executor: trace the memory usage of Selection executors

executor/executor.go

@@ -1029,14 +1029,19 @@ type SelectionExec struct {
 	inputIter   *chunk.Iterator4Chunk
 	inputRow    chunk.Row
 	childResult *chunk.Chunk
+
+	memTracker *memory.Tracker
 }
 
 // Open implements the Executor Open interface.
 func (e *SelectionExec) Open(ctx context.Context) error {
 	if err := e.baseExecutor.Open(ctx); err != nil {
 		return err
 	}
+	e.memTracker = memory.NewTracker(e.id, -1)
+	e.memTracker.AttachTo(e.ctx.GetSessionVars().StmtCtx.MemTracker)
 	e.childResult = newFirstChunk(e.children[0])
+	e.memTracker.Consume(e.childResult.MemoryUsage())
 	e.batched = expression.Vectorizable(e.filters)
 	if e.batched {
 		e.selected = make([]bool, 0, chunk.InitialCapacity)
@@ -1048,6 +1053,7 @@ func (e *SelectionExec) Open(ctx context.Context) error {
 
 // Close implements plannercore.Plan Close interface.
 func (e *SelectionExec) Close() error {
+	e.memTracker.Consume(-e.childResult.MemoryUsage())
 	e.childResult = nil
 	e.selected = nil
 	return e.baseExecutor.Close()
@@ -1071,7 +1077,9 @@ func (e *SelectionExec) Next(ctx context.Context, req *chunk.Chunk) error {
 			}
 			req.AppendRow(e.inputRow)
 		}
+		mSize := e.childResult.MemoryUsage()
 		err := Next(ctx, e.children[0], e.childResult)
+		e.memTracker.Consume(e.childResult.MemoryUsage() - mSize)
 		if err != nil {
 			return err
 		}
@@ -1103,7 +1111,9 @@ func (e *SelectionExec) unBatchedNext(ctx context.Context, chk *chunk.Chunk) err
 				return nil
 			}
 		}
+		mSize := e.childResult.MemoryUsage()
 		err := Next(ctx, e.children[0], e.childResult)
+		e.memTracker.Consume(e.childResult.MemoryUsage() - mSize)
 		if err != nil {
 			return err
 		}

executor/explain_test.go

@@ -129,7 +129,7 @@ func (s *testSuite1) TestExplainAnalyzeMemory(c *C) {
 
 func (s *testSuite1) checkMemoryInfo(c *C, tk *testkit.TestKit, sql string) {
 	memCol := 5
-	ops := []string{"Join", "Reader", "Top", "Sort", "LookUp", "Projection"}
+	ops := []string{"Join", "Reader", "Top", "Sort", "LookUp", "Projection", "Selection"}
 	rows := tk.MustQuery(sql).Rows()
 	for _, row := range rows {
 		strs := make([]string, len(row))
@@ -164,6 +164,7 @@ func (s *testSuite1) TestMemoryUsageAfterClose(c *C) {
 		tk.MustExec(fmt.Sprintf("insert into t values (%v, %v)", i, i))
 	}
 	SQLs := []string{"select v+abs(k) from t",
+		"select v from t where abs(v) > 0",
 		"select v from t order by v"}
 	for _, sql := range SQLs {
 		tk.MustQuery(sql)