diff options
Diffstat (limited to 'src/backend/optimizer/path/allpaths.c')
| -rw-r--r-- | src/backend/optimizer/path/allpaths.c | 69 |
1 files changed, 68 insertions, 1 deletions
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c index 056145ea44c..169b1d53fc8 100644 --- a/src/backend/optimizer/path/allpaths.c +++ b/src/backend/optimizer/path/allpaths.c @@ -1716,6 +1716,7 @@ generate_orderedappend_paths(PlannerInfo *root, RelOptInfo *rel, List *pathkeys = (List *) lfirst(lcp); List *startup_subpaths = NIL; List *total_subpaths = NIL; + List *fractional_subpaths = NIL; bool startup_neq_total = false; ListCell *lcr; bool match_partition_order; @@ -1745,7 +1746,8 @@ generate_orderedappend_paths(PlannerInfo *root, RelOptInfo *rel, { RelOptInfo *childrel = (RelOptInfo *) lfirst(lcr); Path *cheapest_startup, - *cheapest_total; + *cheapest_total, + *cheapest_fractional = NULL; /* Locate the right paths, if they are available. */ cheapest_startup = @@ -1774,6 +1776,37 @@ generate_orderedappend_paths(PlannerInfo *root, RelOptInfo *rel, } /* + * When building a fractional path, determine a cheapest fractional + * path for each child relation too. Looking at startup and total + * costs is not enough, because the cheapest fractional path may be + * dominated by two separate paths (one for startup, one for total). + * + * When needed (building fractional path), determine the cheapest + * fractional path too. + */ + if (root->tuple_fraction > 0) + { + double path_fraction = (1.0 / root->tuple_fraction); + + cheapest_fractional = + get_cheapest_fractional_path_for_pathkeys(childrel->pathlist, + pathkeys, + NULL, + path_fraction); + + /* + * If we found no path with matching pathkeys, use the cheapest + * total path instead. + * + * XXX We might consider partially sorted paths too (with an + * incremental sort on top). But we'd have to build all the + * incremental paths, do the costing etc. + */ + if (!cheapest_fractional) + cheapest_fractional = cheapest_total; + } + + /* * Notice whether we actually have different paths for the * "cheapest" and "total" cases; frequently there will be no point * in two create_merge_append_path() calls. @@ -1799,6 +1832,12 @@ generate_orderedappend_paths(PlannerInfo *root, RelOptInfo *rel, startup_subpaths = lappend(startup_subpaths, cheapest_startup); total_subpaths = lappend(total_subpaths, cheapest_total); + + if (cheapest_fractional) + { + cheapest_fractional = get_singleton_append_subpath(cheapest_fractional); + fractional_subpaths = lappend(fractional_subpaths, cheapest_fractional); + } } else if (match_partition_order_desc) { @@ -1812,6 +1851,12 @@ generate_orderedappend_paths(PlannerInfo *root, RelOptInfo *rel, startup_subpaths = lcons(cheapest_startup, startup_subpaths); total_subpaths = lcons(cheapest_total, total_subpaths); + + if (cheapest_fractional) + { + cheapest_fractional = get_singleton_append_subpath(cheapest_fractional); + fractional_subpaths = lcons(cheapest_fractional, fractional_subpaths); + } } else { @@ -1823,6 +1868,10 @@ generate_orderedappend_paths(PlannerInfo *root, RelOptInfo *rel, &startup_subpaths, NULL); accumulate_append_subpath(cheapest_total, &total_subpaths, NULL); + + if (cheapest_fractional) + accumulate_append_subpath(cheapest_fractional, + &fractional_subpaths, NULL); } } @@ -1849,6 +1898,17 @@ generate_orderedappend_paths(PlannerInfo *root, RelOptInfo *rel, 0, false, -1)); + + if (fractional_subpaths) + add_path(rel, (Path *) create_append_path(root, + rel, + fractional_subpaths, + NIL, + pathkeys, + NULL, + 0, + false, + -1)); } else { @@ -1864,6 +1924,13 @@ generate_orderedappend_paths(PlannerInfo *root, RelOptInfo *rel, total_subpaths, pathkeys, NULL)); + + if (fractional_subpaths) + add_path(rel, (Path *) create_merge_append_path(root, + rel, + fractional_subpaths, + pathkeys, + NULL)); } } } |