diff options
Diffstat (limited to 'src/backend/optimizer/path/allpaths.c')
| -rw-r--r-- | src/backend/optimizer/path/allpaths.c | 47 |
1 files changed, 47 insertions, 0 deletions
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c index 4e6d90d8d8f..0b831891fcb 100644 --- a/src/backend/optimizer/path/allpaths.c +++ b/src/backend/optimizer/path/allpaths.c @@ -61,6 +61,7 @@ set_rel_pathlist_hook_type set_rel_pathlist_hook = NULL; join_search_hook_type join_search_hook = NULL; +static void set_base_rel_consider_startup(PlannerInfo *root); static void set_base_rel_sizes(PlannerInfo *root); static void set_base_rel_pathlists(PlannerInfo *root); static void set_rel_size(PlannerInfo *root, RelOptInfo *rel, @@ -152,6 +153,9 @@ make_one_rel(PlannerInfo *root, List *joinlist) root->all_baserels = bms_add_member(root->all_baserels, brel->relid); } + /* Mark base rels as to whether we care about fast-start plans */ + set_base_rel_consider_startup(root); + /* * Generate access paths for the base rels. */ @@ -172,6 +176,49 @@ make_one_rel(PlannerInfo *root, List *joinlist) } /* + * set_base_rel_consider_startup + * Set the consider_[param_]startup flags for each base-relation entry. + * + * For the moment, we only deal with consider_param_startup here; because the + * logic for consider_startup is pretty trivial and is the same for every base + * relation, we just let build_simple_rel() initialize that flag correctly to + * start with. If that logic ever gets more complicated it would probably + * be better to move it here. + */ +static void +set_base_rel_consider_startup(PlannerInfo *root) +{ + /* + * Since parameterized paths can only be used on the inside of a nestloop + * join plan, there is usually little value in considering fast-start + * plans for them. However, for relations that are on the RHS of a SEMI + * or ANTI join, a fast-start plan can be useful because we're only going + * to care about fetching one tuple anyway. + * + * To minimize growth of planning time, we currently restrict this to + * cases where the RHS is a single base relation, not a join; there is no + * provision for consider_param_startup to get set at all on joinrels. + * Also we don't worry about appendrels. costsize.c's costing rules for + * nestloop semi/antijoins don't consider such cases either. + */ + ListCell *lc; + + foreach(lc, root->join_info_list) + { + SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(lc); + int varno; + + if ((sjinfo->jointype == JOIN_SEMI || sjinfo->jointype == JOIN_ANTI) && + bms_get_singleton_member(sjinfo->syn_righthand, &varno)) + { + RelOptInfo *rel = find_base_rel(root, varno); + + rel->consider_param_startup = true; + } + } +} + +/* * set_base_rel_sizes * Set the size estimates (rows and widths) for each base-relation entry. * |