support _tidb_rowid for table scan range (pingcap#8047)

Author: yu34po

cmd/explaintest/r/explain_easy.result

@@ -390,7 +390,7 @@ Sort_13	2.00	root	a:asc
     └─HashAgg_26	1.00	root	group by:a, funcs:firstrow(a), firstrow(a)
       └─Projection_27	1.00	root	1
         └─TableDual_28	1.00	root	rows:1
-explain SELECT 0 AS a FROM dual UNION (SELECT 1 AS a FROM dual ORDER BY a)
+explain SELECT 0 AS a FROM dual UNION (SELECT 1 AS a FROM dual ORDER BY a);
 id	count	task	operator info
 HashAgg_15	2.00	root	group by:a, funcs:firstrow(join_agg_0)
 └─Union_16	2.00	root	
@@ -400,3 +400,26 @@ HashAgg_15	2.00	root	group by:a, funcs:firstrow(join_agg_0)
   └─StreamAgg_26	1.00	root	group by:a, funcs:firstrow(a), firstrow(a)
     └─Projection_31	1.00	root	1
       └─TableDual_32	1.00	root	rows:1
+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

cmd/explaintest/t/explain_easy.test

@@ -82,4 +82,11 @@ explain select * from ta where a = 1;
 rollback;
 
 explain SELECT 0 AS a FROM dual UNION SELECT 1 AS a FROM dual ORDER BY a;
-explain SELECT 0 AS a FROM dual UNION (SELECT 1 AS a FROM dual ORDER BY a)
+explain SELECT 0 AS a FROM dual UNION (SELECT 1 AS a FROM dual ORDER BY a);
+
+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;

planner/core/logical_plans.go

@@ -340,7 +340,10 @@ 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)
 		}
@@ -349,6 +352,7 @@ 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