Allow treating TABLESAMPLE scans as parallel-safe.

tglsfdc · tglsfdc · commit 2c6e6471af9f · 2016-07-03T16:55:27.000-04:00
This was the intention all along, but an extraneous "return;" in
set_rel_consider_parallel() caused sampled rels to never be marked
consider_parallel.

Since we don't have any partial tablesample path/plan type yet, there's
no possibility of parallelizing the sample scan itself; but this fix
allows such a scan to appear below a parallel join, for example.
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
@@ -538,7 +538,6 @@ set_rel_consider_parallel(PlannerInfo *root, RelOptInfo *rel,
 				if (has_parallel_hazard((Node *) rte->tablesample->args,
 										false))
 					return;
-				return;
 			}
 
 			/*

Original file line number	Diff line number	Diff line change
`@@ -538,7 +538,6 @@ set_rel_consider_parallel(PlannerInfo root, RelOptInfo rel,`
`538`	`538`	`if (has_parallel_hazard((Node *) rte->tablesample->args,`
`539`	`539`	`false))`
`540`	`540`	`return;`
`541`		`- return;`
`542`	`541`	`}`
`543`	`542`
`544`	`543`	`/*`