From 2b438c12cca443fe69852e9b0c678893c8686ac0 Mon Sep 17 00:00:00 2001
From: Alvaro Herrera
Date: Fri, 8 Jun 2007 21:09:49 +0000
Subject: Avoid passing zero as a value for vacuum_cost_limit, because it's not
 a valid value for the vacuum code.  Instead, make zero signify getting the
 value from a higher level configuration facility, just like -1 in the
 original coding.  We still document that -1 is the value that disables the
 feature, to avoid confusing the user unnecessarily.

Reported by Galy Lee in <200705310914.l4V9E6JA094603@wwwmaster.postgresql.org>;
per subsequent discussion.
---
 src/backend/postmaster/autovacuum.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

(limited to 'src')

diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c
index 752af998313..07bf40707e3 100644
--- a/src/backend/postmaster/autovacuum.c
+++ b/src/backend/postmaster/autovacuum.c
@@ -10,7 +10,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/postmaster/autovacuum.c,v 1.47 2007/05/30 20:11:57 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/postmaster/autovacuum.c,v 1.48 2007/06/08 21:09:49 alvherre Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1548,7 +1548,11 @@ static void
 autovac_balance_cost(void)
 {
 	WorkerInfo	worker;
-	int         vac_cost_limit = (autovacuum_vac_cost_limit >= 0 ?
+	/*
+	 * note: in cost_limit, zero also means use value from elsewhere, because
+	 * zero is not a valid value.
+	 */
+	int         vac_cost_limit = (autovacuum_vac_cost_limit > 0 ?
 								  autovacuum_vac_cost_limit : VacuumCostLimit);
 	int         vac_cost_delay = (autovacuum_vac_cost_delay >= 0 ?
 								  autovacuum_vac_cost_delay : VacuumCostDelay);
@@ -2140,12 +2144,14 @@ table_recheck_autovac(Oid relid)
 		 * there is a tuple in pg_autovacuum, use it; else, use the GUC
 		 * defaults.  Note that the fields may contain "-1" (or indeed any
 		 * negative value), which means use the GUC defaults for each setting.
+		 * In cost_limit, the value 0 also means to use the value from
+		 * elsewhere.
 		 */
 		if (avForm != NULL)
 		{
-			vac_cost_limit = (avForm->vac_cost_limit >= 0) ?
+			vac_cost_limit = (avForm->vac_cost_limit > 0) ?
 				avForm->vac_cost_limit :
-				((autovacuum_vac_cost_limit >= 0) ?
+				((autovacuum_vac_cost_limit > 0) ?
 				 autovacuum_vac_cost_limit : VacuumCostLimit);
 
 			vac_cost_delay = (avForm->vac_cost_delay >= 0) ?
@@ -2158,7 +2164,7 @@ table_recheck_autovac(Oid relid)
 		}
 		else
 		{
-			vac_cost_limit = (autovacuum_vac_cost_limit >= 0) ?
+			vac_cost_limit = (autovacuum_vac_cost_limit > 0) ?
 				autovacuum_vac_cost_limit : VacuumCostLimit;
 
 			vac_cost_delay = (autovacuum_vac_cost_delay >= 0) ?
-- 
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