On Thu, Aug 29, 2019 at 3:15 PM Richard Guo <riguo@pivotal.io> wrote: > > > Attached is a patch as an attempt to address this issue. The idea is > quite straightforward. When building partition info for joinrel, we > generate any possible EC-derived joinclauses of form 'outer_em = > inner_em', which will be used together with the original restrictlist to > check if there exists an equi-join condition for each pair of partition > keys. > > Any comments are welcome! /* + * generate_join_implied_equalities_for_all + * Create any EC-derived joinclauses of form 'outer_em = inner_em'. + * + * This is used when building partition info for joinrel. + */ +List * +generate_join_implied_equalities_for_all(PlannerInfo *root, + Relids join_relids, + Relids outer_relids, + Relids inner_relids)
I think we need to have more detailed comments about why we need this separate function, we can also explain that generate_join_implied_equalities function will avoid the join clause if EC has the constant but for partition-wise join, we need that clause too.
Thank you for the suggestion.
+ while ((i = bms_next_member(matching_ecs, i)) >= 0) + { + EquivalenceClass *ec = (EquivalenceClass *) list_nth(root->eq_classes, i); + List *outer_members = NIL; + List *inner_members = NIL; + ListCell *lc1; + + /* Do not consider this EC if it's ec_broken */ + if (ec->ec_broken) + continue; + + /* Single-member ECs won't generate any deductions */ + if (list_length(ec->ec_members) <= 1) + continue; +
I am wondering isn't it possible to just process the missing join clause? I mean 'generate_join_implied_equalities' has only skipped the ECs which has const so can't we create join clause only for those ECs and append it the "Restrictlist" we already have? I might be missing something?
For ECs without const, 'generate_join_implied_equalities' also has skipped some join clauses since it only selects the joinclause with 'best_score' between outer members and inner members. And the missing join clauses are needed to generate partitionwise join. That's why the query below cannot be planned as partitionwise join, as we have missed joinclause 'foo.k = bar.k'.
select * from p as foo join p as bar on foo.k = bar.val and foo.k = bar.k;
And yes 'generate_join_implied_equalities_for_all' will create join clauses that have existed in restrictlist. I think it's OK since the same RestrictInfo deduced from EC will share the same pointer and list_concat_unique_ptr will make sure there are no duplicates in the restrictlist used by have_partkey_equi_join.