* core.c
* Routines copied from PostgreSQL core distribution.
*
- * Portions Copyright (c) 1996-2011, PostgreSQL Global Development Group
- * Portions Copyright (c) 1994, Regents of the University of California
+
+ * The main purpose of this files is having access to static functions in core.
+ * Another purpose is tweaking functions behavior by replacing part of them by
+ * macro definitions. See at the end of pg_hint_plan.c for details. Anyway,
+ * this file *must* contain required functions without making any change.
*
- *-------------------------------------------------------------------------
- */
-/*
- * PostgreSQL 本体から流用した関数
+ * This file contains the following functions from corresponding files.
*
* src/backend/optimizer/path/allpaths.c
- * standard_join_search()
- * set_plain_rel_pathlist()
*
- * src/backend/optimizer/path/joinrels.c:
- * join_search_one_level()
+ * static functions:
+ * set_plain_rel_pathlist()
+ * set_append_rel_pathlist()
+ * add_paths_to_append_rel()
+ * generate_mergeappend_paths()
+ * get_cheapest_parameterized_child_path()
+ * accumulate_append_subpath()
+ *
+ * public functions:
+ * standard_join_search(): This funcion is not static. The reason for
+ * including this function is make_rels_by_clause_joins. In order to
+ * avoid generating apparently unwanted join combination, we decided to
+ * change the behavior of make_join_rel, which is called under this
+ * function.
+ *
+ * src/backend/optimizer/path/joinrels.c
+ *
+ * public functions:
+ * join_search_one_level(): We have to modify this to call my definition of
+ * make_rels_by_clause_joins.
+ *
+ * static functions:
* make_rels_by_clause_joins()
* make_rels_by_clauseless_joins()
+ * join_is_legal()
* has_join_restriction()
+ * is_dummy_rel()
+ * mark_dummy_rel()
+ * restriction_is_constant_false()
+ *
+ *
+ * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *-------------------------------------------------------------------------
+ */
+
+
+/*
+ * set_plain_rel_pathlist
+ * Build access paths for a plain relation (no subquery, no inheritance)
*/
+static void
+set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
+{
+ Relids required_outer;
+
+ /*
+ * We don't support pushing join clauses into the quals of a seqscan, but
+ * it could still have required parameterization due to LATERAL refs in
+ * its tlist.
+ */
+ required_outer = rel->lateral_relids;
+
+ /* Consider sequential scan */
+ add_path(rel, create_seqscan_path(root, rel, required_outer, 0));
+
+ /* If appropriate, consider parallel sequential scan */
+ if (rel->consider_parallel && required_outer == NULL)
+ create_plain_partial_paths(root, rel);
+
+ /* Consider index scans */
+ create_index_paths(root, rel);
+
+ /* Consider TID scans */
+ create_tidscan_paths(root, rel);
+}
+
+
+/*
+ * set_append_rel_pathlist
+ * Build access paths for an "append relation"
+ */
+static void
+set_append_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
+ Index rti, RangeTblEntry *rte)
+{
+ int parentRTindex = rti;
+ List *live_childrels = NIL;
+ ListCell *l;
+
+ /*
+ * Generate access paths for each member relation, and remember the
+ * non-dummy children.
+ */
+ foreach(l, root->append_rel_list)
+ {
+ AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(l);
+ int childRTindex;
+ RangeTblEntry *childRTE;
+ RelOptInfo *childrel;
+
+ /* append_rel_list contains all append rels; ignore others */
+ if (appinfo->parent_relid != parentRTindex)
+ continue;
+
+ /* Re-locate the child RTE and RelOptInfo */
+ childRTindex = appinfo->child_relid;
+ childRTE = root->simple_rte_array[childRTindex];
+ childrel = root->simple_rel_array[childRTindex];
+
+ /*
+ * If set_append_rel_size() decided the parent appendrel was
+ * parallel-unsafe at some point after visiting this child rel, we
+ * need to propagate the unsafety marking down to the child, so that
+ * we don't generate useless partial paths for it.
+ */
+ if (!rel->consider_parallel)
+ childrel->consider_parallel = false;
+
+ /*
+ * Compute the child's access paths.
+ */
+ set_rel_pathlist(root, childrel, childRTindex, childRTE);
+
+ /*
+ * If child is dummy, ignore it.
+ */
+ if (IS_DUMMY_REL(childrel))
+ continue;
+
+ /*
+ * Child is live, so add it to the live_childrels list for use below.
+ */
+ live_childrels = lappend(live_childrels, childrel);
+ }
+
+ /* Add paths to the "append" relation. */
+ add_paths_to_append_rel(root, rel, live_childrels);
+}
+
+/*
+ * add_paths_to_append_rel
+ * Generate paths for given "append" relation given the set of non-dummy
+ * child rels.
+ *
+ * The function collects all parameterizations and orderings supported by the
+ * non-dummy children. For every such parameterization or ordering, it creates
+ * an append path collecting one path from each non-dummy child with given
+ * parameterization or ordering. Similarly it collects partial paths from
+ * non-dummy children to create partial append paths.
+ */
+static void
+add_paths_to_append_rel(PlannerInfo *root, RelOptInfo *rel,
+ List *live_childrels)
+{
+ List *subpaths = NIL;
+ bool subpaths_valid = true;
+ List *partial_subpaths = NIL;
+ bool partial_subpaths_valid = true;
+ List *all_child_pathkeys = NIL;
+ List *all_child_outers = NIL;
+ ListCell *l;
+ List *partitioned_rels = NIL;
+ RangeTblEntry *rte;
+
+ rte = planner_rt_fetch(rel->relid, root);
+ if (rte->relkind == RELKIND_PARTITIONED_TABLE)
+ {
+ partitioned_rels = get_partitioned_child_rels(root, rel->relid);
+ /* The root partitioned table is included as a child rel */
+ Assert(list_length(partitioned_rels) >= 1);
+ }
+
+ /*
+ * For every non-dummy child, remember the cheapest path. Also, identify
+ * all pathkeys (orderings) and parameterizations (required_outer sets)
+ * available for the non-dummy member relations.
+ */
+ foreach(l, live_childrels)
+ {
+ RelOptInfo *childrel = lfirst(l);
+ ListCell *lcp;
+
+ /*
+ * If child has an unparameterized cheapest-total path, add that to
+ * the unparameterized Append path we are constructing for the parent.
+ * If not, there's no workable unparameterized path.
+ */
+ if (childrel->cheapest_total_path->param_info == NULL)
+ subpaths = accumulate_append_subpath(subpaths,
+ childrel->cheapest_total_path);
+ else
+ subpaths_valid = false;
+
+ /* Same idea, but for a partial plan. */
+ if (childrel->partial_pathlist != NIL)
+ partial_subpaths = accumulate_append_subpath(partial_subpaths,
+ linitial(childrel->partial_pathlist));
+ else
+ partial_subpaths_valid = false;
+
+ /*
+ * Collect lists of all the available path orderings and
+ * parameterizations for all the children. We use these as a
+ * heuristic to indicate which sort orderings and parameterizations we
+ * should build Append and MergeAppend paths for.
+ */
+ foreach(lcp, childrel->pathlist)
+ {
+ Path *childpath = (Path *) lfirst(lcp);
+ List *childkeys = childpath->pathkeys;
+ Relids childouter = PATH_REQ_OUTER(childpath);
+
+ /* Unsorted paths don't contribute to pathkey list */
+ if (childkeys != NIL)
+ {
+ ListCell *lpk;
+ bool found = false;
+
+ /* Have we already seen this ordering? */
+ foreach(lpk, all_child_pathkeys)
+ {
+ List *existing_pathkeys = (List *) lfirst(lpk);
+
+ if (compare_pathkeys(existing_pathkeys,
+ childkeys) == PATHKEYS_EQUAL)
+ {
+ found = true;
+ break;
+ }
+ }
+ if (!found)
+ {
+ /* No, so add it to all_child_pathkeys */
+ all_child_pathkeys = lappend(all_child_pathkeys,
+ childkeys);
+ }
+ }
+
+ /* Unparameterized paths don't contribute to param-set list */
+ if (childouter)
+ {
+ ListCell *lco;
+ bool found = false;
+
+ /* Have we already seen this param set? */
+ foreach(lco, all_child_outers)
+ {
+ Relids existing_outers = (Relids) lfirst(lco);
+
+ if (bms_equal(existing_outers, childouter))
+ {
+ found = true;
+ break;
+ }
+ }
+ if (!found)
+ {
+ /* No, so add it to all_child_outers */
+ all_child_outers = lappend(all_child_outers,
+ childouter);
+ }
+ }
+ }
+ }
+
+ /*
+ * If we found unparameterized paths for all children, build an unordered,
+ * unparameterized Append path for the rel. (Note: this is correct even
+ * if we have zero or one live subpath due to constraint exclusion.)
+ */
+ if (subpaths_valid)
+ add_path(rel, (Path *) create_append_path(rel, subpaths, NULL, 0,
+ partitioned_rels));
+
+ /*
+ * Consider an append of partial unordered, unparameterized partial paths.
+ */
+ if (partial_subpaths_valid)
+ {
+ AppendPath *appendpath;
+ ListCell *lc;
+ int parallel_workers = 0;
+
+ /*
+ * Decide on the number of workers to request for this append path.
+ * For now, we just use the maximum value from among the members. It
+ * might be useful to use a higher number if the Append node were
+ * smart enough to spread out the workers, but it currently isn't.
+ */
+ foreach(lc, partial_subpaths)
+ {
+ Path *path = lfirst(lc);
+
+ parallel_workers = Max(parallel_workers, path->parallel_workers);
+ }
+ Assert(parallel_workers > 0);
+
+ /* Generate a partial append path. */
+ appendpath = create_append_path(rel, partial_subpaths, NULL,
+ parallel_workers, partitioned_rels);
+ add_partial_path(rel, (Path *) appendpath);
+ }
+
+ /*
+ * Also build unparameterized MergeAppend paths based on the collected
+ * list of child pathkeys.
+ */
+ if (subpaths_valid)
+ generate_mergeappend_paths(root, rel, live_childrels,
+ all_child_pathkeys,
+ partitioned_rels);
+
+ /*
+ * Build Append paths for each parameterization seen among the child rels.
+ * (This may look pretty expensive, but in most cases of practical
+ * interest, the child rels will expose mostly the same parameterizations,
+ * so that not that many cases actually get considered here.)
+ *
+ * The Append node itself cannot enforce quals, so all qual checking must
+ * be done in the child paths. This means that to have a parameterized
+ * Append path, we must have the exact same parameterization for each
+ * child path; otherwise some children might be failing to check the
+ * moved-down quals. To make them match up, we can try to increase the
+ * parameterization of lesser-parameterized paths.
+ */
+ foreach(l, all_child_outers)
+ {
+ Relids required_outer = (Relids) lfirst(l);
+ ListCell *lcr;
+
+ /* Select the child paths for an Append with this parameterization */
+ subpaths = NIL;
+ subpaths_valid = true;
+ foreach(lcr, live_childrels)
+ {
+ RelOptInfo *childrel = (RelOptInfo *) lfirst(lcr);
+ Path *subpath;
+
+ subpath = get_cheapest_parameterized_child_path(root,
+ childrel,
+ required_outer);
+ if (subpath == NULL)
+ {
+ /* failed to make a suitable path for this child */
+ subpaths_valid = false;
+ break;
+ }
+ subpaths = accumulate_append_subpath(subpaths, subpath);
+ }
+
+ if (subpaths_valid)
+ add_path(rel, (Path *)
+ create_append_path(rel, subpaths, required_outer, 0,
+ partitioned_rels));
+ }
+}
+
+
+/*
+ * generate_mergeappend_paths
+ * Generate MergeAppend paths for an append relation
+ *
+ * Generate a path for each ordering (pathkey list) appearing in
+ * all_child_pathkeys.
+ *
+ * We consider both cheapest-startup and cheapest-total cases, ie, for each
+ * interesting ordering, collect all the cheapest startup subpaths and all the
+ * cheapest total paths, and build a MergeAppend path for each case.
+ *
+ * We don't currently generate any parameterized MergeAppend paths. While
+ * it would not take much more code here to do so, it's very unclear that it
+ * is worth the planning cycles to investigate such paths: there's little
+ * use for an ordered path on the inside of a nestloop. In fact, it's likely
+ * that the current coding of add_path would reject such paths out of hand,
+ * because add_path gives no credit for sort ordering of parameterized paths,
+ * and a parameterized MergeAppend is going to be more expensive than the
+ * corresponding parameterized Append path. If we ever try harder to support
+ * parameterized mergejoin plans, it might be worth adding support for
+ * parameterized MergeAppends to feed such joins. (See notes in
+ * optimizer/README for why that might not ever happen, though.)
+ */
+static void
+generate_mergeappend_paths(PlannerInfo *root, RelOptInfo *rel,
+ List *live_childrels,
+ List *all_child_pathkeys,
+ List *partitioned_rels)
+{
+ ListCell *lcp;
+
+ foreach(lcp, all_child_pathkeys)
+ {
+ List *pathkeys = (List *) lfirst(lcp);
+ List *startup_subpaths = NIL;
+ List *total_subpaths = NIL;
+ bool startup_neq_total = false;
+ ListCell *lcr;
+
+ /* Select the child paths for this ordering... */
+ foreach(lcr, live_childrels)
+ {
+ RelOptInfo *childrel = (RelOptInfo *) lfirst(lcr);
+ Path *cheapest_startup,
+ *cheapest_total;
+
+ /* Locate the right paths, if they are available. */
+ cheapest_startup =
+ get_cheapest_path_for_pathkeys(childrel->pathlist,
+ pathkeys,
+ NULL,
+ STARTUP_COST,
+ false);
+ cheapest_total =
+ get_cheapest_path_for_pathkeys(childrel->pathlist,
+ pathkeys,
+ NULL,
+ TOTAL_COST,
+ false);
+
+ /*
+ * If we can't find any paths with the right order just use the
+ * cheapest-total path; we'll have to sort it later.
+ */
+ if (cheapest_startup == NULL || cheapest_total == NULL)
+ {
+ cheapest_startup = cheapest_total =
+ childrel->cheapest_total_path;
+ /* Assert we do have an unparameterized path for this child */
+ Assert(cheapest_total->param_info == NULL);
+ }
+
+ /*
+ * Notice whether we actually have different paths for the
+ * "cheapest" and "total" cases; frequently there will be no point
+ * in two create_merge_append_path() calls.
+ */
+ if (cheapest_startup != cheapest_total)
+ startup_neq_total = true;
+
+ startup_subpaths =
+ accumulate_append_subpath(startup_subpaths, cheapest_startup);
+ total_subpaths =
+ accumulate_append_subpath(total_subpaths, cheapest_total);
+ }
+
+ /* ... and build the MergeAppend paths */
+ add_path(rel, (Path *) create_merge_append_path(root,
+ rel,
+ startup_subpaths,
+ pathkeys,
+ NULL,
+ partitioned_rels));
+ if (startup_neq_total)
+ add_path(rel, (Path *) create_merge_append_path(root,
+ rel,
+ total_subpaths,
+ pathkeys,
+ NULL,
+ partitioned_rels));
+ }
+}
+
+
+/*
+ * get_cheapest_parameterized_child_path
+ * Get cheapest path for this relation that has exactly the requested
+ * parameterization.
+ *
+ * Returns NULL if unable to create such a path.
+ */
+static Path *
+get_cheapest_parameterized_child_path(PlannerInfo *root, RelOptInfo *rel,
+ Relids required_outer)
+{
+ Path *cheapest;
+ ListCell *lc;
+
+ /*
+ * Look up the cheapest existing path with no more than the needed
+ * parameterization. If it has exactly the needed parameterization, we're
+ * done.
+ */
+ cheapest = get_cheapest_path_for_pathkeys(rel->pathlist,
+ NIL,
+ required_outer,
+ TOTAL_COST,
+ false);
+ Assert(cheapest != NULL);
+ if (bms_equal(PATH_REQ_OUTER(cheapest), required_outer))
+ return cheapest;
+
+ /*
+ * Otherwise, we can "reparameterize" an existing path to match the given
+ * parameterization, which effectively means pushing down additional
+ * joinquals to be checked within the path's scan. However, some existing
+ * paths might check the available joinquals already while others don't;
+ * therefore, it's not clear which existing path will be cheapest after
+ * reparameterization. We have to go through them all and find out.
+ */
+ cheapest = NULL;
+ foreach(lc, rel->pathlist)
+ {
+ Path *path = (Path *) lfirst(lc);
+
+ /* Can't use it if it needs more than requested parameterization */
+ if (!bms_is_subset(PATH_REQ_OUTER(path), required_outer))
+ continue;
+
+ /*
+ * Reparameterization can only increase the path's cost, so if it's
+ * already more expensive than the current cheapest, forget it.
+ */
+ if (cheapest != NULL &&
+ compare_path_costs(cheapest, path, TOTAL_COST) <= 0)
+ continue;
+
+ /* Reparameterize if needed, then recheck cost */
+ if (!bms_equal(PATH_REQ_OUTER(path), required_outer))
+ {
+ path = reparameterize_path(root, path, required_outer, 1.0);
+ if (path == NULL)
+ continue; /* failed to reparameterize this one */
+ Assert(bms_equal(PATH_REQ_OUTER(path), required_outer));
+
+ if (cheapest != NULL &&
+ compare_path_costs(cheapest, path, TOTAL_COST) <= 0)
+ continue;
+ }
+
+ /* We have a new best path */
+ cheapest = path;
+ }
+
+ /* Return the best path, or NULL if we found no suitable candidate */
+ return cheapest;
+}
+
+
+/*
+ * accumulate_append_subpath
+ * Add a subpath to the list being built for an Append or MergeAppend
+ *
+ * It's possible that the child is itself an Append or MergeAppend path, in
+ * which case we can "cut out the middleman" and just add its child paths to
+ * our own list. (We don't try to do this earlier because we need to apply
+ * both levels of transformation to the quals.)
+ *
+ * Note that if we omit a child MergeAppend in this way, we are effectively
+ * omitting a sort step, which seems fine: if the parent is to be an Append,
+ * its result would be unsorted anyway, while if the parent is to be a
+ * MergeAppend, there's no point in a separate sort on a child.
+ */
+static List *
+accumulate_append_subpath(List *subpaths, Path *path)
+{
+ if (IsA(path, AppendPath))
+ {
+ AppendPath *apath = (AppendPath *) path;
+
+ /* list_copy is important here to avoid sharing list substructure */
+ return list_concat(subpaths, list_copy(apath->subpaths));
+ }
+ else if (IsA(path, MergeAppendPath))
+ {
+ MergeAppendPath *mpath = (MergeAppendPath *) path;
+
+ /* list_copy is important here to avoid sharing list substructure */
+ return list_concat(subpaths, list_copy(mpath->subpaths));
+ }
+ else
+ return lappend(subpaths, path);
+}
+
/*
* standard_join_search
* independent jointree items in the query. This is > 1.
*
* 'initial_rels' is a list of RelOptInfo nodes for each independent
- * jointree item. These are the components to be joined together.
+ * jointree item. These are the components to be joined together.
* Note that levels_needed == list_length(initial_rels).
*
* Returns the final level of join relations, i.e., the relation that is
* needed for these paths need have been instantiated.
*
* Note to plugin authors: the functions invoked during standard_join_search()
- * modify root->join_rel_list and root->join_rel_hash. If you want to do more
+ * modify root->join_rel_list and root->join_rel_hash. If you want to do more
* than one join-order search, you'll probably need to save and restore the
* original states of those data structures. See geqo_eval() for an example.
*/
join_search_one_level(root, lev);
/*
- * Do cleanup work on each just-processed rel.
+ * Run generate_gather_paths() for each just-processed joinrel. We
+ * could not do this earlier because both regular and partial paths
+ * can get added to a particular joinrel at multiple times within
+ * join_search_one_level. After that, we're done creating paths for
+ * the joinrel, so run set_cheapest().
*/
foreach(lc, root->join_rel_level[lev])
{
rel = (RelOptInfo *) lfirst(lc);
+ /* Create GatherPaths for any useful partial paths for rel */
+ generate_gather_paths(root, rel);
+
/* Find and save the cheapest paths for this rel */
set_cheapest(rel);
}
/*
- * set_plain_rel_pathlist
- * Build access paths for a plain relation (no subquery, no inheritance)
+ * create_plain_partial_paths
+ * Build partial access paths for parallel scan of a plain relation
*/
static void
-set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
+create_plain_partial_paths(PlannerInfo *root, RelOptInfo *rel)
{
- /* Consider sequential scan */
- add_path(rel, create_seqscan_path(root, rel));
+ int parallel_workers;
- /* Consider index scans */
- create_index_paths(root, rel);
+ parallel_workers = compute_parallel_worker(rel, rel->pages, -1);
- /* Consider TID scans */
- create_tidscan_paths(root, rel);
+ /* If any limit was set to zero, the user doesn't want a parallel scan. */
+ if (parallel_workers <= 0)
+ return;
- /* Now find the cheapest of the paths for this rel */
- set_cheapest(rel);
+ /* Add an unordered partial path based on a parallel sequential scan. */
+ add_partial_path(rel, create_seqscan_path(root, rel, NULL, parallel_workers));
}
+
/*
* join_search_one_level
* Consider ways to produce join relations containing exactly 'level'
* We prefer to join using join clauses, but if we find a rel of level-1
* members that has no join clauses, we will generate Cartesian-product
* joins against all initial rels not already contained in it.
- *
- * In the first pass (level == 2), we try to join each initial rel to each
- * initial rel that appears later in joinrels[1]. (The mirror-image joins
- * are handled automatically by make_join_rel.) In later passes, we try
- * to join rels of size level-1 from joinrels[level-1] to each initial rel
- * in joinrels[1].
*/
foreach(r, joinrels[level - 1])
{
RelOptInfo *old_rel = (RelOptInfo *) lfirst(r);
- ListCell *other_rels;
-
- if (level == 2)
- other_rels = lnext(r); /* only consider remaining initial
- * rels */
- else
- other_rels = list_head(joinrels[1]); /* consider all initial
- * rels */
if (old_rel->joininfo != NIL || old_rel->has_eclass_joins ||
has_join_restriction(root, old_rel))
{
/*
- * Note that if all available join clauses for this rel require
- * more than one other rel, we will fail to make any joins against
- * it here. In most cases that's OK; it'll be considered by
- * "bushy plan" join code in a higher-level pass where we have
- * those other rels collected into a join rel.
+ * There are join clauses or join order restrictions relevant to
+ * this rel, so consider joins between this rel and (only) those
+ * initial rels it is linked to by a clause or restriction.
*
- * See also the last-ditch case below.
+ * At level 2 this condition is symmetric, so there is no need to
+ * look at initial rels before this one in the list; we already
+ * considered such joins when we were at the earlier rel. (The
+ * mirror-image joins are handled automatically by make_join_rel.)
+ * In later passes (level > 2), we join rels of the previous level
+ * to each initial rel they don't already include but have a join
+ * clause or restriction with.
*/
+ ListCell *other_rels;
+
+ if (level == 2) /* consider remaining initial rels */
+ other_rels = lnext(r);
+ else /* consider all initial rels */
+ other_rels = list_head(joinrels[1]);
+
make_rels_by_clause_joins(root,
old_rel,
other_rels);
* Oops, we have a relation that is not joined to any other
* relation, either directly or by join-order restrictions.
* Cartesian product time.
+ *
+ * We consider a cartesian product with each not-already-included
+ * initial rel, whether it has other join clauses or not. At
+ * level 2, if there are two or more clauseless initial rels, we
+ * will redundantly consider joining them in both directions; but
+ * such cases aren't common enough to justify adding complexity to
+ * avoid the duplicated effort.
*/
make_rels_by_clauseless_joins(root,
old_rel,
- other_rels);
+ list_head(joinrels[1]));
}
}
ListCell *r2;
/*
- * We can ignore clauseless joins here, *except* when they
+ * We can ignore relations without join clauses here, unless they
* participate in join-order restrictions --- then we might have
* to force a bushy join plan.
*/
{
/*
* OK, we can build a rel of the right level from this
- * pair of rels. Do so if there is at least one usable
- * join clause or a relevant join restriction.
+ * pair of rels. Do so if there is at least one relevant
+ * join clause or join order restriction.
*/
if (have_relevant_joinclause(root, old_rel, new_rel) ||
have_join_order_restriction(root, old_rel, new_rel))
}
}
- /*
+ /*----------
* Last-ditch effort: if we failed to find any usable joins so far, force
* a set of cartesian-product joins to be generated. This handles the
* special case where all the available rels have join clauses but we
- * cannot use any of those clauses yet. An example is
+ * cannot use any of those clauses yet. This can only happen when we are
+ * considering a join sub-problem (a sub-joinlist) and all the rels in the
+ * sub-problem have only join clauses with rels outside the sub-problem.
+ * An example is
*
- * SELECT * FROM a,b,c WHERE (a.f1 + b.f2 + c.f3) = 0;
+ * SELECT ... FROM a INNER JOIN b ON TRUE, c, d, ...
+ * WHERE a.w = c.x and b.y = d.z;
*
- * The join clause will be usable at level 3, but at level 2 we have no
- * choice but to make cartesian joins. We consider only left-sided and
- * right-sided cartesian joins in this case (no bushy).
+ * If the "a INNER JOIN b" sub-problem does not get flattened into the
+ * upper level, we must be willing to make a cartesian join of a and b;
+ * but the code above will not have done so, because it thought that both
+ * a and b have joinclauses. We consider only left-sided and right-sided
+ * cartesian joins in this case (no bushy).
+ *----------
*/
if (joinrels[level] == NIL)
{
foreach(r, joinrels[level - 1])
{
RelOptInfo *old_rel = (RelOptInfo *) lfirst(r);
- ListCell *other_rels;
-
- if (level == 2)
- other_rels = lnext(r); /* only consider remaining initial
- * rels */
- else
- other_rels = list_head(joinrels[1]); /* consider all initial
- * rels */
make_rels_by_clauseless_joins(root,
old_rel,
- other_rels);
+ list_head(joinrels[1]));
}
/*----------
* When special joins are involved, there may be no legal way
- * to make an N-way join for some values of N. For example consider
+ * to make an N-way join for some values of N. For example consider
*
* SELECT ... FROM t1 WHERE
* x IN (SELECT ... FROM t2,t3 WHERE ...) AND
* to accept failure at level 4 and go on to discover a workable
* bushy plan at level 5.
*
- * However, if there are no special joins then join_is_legal() should
- * never fail, and so the following sanity check is useful.
+ * However, if there are no special joins and no lateral references
+ * then join_is_legal() should never fail, and so the following sanity
+ * check is useful.
*----------
*/
- if (joinrels[level] == NIL && root->join_info_list == NIL)
+ if (joinrels[level] == NIL &&
+ root->join_info_list == NIL &&
+ !root->hasLateralRTEs)
elog(ERROR, "failed to build any %d-way joins", level);
}
}
+
/*
* make_rels_by_clause_joins
* Build joins between the given relation 'old_rel' and other relations
}
}
+
/*
* make_rels_by_clauseless_joins
* Given a relation 'old_rel' and a list of other relations
}
}
+
+/*
+ * join_is_legal
+ * Determine whether a proposed join is legal given the query's
+ * join order constraints; and if it is, determine the join type.
+ *
+ * Caller must supply not only the two rels, but the union of their relids.
+ * (We could simplify the API by computing joinrelids locally, but this
+ * would be redundant work in the normal path through make_join_rel.)
+ *
+ * On success, *sjinfo_p is set to NULL if this is to be a plain inner join,
+ * else it's set to point to the associated SpecialJoinInfo node. Also,
+ * *reversed_p is set TRUE if the given relations need to be swapped to
+ * match the SpecialJoinInfo node.
+ */
+static bool
+join_is_legal(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2,
+ Relids joinrelids,
+ SpecialJoinInfo **sjinfo_p, bool *reversed_p)
+{
+ SpecialJoinInfo *match_sjinfo;
+ bool reversed;
+ bool unique_ified;
+ bool must_be_leftjoin;
+ ListCell *l;
+
+ /*
+ * Ensure output params are set on failure return. This is just to
+ * suppress uninitialized-variable warnings from overly anal compilers.
+ */
+ *sjinfo_p = NULL;
+ *reversed_p = false;
+
+ /*
+ * If we have any special joins, the proposed join might be illegal; and
+ * in any case we have to determine its join type. Scan the join info
+ * list for matches and conflicts.
+ */
+ match_sjinfo = NULL;
+ reversed = false;
+ unique_ified = false;
+ must_be_leftjoin = false;
+
+ foreach(l, root->join_info_list)
+ {
+ SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(l);
+
+ /*
+ * This special join is not relevant unless its RHS overlaps the
+ * proposed join. (Check this first as a fast path for dismissing
+ * most irrelevant SJs quickly.)
+ */
+ if (!bms_overlap(sjinfo->min_righthand, joinrelids))
+ continue;
+
+ /*
+ * Also, not relevant if proposed join is fully contained within RHS
+ * (ie, we're still building up the RHS).
+ */
+ if (bms_is_subset(joinrelids, sjinfo->min_righthand))
+ continue;
+
+ /*
+ * Also, not relevant if SJ is already done within either input.
+ */
+ if (bms_is_subset(sjinfo->min_lefthand, rel1->relids) &&
+ bms_is_subset(sjinfo->min_righthand, rel1->relids))
+ continue;
+ if (bms_is_subset(sjinfo->min_lefthand, rel2->relids) &&
+ bms_is_subset(sjinfo->min_righthand, rel2->relids))
+ continue;
+
+ /*
+ * If it's a semijoin and we already joined the RHS to any other rels
+ * within either input, then we must have unique-ified the RHS at that
+ * point (see below). Therefore the semijoin is no longer relevant in
+ * this join path.
+ */
+ if (sjinfo->jointype == JOIN_SEMI)
+ {
+ if (bms_is_subset(sjinfo->syn_righthand, rel1->relids) &&
+ !bms_equal(sjinfo->syn_righthand, rel1->relids))
+ continue;
+ if (bms_is_subset(sjinfo->syn_righthand, rel2->relids) &&
+ !bms_equal(sjinfo->syn_righthand, rel2->relids))
+ continue;
+ }
+
+ /*
+ * If one input contains min_lefthand and the other contains
+ * min_righthand, then we can perform the SJ at this join.
+ *
+ * Reject if we get matches to more than one SJ; that implies we're
+ * considering something that's not really valid.
+ */
+ if (bms_is_subset(sjinfo->min_lefthand, rel1->relids) &&
+ bms_is_subset(sjinfo->min_righthand, rel2->relids))
+ {
+ if (match_sjinfo)
+ return false; /* invalid join path */
+ match_sjinfo = sjinfo;
+ reversed = false;
+ }
+ else if (bms_is_subset(sjinfo->min_lefthand, rel2->relids) &&
+ bms_is_subset(sjinfo->min_righthand, rel1->relids))
+ {
+ if (match_sjinfo)
+ return false; /* invalid join path */
+ match_sjinfo = sjinfo;
+ reversed = true;
+ }
+ else if (sjinfo->jointype == JOIN_SEMI &&
+ bms_equal(sjinfo->syn_righthand, rel2->relids) &&
+ create_unique_path(root, rel2, rel2->cheapest_total_path,
+ sjinfo) != NULL)
+ {
+ /*----------
+ * For a semijoin, we can join the RHS to anything else by
+ * unique-ifying the RHS (if the RHS can be unique-ified).
+ * We will only get here if we have the full RHS but less
+ * than min_lefthand on the LHS.
+ *
+ * The reason to consider such a join path is exemplified by
+ * SELECT ... FROM a,b WHERE (a.x,b.y) IN (SELECT c1,c2 FROM c)
+ * If we insist on doing this as a semijoin we will first have
+ * to form the cartesian product of A*B. But if we unique-ify
+ * C then the semijoin becomes a plain innerjoin and we can join
+ * in any order, eg C to A and then to B. When C is much smaller
+ * than A and B this can be a huge win. So we allow C to be
+ * joined to just A or just B here, and then make_join_rel has
+ * to handle the case properly.
+ *
+ * Note that actually we'll allow unique-ified C to be joined to
+ * some other relation D here, too. That is legal, if usually not
+ * very sane, and this routine is only concerned with legality not
+ * with whether the join is good strategy.
+ *----------
+ */
+ if (match_sjinfo)
+ return false; /* invalid join path */
+ match_sjinfo = sjinfo;
+ reversed = false;
+ unique_ified = true;
+ }
+ else if (sjinfo->jointype == JOIN_SEMI &&
+ bms_equal(sjinfo->syn_righthand, rel1->relids) &&
+ create_unique_path(root, rel1, rel1->cheapest_total_path,
+ sjinfo) != NULL)
+ {
+ /* Reversed semijoin case */
+ if (match_sjinfo)
+ return false; /* invalid join path */
+ match_sjinfo = sjinfo;
+ reversed = true;
+ unique_ified = true;
+ }
+ else
+ {
+ /*
+ * Otherwise, the proposed join overlaps the RHS but isn't a valid
+ * implementation of this SJ. But don't panic quite yet: the RHS
+ * violation might have occurred previously, in one or both input
+ * relations, in which case we must have previously decided that
+ * it was OK to commute some other SJ with this one. If we need
+ * to perform this join to finish building up the RHS, rejecting
+ * it could lead to not finding any plan at all. (This can occur
+ * because of the heuristics elsewhere in this file that postpone
+ * clauseless joins: we might not consider doing a clauseless join
+ * within the RHS until after we've performed other, validly
+ * commutable SJs with one or both sides of the clauseless join.)
+ * This consideration boils down to the rule that if both inputs
+ * overlap the RHS, we can allow the join --- they are either
+ * fully within the RHS, or represent previously-allowed joins to
+ * rels outside it.
+ */
+ if (bms_overlap(rel1->relids, sjinfo->min_righthand) &&
+ bms_overlap(rel2->relids, sjinfo->min_righthand))
+ continue; /* assume valid previous violation of RHS */
+
+ /*
+ * The proposed join could still be legal, but only if we're
+ * allowed to associate it into the RHS of this SJ. That means
+ * this SJ must be a LEFT join (not SEMI or ANTI, and certainly
+ * not FULL) and the proposed join must not overlap the LHS.
+ */
+ if (sjinfo->jointype != JOIN_LEFT ||
+ bms_overlap(joinrelids, sjinfo->min_lefthand))
+ return false; /* invalid join path */
+
+ /*
+ * To be valid, the proposed join must be a LEFT join; otherwise
+ * it can't associate into this SJ's RHS. But we may not yet have
+ * found the SpecialJoinInfo matching the proposed join, so we
+ * can't test that yet. Remember the requirement for later.
+ */
+ must_be_leftjoin = true;
+ }
+ }
+
+ /*
+ * Fail if violated any SJ's RHS and didn't match to a LEFT SJ: the
+ * proposed join can't associate into an SJ's RHS.
+ *
+ * Also, fail if the proposed join's predicate isn't strict; we're
+ * essentially checking to see if we can apply outer-join identity 3, and
+ * that's a requirement. (This check may be redundant with checks in
+ * make_outerjoininfo, but I'm not quite sure, and it's cheap to test.)
+ */
+ if (must_be_leftjoin &&
+ (match_sjinfo == NULL ||
+ match_sjinfo->jointype != JOIN_LEFT ||
+ !match_sjinfo->lhs_strict))
+ return false; /* invalid join path */
+
+ /*
+ * We also have to check for constraints imposed by LATERAL references.
+ */
+ if (root->hasLateralRTEs)
+ {
+ bool lateral_fwd;
+ bool lateral_rev;
+ Relids join_lateral_rels;
+
+ /*
+ * The proposed rels could each contain lateral references to the
+ * other, in which case the join is impossible. If there are lateral
+ * references in just one direction, then the join has to be done with
+ * a nestloop with the lateral referencer on the inside. If the join
+ * matches an SJ that cannot be implemented by such a nestloop, the
+ * join is impossible.
+ *
+ * Also, if the lateral reference is only indirect, we should reject
+ * the join; whatever rel(s) the reference chain goes through must be
+ * joined to first.
+ *
+ * Another case that might keep us from building a valid plan is the
+ * implementation restriction described by have_dangerous_phv().
+ */
+ lateral_fwd = bms_overlap(rel1->relids, rel2->lateral_relids);
+ lateral_rev = bms_overlap(rel2->relids, rel1->lateral_relids);
+ if (lateral_fwd && lateral_rev)
+ return false; /* have lateral refs in both directions */
+ if (lateral_fwd)
+ {
+ /* has to be implemented as nestloop with rel1 on left */
+ if (match_sjinfo &&
+ (reversed ||
+ unique_ified ||
+ match_sjinfo->jointype == JOIN_FULL))
+ return false; /* not implementable as nestloop */
+ /* check there is a direct reference from rel2 to rel1 */
+ if (!bms_overlap(rel1->relids, rel2->direct_lateral_relids))
+ return false; /* only indirect refs, so reject */
+ /* check we won't have a dangerous PHV */
+ if (have_dangerous_phv(root, rel1->relids, rel2->lateral_relids))
+ return false; /* might be unable to handle required PHV */
+ }
+ else if (lateral_rev)
+ {
+ /* has to be implemented as nestloop with rel2 on left */
+ if (match_sjinfo &&
+ (!reversed ||
+ unique_ified ||
+ match_sjinfo->jointype == JOIN_FULL))
+ return false; /* not implementable as nestloop */
+ /* check there is a direct reference from rel1 to rel2 */
+ if (!bms_overlap(rel2->relids, rel1->direct_lateral_relids))
+ return false; /* only indirect refs, so reject */
+ /* check we won't have a dangerous PHV */
+ if (have_dangerous_phv(root, rel2->relids, rel1->lateral_relids))
+ return false; /* might be unable to handle required PHV */
+ }
+
+ /*
+ * LATERAL references could also cause problems later on if we accept
+ * this join: if the join's minimum parameterization includes any rels
+ * that would have to be on the inside of an outer join with this join
+ * rel, then it's never going to be possible to build the complete
+ * query using this join. We should reject this join not only because
+ * it'll save work, but because if we don't, the clauseless-join
+ * heuristics might think that legality of this join means that some
+ * other join rel need not be formed, and that could lead to failure
+ * to find any plan at all. We have to consider not only rels that
+ * are directly on the inner side of an OJ with the joinrel, but also
+ * ones that are indirectly so, so search to find all such rels.
+ */
+ join_lateral_rels = min_join_parameterization(root, joinrelids,
+ rel1, rel2);
+ if (join_lateral_rels)
+ {
+ Relids join_plus_rhs = bms_copy(joinrelids);
+ bool more;
+
+ do
+ {
+ more = false;
+ foreach(l, root->join_info_list)
+ {
+ SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(l);
+
+ if (bms_overlap(sjinfo->min_lefthand, join_plus_rhs) &&
+ !bms_is_subset(sjinfo->min_righthand, join_plus_rhs))
+ {
+ join_plus_rhs = bms_add_members(join_plus_rhs,
+ sjinfo->min_righthand);
+ more = true;
+ }
+ /* full joins constrain both sides symmetrically */
+ if (sjinfo->jointype == JOIN_FULL &&
+ bms_overlap(sjinfo->min_righthand, join_plus_rhs) &&
+ !bms_is_subset(sjinfo->min_lefthand, join_plus_rhs))
+ {
+ join_plus_rhs = bms_add_members(join_plus_rhs,
+ sjinfo->min_lefthand);
+ more = true;
+ }
+ }
+ } while (more);
+ if (bms_overlap(join_plus_rhs, join_lateral_rels))
+ return false; /* will not be able to join to some RHS rel */
+ }
+ }
+
+ /* Otherwise, it's a valid join */
+ *sjinfo_p = match_sjinfo;
+ *reversed_p = reversed;
+ return true;
+}
+
+
/*
* has_join_restriction
- * Detect whether the specified relation has join-order restrictions
- * due to being inside an outer join or an IN (sub-SELECT).
+ * Detect whether the specified relation has join-order restrictions,
+ * due to being inside an outer join or an IN (sub-SELECT),
+ * or participating in any LATERAL references or multi-rel PHVs.
*
* Essentially, this tests whether have_join_order_restriction() could
* succeed with this rel and some other one. It's OK if we sometimes
- * say "true" incorrectly. (Therefore, we don't bother with the relatively
+ * say "true" incorrectly. (Therefore, we don't bother with the relatively
* expensive has_legal_joinclause test.)
*/
static bool
{
ListCell *l;
+ if (rel->lateral_relids != NULL || rel->lateral_referencers != NULL)
+ return true;
+
+ foreach(l, root->placeholder_list)
+ {
+ PlaceHolderInfo *phinfo = (PlaceHolderInfo *) lfirst(l);
+
+ if (bms_is_subset(rel->relids, phinfo->ph_eval_at) &&
+ !bms_equal(rel->relids, phinfo->ph_eval_at))
+ return true;
+ }
+
foreach(l, root->join_info_list)
{
SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(l);
return false;
}
+
+
+/*
+ * is_dummy_rel --- has relation been proven empty?
+ */
+static bool
+is_dummy_rel(RelOptInfo *rel)
+{
+ return IS_DUMMY_REL(rel);
+}
+
+
+/*
+ * Mark a relation as proven empty.
+ *
+ * During GEQO planning, this can get invoked more than once on the same
+ * baserel struct, so it's worth checking to see if the rel is already marked
+ * dummy.
+ *
+ * Also, when called during GEQO join planning, we are in a short-lived
+ * memory context. We must make sure that the dummy path attached to a
+ * baserel survives the GEQO cycle, else the baserel is trashed for future
+ * GEQO cycles. On the other hand, when we are marking a joinrel during GEQO,
+ * we don't want the dummy path to clutter the main planning context. Upshot
+ * is that the best solution is to explicitly make the dummy path in the same
+ * context the given RelOptInfo is in.
+ */
+static void
+mark_dummy_rel(RelOptInfo *rel)
+{
+ MemoryContext oldcontext;
+
+ /* Already marked? */
+ if (is_dummy_rel(rel))
+ return;
+
+ /* No, so choose correct context to make the dummy path in */
+ oldcontext = MemoryContextSwitchTo(GetMemoryChunkContext(rel));
+
+ /* Set dummy size estimate */
+ rel->rows = 0;
+
+ /* Evict any previously chosen paths */
+ rel->pathlist = NIL;
+ rel->partial_pathlist = NIL;
+
+ /* Set up the dummy path */
+ add_path(rel, (Path *) create_append_path(rel, NIL, NULL, 0, NIL));
+
+ /* Set or update cheapest_total_path and related fields */
+ set_cheapest(rel);
+
+ MemoryContextSwitchTo(oldcontext);
+}
+
+
+/*
+ * restriction_is_constant_false --- is a restrictlist just FALSE?
+ *
+ * In cases where a qual is provably constant FALSE, eval_const_expressions
+ * will generally have thrown away anything that's ANDed with it. In outer
+ * join situations this will leave us computing cartesian products only to
+ * decide there's no match for an outer row, which is pretty stupid. So,
+ * we need to detect the case.
+ *
+ * If only_pushed_down is TRUE, then consider only pushed-down quals.
+ */
+static bool
+restriction_is_constant_false(List *restrictlist, bool only_pushed_down)
+{
+ ListCell *lc;
+
+ /*
+ * Despite the above comment, the restriction list we see here might
+ * possibly have other members besides the FALSE constant, since other
+ * quals could get "pushed down" to the outer join level. So we check
+ * each member of the list.
+ */
+ foreach(lc, restrictlist)
+ {
+ RestrictInfo *rinfo = lfirst_node(RestrictInfo, lc);
+
+ if (only_pushed_down && !rinfo->is_pushed_down)
+ continue;
+
+ if (rinfo->clause && IsA(rinfo->clause, Const))
+ {
+ Const *con = (Const *) rinfo->clause;
+
+ /* constant NULL is as good as constant FALSE for our purposes */
+ if (con->constisnull)
+ return true;
+ if (!DatumGetBool(con->constvalue))
+ return true;
+ }
+ }
+ return false;
+}