/*------------------------------------------------------------------------- * * pathnode.c * Routines to manipulate pathlists and create path nodes * * Portions Copyright (c) 1996-2011, 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 "foreign/fdwapi.h" #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" 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_fuzzy_path_costs * Return -1, 0, or +1 according as path1 is cheaper, the same cost, * or more expensive than path2 for the specified criterion. * * This differs from compare_path_costs in that we consider the costs the * same if they agree to within a "fuzz factor". This is used by add_path * to avoid keeping both of a pair of paths that really have insignificantly * different cost. */ static int compare_fuzzy_path_costs(Path *path1, Path *path2, CostSelector criterion) { /* * We use a fuzz factor of 1% of the smaller cost. * * XXX does this percentage need to be user-configurable? */ if (criterion == STARTUP_COST) { if (path1->startup_cost > path2->startup_cost * 1.01) return +1; if (path2->startup_cost > path1->startup_cost * 1.01) 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 * 1.01) return +1; if (path2->total_cost > path1->total_cost * 1.01) return -1; } else { if (path1->total_cost > path2->total_cost * 1.01) return +1; if (path2->total_cost > path1->total_cost * 1.01) return -1; /* * If paths have the same total cost, order them by startup cost. */ if (path1->startup_cost > path2->startup_cost * 1.01) return +1; if (path2->startup_cost > path1->startup_cost * 1.01) 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; } /* * set_cheapest * Find the minimum-cost paths from among a relation's paths, * and save them in the rel's cheapest-path fields. * * This is normally called only after we've finished constructing the path * list for the rel node. * * 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 it. */ void set_cheapest(RelOptInfo *parent_rel) { List *pathlist = parent_rel->pathlist; ListCell *p; Path *cheapest_startup_path; Path *cheapest_total_path; Assert(IsA(parent_rel, RelOptInfo)); if (pathlist == NIL) elog(ERROR, "could not devise a query plan for the given query"); cheapest_startup_path = cheapest_total_path = (Path *) linitial(pathlist); for_each_cell(p, lnext(list_head(pathlist))) { Path *path = (Path *) lfirst(p); int cmp; 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; } 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 */ } /* * 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. * * We also remove from the rel's pathlist any old paths that are dominated * by new_path --- that is, new_path is both cheaper and at least as well * ordered. * * The pathlist is kept sorted by TOTAL_COST metric, with cheaper paths * at the front. No code depends on that for correctness; it's simply * a speed hack within this routine. Doing it that way makes it more * likely that we will reject an inferior path after a few comparisons, * rather than many comparisons. * * 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 */ 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(); /* * 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 */ int costcmp; p1_next = lnext(p1); /* * As of Postgres 8.0, we use fuzzy cost comparison to avoid wasting * cycles keeping paths that are really not significantly different in * cost. */ costcmp = compare_fuzzy_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_fuzzy_path_costs will only return 0 if both costs are * effectively equal (and, therefore, there's no need to call it twice * in that case). */ if (costcmp == 0 || costcmp == compare_fuzzy_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 */ else if (costcmp > 0) accept_new = false; /* old dominates new */ else { /* * Same pathkeys, 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 */ } break; case PATHKEYS_BETTER1: if (costcmp <= 0) remove_old = true; /* new dominates old */ break; case PATHKEYS_BETTER2: if (costcmp >= 0) accept_new = false; /* old dominates new */ break; case PATHKEYS_DIFFERENT: /* keep both paths, since they have different ordering */ 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 (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 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); } } /***************************************************************************** * 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 */ cost_seqscan(pathnode, root, rel); return pathnode; } /* * create_index_path * Creates a path node for an index scan. * * 'index' is a usable index. * 'clause_groups' is a list of lists of RestrictInfo nodes * to be used as index qual conditions in the scan. * 'indexorderbys' is a list of bare expressions (no RestrictInfos) * to be used as index ordering operators in the scan. * '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. * 'outer_rel' is the outer relation if this is a join inner indexscan path. * (pathkeys and indexscandir are ignored if so.) NULL if not. * * Returns the new path node. */ IndexPath * create_index_path(PlannerInfo *root, IndexOptInfo *index, List *clause_groups, List *indexorderbys, List *pathkeys, ScanDirection indexscandir, bool indexonly, RelOptInfo *outer_rel) { IndexPath *pathnode = makeNode(IndexPath); RelOptInfo *rel = index->rel; List *indexquals, *allclauses; /* * For a join inner scan, there's no point in marking the path with any * pathkeys, since it will only ever be used as the inner path of a * nestloop, and so its ordering does not matter. For the same reason we * don't really care what order it's scanned in. (We could expect the * caller to supply the correct values, but it's easier to force it here.) */ if (outer_rel != NULL) { pathkeys = NIL; indexscandir = NoMovementScanDirection; } pathnode->path.pathtype = T_IndexScan; pathnode->path.parent = rel; pathnode->path.pathkeys = pathkeys; /* Convert clauses to indexquals the executor can handle */ indexquals = expand_indexqual_conditions(index, clause_groups); /* Flatten the clause-groups list to produce indexclauses list */ allclauses = flatten_clausegroups_list(clause_groups); /* Fill in the pathnode */ pathnode->indexinfo = index; pathnode->indexclauses = allclauses; pathnode->indexquals = indexquals; pathnode->indexorderbys = indexorderbys; pathnode->isjoininner = (outer_rel != NULL); pathnode->indexscandir = indexscandir; pathnode->indexonly = indexonly; if (outer_rel != NULL) { /* * We must compute the estimated number of output rows for the * indexscan. This is less than rel->rows because of the additional * selectivity of the join clauses. Since clause_groups may contain * both restriction and join clauses, we have to do a set union to get * the full set of clauses that must be considered to compute the * correct selectivity. (Without the union operation, we might have * some restriction clauses appearing twice, which'd mislead * clauselist_selectivity into double-counting their selectivity. * However, since RestrictInfo nodes aren't copied when linking them * into different lists, it should be sufficient to use pointer * comparison to remove duplicates.) * * Note that we force the clauses to be treated as non-join clauses * during selectivity estimation. */ allclauses = list_union_ptr(rel->baserestrictinfo, allclauses); pathnode->rows = rel->tuples * clauselist_selectivity(root, allclauses, rel->relid, /* do not use 0! */ JOIN_INNER, NULL); /* Like costsize.c, force estimate to be at least one row */ pathnode->rows = clamp_row_est(pathnode->rows); } else { /* * The number of rows is the same as the parent rel's estimate, since * this isn't a join inner indexscan. */ pathnode->rows = rel->rows; } cost_index(pathnode, root, index, indexquals, indexorderbys, indexonly, outer_rel); return pathnode; } /* * create_bitmap_heap_path * Creates a path node for a bitmap scan. * * 'bitmapqual' is a tree of IndexPath, BitmapAndPath, and BitmapOrPath nodes. * * If this is a join inner indexscan path, 'outer_rel' is the outer relation, * and all the component IndexPaths should have been costed accordingly. */ BitmapHeapPath * create_bitmap_heap_path(PlannerInfo *root, RelOptInfo *rel, Path *bitmapqual, RelOptInfo *outer_rel) { BitmapHeapPath *pathnode = makeNode(BitmapHeapPath); pathnode->path.pathtype = T_BitmapHeapScan; pathnode->path.parent = rel; pathnode->path.pathkeys = NIL; /* always unordered */ pathnode->bitmapqual = bitmapqual; pathnode->isjoininner = (outer_rel != NULL); if (pathnode->isjoininner) { /* * We must compute the estimated number of output rows for the * indexscan. This is less than rel->rows because of the additional * selectivity of the join clauses. We make use of the selectivity * estimated for the bitmap to do this; this isn't really quite right * since there may be restriction conditions not included in the * bitmap ... */ Cost indexTotalCost; Selectivity indexSelectivity; cost_bitmap_tree_node(bitmapqual, &indexTotalCost, &indexSelectivity); pathnode->rows = rel->tuples * indexSelectivity; if (pathnode->rows > rel->rows) pathnode->rows = rel->rows; /* Like costsize.c, force estimate to be at least one row */ pathnode->rows = clamp_row_est(pathnode->rows); } else { /* * The number of rows is the same as the parent rel's estimate, since * this isn't a join inner indexscan. */ pathnode->rows = rel->rows; } cost_bitmap_heap_scan(&pathnode->path, root, rel, bitmapqual, outer_rel); 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); pathnode->path.pathtype = T_BitmapAnd; pathnode->path.parent = rel; pathnode->path.pathkeys = NIL; /* always unordered */ pathnode->bitmapquals = bitmapquals; /* 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); pathnode->path.pathtype = T_BitmapOr; pathnode->path.parent = rel; pathnode->path.pathkeys = NIL; /* always unordered */ pathnode->bitmapquals = bitmapquals; /* 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->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->subpaths = subpaths; /* * Compute cost as sum of subplan 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(). */ pathnode->path.startup_cost = 0; pathnode->path.total_cost = 0; foreach(l, subpaths) { Path *subpath = (Path *) lfirst(l); if (l == list_head(subpaths)) /* first node? */ pathnode->path.startup_cost = subpath->startup_cost; pathnode->path.total_cost += subpath->total_cost; } 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->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 all the costs of the input paths */ input_startup_cost = 0; input_total_cost = 0; foreach(l, subpaths) { Path *subpath = (Path *) lfirst(l); 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; } } /* 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->quals = quals; /* Ideally should define cost_result(), but I'm too lazy */ 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->subpath = subpath; cost_material(&pathnode->path, subpath->startup_cost, subpath->total_cost, rel->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. * (Compare best_inner_indexscan().) */ 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; /* * Treat the output as always unsorted, since we don't necessarily have * pathkeys to represent it. */ pathnode->path.pathkeys = NIL; pathnode->subpath = subpath; pathnode->in_operators = in_operators; pathnode->uniq_exprs = uniq_exprs; /* * 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->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->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->rows > work_mem * 1024L) all_hash = false; /* don't try to hash */ else cost_agg(&agg_path, root, AGG_HASHED, NULL, numCols, pathnode->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; 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 */ 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 */ 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 */ 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 */ /* 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. */ ForeignPath * create_foreignscan_path(PlannerInfo *root, RelOptInfo *rel) { ForeignPath *pathnode = makeNode(ForeignPath); RangeTblEntry *rte; FdwRoutine *fdwroutine; FdwPlan *fdwplan; pathnode->path.pathtype = T_ForeignScan; pathnode->path.parent = rel; pathnode->path.pathkeys = NIL; /* result is always unordered */ /* Get FDW's callback info */ rte = planner_rt_fetch(rel->relid, root); fdwroutine = GetFdwRoutineByRelId(rte->relid); /* Let the FDW do its planning */ fdwplan = fdwroutine->PlanForeignScan(rte->relid, root, rel); if (fdwplan == NULL || !IsA(fdwplan, FdwPlan)) elog(ERROR, "foreign-data wrapper PlanForeignScan function for relation %u did not return an FdwPlan struct", rte->relid); pathnode->fdwplan = fdwplan; /* use costs estimated by FDW */ pathnode->path.startup_cost = fdwplan->startup_cost; pathnode->path.total_cost = fdwplan->total_cost; return pathnode; } /* * 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 * '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 * * Returns the resulting path node. */ NestPath * create_nestloop_path(PlannerInfo *root, RelOptInfo *joinrel, JoinType jointype, SpecialJoinInfo *sjinfo, Path *outer_path, Path *inner_path, List *restrict_clauses, List *pathkeys) { NestPath *pathnode = makeNode(NestPath); pathnode->path.pathtype = T_NestLoop; pathnode->path.parent = joinrel; pathnode->jointype = jointype; pathnode->outerjoinpath = outer_path; pathnode->innerjoinpath = inner_path; pathnode->joinrestrictinfo = restrict_clauses; pathnode->path.pathkeys = pathkeys; cost_nestloop(pathnode, root, sjinfo); 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 * '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 * '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, SpecialJoinInfo *sjinfo, Path *outer_path, Path *inner_path, List *restrict_clauses, List *pathkeys, List *mergeclauses, List *outersortkeys, List *innersortkeys) { MergePath *pathnode = makeNode(MergePath); /* * If the given paths are already well enough ordered, we can skip doing * an explicit sort. */ if (outersortkeys && pathkeys_contained_in(outersortkeys, outer_path->pathkeys)) outersortkeys = NIL; if (innersortkeys && pathkeys_contained_in(innersortkeys, inner_path->pathkeys)) innersortkeys = NIL; pathnode->jpath.path.pathtype = T_MergeJoin; pathnode->jpath.path.parent = joinrel; pathnode->jpath.jointype = jointype; pathnode->jpath.outerjoinpath = outer_path; pathnode->jpath.innerjoinpath = inner_path; pathnode->jpath.joinrestrictinfo = restrict_clauses; pathnode->jpath.path.pathkeys = pathkeys; pathnode->path_mergeclauses = mergeclauses; pathnode->outersortkeys = outersortkeys; pathnode->innersortkeys = innersortkeys; /* pathnode->materialize_inner will be set by cost_mergejoin */ cost_mergejoin(pathnode, root, 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 * 'sjinfo' is extra info about the join for selectivity estimation * '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 * '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, SpecialJoinInfo *sjinfo, Path *outer_path, Path *inner_path, List *restrict_clauses, List *hashclauses) { HashPath *pathnode = makeNode(HashPath); pathnode->jpath.path.pathtype = T_HashJoin; pathnode->jpath.path.parent = joinrel; pathnode->jpath.jointype = jointype; pathnode->jpath.outerjoinpath = outer_path; pathnode->jpath.innerjoinpath = inner_path; pathnode->jpath.joinrestrictinfo = restrict_clauses; /* * 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->path_hashclauses = hashclauses; /* cost_hashjoin will fill in pathnode->num_batches */ cost_hashjoin(pathnode, root, sjinfo); return pathnode; }