Simplify the planner's new representation of indexable clauses a little.

In commit 1a8d5afb0, I thought it'd be a good idea to define
IndexClause.indexquals as NIL in the most common case where the given
clause (IndexClause.rinfo) is usable exactly as-is.  It'd be more
consistent to define the indexquals in that case as being a one-element
list containing IndexClause.rinfo, but I thought saving the palloc
overhead for making such a list would be worthwhile.

In hindsight, that was a great example of "premature optimization is the
root of all evil": it's complicated everyplace that needs to deal with
the indexquals, requiring duplicative code to handle both the simple
case and the not-simple case.  I'd initially found that tolerable but
it's getting less so as I mop up some areas that I'd not touched in
1a8d5afb0.  In any case, two more pallocs during a planner run are
surely at the noise level (a conclusion confirmed by a bit of
microbenchmarking).  So let's change this decision before it becomes
set in stone, and insist that IndexClause.indexquals always be a valid
list of the actual index quals for the clause.

Discussion: https://postgr.es/m/24586.1550106354@sss.pgh.pa.us

1 files changed, 6 insertions, 24 deletions

diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index c7645acad2c..236f506cfb2 100644
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -3075,11 +3075,8 @@ create_bitmap_subplan(PlannerInfo *root, Path *bitmapqual,
 
 			Assert(!rinfo->pseudoconstant);
 			subquals = lappend(subquals, rinfo->clause);
-			if (iclause->indexquals)
-				subindexquals = list_concat(subindexquals,
-											get_actual_clauses(iclause->indexquals));
-			else
-				subindexquals = lappend(subindexquals, rinfo->clause);
+			subindexquals = list_concat(subindexquals,
+										get_actual_clauses(iclause->indexquals));
 			if (rinfo->parent_ec)
 				subindexECs = lappend(subindexECs, rinfo->parent_ec);
 		}
@@ -4491,33 +4488,18 @@ fix_indexqual_references(PlannerInfo *root, IndexPath *index_path,
 	{
 		IndexClause *iclause = lfirst_node(IndexClause, lc);
 		int			indexcol = iclause->indexcol;
+		ListCell   *lc2;
 
-		if (iclause->indexquals == NIL)
+		foreach(lc2, iclause->indexquals)
 		{
-			/* rinfo->clause is directly usable as an indexqual */
-			Node	   *clause = (Node *) iclause->rinfo->clause;
+			RestrictInfo *rinfo = lfirst_node(RestrictInfo, lc2);
+			Node	   *clause = (Node *) rinfo->clause;
 
 			stripped_indexquals = lappend(stripped_indexquals, clause);
 			clause = fix_indexqual_clause(root, index, indexcol,
 										  clause, iclause->indexcols);
 			fixed_indexquals = lappend(fixed_indexquals, clause);
 		}
-		else
-		{
-			/* Process the derived indexquals */
-			ListCell   *lc2;
-
-			foreach(lc2, iclause->indexquals)
-			{
-				RestrictInfo *rinfo = lfirst_node(RestrictInfo, lc2);
-				Node	   *clause = (Node *) rinfo->clause;
-
-				stripped_indexquals = lappend(stripped_indexquals, clause);
-				clause = fix_indexqual_clause(root, index, indexcol,
-											  clause, iclause->indexcols);
-				fixed_indexquals = lappend(fixed_indexquals, clause);
-			}
-		}
 	}
 
 	*stripped_indexquals_p = stripped_indexquals;