postgres_fdw: Fix test for cached costs in estimate_path_cost_size().

Etsuro Fujita · Etsuro Fujita · commit 449d0a85507b · 2019-01-29T12:27:13.000+09:00
estimate_path_cost_size() failed to re-use cached costs when the cached startup/total cost was 0, so it calculated the costs redundantly. This is an oversight in commit aa09cd2; but apply the patch to HEAD only because there are no reports of actual trouble from that. Author: Etsuro Fujita Discussion: https://postgr.es/m/5C4AF3F3.4060409%40lab.ntt.co.jp
diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c
@@ -2625,7 +2625,7 @@ estimate_path_cost_size(PlannerInfo *root,
 		 * bare scan each time. Instead, use the costs if we have cached them
 		 * already.
 		 */
-		if (fpinfo->rel_startup_cost > 0 && fpinfo->rel_total_cost > 0)
+		if (fpinfo->rel_startup_cost >= 0 && fpinfo->rel_total_cost >= 0)
 		{
 			startup_cost = fpinfo->rel_startup_cost;
 			run_cost = fpinfo->rel_total_cost - fpinfo->rel_startup_cost;

Original file line number	Diff line number	Diff line change
`@@ -2625,7 +2625,7 @@ estimate_path_cost_size(PlannerInfo *root,`
`2625`	`2625`	`* bare scan each time. Instead, use the costs if we have cached them`
`2626`	`2626`	`* already.`
`2627`	`2627`	`*/`
`2628`		`- if (fpinfo->rel_startup_cost > 0 && fpinfo->rel_total_cost > 0)`
	`2628`	`+ if (fpinfo->rel_startup_cost >= 0 && fpinfo->rel_total_cost >= 0)`
`2629`	`2629`	`{`
`2630`	`2630`	`startup_cost = fpinfo->rel_startup_cost;`
`2631`	`2631`	`run_cost = fpinfo->rel_total_cost - fpinfo->rel_startup_cost;`