Simplify LATERAL-related calculations within add_paths_to_joinrel().

While convincing myself that commit 7e19db0c09719d79 would solve both of
the problems recently reported by Andreas Seltenreich, I realized that
add_paths_to_joinrel's handling of LATERAL restrictions could be made
noticeably simpler and faster if we were to retain the minimum possible
parameterization for each joinrel (that is, the set of relids supplying
unsatisfied lateral references in it).  We already retain that for
baserels, in RelOptInfo.lateral_relids, so we can use that field for
joinrels too.

I re-pgindent'd the files touched here, which affects some unrelated
comments.

This is, I believe, just a minor optimization not a bug fix, so no
back-patch.

3 files changed, 27 insertions, 70 deletions

diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index 012c14bf29a..c709105d4fe 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -1891,13 +1891,13 @@ _outRelOptInfo(StringInfo str, const RelOptInfo *node)
 	WRITE_NODE_FIELD(cheapest_total_path);
 	WRITE_NODE_FIELD(cheapest_unique_path);
 	WRITE_NODE_FIELD(cheapest_parameterized_paths);
+	WRITE_BITMAPSET_FIELD(lateral_relids);
 	WRITE_UINT_FIELD(relid);
 	WRITE_OID_FIELD(reltablespace);
 	WRITE_ENUM_FIELD(rtekind, RTEKind);
 	WRITE_INT_FIELD(min_attr);
 	WRITE_INT_FIELD(max_attr);
 	WRITE_NODE_FIELD(lateral_vars);
-	WRITE_BITMAPSET_FIELD(lateral_relids);
 	WRITE_BITMAPSET_FIELD(lateral_referencers);
 	WRITE_NODE_FIELD(indexlist);
 	WRITE_UINT_FIELD(pages);
diff --git a/src/backend/optimizer/path/joinpath.c b/src/backend/optimizer/path/joinpath.c
index a35c881fd92..0f040331665 100644
--- a/src/backend/optimizer/path/joinpath.c
+++ b/src/backend/optimizer/path/joinpath.c
@@ -86,7 +86,6 @@ add_paths_to_joinrel(PlannerInfo *root,
 	extra.mergeclause_list = NIL;
 	extra.sjinfo = sjinfo;
 	extra.param_source_rels = NULL;
-	extra.extra_lateral_rels = NULL;
 
 	/*
 	 * Find potential mergejoin clauses.  We can skip this if we are not
@@ -151,60 +150,14 @@ add_paths_to_joinrel(PlannerInfo *root,
 	}
 
 	/*
-	 * However, when a LATERAL subquery is involved, we have to be a bit
-	 * laxer, because there will simply not be any paths for the joinrel that
-	 * aren't parameterized by whatever the subquery is parameterized by,
-	 * unless its parameterization is resolved within the joinrel.  Hence, add
-	 * to param_source_rels anything that is laterally referenced in either
-	 * input and is not in the join already.
+	 * However, when a LATERAL subquery is involved, there will simply not be
+	 * any paths for the joinrel that aren't parameterized by whatever the
+	 * subquery is parameterized by, unless its parameterization is resolved
+	 * within the joinrel.  So we might as well allow additional dependencies
+	 * on whatever residual lateral dependencies the joinrel will have.
 	 */
-	foreach(lc, root->lateral_info_list)
-	{
-		LateralJoinInfo *ljinfo = (LateralJoinInfo *) lfirst(lc);
-
-		if (bms_is_subset(ljinfo->lateral_rhs, joinrel->relids))
-			extra.param_source_rels = bms_join(extra.param_source_rels,
-										  bms_difference(ljinfo->lateral_lhs,
-														 joinrel->relids));
-	}
-
-	/*
-	 * Another issue created by LATERAL references is that PlaceHolderVars
-	 * that need to be computed at this join level might contain lateral
-	 * references to rels not in the join, meaning that the paths for the join
-	 * would need to be marked as parameterized by those rels, independently
-	 * of all other considerations.  Set extra_lateral_rels to the set of such
-	 * rels.  This will not affect our decisions as to which paths to
-	 * generate; we merely add these rels to their required_outer sets.
-	 */
-	foreach(lc, root->placeholder_list)
-	{
-		PlaceHolderInfo *phinfo = (PlaceHolderInfo *) lfirst(lc);
-
-		/* PHVs without lateral refs can be skipped over quickly */
-		if (phinfo->ph_lateral == NULL)
-			continue;
-		/* Is it due to be evaluated at this join, and not in either input? */
-		if (bms_is_subset(phinfo->ph_eval_at, joinrel->relids) &&
-			!bms_is_subset(phinfo->ph_eval_at, outerrel->relids) &&
-			!bms_is_subset(phinfo->ph_eval_at, innerrel->relids))
-		{
-			/* Yes, remember its lateral rels */
-			extra.extra_lateral_rels = bms_add_members(extra.extra_lateral_rels,
-													   phinfo->ph_lateral);
-		}
-	}
-
-	/*
-	 * Make sure extra_lateral_rels doesn't list anything within the join, and
-	 * that it's NULL if empty.  (This allows us to use bms_add_members to add
-	 * it to required_outer below, while preserving the property that
-	 * required_outer is exactly NULL if empty.)
-	 */
-	extra.extra_lateral_rels = bms_del_members(extra.extra_lateral_rels,
-											   joinrel->relids);
-	if (bms_is_empty(extra.extra_lateral_rels))
-		extra.extra_lateral_rels = NULL;
+	extra.param_source_rels = bms_add_members(extra.param_source_rels,
+											  joinrel->lateral_relids);
 
 	/*
 	 * 1. Consider mergejoin paths where both relations must be explicitly
@@ -386,9 +339,13 @@ try_nestloop_path(PlannerInfo *root,
 
 	/*
 	 * Independently of that, add parameterization needed for any
-	 * PlaceHolderVars that need to be computed at the join.
+	 * PlaceHolderVars that need to be computed at the join.  We can handle
+	 * that just by adding joinrel->lateral_relids; that might include some
+	 * rels that are already in required_outer, but no harm done.  (Note that
+	 * lateral_relids is exactly NULL if empty, so this will not break the
+	 * property that required_outer is too.)
 	 */
-	required_outer = bms_add_members(required_outer, extra->extra_lateral_rels);
+	required_outer = bms_add_members(required_outer, joinrel->lateral_relids);
 
 	/*
 	 * Do a precheck to quickly eliminate obviously-inferior paths.  We
@@ -465,7 +422,7 @@ try_mergejoin_path(PlannerInfo *root,
 	 * Independently of that, add parameterization needed for any
 	 * PlaceHolderVars that need to be computed at the join.
 	 */
-	required_outer = bms_add_members(required_outer, extra->extra_lateral_rels);
+	required_outer = bms_add_members(required_outer, joinrel->lateral_relids);
 
 	/*
 	 * If the given paths are already well enough ordered, we can skip doing
@@ -547,7 +504,7 @@ try_hashjoin_path(PlannerInfo *root,
 	 * Independently of that, add parameterization needed for any
 	 * PlaceHolderVars that need to be computed at the join.
 	 */
-	required_outer = bms_add_members(required_outer, extra->extra_lateral_rels);
+	required_outer = bms_add_members(required_outer, joinrel->lateral_relids);
 
 	/*
 	 * See comments in try_nestloop_path().  Also note that hashjoin paths
diff --git a/src/backend/optimizer/util/relnode.c b/src/backend/optimizer/util/relnode.c
index 8cc7bd771b3..b197f144117 100644
--- a/src/backend/optimizer/util/relnode.c
+++ b/src/backend/optimizer/util/relnode.c
@@ -103,7 +103,7 @@ build_simple_rel(PlannerInfo *root, int relid, RelOptKind reloptkind)
 	/* cheap startup cost is interesting iff not all tuples to be retrieved */
 	rel->consider_startup = (root->tuple_fraction > 0);
 	rel->consider_param_startup = false;		/* might get changed later */
-	rel->consider_parallel = false;				/* might get changed later */
+	rel->consider_parallel = false;		/* might get changed later */
 	rel->reltargetlist = NIL;
 	rel->pathlist = NIL;
 	rel->ppilist = NIL;
@@ -111,11 +111,11 @@ build_simple_rel(PlannerInfo *root, int relid, RelOptKind reloptkind)
 	rel->cheapest_total_path = NULL;
 	rel->cheapest_unique_path = NULL;
 	rel->cheapest_parameterized_paths = NIL;
+	rel->lateral_relids = NULL;
 	rel->relid = relid;
 	rel->rtekind = rte->rtekind;
 	/* min_attr, max_attr, attr_needed, attr_widths are set below */
 	rel->lateral_vars = NIL;
-	rel->lateral_relids = NULL;
 	rel->lateral_referencers = NULL;
 	rel->indexlist = NIL;
 	rel->pages = 0;
@@ -373,6 +373,7 @@ build_join_rel(PlannerInfo *root,
 	joinrel->cheapest_total_path = NULL;
 	joinrel->cheapest_unique_path = NULL;
 	joinrel->cheapest_parameterized_paths = NIL;
+	joinrel->lateral_relids = min_join_parameterization(root, joinrel->relids);
 	joinrel->relid = 0;			/* indicates not a baserel */
 	joinrel->rtekind = RTE_JOIN;
 	joinrel->min_attr = 0;
@@ -380,7 +381,6 @@ build_join_rel(PlannerInfo *root,
 	joinrel->attr_needed = NULL;
 	joinrel->attr_widths = NULL;
 	joinrel->lateral_vars = NIL;
-	joinrel->lateral_relids = NULL;
 	joinrel->lateral_referencers = NULL;
 	joinrel->indexlist = NIL;
 	joinrel->pages = 0;
@@ -448,15 +448,15 @@ build_join_rel(PlannerInfo *root,
 	 * Set the consider_parallel flag if this joinrel could potentially be
 	 * scanned within a parallel worker.  If this flag is false for either
 	 * inner_rel or outer_rel, then it must be false for the joinrel also.
-	 * Even if both are true, there might be parallel-restricted quals at
-	 * our level.
+	 * Even if both are true, there might be parallel-restricted quals at our
+	 * level.
 	 *
-	 * Note that if there are more than two rels in this relation, they
-	 * could be divided between inner_rel and outer_rel in any arbitary
-	 * way.  We assume this doesn't matter, because we should hit all the
-	 * same baserels and joinclauses while building up to this joinrel no
-	 * matter which we take; therefore, we should make the same decision
-	 * here however we get here.
+	 * Note that if there are more than two rels in this relation, they could
+	 * be divided between inner_rel and outer_rel in any arbitary way.  We
+	 * assume this doesn't matter, because we should hit all the same baserels
+	 * and joinclauses while building up to this joinrel no matter which we
+	 * take; therefore, we should make the same decision here however we get
+	 * here.
 	 */
 	if (inner_rel->consider_parallel && outer_rel->consider_parallel &&
 		!has_parallel_hazard((Node *) restrictlist, false))