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Use CP_SMALL_TLIST for hash aggregate

Commit1f39bce added disk-based hash aggregation, which may spillincoming tuples to disk. It however did not request projection to makethe tuples as narrow as possible, which may mean having to spill muchmore data than necessary (increasing I/O, pushing other stuff from pagecache, etc.).This adds CP_SMALL_TLIST in places that may use hash aggregation - we dothat only for AGG_HASHED. It's unnecessary for AGG_SORTED, because thateither uses explicit Sort (which already does projection) or pre-sortedinput (which does not need spilling to disk).Author: Tomas VondraReviewed-by: Jeff DavisDiscussion:https://postgr.es/m/20200519151202.u2p2gpiawoaznsv2%40development

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2 files changed

+26

-6

lines changed

contrib/postgres_fdw/expected
- postgres_fdw.out
src/backend/optimizer/plan
- createplan.c

2 files changed

+26

-6

lines changed

`‎contrib/postgres_fdw/expected/postgres_fdw.out`

Lines changed: 2 additions & 2 deletions

Original file line number	Diff line number	Diff line change
`@@ -2715,7 +2715,7 @@ select sum(c1) from ft1 group by c2 having avg(c1 * (random() <= 1)::int) > 100`
`2715`	`2715`	`Group Key: ft1.c2`
`2716`	`2716`	`Filter: (avg((ft1.c1 * ((random() <= '1'::double precision))::integer)) > '100'::numeric)`
`2717`	`2717`	`-> Foreign Scan on public.ft1`
`2718`		`- Output:c1, c2`
	`2718`	`+ Output:c2, c1`
`2719`	`2719`	`Remote SQL: SELECT "C 1", c2 FROM "S 1"."T 1"`
`2720`	`2720`	`(10 rows)`
`2721`	`2721`
`@@ -2964,7 +2964,7 @@ select sum(c1) filter (where (c1 / c1) * random() <= 1) from ft1 group by c2 ord`
`2964`	`2964`	`Output: sum(c1) FILTER (WHERE ((((c1 / c1))::double precision * random()) <= '1'::double precision)), c2`
`2965`	`2965`	`Group Key: ft1.c2`
`2966`	`2966`	`-> Foreign Scan on public.ft1`
`2967`		`- Output:c1, c2`
	`2967`	`+ Output:c2, c1`
`2968`	`2968`	`Remote SQL: SELECT "C 1", c2 FROM "S 1"."T 1"`
`2969`	`2969`	`(9 rows)`
`2970`	`2970`

`‎src/backend/optimizer/plan/createplan.c`

Lines changed: 24 additions & 4 deletions

Original file line number	Diff line number	Diff line change
`@@ -2113,12 +2113,22 @@ create_agg_plan(PlannerInfo root, AggPath best_path)`
`2113`	`2113`	`Plan*subplan;`
`2114`	`2114`	`List*tlist;`
`2115`	`2115`	`List*quals;`
	`2116`	`+intflags;`
`2116`	`2117`
`2117`	`2118`	`/*`
`2118`	`2119`	`* Agg can project, so no need to be terribly picky about child tlist, but`
`2119`		`- * we do need grouping columns to be available`
	`2120`	`+ * we do need grouping columns to be available. We are a bit more careful`
	`2121`	`+ * with hash aggregate, where we explicitly request small tlist to minimize`
	`2122`	`+ * I/O needed for spilling (we can't be sure spilling won't be necessary,`
	`2123`	`+ * so we just do it every time).`
`2120`	`2124`	`*/`
`2121`		`-subplan=create_plan_recurse(root,best_path->subpath,CP_LABEL_TLIST);`
	`2125`	`+flags=CP_LABEL_TLIST;`
	`2126`	`+`
	`2127`	`+/* ensure small tlist for hash aggregate */`
	`2128`	`+if (best_path->aggstrategy==AGG_HASHED)`
	`2129`	`+flags \|=CP_SMALL_TLIST;`
	`2130`	`+`
	`2131`	`+subplan=create_plan_recurse(root,best_path->subpath,flags);`
`2122`	`2132`
`2123`	`2133`	`tlist=build_path_tlist(root,&best_path->path);`
`2124`	`2134`
`@@ -2200,16 +2210,26 @@ create_groupingsets_plan(PlannerInfo root, GroupingSetsPath best_path)`
`2200`	`2210`	`intmaxref;`
`2201`	`2211`	`List*chain;`
`2202`	`2212`	`ListCell*lc;`
	`2213`	`+intflags;`
`2203`	`2214`
`2204`	`2215`	`/* Shouldn't get here without grouping sets */`
`2205`	`2216`	`Assert(root->parse->groupingSets);`
`2206`	`2217`	`Assert(rollups!=NIL);`
`2207`	`2218`
`2208`	`2219`	`/*`
`2209`	`2220`	`* Agg can project, so no need to be terribly picky about child tlist, but`
`2210`		`- * we do need grouping columns to be available`
	`2221`	`+ * we do need grouping columns to be available. We are a bit more careful`
	`2222`	`+ * with hash aggregate, where we explicitly request small tlist to minimize`
	`2223`	`+ * I/O needed for spilling (we can't be sure spilling won't be necessary,`
	`2224`	`+ * so we just do it every time).`
`2211`	`2225`	`*/`
`2212`		`-subplan=create_plan_recurse(root,best_path->subpath,CP_LABEL_TLIST);`
	`2226`	`+flags=CP_LABEL_TLIST;`
	`2227`	`+`
	`2228`	`+/* ensure small tlist for hash aggregate */`
	`2229`	`+if (best_path->aggstrategy==AGG_HASHED)`
	`2230`	`+flags \|=CP_SMALL_TLIST;`
	`2231`	`+`
	`2232`	`+subplan=create_plan_recurse(root,best_path->subpath,flags);`
`2213`	`2233`
`2214`	`2234`	`/*`
`2215`	`2235`	`* Compute the mapping from tleSortGroupRef to column index in the child's`

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Commit4cad253

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`‎contrib/postgres_fdw/expected/postgres_fdw.out`

`‎src/backend/optimizer/plan/createplan.c`

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