Columnar: add GUC to control qual pushdown. (#4586)

src/backend/columnar/cstore_customscan.c

@@ -76,6 +76,7 @@ static void ColumnarScan_ExplainCustomScan(CustomScanState *node, List *ancestor
 static set_rel_pathlist_hook_type PreviousSetRelPathlistHook = NULL;
 
 static bool EnableColumnarCustomScan = true;
+static bool EnableColumnarQualPushdown = true;
 
 
 const struct CustomPathMethods ColumnarScanPathMethods = {
@@ -114,13 +115,23 @@ columnar_customscan_init()
 	DefineCustomBoolVariable(
 		"columnar.enable_custom_scan",
 		gettext_noop("Enables the use of a custom scan to push projections and quals "
-					 "into the storage layer"),
+					 "into the storage layer."),
 		NULL,
 		&EnableColumnarCustomScan,
 		true,
 		PGC_USERSET,
 		GUC_NO_SHOW_ALL,
 		NULL, NULL, NULL);
+	DefineCustomBoolVariable(
+		"columnar.enable_qual_pushdown",
+		gettext_noop("Enables qual pushdown into columnar. This has no effect unless "
+					 "columnar.enable_custom_scan is true."),
+		NULL,
+		&EnableColumnarQualPushdown,
+		true,
+		PGC_USERSET,
+		GUC_NO_SHOW_ALL,
+		NULL, NULL, NULL);
 }
 
 
@@ -294,7 +305,10 @@ ColumnarScan_CreateCustomScanState(CustomScan *cscan)
 	CustomScanState *cscanstate = &columnarScanState->custom_scanstate;
 	cscanstate->methods = &ColumnarExecuteMethods;
 
+	if (EnableColumnarQualPushdown)
+	{
 		columnarScanState->qual = cscan->scan.plan.qual;
+	}
 
 	return (Node *) cscanstate;
 }

src/test/regress/input/am_chunk_filtering.source

@@ -76,6 +76,10 @@ CREATE TABLE simple_chunk_filtering(i int) USING COLUMNAR;
 INSERT INTO simple_chunk_filtering SELECT generate_series(0,234567);
 EXPLAIN (analyze on, costs off, timing off, summary off)
   SELECT * FROM simple_chunk_filtering WHERE i > 123456;
+SET columnar.enable_qual_pushdown = false;
+EXPLAIN (analyze on, costs off, timing off, summary off)
+  SELECT * FROM simple_chunk_filtering WHERE i > 123456;
+SET columnar.enable_qual_pushdown TO DEFAULT;
 
 -- https://github.com/citusdata/citus/issues/4555
 TRUNCATE simple_chunk_filtering;

src/test/regress/output/am_chunk_filtering.source

@@ -130,6 +130,18 @@ EXPLAIN (analyze on, costs off, timing off, summary off)
    Columnar Chunks Removed by Filter: 12
 (4 rows)
 
+SET columnar.enable_qual_pushdown = false;
+EXPLAIN (analyze on, costs off, timing off, summary off)
+  SELECT * FROM simple_chunk_filtering WHERE i > 123456;
+                                    QUERY PLAN
+---------------------------------------------------------------------
+ Custom Scan (ColumnarScan) on simple_chunk_filtering (actual rows=111111 loops=1)
+   Filter: (i > 123456)
+   Rows Removed by Filter: 123457
+   Columnar Chunks Removed by Filter: 0
+(4 rows)
+
+SET columnar.enable_qual_pushdown TO DEFAULT;
 -- https://github.com/citusdata/citus/issues/4555
 TRUNCATE simple_chunk_filtering;
 INSERT INTO simple_chunk_filtering SELECT generate_series(0,200000);