Modify planner's implied-equality-deduction code so that when a set

of known-equal expressions includes any constant expressions (including
Params from outer queries), we actively suppress any 'var = var'
clauses that are or could be deduced from the set, generating only the
deducible 'var = const' clauses instead.  The idea here is to push down
the restrictions implied by the equality set to base relations whenever
possible.  Once we have applied the 'var = const' clauses, the 'var = var'
clauses are redundant, and should be suppressed both to save work at
execution and to avoid double-counting restrictivity.

src/backend/optimizer/util/joininfo.c

@@ -8,13 +8,14 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/optimizer/util/joininfo.c,v 1.32 2003/01/20 18:54:56 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/optimizer/util/joininfo.c,v 1.33 2003/01/24 03:58:43 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
 #include "postgres.h"
 
 #include "optimizer/joininfo.h"
+#include "optimizer/pathnode.h"
 
 
 /*
@@ -63,3 +64,110 @@ make_joininfo_node(RelOptInfo *this_rel, Relids join_relids)
 	}
 	return joininfo;
 }
+
+
+/*
+ * add_join_clause_to_rels
+ *	  For every relation participating in a join clause, add 'restrictinfo' to
+ *	  the appropriate joininfo list (creating a new list and adding it to the
+ *	  appropriate rel node if necessary).
+ *
+ * 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(Query *root,
+						RestrictInfo *restrictinfo,
+						Relids join_relids)
+{
+	List	   *join_relid;
+
+	/* For every relid, find the joininfo, and add the proper join entries */
+	foreach(join_relid, join_relids)
+	{
+		int			cur_relid = lfirsti(join_relid);
+		Relids		unjoined_relids = NIL;
+		JoinInfo   *joininfo;
+		List	   *otherrel;
+
+		/* Get the relids not equal to the current relid */
+		foreach(otherrel, join_relids)
+		{
+			if (lfirsti(otherrel) != cur_relid)
+				unjoined_relids = lappendi(unjoined_relids, lfirsti(otherrel));
+		}
+		Assert(unjoined_relids != NIL);
+
+		/*
+		 * Find or make the joininfo node for this combination of rels,
+		 * and add the restrictinfo node to it.
+		 */
+		joininfo = make_joininfo_node(find_base_rel(root, cur_relid),
+									  unjoined_relids);
+		joininfo->jinfo_restrictinfo = lappend(joininfo->jinfo_restrictinfo,
+											   restrictinfo);
+		/*
+		 * Can't freeList(unjoined_relids) because new joininfo node may
+		 * link to it.  We could avoid leaking memory by doing listCopy()
+		 * in make_joininfo_node, but for now speed seems better.
+		 */
+	}
+}
+
+/*
+ * 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 join clause is redundant.
+ *
+ * '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(Query *root,
+							 RestrictInfo *restrictinfo,
+							 Relids join_relids)
+{
+	List	   *join_relid;
+
+	/* For every relid, find the joininfo */
+	foreach(join_relid, join_relids)
+	{
+		int			cur_relid = lfirsti(join_relid);
+		Relids		unjoined_relids = NIL;
+		JoinInfo   *joininfo;
+		List	   *otherrel;
+
+		/* Get the relids not equal to the current relid */
+		foreach(otherrel, join_relids)
+		{
+			if (lfirsti(otherrel) != cur_relid)
+				unjoined_relids = lappendi(unjoined_relids, lfirsti(otherrel));
+		}
+		Assert(unjoined_relids != NIL);
+
+		/*
+		 * Find the joininfo node for this combination of rels; it should
+		 * exist already, if add_join_clause_to_rels was called.
+		 */
+		joininfo = find_joininfo_node(find_base_rel(root, cur_relid),
+									  unjoined_relids);
+		Assert(joininfo);
+		/*
+		 * Remove the restrictinfo from the list.  Pointer comparison
+		 * is sufficient.
+		 */
+		Assert(ptrMember(restrictinfo, joininfo->jinfo_restrictinfo));
+		joininfo->jinfo_restrictinfo = lremove(restrictinfo,
+											   joininfo->jinfo_restrictinfo);
+		freeList(unjoined_relids);
+	}
+}