/*------------------------------------------------------------------------- * * pathnode.c * Routines to manipulate pathlists and create path nodes * * Portions Copyright (c) 1996-2012, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * * * IDENTIFICATION * src/backend/optimizer/util/pathnode.c * *------------------------------------------------------------------------- */ #include "postgres.h" #include #include "miscadmin.h" #include "nodes/nodeFuncs.h" #include "optimizer/clauses.h" #include "optimizer/cost.h" #include "optimizer/pathnode.h" #include "optimizer/paths.h" #include "optimizer/tlist.h" #include "parser/parsetree.h" #include "utils/lsyscache.h" #include "utils/selfuncs.h" typedef enum { COSTS_EQUAL, /* path costs are fuzzily equal */ COSTS_BETTER1, /* first path is cheaper than second */ COSTS_BETTER2, /* second path is cheaper than first */ COSTS_DIFFERENT /* neither path dominates the other on cost */ } PathCostComparison; static void add_parameterized_path(RelOptInfo *parent_rel, Path *new_path); static List *translate_sub_tlist(List *tlist, int relid); static bool query_is_distinct_for(Query *query, List *colnos, List *opids); static Oid distinct_col_search(int colno, List *colnos, List *opids); /***************************************************************************** * MISC. PATH UTILITIES *****************************************************************************/ /* * compare_path_costs * Return -1, 0, or +1 according as path1 is cheaper, the same cost, * or more expensive than path2 for the specified criterion. */ int compare_path_costs(Path *path1, Path *path2, CostSelector criterion) { if (criterion == STARTUP_COST) { if (path1->startup_cost < path2->startup_cost) 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. */ if (path1->total_cost < path2->total_cost) return -1; if (path1->total_cost > path2->total_cost) return +1; } else { if (path1->total_cost < path2->total_cost) return -1; if (path1->total_cost > path2->total_cost) return +1; /* * If paths have the same total cost, order them by startup cost. */ if (path1->startup_cost < path2->startup_cost) return -1; if (path1->startup_cost > path2->startup_cost) return +1; } return 0; } /* * compare_path_fractional_costs * Return -1, 0, or +1 according as path1 is cheaper, the same cost, * or more expensive than path2 for fetching the specified fraction * of the total tuples. * * If fraction is <= 0 or > 1, we interpret it as 1, ie, we select the * path with the cheaper total_cost. */ int compare_fractional_path_costs(Path *path1, Path *path2, double fraction) { Cost cost1, cost2; if (fraction <= 0.0 || fraction >= 1.0) return compare_path_costs(path1, path2, TOTAL_COST); cost1 = path1->startup_cost + fraction * (path1->total_cost - path1->startup_cost); cost2 = path2->startup_cost + fraction * (path2->total_cost - path2->startup_cost); if (cost1 < cost2) return -1; if (cost1 > cost2) return +1; return 0; } /* * compare_path_costs_fuzzily * Compare the costs of two paths to see if either can be said to * dominate the other. * * We use fuzzy comparisons so that add_path() can avoid keeping both of * a pair of paths that really have insignificantly different cost. * The fuzz factor is 1% of the smaller cost. (XXX does this percentage * need to be user-configurable?) * * The two paths are said to have "equal" costs if both startup and total * costs are fuzzily the same. Path1 is said to be better than path2 if * it has fuzzily better startup cost and fuzzily no worse total cost, * or if it has fuzzily better total cost and fuzzily no worse startup cost. * Path2 is better than path1 if the reverse holds. Finally, if one path * is fuzzily better than the other on startup cost and fuzzily worse on * total cost, we just say that their costs are "different", since neither * dominates the other across the whole performance spectrum. */ static PathCostComparison compare_path_costs_fuzzily(Path *path1, Path *path2) { /* * Check total cost first since it's more likely to be different; many * paths have zero startup cost. */ if (path1->total_cost > path2->total_cost * 1.01) { /* path1 fuzzily worse on total cost */ if (path2->startup_cost > path1->startup_cost * 1.01) { /* ... but path2 fuzzily worse on startup, so DIFFERENT */ return COSTS_DIFFERENT; } /* else path2 dominates */ return COSTS_BETTER2; } if (path2->total_cost > path1->total_cost * 1.01) { /* path2 fuzzily worse on total cost */ if (path1->startup_cost > path2->startup_cost * 1.01) { /* ... but path1 fuzzily worse on startup, so DIFFERENT */ return COSTS_DIFFERENT; } /* else path1 dominates */ return COSTS_BETTER1; } /* fuzzily the same on total cost */ if (path1->startup_cost > path2->startup_cost * 1.01) { /* ... but path1 fuzzily worse on startup, so path2 wins */ return COSTS_BETTER2; } if (path2->startup_cost > path1->startup_cost * 1.01) { /* ... but path2 fuzzily worse on startup, so path1 wins */ return COSTS_BETTER1; } /* fuzzily the same on both costs */ return COSTS_EQUAL; } /* * set_cheapest * Find the minimum-cost paths from among a relation's paths, * and save them in the rel's cheapest-path fields. * * Only unparameterized paths are considered candidates for cheapest_startup * and cheapest_total. The cheapest_parameterized_paths list collects paths * that are cheapest-total for their parameterization (i.e., there is no * cheaper path with the same or weaker parameterization). This list always * includes the unparameterized cheapest-total path, too. * * This is normally called only after we've finished constructing the path * list for the rel node. */ void set_cheapest(RelOptInfo *parent_rel) { Path *cheapest_startup_path; Path *cheapest_total_path; bool have_parameterized_paths; ListCell *p; Assert(IsA(parent_rel, RelOptInfo)); cheapest_startup_path = cheapest_total_path = NULL; have_parameterized_paths = false; foreach(p, parent_rel->pathlist) { Path *path = (Path *) lfirst(p); int cmp; /* We only consider unparameterized paths in this step */ if (path->required_outer) { have_parameterized_paths = true; continue; } if (cheapest_total_path == NULL) { cheapest_startup_path = cheapest_total_path = path; continue; } /* * If we find two paths of identical costs, try to keep the * better-sorted one. The paths might have unrelated sort orderings, * in which case we can only guess which might be better to keep, but * if one is superior then we definitely should keep that one. */ cmp = compare_path_costs(cheapest_startup_path, path, STARTUP_COST); if (cmp > 0 || (cmp == 0 && compare_pathkeys(cheapest_startup_path->pathkeys, path->pathkeys) == PATHKEYS_BETTER2)) cheapest_startup_path = path; cmp = compare_path_costs(cheapest_total_path, path, TOTAL_COST); if (cmp > 0 || (cmp == 0 && compare_pathkeys(cheapest_total_path->pathkeys, path->pathkeys) == PATHKEYS_BETTER2)) cheapest_total_path = path; } if (cheapest_total_path == NULL) elog(ERROR, "could not devise a query plan for the given query"); parent_rel->cheapest_startup_path = cheapest_startup_path; parent_rel->cheapest_total_path = cheapest_total_path; parent_rel->cheapest_unique_path = NULL; /* computed only if needed */ /* Seed the parameterized-paths list with the cheapest total */ parent_rel->cheapest_parameterized_paths = list_make1(cheapest_total_path); /* And, if there are any parameterized paths, add them in one at a time */ if (have_parameterized_paths) { foreach(p, parent_rel->pathlist) { Path *path = (Path *) lfirst(p); if (path->required_outer) add_parameterized_path(parent_rel, path); } } } /* * add_path * Consider a potential implementation path for the specified parent rel, * and add it to the rel's pathlist if it is worthy of consideration. * A path is worthy if it has either a better sort order (better pathkeys) * or cheaper cost (on either dimension) than any of the existing old paths * that have the same or superset required_outer rels. * * We also remove from the rel's pathlist any old paths that are dominated * by new_path --- that is, new_path is cheaper, at least as well ordered, * and requires no outer rels not required by old path. * * There is one policy decision embedded in this function, along with its * sibling add_path_precheck: we treat all parameterized paths as having * NIL pathkeys, so that they compete only on cost. This is to reduce * the number of parameterized paths that are kept. See discussion in * src/backend/optimizer/README. * * The pathlist is kept sorted by total_cost, with cheaper paths * at the front. Within this routine, that's simply a speed hack: * doing it that way makes it more likely that we will reject an inferior * path after a few comparisons, rather than many comparisons. * However, add_path_precheck relies on this ordering to exit early * when possible. * * NOTE: discarded Path objects are immediately pfree'd to reduce planner * memory consumption. We dare not try to free the substructure of a Path, * since much of it may be shared with other Paths or the query tree itself; * but just recycling discarded Path nodes is a very useful savings in * a large join tree. We can recycle the List nodes of pathlist, too. * * BUT: we do not pfree IndexPath objects, since they may be referenced as * children of BitmapHeapPaths as well as being paths in their own right. * * 'parent_rel' is the relation entry to which the path corresponds. * 'new_path' is a potential path for parent_rel. * * Returns nothing, but modifies parent_rel->pathlist. */ void add_path(RelOptInfo *parent_rel, Path *new_path) { bool accept_new = true; /* unless we find a superior old path */ ListCell *insert_after = NULL; /* where to insert new item */ List *new_path_pathkeys; ListCell *p1; ListCell *p1_prev; ListCell *p1_next; /* * This is a convenient place to check for query cancel --- no part of the * planner goes very long without calling add_path(). */ CHECK_FOR_INTERRUPTS(); /* Pretend parameterized paths have no pathkeys, per comment above */ new_path_pathkeys = new_path->required_outer ? NIL : new_path->pathkeys; /* * Loop to check proposed new path against old paths. Note it is possible * for more than one old path to be tossed out because new_path dominates * it. * * We can't use foreach here because the loop body may delete the current * list cell. */ p1_prev = NULL; for (p1 = list_head(parent_rel->pathlist); p1 != NULL; p1 = p1_next) { Path *old_path = (Path *) lfirst(p1); bool remove_old = false; /* unless new proves superior */ PathCostComparison costcmp; PathKeysComparison keyscmp; BMS_Comparison outercmp; p1_next = lnext(p1); costcmp = compare_path_costs_fuzzily(new_path, old_path); /* * If the two paths compare differently for startup and total cost, * then we want to keep both, and we can skip comparing pathkeys and * required_outer rels. If they compare the same, proceed with the * other comparisons. (We make the tests in this order because the * cost comparison is most likely to turn out "different", and the * pathkeys comparison next most likely.) */ if (costcmp != COSTS_DIFFERENT) { /* Similarly check to see if either dominates on pathkeys */ List *old_path_pathkeys; old_path_pathkeys = old_path->required_outer ? NIL : old_path->pathkeys; keyscmp = compare_pathkeys(new_path_pathkeys, old_path_pathkeys); if (keyscmp != PATHKEYS_DIFFERENT) { switch (costcmp) { case COSTS_EQUAL: outercmp = bms_subset_compare(new_path->required_outer, old_path->required_outer); if (keyscmp == PATHKEYS_BETTER1) { if (outercmp == BMS_EQUAL || outercmp == BMS_SUBSET1) remove_old = true; /* new dominates old */ } else if (keyscmp == PATHKEYS_BETTER2) { if (outercmp == BMS_EQUAL || outercmp == BMS_SUBSET2) accept_new = false; /* old dominates new */ } else /* keyscmp == PATHKEYS_EQUAL */ { if (outercmp == BMS_EQUAL) { /* * Same pathkeys and outer rels, and fuzzily * the same cost, so keep just one --- but * we'll do an exact cost comparison to decide * which. */ if (compare_path_costs(new_path, old_path, TOTAL_COST) < 0) remove_old = true; /* new dominates old */ else accept_new = false; /* old equals or dominates new */ } else if (outercmp == BMS_SUBSET1) remove_old = true; /* new dominates old */ else if (outercmp == BMS_SUBSET2) accept_new = false; /* old dominates new */ /* else different parameterizations, keep both */ } break; case COSTS_BETTER1: if (keyscmp != PATHKEYS_BETTER2) { outercmp = bms_subset_compare(new_path->required_outer, old_path->required_outer); if (outercmp == BMS_EQUAL || outercmp == BMS_SUBSET1) remove_old = true; /* new dominates old */ } break; case COSTS_BETTER2: if (keyscmp != PATHKEYS_BETTER1) { outercmp = bms_subset_compare(new_path->required_outer, old_path->required_outer); if (outercmp == BMS_EQUAL || outercmp == BMS_SUBSET2) accept_new = false; /* old dominates new */ } break; case COSTS_DIFFERENT: /* * can't get here, but keep this case to keep compiler * quiet */ break; } } } /* * Remove current element from pathlist if dominated by new. */ if (remove_old) { parent_rel->pathlist = list_delete_cell(parent_rel->pathlist, p1, p1_prev); /* * Delete the data pointed-to by the deleted cell, if possible */ if (!IsA(old_path, IndexPath)) pfree(old_path); /* p1_prev does not advance */ } else { /* new belongs after this old path if it has cost >= old's */ if (new_path->total_cost >= old_path->total_cost) insert_after = p1; /* p1_prev advances */ p1_prev = p1; } /* * If we found an old path that dominates new_path, we can quit * 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) break; } if (accept_new) { /* Accept the new path: insert it at proper place in pathlist */ if (insert_after) lappend_cell(parent_rel->pathlist, insert_after, new_path); else parent_rel->pathlist = lcons(new_path, parent_rel->pathlist); } else { /* Reject and recycle the new path */ if (!IsA(new_path, IndexPath)) pfree(new_path); } } /* * add_path_precheck * Check whether a proposed new path could possibly get accepted. * We assume we know the path's pathkeys and parameterization accurately, * and have lower bounds for its costs. * * At the time this is called, we haven't actually built a Path structure, * so the required information has to be passed piecemeal. */ bool add_path_precheck(RelOptInfo *parent_rel, Cost startup_cost, Cost total_cost, List *pathkeys, Relids required_outer) { List *new_path_pathkeys; ListCell *p1; /* Pretend parameterized paths have no pathkeys, per comment above */ new_path_pathkeys = required_outer ? NIL : pathkeys; foreach(p1, parent_rel->pathlist) { Path *old_path = (Path *) lfirst(p1); PathKeysComparison keyscmp; BMS_Comparison outercmp; /* * We are looking for an old_path that dominates the new path across * all four metrics. If we find one, we can reject the new path. * * For speed, we make exact rather than fuzzy cost comparisons. * If an old path dominates the new path exactly on both costs, it * will surely do so fuzzily. */ if (total_cost >= old_path->total_cost) { if (startup_cost >= old_path->startup_cost) { List *old_path_pathkeys; old_path_pathkeys = old_path->required_outer ? NIL : old_path->pathkeys; keyscmp = compare_pathkeys(new_path_pathkeys, old_path_pathkeys); if (keyscmp == PATHKEYS_EQUAL || keyscmp == PATHKEYS_BETTER2) { outercmp = bms_subset_compare(required_outer, old_path->required_outer); if (outercmp == BMS_EQUAL || outercmp == BMS_SUBSET2) return false; } } } else { /* * Since the pathlist is sorted by total_cost, we can stop * looking once we reach a path with a total_cost larger * than the new path's. */ break; } } return true; } /* * add_parameterized_path * Consider a parameterized implementation path for the specified rel, * and add it to the rel's cheapest_parameterized_paths list if it * belongs there, removing any old entries that it dominates. * * This is essentially a cut-down form of add_path(): we do not care about * startup cost or sort ordering, only total cost and parameterization. * Also, we should not recycle rejected paths, since they will still be * present in the rel's pathlist. * * 'parent_rel' is the relation entry to which the path corresponds. * 'new_path' is a parameterized path for parent_rel. * * Returns nothing, but modifies parent_rel->cheapest_parameterized_paths. */ static void add_parameterized_path(RelOptInfo *parent_rel, Path *new_path) { bool accept_new = true; /* unless we find a superior old path */ ListCell *insert_after = NULL; /* where to insert new item */ ListCell *p1; ListCell *p1_prev; ListCell *p1_next; /* * Loop to check proposed new path against old paths. Note it is possible * for more than one old path to be tossed out because new_path dominates * it. * * We can't use foreach here because the loop body may delete the current * list cell. */ p1_prev = NULL; for (p1 = list_head(parent_rel->cheapest_parameterized_paths); p1 != NULL; p1 = p1_next) { Path *old_path = (Path *) lfirst(p1); bool remove_old = false; /* unless new proves superior */ int costcmp; BMS_Comparison outercmp; p1_next = lnext(p1); costcmp = compare_path_costs(new_path, old_path, TOTAL_COST); outercmp = bms_subset_compare(new_path->required_outer, old_path->required_outer); if (outercmp != BMS_DIFFERENT) { if (costcmp < 0) { if (outercmp != BMS_SUBSET2) remove_old = true; /* new dominates old */ } else if (costcmp > 0) { if (outercmp != BMS_SUBSET1) accept_new = false; /* old dominates new */ } else if (outercmp == BMS_SUBSET1) remove_old = true; /* new dominates old */ else if (outercmp == BMS_SUBSET2) accept_new = false; /* old dominates new */ else { /* Same cost and outer rels, arbitrarily keep the old */ accept_new = false; /* old equals or dominates new */ } } /* * Remove current element from cheapest_parameterized_paths if * dominated by new. */ if (remove_old) { parent_rel->cheapest_parameterized_paths = list_delete_cell(parent_rel->cheapest_parameterized_paths, p1, p1_prev); /* p1_prev does not advance */ } else { /* new belongs after this old path if it has cost >= old's */ if (costcmp >= 0) insert_after = p1; /* p1_prev advances */ p1_prev = p1; } /* * If we found an old path that dominates new_path, we can quit * scanning the list; we will not add new_path, and we assume * new_path cannot dominate any other elements of the list. */ if (!accept_new) break; } if (accept_new) { /* Accept the new path: insert it at proper place in list */ if (insert_after) lappend_cell(parent_rel->cheapest_parameterized_paths, insert_after, new_path); else parent_rel->cheapest_parameterized_paths = lcons(new_path, parent_rel->cheapest_parameterized_paths); } } /***************************************************************************** * PATH NODE CREATION ROUTINES *****************************************************************************/ /* * create_seqscan_path * Creates a path corresponding to a sequential scan, returning the * pathnode. */ Path * create_seqscan_path(PlannerInfo *root, RelOptInfo *rel) { Path *pathnode = makeNode(Path); pathnode->pathtype = T_SeqScan; pathnode->parent = rel; pathnode->pathkeys = NIL; /* seqscan has unordered result */ pathnode->required_outer = NULL; pathnode->param_clauses = NIL; cost_seqscan(pathnode, root, rel); return pathnode; } /* * create_index_path * Creates a path node for an index scan. * * 'index' is a usable index. * 'indexclauses' is a list of RestrictInfo nodes representing clauses * to be used as index qual conditions in the scan. * 'indexclausecols' is an integer list of index column numbers (zero based) * the indexclauses can be used with. * 'indexorderbys' is a list of bare expressions (no RestrictInfos) * to be used as index ordering operators in the scan. * 'indexorderbycols' is an integer list of index column numbers (zero based) * the ordering operators can be used with. * 'pathkeys' describes the ordering of the path. * 'indexscandir' is ForwardScanDirection or BackwardScanDirection * for an ordered index, or NoMovementScanDirection for * an unordered index. * 'indexonly' is true if an index-only scan is wanted. * 'required_outer' is the set of outer relids referenced in indexclauses. * 'loop_count' is the number of repetitions of the indexscan to factor into * estimates of caching behavior. * * Returns the new path node. */ IndexPath * create_index_path(PlannerInfo *root, IndexOptInfo *index, List *indexclauses, List *indexclausecols, List *indexorderbys, List *indexorderbycols, List *pathkeys, ScanDirection indexscandir, bool indexonly, Relids required_outer, double loop_count) { IndexPath *pathnode = makeNode(IndexPath); RelOptInfo *rel = index->rel; List *indexquals, *indexqualcols; pathnode->path.pathtype = indexonly ? T_IndexOnlyScan : T_IndexScan; pathnode->path.parent = rel; pathnode->path.pathkeys = pathkeys; pathnode->path.required_outer = required_outer; if (required_outer) { /* Identify index clauses that are join clauses */ List *jclauses = NIL; ListCell *lc; foreach(lc, indexclauses) { RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc); if (!bms_is_subset(rinfo->clause_relids, rel->relids)) jclauses = lappend(jclauses, rinfo); } pathnode->path.param_clauses = jclauses; } else pathnode->path.param_clauses = NIL; /* Convert clauses to indexquals the executor can handle */ expand_indexqual_conditions(index, indexclauses, indexclausecols, &indexquals, &indexqualcols); /* Fill in the pathnode */ pathnode->indexinfo = index; pathnode->indexclauses = indexclauses; pathnode->indexquals = indexquals; pathnode->indexqualcols = indexqualcols; pathnode->indexorderbys = indexorderbys; pathnode->indexorderbycols = indexorderbycols; pathnode->indexscandir = indexscandir; cost_index(pathnode, root, loop_count); return pathnode; } /* * create_bitmap_heap_path * Creates a path node for a bitmap scan. * * 'bitmapqual' is a tree of IndexPath, BitmapAndPath, and BitmapOrPath nodes. * 'loop_count' is the number of repetitions of the indexscan to factor into * estimates of caching behavior. * * loop_count should match the value used when creating the component * IndexPaths. */ BitmapHeapPath * create_bitmap_heap_path(PlannerInfo *root, RelOptInfo *rel, Path *bitmapqual, double loop_count) { BitmapHeapPath *pathnode = makeNode(BitmapHeapPath); pathnode->path.pathtype = T_BitmapHeapScan; pathnode->path.parent = rel; pathnode->path.pathkeys = NIL; /* always unordered */ pathnode->path.required_outer = bitmapqual->required_outer; pathnode->path.param_clauses = bitmapqual->param_clauses; pathnode->bitmapqual = bitmapqual; cost_bitmap_heap_scan(&pathnode->path, root, rel, bitmapqual, loop_count); return pathnode; } /* * create_bitmap_and_path * Creates a path node representing a BitmapAnd. */ BitmapAndPath * create_bitmap_and_path(PlannerInfo *root, RelOptInfo *rel, List *bitmapquals) { BitmapAndPath *pathnode = makeNode(BitmapAndPath); ListCell *lc; pathnode->path.pathtype = T_BitmapAnd; pathnode->path.parent = rel; pathnode->path.pathkeys = NIL; /* always unordered */ pathnode->path.required_outer = NULL; pathnode->path.param_clauses = NIL; pathnode->bitmapquals = bitmapquals; /* required_outer and param_clauses are the union of the inputs' values */ foreach(lc, bitmapquals) { Path *bpath = (Path *) lfirst(lc); pathnode->path.required_outer = bms_add_members(pathnode->path.required_outer, bpath->required_outer); pathnode->path.param_clauses = list_concat(pathnode->path.param_clauses, list_copy(bpath->param_clauses)); } /* this sets bitmapselectivity as well as the regular cost fields: */ cost_bitmap_and_node(pathnode, root); return pathnode; } /* * create_bitmap_or_path * Creates a path node representing a BitmapOr. */ BitmapOrPath * create_bitmap_or_path(PlannerInfo *root, RelOptInfo *rel, List *bitmapquals) { BitmapOrPath *pathnode = makeNode(BitmapOrPath); ListCell *lc; pathnode->path.pathtype = T_BitmapOr; pathnode->path.parent = rel; pathnode->path.pathkeys = NIL; /* always unordered */ pathnode->path.required_outer = NULL; pathnode->path.param_clauses = NIL; pathnode->bitmapquals = bitmapquals; /* required_outer and param_clauses are the union of the inputs' values */ foreach(lc, bitmapquals) { Path *bpath = (Path *) lfirst(lc); pathnode->path.required_outer = bms_add_members(pathnode->path.required_outer, bpath->required_outer); pathnode->path.param_clauses = list_concat(pathnode->path.param_clauses, list_copy(bpath->param_clauses)); } /* this sets bitmapselectivity as well as the regular cost fields: */ cost_bitmap_or_node(pathnode, root); return pathnode; } /* * create_tidscan_path * Creates a path corresponding to a scan by TID, returning the pathnode. */ TidPath * create_tidscan_path(PlannerInfo *root, RelOptInfo *rel, List *tidquals) { TidPath *pathnode = makeNode(TidPath); pathnode->path.pathtype = T_TidScan; pathnode->path.parent = rel; pathnode->path.pathkeys = NIL; pathnode->path.required_outer = NULL; pathnode->path.param_clauses = NIL; pathnode->tidquals = tidquals; cost_tidscan(&pathnode->path, root, rel, tidquals); return pathnode; } /* * create_append_path * Creates a path corresponding to an Append plan, returning the * pathnode. * * Note that we must handle subpaths = NIL, representing a dummy access path. */ AppendPath * create_append_path(RelOptInfo *rel, List *subpaths) { AppendPath *pathnode = makeNode(AppendPath); ListCell *l; pathnode->path.pathtype = T_Append; pathnode->path.parent = rel; pathnode->path.pathkeys = NIL; /* result is always considered * unsorted */ pathnode->path.required_outer = NULL; /* updated below */ pathnode->path.param_clauses = NIL; /* XXX see below */ pathnode->subpaths = subpaths; /* * We don't bother with inventing a cost_append(), but just do it here. * * Compute rows and costs as sums of subplan rows and costs. We charge * nothing extra for the Append itself, which perhaps is too optimistic, * but since it doesn't do any selection or projection, it is a pretty * cheap node. If you change this, see also make_append(). * * We also compute the correct required_outer set, namely the union of * the input paths' requirements. * * XXX We should also compute a proper param_clauses list, but that * will require identifying which joinclauses are enforced by all the * subplans, as well as locating the original parent RestrictInfo from * which they were generated. For the moment we punt and leave the list * as NIL. This will result in uselessly rechecking such joinclauses * at the parameter-supplying nestloop join, which is slightly annoying, * as well as overestimating the sizes of any intermediate joins, which * is significantly more annoying. */ pathnode->path.rows = 0; pathnode->path.startup_cost = 0; pathnode->path.total_cost = 0; foreach(l, subpaths) { Path *subpath = (Path *) lfirst(l); pathnode->path.rows += subpath->rows; if (l == list_head(subpaths)) /* first node? */ pathnode->path.startup_cost = subpath->startup_cost; pathnode->path.total_cost += subpath->total_cost; pathnode->path.required_outer = bms_add_members(pathnode->path.required_outer, subpath->required_outer); } return pathnode; } /* * create_merge_append_path * Creates a path corresponding to a MergeAppend plan, returning the * pathnode. */ MergeAppendPath * create_merge_append_path(PlannerInfo *root, RelOptInfo *rel, List *subpaths, List *pathkeys) { MergeAppendPath *pathnode = makeNode(MergeAppendPath); Cost input_startup_cost; Cost input_total_cost; ListCell *l; pathnode->path.pathtype = T_MergeAppend; pathnode->path.parent = rel; pathnode->path.pathkeys = pathkeys; pathnode->path.required_outer = NULL; /* updated below */ pathnode->path.param_clauses = NIL; /* XXX see below */ pathnode->subpaths = subpaths; /* * Apply query-wide LIMIT if known and path is for sole base relation. * Finding out the latter at this low level is a bit klugy. */ pathnode->limit_tuples = root->limit_tuples; if (pathnode->limit_tuples >= 0) { Index rti; for (rti = 1; rti < root->simple_rel_array_size; rti++) { RelOptInfo *brel = root->simple_rel_array[rti]; if (brel == NULL) continue; /* ignore RTEs that are "other rels" */ if (brel->reloptkind != RELOPT_BASEREL) continue; if (brel != rel) { /* Oops, it's a join query */ pathnode->limit_tuples = -1.0; break; } } } /* * Add up the sizes and costs of the input paths, and also compute the * real required_outer value. * * XXX as in create_append_path(), we should compute param_clauses but * it will require more work. */ pathnode->path.rows = 0; input_startup_cost = 0; input_total_cost = 0; foreach(l, subpaths) { Path *subpath = (Path *) lfirst(l); pathnode->path.rows += subpath->rows; if (pathkeys_contained_in(pathkeys, subpath->pathkeys)) { /* Subpath is adequately ordered, we won't need to sort it */ input_startup_cost += subpath->startup_cost; input_total_cost += subpath->total_cost; } else { /* We'll need to insert a Sort node, so include cost for that */ Path sort_path; /* dummy for result of cost_sort */ cost_sort(&sort_path, root, pathkeys, subpath->total_cost, subpath->parent->tuples, subpath->parent->width, 0.0, work_mem, pathnode->limit_tuples); input_startup_cost += sort_path.startup_cost; input_total_cost += sort_path.total_cost; } pathnode->path.required_outer = bms_add_members(pathnode->path.required_outer, subpath->required_outer); } /* Now we can compute total costs of the MergeAppend */ cost_merge_append(&pathnode->path, root, pathkeys, list_length(subpaths), input_startup_cost, input_total_cost, rel->tuples); return pathnode; } /* * create_result_path * Creates a path representing a Result-and-nothing-else plan. * This is only used for the case of a query with an empty jointree. */ ResultPath * create_result_path(List *quals) { ResultPath *pathnode = makeNode(ResultPath); pathnode->path.pathtype = T_Result; pathnode->path.parent = NULL; pathnode->path.pathkeys = NIL; pathnode->path.required_outer = NULL; pathnode->path.param_clauses = NIL; pathnode->quals = quals; /* Hardly worth defining a cost_result() function ... just do it */ pathnode->path.rows = 1; pathnode->path.startup_cost = 0; pathnode->path.total_cost = cpu_tuple_cost; /* * In theory we should include the qual eval cost as well, but at present * that doesn't accomplish much except duplicate work that will be done * again in make_result; since this is only used for degenerate cases, * nothing interesting will be done with the path cost values... */ return pathnode; } /* * create_material_path * Creates a path corresponding to a Material plan, returning the * pathnode. */ MaterialPath * create_material_path(RelOptInfo *rel, Path *subpath) { MaterialPath *pathnode = makeNode(MaterialPath); pathnode->path.pathtype = T_Material; pathnode->path.parent = rel; pathnode->path.pathkeys = subpath->pathkeys; pathnode->path.required_outer = subpath->required_outer; pathnode->path.param_clauses = subpath->param_clauses; pathnode->subpath = subpath; cost_material(&pathnode->path, subpath->startup_cost, subpath->total_cost, subpath->rows, rel->width); return pathnode; } /* * create_unique_path * Creates a path representing elimination of distinct rows from the * input data. Distinct-ness is defined according to the needs of the * semijoin represented by sjinfo. If it is not possible to identify * how to make the data unique, NULL is returned. * * If used at all, this is likely to be called repeatedly on the same rel; * and the input subpath should always be the same (the cheapest_total path * for the rel). So we cache the result. */ UniquePath * create_unique_path(PlannerInfo *root, RelOptInfo *rel, Path *subpath, SpecialJoinInfo *sjinfo) { UniquePath *pathnode; Path sort_path; /* dummy for result of cost_sort */ Path agg_path; /* dummy for result of cost_agg */ MemoryContext oldcontext; List *in_operators; List *uniq_exprs; bool all_btree; bool all_hash; int numCols; ListCell *lc; /* Caller made a mistake if subpath isn't cheapest_total ... */ Assert(subpath == rel->cheapest_total_path); /* ... or if SpecialJoinInfo is the wrong one */ Assert(sjinfo->jointype == JOIN_SEMI); Assert(bms_equal(rel->relids, sjinfo->syn_righthand)); /* If result already cached, return it */ if (rel->cheapest_unique_path) return (UniquePath *) rel->cheapest_unique_path; /* If we previously failed, return NULL quickly */ if (sjinfo->join_quals == NIL) return NULL; /* * We must ensure path struct and subsidiary data are allocated in main * planning context; otherwise GEQO memory management causes trouble. */ oldcontext = MemoryContextSwitchTo(root->planner_cxt); /*---------- * Look to see whether the semijoin's join quals consist of AND'ed * equality operators, with (only) RHS variables on only one side of * each one. If so, we can figure out how to enforce uniqueness for * the RHS. * * Note that the input join_quals list is the list of quals that are * *syntactically* associated with the semijoin, which in practice means * the synthesized comparison list for an IN or the WHERE of an EXISTS. * Particularly in the latter case, it might contain clauses that aren't * *semantically* associated with the join, but refer to just one side or * the other. We can ignore such clauses here, as they will just drop * down to be processed within one side or the other. (It is okay to * consider only the syntactically-associated clauses here because for a * semijoin, no higher-level quals could refer to the RHS, and so there * can be no other quals that are semantically associated with this join. * We do things this way because it is useful to be able to run this test * before we have extracted the list of quals that are actually * semantically associated with the particular join.) * * Note that the in_operators list consists of the joinqual operators * themselves (but commuted if needed to put the RHS value on the right). * These could be cross-type operators, in which case the operator * actually needed for uniqueness is a related single-type operator. * We assume here that that operator will be available from the btree * or hash opclass when the time comes ... if not, create_unique_plan() * will fail. *---------- */ in_operators = NIL; uniq_exprs = NIL; all_btree = true; all_hash = enable_hashagg; /* don't consider hash if not enabled */ foreach(lc, sjinfo->join_quals) { OpExpr *op = (OpExpr *) lfirst(lc); Oid opno; Node *left_expr; Node *right_expr; Relids left_varnos; Relids right_varnos; Relids all_varnos; Oid opinputtype; /* Is it a binary opclause? */ if (!IsA(op, OpExpr) || list_length(op->args) != 2) { /* No, but does it reference both sides? */ all_varnos = pull_varnos((Node *) op); if (!bms_overlap(all_varnos, sjinfo->syn_righthand) || bms_is_subset(all_varnos, sjinfo->syn_righthand)) { /* * Clause refers to only one rel, so ignore it --- unless it * contains volatile functions, in which case we'd better * punt. */ if (contain_volatile_functions((Node *) op)) goto no_unique_path; continue; } /* Non-operator clause referencing both sides, must punt */ goto no_unique_path; } /* Extract data from binary opclause */ opno = op->opno; left_expr = linitial(op->args); right_expr = lsecond(op->args); left_varnos = pull_varnos(left_expr); right_varnos = pull_varnos(right_expr); all_varnos = bms_union(left_varnos, right_varnos); opinputtype = exprType(left_expr); /* Does it reference both sides? */ if (!bms_overlap(all_varnos, sjinfo->syn_righthand) || bms_is_subset(all_varnos, sjinfo->syn_righthand)) { /* * Clause refers to only one rel, so ignore it --- unless it * contains volatile functions, in which case we'd better punt. */ if (contain_volatile_functions((Node *) op)) goto no_unique_path; continue; } /* check rel membership of arguments */ if (!bms_is_empty(right_varnos) && bms_is_subset(right_varnos, sjinfo->syn_righthand) && !bms_overlap(left_varnos, sjinfo->syn_righthand)) { /* typical case, right_expr is RHS variable */ } else if (!bms_is_empty(left_varnos) && bms_is_subset(left_varnos, sjinfo->syn_righthand) && !bms_overlap(right_varnos, sjinfo->syn_righthand)) { /* flipped case, left_expr is RHS variable */ opno = get_commutator(opno); if (!OidIsValid(opno)) goto no_unique_path; right_expr = left_expr; } else goto no_unique_path; /* all operators must be btree equality or hash equality */ if (all_btree) { /* oprcanmerge is considered a hint... */ if (!op_mergejoinable(opno, opinputtype) || get_mergejoin_opfamilies(opno) == NIL) all_btree = false; } if (all_hash) { /* ... but oprcanhash had better be correct */ if (!op_hashjoinable(opno, opinputtype)) all_hash = false; } if (!(all_btree || all_hash)) goto no_unique_path; /* so far so good, keep building lists */ in_operators = lappend_oid(in_operators, opno); uniq_exprs = lappend(uniq_exprs, copyObject(right_expr)); } /* Punt if we didn't find at least one column to unique-ify */ if (uniq_exprs == NIL) goto no_unique_path; /* * The expressions we'd need to unique-ify mustn't be volatile. */ if (contain_volatile_functions((Node *) uniq_exprs)) goto no_unique_path; /* * If we get here, we can unique-ify using at least one of sorting and * hashing. Start building the result Path object. */ pathnode = makeNode(UniquePath); pathnode->path.pathtype = T_Unique; pathnode->path.parent = rel; /* * Assume the output is unsorted, since we don't necessarily have pathkeys * to represent it. (This might get overridden below.) */ pathnode->path.pathkeys = NIL; pathnode->path.required_outer = subpath->required_outer; pathnode->path.param_clauses = subpath->param_clauses; pathnode->subpath = subpath; pathnode->in_operators = in_operators; pathnode->uniq_exprs = uniq_exprs; /* * If the input is a relation and it has a unique index that proves the * uniq_exprs are unique, then we don't need to do anything. Note that * relation_has_unique_index_for automatically considers restriction * clauses for the rel, as well. */ if (rel->rtekind == RTE_RELATION && all_btree && relation_has_unique_index_for(root, rel, NIL, uniq_exprs, in_operators)) { pathnode->umethod = UNIQUE_PATH_NOOP; pathnode->path.rows = rel->rows; pathnode->path.startup_cost = subpath->startup_cost; pathnode->path.total_cost = subpath->total_cost; pathnode->path.pathkeys = subpath->pathkeys; rel->cheapest_unique_path = (Path *) pathnode; MemoryContextSwitchTo(oldcontext); return pathnode; } /* * If the input is a subquery whose output must be unique already, then we * don't need to do anything. The test for uniqueness has to consider * exactly which columns we are extracting; for example "SELECT DISTINCT * x,y" doesn't guarantee that x alone is distinct. So we cannot check for * this optimization unless uniq_exprs consists only of simple Vars * referencing subquery outputs. (Possibly we could do something with * expressions in the subquery outputs, too, but for now keep it simple.) */ if (rel->rtekind == RTE_SUBQUERY) { RangeTblEntry *rte = planner_rt_fetch(rel->relid, root); List *sub_tlist_colnos; sub_tlist_colnos = translate_sub_tlist(uniq_exprs, rel->relid); if (sub_tlist_colnos && query_is_distinct_for(rte->subquery, sub_tlist_colnos, in_operators)) { pathnode->umethod = UNIQUE_PATH_NOOP; pathnode->path.rows = rel->rows; pathnode->path.startup_cost = subpath->startup_cost; pathnode->path.total_cost = subpath->total_cost; pathnode->path.pathkeys = subpath->pathkeys; rel->cheapest_unique_path = (Path *) pathnode; MemoryContextSwitchTo(oldcontext); return pathnode; } } /* Estimate number of output rows */ pathnode->path.rows = estimate_num_groups(root, uniq_exprs, rel->rows); numCols = list_length(uniq_exprs); if (all_btree) { /* * Estimate cost for sort+unique implementation */ cost_sort(&sort_path, root, NIL, subpath->total_cost, rel->rows, rel->width, 0.0, work_mem, -1.0); /* * Charge one cpu_operator_cost per comparison per input tuple. We * assume all columns get compared at most of the tuples. (XXX * probably this is an overestimate.) This should agree with * make_unique. */ sort_path.total_cost += cpu_operator_cost * rel->rows * numCols; } if (all_hash) { /* * Estimate the overhead per hashtable entry at 64 bytes (same as in * planner.c). */ int hashentrysize = rel->width + 64; if (hashentrysize * pathnode->path.rows > work_mem * 1024L) all_hash = false; /* don't try to hash */ else cost_agg(&agg_path, root, AGG_HASHED, NULL, numCols, pathnode->path.rows, subpath->startup_cost, subpath->total_cost, rel->rows); } if (all_btree && all_hash) { if (agg_path.total_cost < sort_path.total_cost) pathnode->umethod = UNIQUE_PATH_HASH; else pathnode->umethod = UNIQUE_PATH_SORT; } else if (all_btree) pathnode->umethod = UNIQUE_PATH_SORT; else if (all_hash) pathnode->umethod = UNIQUE_PATH_HASH; else goto no_unique_path; if (pathnode->umethod == UNIQUE_PATH_HASH) { pathnode->path.startup_cost = agg_path.startup_cost; pathnode->path.total_cost = agg_path.total_cost; } else { pathnode->path.startup_cost = sort_path.startup_cost; pathnode->path.total_cost = sort_path.total_cost; } rel->cheapest_unique_path = (Path *) pathnode; MemoryContextSwitchTo(oldcontext); return pathnode; no_unique_path: /* failure exit */ /* Mark the SpecialJoinInfo as not unique-able */ sjinfo->join_quals = NIL; MemoryContextSwitchTo(oldcontext); return NULL; } /* * translate_sub_tlist - get subquery column numbers represented by tlist * * The given targetlist usually contains only Vars referencing the given relid. * Extract their varattnos (ie, the column numbers of the subquery) and return * as an integer List. * * If any of the tlist items is not a simple Var, we cannot determine whether * the subquery's uniqueness condition (if any) matches ours, so punt and * return NIL. */ static List * translate_sub_tlist(List *tlist, int relid) { List *result = NIL; ListCell *l; foreach(l, tlist) { Var *var = (Var *) lfirst(l); if (!var || !IsA(var, Var) || var->varno != relid) return NIL; /* punt */ result = lappend_int(result, var->varattno); } return result; } /* * query_is_distinct_for - does query never return duplicates of the * specified columns? * * colnos is an integer list of output column numbers (resno's). We are * interested in whether rows consisting of just these columns are certain * to be distinct. "Distinctness" is defined according to whether the * corresponding upper-level equality operators listed in opids would think * the values are distinct. (Note: the opids entries could be cross-type * operators, and thus not exactly the equality operators that the subquery * would use itself. We use equality_ops_are_compatible() to check * compatibility. That looks at btree or hash opfamily membership, and so * should give trustworthy answers for all operators that we might need * to deal with here.) */ static bool query_is_distinct_for(Query *query, List *colnos, List *opids) { ListCell *l; Oid opid; Assert(list_length(colnos) == list_length(opids)); /* * DISTINCT (including DISTINCT ON) guarantees uniqueness if all the * columns in the DISTINCT clause appear in colnos and operator semantics * match. */ if (query->distinctClause) { foreach(l, query->distinctClause) { SortGroupClause *sgc = (SortGroupClause *) lfirst(l); TargetEntry *tle = get_sortgroupclause_tle(sgc, query->targetList); opid = distinct_col_search(tle->resno, colnos, opids); if (!OidIsValid(opid) || !equality_ops_are_compatible(opid, sgc->eqop)) break; /* exit early if no match */ } if (l == NULL) /* had matches for all? */ return true; } /* * Similarly, GROUP BY guarantees uniqueness if all the grouped columns * appear in colnos and operator semantics match. */ if (query->groupClause) { foreach(l, query->groupClause) { SortGroupClause *sgc = (SortGroupClause *) lfirst(l); TargetEntry *tle = get_sortgroupclause_tle(sgc, query->targetList); opid = distinct_col_search(tle->resno, colnos, opids); if (!OidIsValid(opid) || !equality_ops_are_compatible(opid, sgc->eqop)) break; /* exit early if no match */ } if (l == NULL) /* had matches for all? */ return true; } else { /* * If we have no GROUP BY, but do have aggregates or HAVING, then the * result is at most one row so it's surely unique, for any operators. */ if (query->hasAggs || query->havingQual) return true; } /* * UNION, INTERSECT, EXCEPT guarantee uniqueness of the whole output row, * except with ALL. */ if (query->setOperations) { SetOperationStmt *topop = (SetOperationStmt *) query->setOperations; Assert(IsA(topop, SetOperationStmt)); Assert(topop->op != SETOP_NONE); if (!topop->all) { ListCell *lg; /* We're good if all the nonjunk output columns are in colnos */ lg = list_head(topop->groupClauses); foreach(l, query->targetList) { TargetEntry *tle = (TargetEntry *) lfirst(l); SortGroupClause *sgc; if (tle->resjunk) continue; /* ignore resjunk columns */ /* non-resjunk columns should have grouping clauses */ Assert(lg != NULL); sgc = (SortGroupClause *) lfirst(lg); lg = lnext(lg); opid = distinct_col_search(tle->resno, colnos, opids); if (!OidIsValid(opid) || !equality_ops_are_compatible(opid, sgc->eqop)) break; /* exit early if no match */ } if (l == NULL) /* had matches for all? */ return true; } } /* * XXX Are there any other cases in which we can easily see the result * must be distinct? */ return false; } /* * distinct_col_search - subroutine for query_is_distinct_for * * If colno is in colnos, return the corresponding element of opids, * else return InvalidOid. (We expect colnos does not contain duplicates, * so the result is well-defined.) */ static Oid distinct_col_search(int colno, List *colnos, List *opids) { ListCell *lc1, *lc2; forboth(lc1, colnos, lc2, opids) { if (colno == lfirst_int(lc1)) return lfirst_oid(lc2); } return InvalidOid; } /* * create_subqueryscan_path * Creates a path corresponding to a sequential scan of a subquery, * returning the pathnode. */ Path * create_subqueryscan_path(RelOptInfo *rel, List *pathkeys) { Path *pathnode = makeNode(Path); pathnode->pathtype = T_SubqueryScan; pathnode->parent = rel; pathnode->pathkeys = pathkeys; pathnode->required_outer = NULL; pathnode->param_clauses = NIL; cost_subqueryscan(pathnode, rel); return pathnode; } /* * create_functionscan_path * Creates a path corresponding to a sequential scan of a function, * returning the pathnode. */ Path * create_functionscan_path(PlannerInfo *root, RelOptInfo *rel) { Path *pathnode = makeNode(Path); pathnode->pathtype = T_FunctionScan; pathnode->parent = rel; pathnode->pathkeys = NIL; /* for now, assume unordered result */ pathnode->required_outer = NULL; pathnode->param_clauses = NIL; cost_functionscan(pathnode, root, rel); return pathnode; } /* * create_valuesscan_path * Creates a path corresponding to a scan of a VALUES list, * returning the pathnode. */ Path * create_valuesscan_path(PlannerInfo *root, RelOptInfo *rel) { Path *pathnode = makeNode(Path); pathnode->pathtype = T_ValuesScan; pathnode->parent = rel; pathnode->pathkeys = NIL; /* result is always unordered */ pathnode->required_outer = NULL; pathnode->param_clauses = NIL; cost_valuesscan(pathnode, root, rel); return pathnode; } /* * create_ctescan_path * Creates a path corresponding to a scan of a non-self-reference CTE, * returning the pathnode. */ Path * create_ctescan_path(PlannerInfo *root, RelOptInfo *rel) { Path *pathnode = makeNode(Path); pathnode->pathtype = T_CteScan; pathnode->parent = rel; pathnode->pathkeys = NIL; /* XXX for now, result is always unordered */ pathnode->required_outer = NULL; pathnode->param_clauses = NIL; cost_ctescan(pathnode, root, rel); return pathnode; } /* * create_worktablescan_path * Creates a path corresponding to a scan of a self-reference CTE, * returning the pathnode. */ Path * create_worktablescan_path(PlannerInfo *root, RelOptInfo *rel) { Path *pathnode = makeNode(Path); pathnode->pathtype = T_WorkTableScan; pathnode->parent = rel; pathnode->pathkeys = NIL; /* result is always unordered */ pathnode->required_outer = NULL; pathnode->param_clauses = NIL; /* Cost is the same as for a regular CTE scan */ cost_ctescan(pathnode, root, rel); return pathnode; } /* * create_foreignscan_path * Creates a path corresponding to a scan of a foreign table, * returning the pathnode. * * This function is never called from core Postgres; rather, it's expected * to be called by the GetForeignPaths function of a foreign data wrapper. * We make the FDW supply all fields of the path, since we do not have any * way to calculate them in core. */ ForeignPath * create_foreignscan_path(PlannerInfo *root, RelOptInfo *rel, double rows, Cost startup_cost, Cost total_cost, List *pathkeys, Relids required_outer, List *param_clauses, List *fdw_private) { ForeignPath *pathnode = makeNode(ForeignPath); pathnode->path.pathtype = T_ForeignScan; pathnode->path.parent = rel; pathnode->path.rows = rows; pathnode->path.startup_cost = startup_cost; pathnode->path.total_cost = total_cost; pathnode->path.pathkeys = pathkeys; pathnode->path.required_outer = required_outer; pathnode->path.param_clauses = param_clauses; pathnode->fdw_private = fdw_private; return pathnode; } /* * calc_nestloop_required_outer * Compute the required_outer set for a nestloop join path * * Note: result must not share storage with either input */ Relids calc_nestloop_required_outer(Path *outer_path, Path *inner_path) { Relids required_outer; /* inner_path can require rels from outer path, but not vice versa */ Assert(!bms_overlap(outer_path->required_outer, inner_path->parent->relids)); /* easy case if inner path is not parameterized */ if (!inner_path->required_outer) return bms_copy(outer_path->required_outer); /* else, form the union ... */ required_outer = bms_union(outer_path->required_outer, inner_path->required_outer); /* ... and remove any mention of now-satisfied outer rels */ required_outer = bms_del_members(required_outer, outer_path->parent->relids); /* maintain invariant that required_outer is exactly NULL if empty */ if (bms_is_empty(required_outer)) { bms_free(required_outer); required_outer = NULL; } return required_outer; } /* * calc_non_nestloop_required_outer * Compute the required_outer set for a merge or hash join path * * Note: result must not share storage with either input */ Relids calc_non_nestloop_required_outer(Path *outer_path, Path *inner_path) { Relids required_outer; /* neither path can require rels from the other */ Assert(!bms_overlap(outer_path->required_outer, inner_path->parent->relids)); Assert(!bms_overlap(inner_path->required_outer, outer_path->parent->relids)); /* form the union ... */ required_outer = bms_union(outer_path->required_outer, inner_path->required_outer); /* we do not need an explicit test for empty; bms_union gets it right */ return required_outer; } /* * create_nestloop_path * Creates a pathnode corresponding to a nestloop join between two * relations. * * 'joinrel' is the join relation. * 'jointype' is the type of join required * 'workspace' is the result from initial_cost_nestloop * 'sjinfo' is extra info about the join for selectivity estimation * 'semifactors' contains valid data if jointype is SEMI or ANTI * 'outer_path' is the outer path * 'inner_path' is the inner path * 'restrict_clauses' are the RestrictInfo nodes to apply at the join * 'pathkeys' are the path keys of the new join path * 'required_outer' is the set of required outer rels * * Returns the resulting path node. */ NestPath * create_nestloop_path(PlannerInfo *root, RelOptInfo *joinrel, JoinType jointype, JoinCostWorkspace *workspace, SpecialJoinInfo *sjinfo, SemiAntiJoinFactors *semifactors, Path *outer_path, Path *inner_path, List *restrict_clauses, List *pathkeys, Relids required_outer) { NestPath *pathnode = makeNode(NestPath); pathnode->path.pathtype = T_NestLoop; pathnode->path.parent = joinrel; pathnode->path.pathkeys = pathkeys; pathnode->path.required_outer = required_outer; if (pathnode->path.required_outer) { /* Identify parameter clauses not yet applied here */ List *jclauses; ListCell *lc; /* LHS clauses could not be satisfied here */ jclauses = list_copy(outer_path->param_clauses); foreach(lc, inner_path->param_clauses) { RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc); if (!bms_is_subset(rinfo->clause_relids, joinrel->relids)) jclauses = lappend(jclauses, rinfo); } pathnode->path.param_clauses = jclauses; } else pathnode->path.param_clauses = NIL; pathnode->jointype = jointype; pathnode->outerjoinpath = outer_path; pathnode->innerjoinpath = inner_path; pathnode->joinrestrictinfo = restrict_clauses; final_cost_nestloop(root, pathnode, workspace, sjinfo, semifactors); return pathnode; } /* * create_mergejoin_path * Creates a pathnode corresponding to a mergejoin join between * two relations * * 'joinrel' is the join relation * 'jointype' is the type of join required * 'workspace' is the result from initial_cost_mergejoin * 'sjinfo' is extra info about the join for selectivity estimation * 'outer_path' is the outer path * 'inner_path' is the inner path * 'restrict_clauses' are the RestrictInfo nodes to apply at the join * 'pathkeys' are the path keys of the new join path * 'required_outer' is the set of required outer rels * 'mergeclauses' are the RestrictInfo nodes to use as merge clauses * (this should be a subset of the restrict_clauses list) * 'outersortkeys' are the sort varkeys for the outer relation * 'innersortkeys' are the sort varkeys for the inner relation */ MergePath * create_mergejoin_path(PlannerInfo *root, RelOptInfo *joinrel, JoinType jointype, JoinCostWorkspace *workspace, SpecialJoinInfo *sjinfo, Path *outer_path, Path *inner_path, List *restrict_clauses, List *pathkeys, Relids required_outer, List *mergeclauses, List *outersortkeys, List *innersortkeys) { MergePath *pathnode = makeNode(MergePath); pathnode->jpath.path.pathtype = T_MergeJoin; pathnode->jpath.path.parent = joinrel; pathnode->jpath.path.pathkeys = pathkeys; pathnode->jpath.path.required_outer = required_outer; pathnode->jpath.path.param_clauses = list_concat(list_copy(outer_path->param_clauses), inner_path->param_clauses); pathnode->jpath.jointype = jointype; pathnode->jpath.outerjoinpath = outer_path; pathnode->jpath.innerjoinpath = inner_path; pathnode->jpath.joinrestrictinfo = restrict_clauses; pathnode->path_mergeclauses = mergeclauses; pathnode->outersortkeys = outersortkeys; pathnode->innersortkeys = innersortkeys; /* pathnode->materialize_inner will be set by final_cost_mergejoin */ final_cost_mergejoin(root, pathnode, workspace, sjinfo); return pathnode; } /* * create_hashjoin_path * Creates a pathnode corresponding to a hash join between two relations. * * 'joinrel' is the join relation * 'jointype' is the type of join required * 'workspace' is the result from initial_cost_hashjoin * 'sjinfo' is extra info about the join for selectivity estimation * 'semifactors' contains valid data if jointype is SEMI or ANTI * 'outer_path' is the cheapest outer path * 'inner_path' is the cheapest inner path * 'restrict_clauses' are the RestrictInfo nodes to apply at the join * 'required_outer' is the set of required outer rels * 'hashclauses' are the RestrictInfo nodes to use as hash clauses * (this should be a subset of the restrict_clauses list) */ HashPath * create_hashjoin_path(PlannerInfo *root, RelOptInfo *joinrel, JoinType jointype, JoinCostWorkspace *workspace, SpecialJoinInfo *sjinfo, SemiAntiJoinFactors *semifactors, Path *outer_path, Path *inner_path, List *restrict_clauses, Relids required_outer, List *hashclauses) { HashPath *pathnode = makeNode(HashPath); pathnode->jpath.path.pathtype = T_HashJoin; pathnode->jpath.path.parent = joinrel; /* * A hashjoin never has pathkeys, since its output ordering is * unpredictable due to possible batching. XXX If the inner relation is * small enough, we could instruct the executor that it must not batch, * and then we could assume that the output inherits the outer relation's * ordering, which might save a sort step. However there is considerable * downside if our estimate of the inner relation size is badly off. For * the moment we don't risk it. (Note also that if we wanted to take this * seriously, joinpath.c would have to consider many more paths for the * outer rel than it does now.) */ pathnode->jpath.path.pathkeys = NIL; pathnode->jpath.path.required_outer = required_outer; pathnode->jpath.path.param_clauses = list_concat(list_copy(outer_path->param_clauses), inner_path->param_clauses); pathnode->jpath.jointype = jointype; pathnode->jpath.outerjoinpath = outer_path; pathnode->jpath.innerjoinpath = inner_path; pathnode->jpath.joinrestrictinfo = restrict_clauses; pathnode->path_hashclauses = hashclauses; /* final_cost_hashjoin will fill in pathnode->num_batches */ final_cost_hashjoin(root, pathnode, workspace, sjinfo, semifactors); return pathnode; }