diff options
Diffstat (limited to 'src/backend/optimizer/path/allpaths.c')
| -rw-r--r-- | src/backend/optimizer/path/allpaths.c | 40 |
1 files changed, 29 insertions, 11 deletions
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c index 0ad3dc5aae1..cc82380dc6d 100644 --- a/src/backend/optimizer/path/allpaths.c +++ b/src/backend/optimizer/path/allpaths.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/optimizer/path/allpaths.c,v 1.164 2007/05/26 18:23:01 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/optimizer/path/allpaths.c,v 1.165 2007/09/26 18:51:50 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -37,6 +37,9 @@ bool enable_geqo = false; /* just in case GUC doesn't set it */ int geqo_threshold; +/* Hook for plugins to replace standard_join_search() */ +join_search_hook_type join_search_hook = NULL; + static void set_base_rel_pathlists(PlannerInfo *root); static void set_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, @@ -53,8 +56,6 @@ static void set_function_pathlist(PlannerInfo *root, RelOptInfo *rel, static void set_values_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte); static RelOptInfo *make_rel_from_joinlist(PlannerInfo *root, List *joinlist); -static RelOptInfo *make_one_rel_by_joins(PlannerInfo *root, int levels_needed, - List *initial_rels); static bool subquery_is_pushdown_safe(Query *subquery, Query *topquery, bool *differentTypes); static bool recurse_pushdown_safe(Node *setOp, Query *topquery, @@ -672,18 +673,20 @@ make_rel_from_joinlist(PlannerInfo *root, List *joinlist) { /* * Consider the different orders in which we could join the rels, - * using either GEQO or regular optimizer. + * using a plugin, GEQO, or the regular join search code. */ - if (enable_geqo && levels_needed >= geqo_threshold) + if (join_search_hook) + return (*join_search_hook) (root, levels_needed, initial_rels); + else if (enable_geqo && levels_needed >= geqo_threshold) return geqo(root, levels_needed, initial_rels); else - return make_one_rel_by_joins(root, levels_needed, initial_rels); + return standard_join_search(root, levels_needed, initial_rels); } } /* - * make_one_rel_by_joins - * Find all possible joinpaths for a query by successively finding ways + * standard_join_search + * Find possible joinpaths for a query by successively finding ways * to join component relations into join relations. * * 'levels_needed' is the number of iterations needed, ie, the number of @@ -691,12 +694,27 @@ make_rel_from_joinlist(PlannerInfo *root, List *joinlist) * * 'initial_rels' is a list of RelOptInfo nodes for each independent * jointree item. These are the components to be joined together. + * Note that levels_needed == list_length(initial_rels). * * Returns the final level of join relations, i.e., the relation that is * the result of joining all the original relations together. + * At least one implementation path must be provided for this relation and + * all required sub-relations. + * + * To support loadable plugins that modify planner behavior by changing the + * join searching algorithm, we provide a hook variable that lets a plugin + * replace or supplement this function. Any such hook must return the same + * final join relation as the standard code would, but it might have a + * different set of implementation paths attached, and only the sub-joinrels + * needed for these paths need have been instantiated. + * + * Note to plugin authors: the functions invoked during standard_join_search() + * modify root->join_rel_list and root->join_rel_hash. If you want to do more + * than one join-order search, you'll probably need to save and restore the + * original states of those data structures. See geqo_eval() for an example. */ -static RelOptInfo * -make_one_rel_by_joins(PlannerInfo *root, int levels_needed, List *initial_rels) +RelOptInfo * +standard_join_search(PlannerInfo *root, int levels_needed, List *initial_rels) { List **joinitems; int lev; @@ -725,7 +743,7 @@ make_one_rel_by_joins(PlannerInfo *root, int levels_needed, List *initial_rels) * level, and build paths for making each one from every available * pair of lower-level relations. */ - joinitems[lev] = make_rels_by_joins(root, lev, joinitems); + joinitems[lev] = join_search_one_level(root, lev, joinitems); /* * Do cleanup work on each just-processed rel. |