this is the wrong place to test at all. I put a PQntuples check > into update_table_thresholds() instead, which seems a far more direct > defense against trouble. (Consider eg the case where someone drops the > table just after your VACUUM completes successfully. Also there are > drop/rename scenarios to think about: success of the VACUUM proves that > there is a table named FOO, not that there is still a table with the OID > you have on record.) Yes, I agree, update_table_thresholds() is the right place for the check. Please ignore the earlier patch. Thanks -dg -- David Gould [EMAIL PROTECTED] If simplicity worked, the world would be overrun with insects. ---(end of broadcast)--- TIP 9: In versions below 8.0, the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match
Re: [PATCHES] patch for pg_autovacuum 8.0.x prevent segv for dropped tables
"Matthew T. O'Connor" writes: > Tom Lane wrote: >> Surely this is completely broken? AFAICT you are testing the result >> from a VACUUM or ANALYZE command, which is not going to return any >> tuples. > Upon further inspection, I think you are right. I would think that > instead of checking the query result with PQntuples, it should probably > be checked with |PQresultStatus. ISTM this is the wrong place to test at all. I put a PQntuples check into update_table_thresholds() instead, which seems a far more direct defense against trouble. (Consider eg the case where someone drops the table just after your VACUUM completes successfully. Also there are drop/rename scenarios to think about: success of the VACUUM proves that there is a table named FOO, not that there is still a table with the OID you have on record.) regards, tom lane ---(end of broadcast)--- TIP 3: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faq
Re: [PATCHES] patch for pg_autovacuum 8.0.x prevent segv for dropped tables
daveg <[EMAIL PROTECTED]> writes: > Below is a patch for this that should apply against any 8.0.x. The change > verifies that the catalog query returned some rows before accessing the row > data. Surely this is completely broken? AFAICT you are testing the result from a VACUUM or ANALYZE command, which is not going to return any tuples. regards, tom lane ---(end of broadcast)--- TIP 9: In versions below 8.0, the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match
[PATCHES] patch for pg_autovacuum 8.0.x prevent segv for dropped tables
Apologies if this is old news, but pg_autovacuum in 8.0.x has the bad habit
of SEGVing and exiting when a table gets dropped out from under it. This
creates problems if you rely on pg_autovacuum for the bulk of your vacuuming
as it forgets it's statistics when it is restarted and so will skip some
desireable vacuums.
I looked at the new autovacuum in 8.1 and it appears from casual inspection
not to have the same problem.
Below is a patch for this that should apply against any 8.0.x. The change
verifies that the catalog query returned some rows before accessing the row
data.
-dg
diff -Naur source/postgresql-8.0.2/contrib/pg_autovacuum/pg_autovacuum.c
build/postgresql-8.0.2/contrib/pg_autovacuum/pg_autovacuum.c
--- source/postgresql-8.0.2/contrib/pg_autovacuum/pg_autovacuum.c
2005-04-02 16:02:03.0 -0800
+++ build/postgresql-8.0.2/contrib/pg_autovacuum/pg_autovacuum.c
2005-09-28 22:15:25.428710172 -0700
@@ -1013,6 +1013,7 @@
static void
perform_maintenance_command(db_info * dbi, tbl_info * tbl, int operation)
{
+ PGresult*res;
charbuf[256];
/*
@@ -1069,10 +1070,16 @@
fflush(LOGOUTPUT);
}
- send_query(buf, dbi);
-
- update_table_thresholds(dbi, tbl, operation);
-
+ res = send_query(buf, dbi);
+ if (PQntuples(res)) {
+ update_table_thresholds(dbi, tbl, operation);
+ } else {
+ if (args->debug >= 1) {
+ sprintf(logbuffer, "Cannot refind table %s",
tbl->table_name);
+ log_entry(logbuffer, LVL_DEBUG);
+ fflush(LOGOUTPUT);
+ }
+ }
if (args->debug >= 2)
print_table_info(tbl);
}
--
David Gould [EMAIL PROTECTED]
If simplicity worked, the world would be overrun with insects.
---(end of broadcast)---
TIP 6: explain analyze is your friend
