diff options
Diffstat (limited to 'src/backend/optimizer/util/pathnode.c')
| -rw-r--r-- | src/backend/optimizer/util/pathnode.c | 65 |
1 files changed, 38 insertions, 27 deletions
diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c index 400c813125c..69a28138d8a 100644 --- a/src/backend/optimizer/util/pathnode.c +++ b/src/backend/optimizer/util/pathnode.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/optimizer/util/pathnode.c,v 1.62 2000/03/22 22:08:35 tgl Exp $ + * $Header: /cvsroot/pgsql/src/backend/optimizer/util/pathnode.c,v 1.63 2000/04/12 17:15:24 momjian Exp $ * *------------------------------------------------------------------------- */ @@ -42,6 +42,7 @@ compare_path_costs(Path *path1, Path *path2, CostSelector criterion) return -1; if (path1->startup_cost > path2->startup_cost) return +1; + /* * If paths have the same startup cost (not at all unlikely), * order them by total cost. @@ -57,6 +58,7 @@ compare_path_costs(Path *path1, Path *path2, CostSelector criterion) return -1; if (path1->total_cost > path2->total_cost) return +1; + /* * If paths have the same total cost, order them by startup cost. */ @@ -172,7 +174,8 @@ set_cheapest(RelOptInfo *parent_rel) void add_path(RelOptInfo *parent_rel, Path *new_path) { - bool accept_new = true; /* unless we find a superior old path */ + bool accept_new = true; /* unless we find a superior old + * path */ List *p1_prev = NIL; List *p1; @@ -184,36 +187,39 @@ add_path(RelOptInfo *parent_rel, Path *new_path) foreach(p1, parent_rel->pathlist) { Path *old_path = (Path *) lfirst(p1); - bool remove_old = false; /* unless new proves superior */ + bool remove_old = false; /* unless new proves superior */ int costcmp; costcmp = compare_path_costs(new_path, old_path, TOTAL_COST); + /* - * If the two paths compare differently for startup and total cost, - * then we want to keep both, and we can skip the (much slower) - * comparison of pathkeys. If they compare the same, proceed with - * the pathkeys comparison. Note this test relies on the fact that - * compare_path_costs will only return 0 if both costs are equal - * (and, therefore, there's no need to call it twice in that case). + * If the two paths compare differently for startup and total + * cost, then we want to keep both, and we can skip the (much + * slower) comparison of pathkeys. If they compare the same, + * proceed with the pathkeys comparison. Note this test relies on + * the fact that compare_path_costs will only return 0 if both + * costs are equal (and, therefore, there's no need to call it + * twice in that case). */ if (costcmp == 0 || - costcmp == compare_path_costs(new_path, old_path, STARTUP_COST)) + costcmp == compare_path_costs(new_path, old_path, STARTUP_COST)) { switch (compare_pathkeys(new_path->pathkeys, old_path->pathkeys)) { case PATHKEYS_EQUAL: if (costcmp < 0) - remove_old = true; /* new dominates old */ + remove_old = true; /* new dominates old */ else - accept_new = false; /* old equals or dominates new */ + accept_new = false; /* old equals or dominates + * new */ break; case PATHKEYS_BETTER1: if (costcmp <= 0) - remove_old = true; /* new dominates old */ + remove_old = true; /* new dominates old */ break; case PATHKEYS_BETTER2: if (costcmp >= 0) - accept_new = false; /* old dominates new */ + accept_new = false; /* old dominates new */ break; case PATHKEYS_DIFFERENT: /* keep both paths, since they have different ordering */ @@ -241,7 +247,7 @@ add_path(RelOptInfo *parent_rel, Path *new_path) * scanning the pathlist; we will not add new_path, and we assume * new_path cannot dominate any other elements of the pathlist. */ - if (! accept_new) + if (!accept_new) break; } @@ -315,12 +321,14 @@ create_index_path(Query *root, if (pathnode->path.pathkeys == NIL) { /* No ordering available from index, is that OK? */ - if (! ScanDirectionIsNoMovement(indexscandir)) + if (!ScanDirectionIsNoMovement(indexscandir)) elog(ERROR, "create_index_path: failed to create ordered index scan"); } else { - /* The index is ordered, and build_index_pathkeys defaulted to + + /* + * The index is ordered, and build_index_pathkeys defaulted to * forward scan, so make sure we mark the pathnode properly. */ if (ScanDirectionIsNoMovement(indexscandir)) @@ -341,11 +349,11 @@ create_index_path(Query *root, pathnode->indexscandir = indexscandir; /* - * This routine is only used to generate "standalone" indexpaths, - * not nestloop inner indexpaths. So joinrelids is always NIL - * and the number of rows is the same as the parent rel's estimate. + * This routine is only used to generate "standalone" indexpaths, not + * nestloop inner indexpaths. So joinrelids is always NIL and the + * number of rows is the same as the parent rel's estimate. */ - pathnode->joinrelids = NIL; /* no join clauses here */ + pathnode->joinrelids = NIL; /* no join clauses here */ pathnode->rows = rel->rows; cost_index(&pathnode->path, root, rel, index, indexquals, false); @@ -359,20 +367,23 @@ create_index_path(Query *root, * pathnode. * */ -TidPath * +TidPath * create_tidscan_path(RelOptInfo *rel, List *tideval) { - TidPath *pathnode = makeNode(TidPath); + TidPath *pathnode = makeNode(TidPath); pathnode->path.pathtype = T_TidScan; pathnode->path.parent = rel; pathnode->path.pathkeys = NIL; - pathnode->tideval = copyObject(tideval); /* is copy really necessary? */ + pathnode->tideval = copyObject(tideval); /* is copy really + * necessary? */ pathnode->unjoined_relids = NIL; cost_tidscan(&pathnode->path, rel, tideval); - /* divide selectivity for each clause to get an equal selectivity - * as IndexScan does OK ? + + /* + * divide selectivity for each clause to get an equal selectivity as + * IndexScan does OK ? */ return pathnode; @@ -485,7 +496,7 @@ create_mergejoin_path(RelOptInfo *joinrel, * 'innerdisbursion' is an estimate of the disbursion of the inner hash key * */ -HashPath * +HashPath * create_hashjoin_path(RelOptInfo *joinrel, Path *outer_path, Path *inner_path, |