Refactor the table AM: scan_begin_extractcolumns to contain execution…

… context

Refactor the signature of scan_begin_extractcolumns to contain execution
context, so that the scan node is able to filter data by evaluating
expressions in low level. Low-level filter may have less cost than extracting
all columns in a row and filtered out by the upper execution node.

src/backend/access/aocs/aocsam_handler.c

@@ -590,12 +590,14 @@ extractcolumns_from_node(Node *expr, bool *cols, AttrNumber natts)
 }
 
 static TableScanDesc
-aoco_beginscan_extractcolumns(Relation rel, Snapshot snapshot, ParallelTableScanDesc parallel_scan,
-							  List *targetlist, List *qual,
-							  uint32 flags)
+aoco_beginscan_extractcolumns(Relation rel, Snapshot snapshot, int nkeys, struct ScanKeyData *key,
+							  ParallelTableScanDesc parallel_scan,
+							  PlanState *ps, uint32 flags)
 {
 	AOCSScanDesc	aoscan;
 	AttrNumber		natts = RelationGetNumberOfAttributes(rel);
+	List *targetlist = ps->plan->targetlist;
+	List *qual = ps->plan->qual;
 	bool		   *cols;
 	bool			found = false;
 
@@ -620,6 +622,9 @@ aoco_beginscan_extractcolumns(Relation rel, Snapshot snapshot, ParallelTableScan
 
 	pfree(cols);
 
+	if (gp_enable_predicate_pushdown)
+		ps->qual = aocs_predicate_pushdown_prepare(aoscan, qual, ps->qual, ps->ps_ExprContext, ps);
+
 	return (TableScanDesc)aoscan;
 }
 

src/backend/access/appendonly/appendonlyam.c

@@ -1663,6 +1663,18 @@ appendonly_beginscan(Relation relation,
 	return (TableScanDesc) aoscan;
 }
 
+TableScanDesc
+appendonly_beginscan_extractcolumns(Relation rel, Snapshot snapshot, int nkeys, struct ScanKeyData *key,
+									ParallelTableScanDesc parallel_scan,
+									PlanState *ps, uint32 flags)
+{
+	AppendOnlyScanDesc aoscan;
+	aoscan = (AppendOnlyScanDesc) appendonly_beginscan(rel, snapshot, nkeys, key, parallel_scan, flags);
+	if (gp_enable_predicate_pushdown)
+		ps->qual = appendonly_predicate_pushdown_prepare(aoscan, ps->qual, ps->ps_ExprContext);
+	return (TableScanDesc) aoscan;
+}
+
 /* ----------------
  *		appendonly_rescan		- restart a relation scan
  *

src/backend/access/appendonly/appendonlyam_handler.c

@@ -2327,6 +2327,11 @@ static const TableAmRoutine ao_row_methods = {
 
 	.slot_callbacks = appendonly_slot_callbacks,
 
+	/*
+	 * appendonly row table doesn't extract columns, but handles
+	 * predicate pushdown.
+	 */
+	.scan_begin_extractcolumns = appendonly_beginscan_extractcolumns,
 	.scan_begin = appendonly_beginscan,
 	.scan_end = appendonly_endscan,
 	.scan_rescan = appendonly_rescan,

src/backend/executor/nodeSeqscan.c

@@ -100,9 +100,9 @@ SeqNext(SeqScanState *node)
 				/* try parallel mode for AOCO extract columns */
 				scandesc = table_beginscan_es(node->ss.ss_currentRelation,
 											  estate->es_snapshot,
+											  0, NULL,
 											  pscan,
-											  node->ss.ps.plan->targetlist,
-											  node->ss.ps.plan->qual);
+											  &node->ss.ps);
 			}
 			else
 			{
@@ -120,31 +120,11 @@ SeqNext(SeqScanState *node)
 			 */
 			scandesc = table_beginscan_es(node->ss.ss_currentRelation,
 										  estate->es_snapshot,
+										  0, NULL,
 										  NULL,
-										  node->ss.ps.plan->targetlist,
-										  node->ss.ps.plan->qual);
+										  &node->ss.ps);
 			node->ss.ss_currentScanDesc = scandesc;
 		}
-		if (gp_enable_predicate_pushdown)
-		{
-			if (RelationIsAoRows(node->ss.ss_currentRelation))
-			{
-				/* eval predicate push down */
-				node->ss.ps.qual =
-					appendonly_predicate_pushdown_prepare((AppendOnlyScanDesc)node->ss.ss_currentScanDesc,
-														  node->ss.ps.qual,
-														  node->ss.ps.ps_ExprContext);
-			}
-			else if (RelationIsAoCols(node->ss.ss_currentRelation))
-			{
-				node->ss.ps.qual =
-					aocs_predicate_pushdown_prepare((AOCSScanDesc)node->ss.ss_currentScanDesc,
-													node->ss.ps.plan->qual,
-													node->ss.ps.qual,
-													node->ss.ps.ps_ExprContext,
-													&node->ss.ps);
-			}
-		}
 	}
 
 	/*

src/include/access/tableam.h

@@ -254,6 +254,13 @@ typedef void (*IndexBuildCallback) (Relation index,
 									bool tupleIsAlive,
 									void *state);
 
+/*
+ * CBDB: Execution structure shouldn't appear here in PG design. We need to
+ * tell the scan node to do low-level and efficient filtering. The scan node
+ * will use low-level APIs exposed by the storage.
+ */
+struct PlanState;
+
 /*
  * API struct for a table AM.  Note this must be allocated in a
  * server-lifetime manner, typically as a static const struct, which then gets
@@ -315,9 +322,9 @@ typedef struct TableAmRoutine
 	 */
 	TableScanDesc	(*scan_begin_extractcolumns) (Relation rel,
 												  Snapshot snapshot,
+												  int nkeys, struct ScanKeyData *key,
 												  ParallelTableScanDesc parallel_scan,
-												  List *targetlist,
-												  List *qual,
+												  struct PlanState *ps,
 												  uint32 flags);
 
 	/*
@@ -925,8 +932,10 @@ table_beginscan(Relation rel, Snapshot snapshot,
  * Like table_beginscan_parallel, it will be parallel mode if parallel_scan is not NULL.
  */
 static inline TableScanDesc
-table_beginscan_es(Relation relation, Snapshot snapshot, ParallelTableScanDesc parallel_scan,
-				   List *targetList, List *qual)
+table_beginscan_es(Relation relation, Snapshot snapshot,
+				   int nkeys, struct ScanKeyData *key,
+				   ParallelTableScanDesc parallel_scan,
+				   struct PlanState *ps)
 {
 	bool isParallel = parallel_scan != NULL;
 	uint32		flags = SO_TYPE_SEQSCAN |
@@ -951,12 +960,13 @@ table_beginscan_es(Relation relation, Snapshot snapshot, ParallelTableScanDesc p
 	}
 
 	if (relation->rd_tableam->scan_begin_extractcolumns)
-		return relation->rd_tableam->scan_begin_extractcolumns(relation, snapshot, parallel_scan,
-														  targetList, qual,
-														  flags);
+		return relation->rd_tableam->scan_begin_extractcolumns(relation, snapshot,
+															   nkeys, key,
+															   parallel_scan,
+															   ps, flags);
 
 	return relation->rd_tableam->scan_begin(relation, snapshot,
-									   0, NULL,
+									   nkeys, key,
 									   parallel_scan, flags);
 }
 

src/include/cdb/cdbappendonlyam.h

@@ -432,6 +432,12 @@ extern TableScanDesc appendonly_beginscan(Relation relation,
 										  int nkeys, struct ScanKeyData *key,
 										  ParallelTableScanDesc pscan,
 										  uint32 flags);
+extern TableScanDesc appendonly_beginscan_extractcolumns(Relation rel,
+														 Snapshot snapshot,
+														 int nkeys, struct ScanKeyData *key,
+														 ParallelTableScanDesc parallel_scan,
+														 PlanState *ps,
+														 uint32 flags);
 extern void appendonly_rescan(TableScanDesc scan, ScanKey key,
 								bool set_params, bool allow_strat,
 								bool allow_sync, bool allow_pagemode);