From 2e612e565918608e192125830b821df5d1aa3c84 Mon Sep 17 00:00:00 2001 From: Robert Haas Date: Wed, 18 Sep 2024 10:13:19 -0400 Subject: [PATCH v3 3/3] New contrib module: hint_via_alias. This forces a table to be merge joined, hash joined, or joined via a nested loop if the table alias starts with mj_, hj_, or nl_, respectively. It demonstrates that join_path_setup_hook is sufficient to control the join method, and is not intended for commit. --- contrib/Makefile | 1 + contrib/hint_via_alias/Makefile | 17 ++++ contrib/hint_via_alias/hint_via_alias.c | 114 ++++++++++++++++++++++++ contrib/hint_via_alias/meson.build | 12 +++ contrib/meson.build | 1 + 5 files changed, 145 insertions(+) create mode 100644 contrib/hint_via_alias/Makefile create mode 100644 contrib/hint_via_alias/hint_via_alias.c create mode 100644 contrib/hint_via_alias/meson.build diff --git a/contrib/Makefile b/contrib/Makefile index b3422616698..2b47095ce18 100644 --- a/contrib/Makefile +++ b/contrib/Makefile @@ -22,6 +22,7 @@ SUBDIRS = \ earthdistance \ file_fdw \ fuzzystrmatch \ + hint_via_alias \ hstore \ intagg \ intarray \ diff --git a/contrib/hint_via_alias/Makefile b/contrib/hint_via_alias/Makefile new file mode 100644 index 00000000000..2e0e540d352 --- /dev/null +++ b/contrib/hint_via_alias/Makefile @@ -0,0 +1,17 @@ +# contrib/hint_via_alias/Makefile + +MODULE_big = hint_via_alias +OBJS = \ + $(WIN32RES) \ + hint_via_alias.o + +ifdef USE_PGXS +PG_CONFIG = pg_config +PGXS := $(shell $(PG_CONFIG) --pgxs) +include $(PGXS) +else +subdir = contrib/hint_via_alias +top_builddir = ../.. +include $(top_builddir)/src/Makefile.global +include $(top_srcdir)/contrib/contrib-global.mk +endif diff --git a/contrib/hint_via_alias/hint_via_alias.c b/contrib/hint_via_alias/hint_via_alias.c new file mode 100644 index 00000000000..fc0fbd85c22 --- /dev/null +++ b/contrib/hint_via_alias/hint_via_alias.c @@ -0,0 +1,114 @@ +/*------------------------------------------------------------------------- + * + * hint_via_alias.c + * force tables to be joined in using a nestedloop, mergejoin, or hash + * join if their alias name begins with nl_, mj_, or hj_. + * + * Copyright (c) 2016-2024, PostgreSQL Global Development Group + * + * contrib/hint_via_alias/hint_via_alias.c + *------------------------------------------------------------------------- + */ +#include "postgres.h" + +#include "fmgr.h" +#include "optimizer/paths.h" +#include "parser/parsetree.h" + +typedef enum +{ + HVA_UNSPECIFIED, + HVA_HASHJOIN, + HVA_MERGEJOIN, + HVA_NESTLOOP +} hva_hint; + +static void hva_join_path_setup_hook(PlannerInfo *root, + RelOptInfo *joinrel, + RelOptInfo *outerrel, + RelOptInfo *innerrel, + JoinType jointype, + JoinPathExtraData *extra); +static hva_hint get_hint(PlannerInfo *root, Index relid); + +static join_path_setup_hook_type prev_join_path_setup_hook = NULL; + +PG_MODULE_MAGIC; + +void +_PG_init(void) +{ + prev_join_path_setup_hook = join_path_setup_hook; + join_path_setup_hook = hva_join_path_setup_hook; +} + +static void +hva_join_path_setup_hook(PlannerInfo *root, RelOptInfo *joinrel, + RelOptInfo *outerrel, RelOptInfo *innerrel, + JoinType jointype, JoinPathExtraData *extra) +{ + hva_hint outerhint = HVA_UNSPECIFIED; + hva_hint innerhint = HVA_UNSPECIFIED; + hva_hint hint; + + if (outerrel->reloptkind == RELOPT_BASEREL || + outerrel->reloptkind == RELOPT_OTHER_MEMBER_REL) + outerhint = get_hint(root, outerrel->relid); + + if (innerrel->reloptkind == RELOPT_BASEREL || + innerrel->reloptkind == RELOPT_OTHER_MEMBER_REL) + innerhint = get_hint(root, innerrel->relid); + + /* + * If the hints conflict, that's not necessarily an indication of user error. + * For example, if the user joins A to B and supplies different join method hints + * for A and B, we will end up using a disabled path. However, if they are joining + * A, B, and C and supply different join method hints for A and B, we could + * potentially respect both hints by avoiding a direct A-B join altogether. Even if + * it does turn out that we can't respect all the hints, we don't need any special + * handling for that here: the planner will just return a disabled path. + */ + if (outerhint != HVA_UNSPECIFIED && innerhint != HVA_UNSPECIFIED && + outerhint != innerhint) + { + extra->jsa_mask = 0; + return; + } + + if (outerhint != HVA_UNSPECIFIED) + hint = outerhint; + else + hint = innerhint; + + switch (hint) + { + case HVA_UNSPECIFIED: + break; + case HVA_NESTLOOP: + extra->jsa_mask &= JSA_NESTLOOP_ANY; + break; + case HVA_HASHJOIN: + extra->jsa_mask &= JSA_HASHJOIN; + break; + case HVA_MERGEJOIN: + extra->jsa_mask &= JSA_MERGEJOIN_ANY; + break; + } +} + +static hva_hint +get_hint(PlannerInfo *root, Index relid) +{ + RangeTblEntry *rte = planner_rt_fetch(relid, root); + + Assert(rte->eref != NULL && rte->eref->aliasname != NULL); + + if (strncmp(rte->eref->aliasname, "nl_", 3) == 0) + return HVA_NESTLOOP; + else if (strncmp(rte->eref->aliasname, "hj_", 3) == 0) + return HVA_HASHJOIN; + else if (strncmp(rte->eref->aliasname, "mj_", 3) == 0) + return HVA_MERGEJOIN; + else + return HVA_UNSPECIFIED; +} diff --git a/contrib/hint_via_alias/meson.build b/contrib/hint_via_alias/meson.build new file mode 100644 index 00000000000..7e42c5783ab --- /dev/null +++ b/contrib/hint_via_alias/meson.build @@ -0,0 +1,12 @@ +# Copyright (c) 2022-2024, PostgreSQL Global Development Group + +hint_via_alias_sources = files( + 'hint_via_alias.c', +) + +hint_via_alias = shared_module('hint_via_alias', + hint_via_alias_sources, + kwargs: contrib_mod_args, +) + +contrib_targets += hint_via_alias diff --git a/contrib/meson.build b/contrib/meson.build index 4372242c8f3..261e4c480e2 100644 --- a/contrib/meson.build +++ b/contrib/meson.build @@ -30,6 +30,7 @@ subdir('dict_xsyn') subdir('earthdistance') subdir('file_fdw') subdir('fuzzystrmatch') +subdir('hint_via_alias') subdir('hstore') subdir('hstore_plperl') subdir('hstore_plpython') -- 2.39.3 (Apple Git-145)