(2019/01/04 20:33), Etsuro Fujita wrote: > Here is a new version of the patch.
Attached is an updated version of the patch. Changes: * Fixed a stupid bug in the case when use_remote_estimate * Fixed a typo in a comment I added * Modified comments I added a little bit further * Added the commit message If there are no objections, I'll push that. Best regards, Etsuro Fujita
>From 3ff65a6f05a330140bf5de94fbcf6ab2a04f040b Mon Sep 17 00:00:00 2001 From: Etsuro Fujita <efuj...@postgresql.org> Date: Wed, 23 Jan 2019 20:30:30 +0900 Subject: [PATCH] postgres_fdw: Account for tlist eval costs in estimate_path_cost_size() Previously, estimate_path_cost_size() didn't account for tlist eval costs, except when costing a foreign-grouping path using local statistics, but such costs should be accounted for when costing that path using remote estimates, because some of the tlist expressions might be evaluated locally. Also, such costs should be accounted for in the case of a foreign-scan or foreign-join path, because currently, postgres_fdw evaluates PlaceHolderVars (if any) locally. This also fixes an oversight in my commit f8f6e44676ef38fee7a5bbe4f256a34ea7799ac1. Like that commit, apply this to HEAD only to avoid destabilizing existing plan choices. Author: Etsuro Fujita Discussion: https://postgr.es/m/5BFD3EAD.2060301%40lab.ntt.co.jp --- contrib/postgres_fdw/postgres_fdw.c | 41 +++++++++++++++++++++++------ 1 file changed, 33 insertions(+), 8 deletions(-) diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c index d85a83abe9..f460fd2ec4 100644 --- a/contrib/postgres_fdw/postgres_fdw.c +++ b/contrib/postgres_fdw/postgres_fdw.c @@ -2499,6 +2499,9 @@ estimate_path_cost_size(PlannerInfo *root, Cost total_cost; Cost cpu_per_tuple; + /* Make sure the core code has set up the relation's reltarget */ + Assert(foreignrel->reltarget); + /* * If the table or the server is configured to use remote estimates, * connect to the foreign server and execute EXPLAIN to estimate the @@ -2576,6 +2579,24 @@ estimate_path_cost_size(PlannerInfo *root, cost_qual_eval(&local_cost, local_param_join_conds, root); startup_cost += local_cost.startup; total_cost += local_cost.per_tuple * retrieved_rows; + + /* + * Add in tlist eval cost for each output row. In case of an + * aggregate, some of the tlist expressions such as grouping + * exressions will be evaluated remotely, so adjust the costs. + */ + startup_cost += foreignrel->reltarget->cost.startup; + total_cost += foreignrel->reltarget->cost.startup; + total_cost += foreignrel->reltarget->cost.per_tuple * rows; + if (IS_UPPER_REL(foreignrel)) + { + QualCost tlist_cost; + + cost_qual_eval(&tlist_cost, fdw_scan_tlist, root); + startup_cost -= tlist_cost.startup; + total_cost -= tlist_cost.startup; + total_cost -= tlist_cost.per_tuple * rows; + } } else { @@ -2674,19 +2695,19 @@ estimate_path_cost_size(PlannerInfo *root, nrows = clamp_row_est(nrows * fpinfo->joinclause_sel); run_cost += nrows * remote_conds_cost.per_tuple; run_cost += fpinfo->local_conds_cost.per_tuple * retrieved_rows; + + /* Add in tlist eval cost for each output row */ + startup_cost += foreignrel->reltarget->cost.startup; + run_cost += foreignrel->reltarget->cost.per_tuple * rows; } else if (IS_UPPER_REL(foreignrel)) { PgFdwRelationInfo *ofpinfo; - PathTarget *ptarget = foreignrel->reltarget; AggClauseCosts aggcosts; double input_rows; int numGroupCols; double numGroups = 1; - /* Make sure the core code set the pathtarget. */ - Assert(ptarget != NULL); - /* * This cost model is mixture of costing done for sorted and * hashed aggregates in cost_agg(). We are not sure which @@ -2750,26 +2771,22 @@ estimate_path_cost_size(PlannerInfo *root, * Startup cost includes: * 1. Startup cost for underneath input relation * 2. Cost of performing aggregation, per cost_agg() - * 3. Startup cost for PathTarget eval *----- */ startup_cost = ofpinfo->rel_startup_cost; startup_cost += aggcosts.transCost.startup; startup_cost += aggcosts.transCost.per_tuple * input_rows; startup_cost += (cpu_operator_cost * numGroupCols) * input_rows; - startup_cost += ptarget->cost.startup; /*----- * Run time cost includes: * 1. Run time cost of underneath input relation * 2. Run time cost of performing aggregation, per cost_agg() - * 3. PathTarget eval cost for each output row *----- */ run_cost = ofpinfo->rel_total_cost - ofpinfo->rel_startup_cost; run_cost += aggcosts.finalCost * numGroups; run_cost += cpu_tuple_cost * numGroups; - run_cost += ptarget->cost.per_tuple * numGroups; /* Accout for the eval cost of HAVING quals, if any */ if (root->parse->havingQual) @@ -2784,6 +2801,10 @@ estimate_path_cost_size(PlannerInfo *root, startup_cost += fpinfo->local_conds_cost.startup; run_cost += fpinfo->local_conds_cost.per_tuple * retrieved_rows; } + + /* Add in tlist eval cost for each output row */ + startup_cost += foreignrel->reltarget->cost.startup; + run_cost += foreignrel->reltarget->cost.per_tuple * rows; } else { @@ -2802,6 +2823,10 @@ estimate_path_cost_size(PlannerInfo *root, startup_cost += foreignrel->baserestrictcost.startup; cpu_per_tuple = cpu_tuple_cost + foreignrel->baserestrictcost.per_tuple; run_cost += cpu_per_tuple * foreignrel->tuples; + + /* Add in tlist eval cost for each output row */ + startup_cost += foreignrel->reltarget->cost.startup; + run_cost += foreignrel->reltarget->cost.per_tuple * rows; } /* -- 2.19.2
