1 files changed, 140 insertions, 0 deletions
diff --git a/src/backend/optimizer/util/joininfo.c b/src/backend/optimizer/util/joininfo.c
new file mode 100644
index 0000000..717808b
--- /dev/null
+++ b/src/backend/optimizer/util/joininfo.c
@@ -0,0 +1,140 @@
+/*-------------------------------------------------------------------------
+ *
+ * joininfo.c
+ *	  joininfo list manipulation routines
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/optimizer/util/joininfo.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "optimizer/joininfo.h"
+#include "optimizer/pathnode.h"
+#include "optimizer/paths.h"
+
+
+/*
+ * have_relevant_joinclause
+ *		Detect whether there is a joinclause that involves
+ *		the two given relations.
+ *
+ * Note: the joinclause does not have to be evaluable with only these two
+ * relations.  This is intentional.  For example consider
+ *		SELECT * FROM a, b, c WHERE a.x = (b.y + c.z)
+ * If a is much larger than the other tables, it may be worthwhile to
+ * cross-join b and c and then use an inner indexscan on a.x.  Therefore
+ * we should consider this joinclause as reason to join b to c, even though
+ * it can't be applied at that join step.
+ */
+bool
+have_relevant_joinclause(PlannerInfo *root,
+						 RelOptInfo *rel1, RelOptInfo *rel2)
+{
+	bool		result = false;
+	List	   *joininfo;
+	Relids		other_relids;
+	ListCell   *l;
+
+	/*
+	 * We could scan either relation's joininfo list; may as well use the
+	 * shorter one.
+	 */
+	if (list_length(rel1->joininfo) <= list_length(rel2->joininfo))
+	{
+		joininfo = rel1->joininfo;
+		other_relids = rel2->relids;
+	}
+	else
+	{
+		joininfo = rel2->joininfo;
+		other_relids = rel1->relids;
+	}
+
+	foreach(l, joininfo)
+	{
+		RestrictInfo *rinfo = (RestrictInfo *) lfirst(l);
+
+		if (bms_overlap(other_relids, rinfo->required_relids))
+		{
+			result = true;
+			break;
+		}
+	}
+
+	/*
+	 * We also need to check the EquivalenceClass data structure, which might
+	 * contain relationships not emitted into the joininfo lists.
+	 */
+	if (!result && rel1->has_eclass_joins && rel2->has_eclass_joins)
+		result = have_relevant_eclass_joinclause(root, rel1, rel2);
+
+	return result;
+}
+
+
+/*
+ * add_join_clause_to_rels
+ *	  Add 'restrictinfo' to the joininfo list of each relation it requires.
+ *
+ * Note that the same copy of the restrictinfo node is linked to by all the
+ * lists it is in.  This allows us to exploit caching of information about
+ * the restriction clause (but we must be careful that the information does
+ * not depend on context).
+ *
+ * 'restrictinfo' describes the join clause
+ * 'join_relids' is the list of relations participating in the join clause
+ *				 (there must be more than one)
+ */
+void
+add_join_clause_to_rels(PlannerInfo *root,
+						RestrictInfo *restrictinfo,
+						Relids join_relids)
+{
+	int			cur_relid;
+
+	cur_relid = -1;
+	while ((cur_relid = bms_next_member(join_relids, cur_relid)) >= 0)
+	{
+		RelOptInfo *rel = find_base_rel(root, cur_relid);
+
+		rel->joininfo = lappend(rel->joininfo, restrictinfo);
+	}
+}
+
+/*
+ * remove_join_clause_from_rels
+ *	  Delete 'restrictinfo' from all the joininfo lists it is in
+ *
+ * This reverses the effect of add_join_clause_to_rels.  It's used when we
+ * discover that a relation need not be joined at all.
+ *
+ * 'restrictinfo' describes the join clause
+ * 'join_relids' is the list of relations participating in the join clause
+ *				 (there must be more than one)
+ */
+void
+remove_join_clause_from_rels(PlannerInfo *root,
+							 RestrictInfo *restrictinfo,
+							 Relids join_relids)
+{
+	int			cur_relid;
+
+	cur_relid = -1;
+	while ((cur_relid = bms_next_member(join_relids, cur_relid)) >= 0)
+	{
+		RelOptInfo *rel = find_base_rel(root, cur_relid);
+
+		/*
+		 * Remove the restrictinfo from the list.  Pointer comparison is
+		 * sufficient.
+		 */
+		Assert(list_member_ptr(rel->joininfo, restrictinfo));
+		rel->joininfo = list_delete_ptr(rel->joininfo, restrictinfo);
+	}
+}