statistics: update stats per table in the pipeline

statistics/handle/update.go

@@ -27,6 +27,7 @@ import (
 	"github.com/pingcap/log"
 	"github.com/pingcap/parser/model"
 	"github.com/pingcap/parser/mysql"
+	"github.com/pingcap/parser/terror"
 	"github.com/pingcap/tidb/infoschema"
 	"github.com/pingcap/tidb/kv"
 	"github.com/pingcap/tidb/metrics"
@@ -502,28 +503,62 @@ func (h *Handle) UpdateErrorRate(is infoschema.InfoSchema) {
 
 // HandleUpdateStats update the stats using feedback.
 func (h *Handle) HandleUpdateStats(is infoschema.InfoSchema) error {
-	sql := "select table_id, hist_id, is_index, feedback from mysql.stats_feedback order by table_id, hist_id, is_index"
-	rows, _, err := h.restrictedExec.ExecRestrictedSQL(sql)
-	if len(rows) == 0 || err != nil {
+	sql := "SELECT distinct table_id from mysql.stats_feedback"
+	tables, _, err := h.restrictedExec.ExecRestrictedSQL(sql)
+	if err != nil {
 		return errors.Trace(err)
 	}
-
-	var groupedRows [][]chunk.Row
-	preIdx := 0
-	tableID, histID, isIndex := rows[0].GetInt64(0), rows[0].GetInt64(1), rows[0].GetInt64(2)
-	for i := 1; i < len(rows); i++ {
-		row := rows[i]
-		if row.GetInt64(0) != tableID || row.GetInt64(1) != histID || row.GetInt64(2) != isIndex {
-			groupedRows = append(groupedRows, rows[preIdx:i])
-			tableID, histID, isIndex = row.GetInt64(0), row.GetInt64(1), row.GetInt64(2)
-			preIdx = i
-		}
+	if len(tables) == 0 {
+		return nil
 	}
-	groupedRows = append(groupedRows, rows[preIdx:])
 
-	for _, rows := range groupedRows {
-		if err := h.handleSingleHistogramUpdate(is, rows); err != nil {
-			return errors.Trace(err)
+	for _, ptbl := range tables {
+		// this func lets `defer` works normally, where `Close()` should be called before any return
+		err = func() error {
+			tbl := ptbl.GetInt64(0)
+			sql = fmt.Sprintf("select table_id, hist_id, is_index, feedback from mysql.stats_feedback where table_id=%d order by hist_id, is_index", tbl)
+			rc, err := h.mu.ctx.(sqlexec.SQLExecutor).Execute(context.TODO(), sql)
+			if len(rc) > 0 {
+				defer terror.Call(rc[0].Close)
+			}
+			if err != nil {
+				return errors.Trace(err)
+			}
+			req := rc[0].NewChunk()
+			iter := chunk.NewIterator4Chunk(req)
+			tableID, histID, isIndex := int64(-1), int64(-1), int64(-1)
+			var rows []chunk.Row
+			for {
+				err := rc[0].Next(context.TODO(), req)
+				if err != nil {
+					return errors.Trace(err)
+				}
+				if req.NumRows() == 0 {
+					if len(rows) > 0 {
+						if err := h.handleSingleHistogramUpdate(is, rows); err != nil {
+							return errors.Trace(err)
+						}
+					}
+					break
+				}
+				for row := iter.Begin(); row != iter.End(); row = iter.Next() {
+					// len(rows) > 100000 limits the rows to avoid OOM
+					if row.GetInt64(0) != tableID || row.GetInt64(1) != histID || row.GetInt64(2) != isIndex || len(rows) > 100000 {
+						if len(rows) > 0 {
+							if err := h.handleSingleHistogramUpdate(is, rows); err != nil {
+								return errors.Trace(err)
+							}
+						}
+						tableID, histID, isIndex = row.GetInt64(0), row.GetInt64(1), row.GetInt64(2)
+						rows = rows[:0]
+					}
+					rows = append(rows, row)
+				}
+			}
+			return nil
+		}()
+		if err != nil {
+			return err
 		}
 	}
 	return nil