X-Git-Url: http://git.osdn.net/view?a=blobdiff_plain;f=core.c;h=aa8d868b6ecf5df88cd146a40eccf1da6cbdbcdb;hb=2a9e14e50905decc0d37506284fbfb5bf1e094ac;hp=59b2a2a20507ea1caad9e84be04d2a41e3f92b12;hpb=9f444026f40b7561a311ca9ea881ebcf29e7852f;p=pghintplan%2Fpg_hint_plan.git

diff --git a/core.c b/core.c
index 59b2a2a..aa8d868 100644
--- a/core.c
+++ b/core.c
@@ -1,16 +1,582 @@
-/*
- * PostgreSQL 本体から流用した関数
+/*-------------------------------------------------------------------------
+ *
+ * core.c
+ *	  Routines copied from PostgreSQL core distribution.
+ *
+
+ * 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.
+ *
+ * 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
@@ -21,7 +587,7 @@
  *		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
@@ -37,7 +603,7 @@
  * 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.
  */
@@ -80,12 +646,19 @@ standard_join_search(PlannerInfo *root, int levels_needed, List *initial_rels)
 		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);
 
@@ -110,25 +683,25 @@ standard_join_search(PlannerInfo *root, int levels_needed, List *initial_rels)
 }
 
 /*
- * 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'
@@ -160,37 +733,34 @@ join_search_one_level(PlannerInfo *root, int 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);
@@ -201,10 +771,17 @@ join_search_one_level(PlannerInfo *root, int level)
 			 * 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]));
 		}
 	}
 
@@ -234,7 +811,7 @@ join_search_one_level(PlannerInfo *root, int level)
 			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.
 			 */
@@ -255,8 +832,8 @@ join_search_one_level(PlannerInfo *root, int level)
 				{
 					/*
 					 * 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))
@@ -268,17 +845,24 @@ join_search_one_level(PlannerInfo *root, int level)
 		}
 	}
 
-	/*
+	/*----------
 	 * 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)
 	{
@@ -289,23 +873,15 @@ join_search_one_level(PlannerInfo *root, int level)
 		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
@@ -316,15 +892,19 @@ join_search_one_level(PlannerInfo *root, int level)
 		 * 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
@@ -365,6 +945,7 @@ make_rels_by_clause_joins(PlannerInfo *root,
 	}
 }
 
+
 /*
  * make_rels_by_clauseless_joins
  *	  Given a relation 'old_rel' and a list of other relations
@@ -397,14 +978,345 @@ make_rels_by_clauseless_joins(PlannerInfo *root,
 	}
 }
 
+
+/*
+ * 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
@@ -412,6 +1324,18 @@ has_join_restriction(PlannerInfo *root, RelOptInfo *rel)
 {
 	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);
@@ -433,3 +1357,101 @@ has_join_restriction(PlannerInfo *root, RelOptInfo *rel)
 
 	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;
+}