support _tidb_rowid for table scan range (#8047)

Author: yu34po

cmd/explaintest/r/explain_easy.result

@@ -422,3 +422,26 @@ Projection_3	10000.00	root	plus(1, ifnull(test.t.a, 0))
   └─TableScan_4	10000.00	cop	table:t, range:[-inf,+inf], keep order:false, stats:pseudo
 drop table if exists t;
 drop table if exists t;
+create table t(a int);
+explain select * from t where _tidb_rowid = 0;
+id	count	task	operator info
+Projection_4	8000.00	root	test.t.a
+└─TableReader_6	10000.00	root	data:TableScan_5
+  └─TableScan_5	10000.00	cop	table:t, range:[0,0], keep order:false, stats:pseudo
+explain select * from t where _tidb_rowid > 0;
+id	count	task	operator info
+Projection_4	8000.00	root	test.t.a
+└─TableReader_6	10000.00	root	data:TableScan_5
+  └─TableScan_5	10000.00	cop	table:t, range:(0,+inf], keep order:false, stats:pseudo
+explain select a, _tidb_rowid from t where a > 0;
+id	count	task	operator info
+TableReader_7	3333.33	root	data:Selection_6
+└─Selection_6	3333.33	cop	gt(test.t.a, 0)
+  └─TableScan_5	10000.00	cop	table:t, range:[-inf,+inf], keep order:false, stats:pseudo
+explain select * from t where _tidb_rowid > 0 and a > 0;
+id	count	task	operator info
+Projection_4	2666.67	root	test.t.a
+└─TableReader_7	2666.67	root	data:Selection_6
+  └─Selection_6	2666.67	cop	gt(test.t.a, 0)
+    └─TableScan_5	3333.33	cop	table:t, range:(0,+inf], keep order:false, stats:pseudo
+drop table if exists t;

cmd/explaintest/t/explain_easy.test

@@ -93,3 +93,10 @@ explain select ifnull(nb, 0), ifnull(nb, 0) from t;
 explain select 1+ifnull(nb, 0) from t;
 explain select 1+ifnull(a, 0) from t;
 drop table if exists t;
+drop table if exists t;
+create table t(a int);
+explain select * from t where _tidb_rowid = 0;
+explain select * from t where _tidb_rowid > 0;
+explain select a, _tidb_rowid from t where a > 0;
+explain select * from t where _tidb_rowid > 0 and a > 0;
+drop table if exists t;

planner/core/logical_plans.go

@@ -333,7 +333,10 @@ func (ds *DataSource) deriveTablePathStats(path *accessPath) (bool, error) {
 	path.countAfterAccess = float64(ds.statisticTable.Count)
 	path.tableFilters = ds.pushedDownConds
 	var pkCol *expression.Column
-	if ds.tableInfo.PKIsHandle {
+	columnLen := len(ds.schema.Columns)
+	if columnLen > 0 && ds.schema.Columns[columnLen-1].ID == model.ExtraHandleID {
+		pkCol = ds.schema.Columns[columnLen-1]
+	} else if ds.tableInfo.PKIsHandle {
 		if pkColInfo := ds.tableInfo.GetPkColInfo(); pkColInfo != nil {
 			pkCol = expression.ColInfo2Col(ds.schema.Columns, pkColInfo)
 		}
@@ -342,6 +345,7 @@ func (ds *DataSource) deriveTablePathStats(path *accessPath) (bool, error) {
 		path.ranges = ranger.FullIntRange(false)
 		return false, nil
 	}
+
 	path.ranges = ranger.FullIntRange(mysql.HasUnsignedFlag(pkCol.RetType.Flag))
 	if len(ds.pushedDownConds) == 0 {
 		return false, nil