*: fix data race in the statsCache (#37753)

close #37603

executor/infoschema_reader.go

@@ -265,7 +265,7 @@ func getColLengthTables(ctx context.Context, sctx sessionctx.Context, tableIDs .
 	return colLengthMap, nil
 }
 
-func getDataAndIndexLength(info *model.TableInfo, physicalID int64, rowCount uint64, columnLengthMap map[tableHistID]uint64) (uint64, uint64) {
+func getDataAndIndexLength(info *model.TableInfo, physicalID int64, rowCount uint64) (uint64, uint64) {
 	columnLength := make(map[string]uint64, len(info.Columns))
 	for _, col := range info.Columns {
 		if col.State != model.StatePublic {
@@ -275,7 +275,7 @@ func getDataAndIndexLength(info *model.TableInfo, physicalID int64, rowCount uin
 		if length != types.VarStorageLen {
 			columnLength[col.Name.L] = rowCount * uint64(length)
 		} else {
-			length := columnLengthMap[tableHistID{tableID: physicalID, histID: col.ID}]
+			length := tableStatsCache.GetColLength(tableHistID{tableID: physicalID, histID: col.ID})
 			columnLength[col.Name.L] = length
 		}
 	}
@@ -317,45 +317,55 @@ func invalidInfoSchemaStatCache(tblID int64) {
 	tableStatsCache.dirtyIDs = append(tableStatsCache.dirtyIDs, tblID)
 }
 
-func (c *statsCache) get(ctx context.Context, sctx sessionctx.Context) (map[int64]uint64, map[tableHistID]uint64, error) {
+func (c *statsCache) GetTableRows(id int64) uint64 {
+	c.mu.RLock()
+	defer c.mu.RUnlock()
+	return c.tableRows[id]
+}
+
+func (c *statsCache) GetColLength(id tableHistID) uint64 {
+	c.mu.RLock()
+	defer c.mu.RUnlock()
+	return c.colLength[id]
+}
+
+func (c *statsCache) update(ctx context.Context, sctx sessionctx.Context) error {
 	c.mu.Lock()
 	defer c.mu.Unlock()
 	ctx = kv.WithInternalSourceType(ctx, kv.InternalTxnStats)
 	if time.Since(c.modifyTime) < TableStatsCacheExpiry {
 		if len(c.dirtyIDs) > 0 {
 			tableRows, err := getRowCountTables(ctx, sctx, c.dirtyIDs...)
 			if err != nil {
-				return nil, nil, err
+				return err
 			}
 			for id, tr := range tableRows {
 				c.tableRows[id] = tr
 			}
 			colLength, err := getColLengthTables(ctx, sctx, c.dirtyIDs...)
 			if err != nil {
-				return nil, nil, err
+				return err
 			}
 			for id, cl := range colLength {
 				c.colLength[id] = cl
 			}
 			c.dirtyIDs = nil
 		}
-		tableRows, colLength := c.tableRows, c.colLength
-		return tableRows, colLength, nil
+		return nil
 	}
 	tableRows, err := getRowCountTables(ctx, sctx)
 	if err != nil {
-		return nil, nil, err
+		return err
 	}
 	colLength, err := getColLengthTables(ctx, sctx)
 	if err != nil {
-		return nil, nil, err
+		return err
 	}
-
 	c.tableRows = tableRows
 	c.colLength = colLength
 	c.modifyTime = time.Now()
 	c.dirtyIDs = nil
-	return tableRows, colLength, nil
+	return nil
 }
 
 func getAutoIncrementID(ctx sessionctx.Context, schema *model.DBInfo, tblInfo *model.TableInfo) (int64, error) {
@@ -616,7 +626,7 @@ func (e *memtableRetriever) setDataFromReferConst(ctx context.Context, sctx sess
 }
 
 func (e *memtableRetriever) setDataFromTables(ctx context.Context, sctx sessionctx.Context, schemas []*model.DBInfo) error {
-	tableRowsMap, colLengthMap, err := tableStatsCache.get(ctx, sctx)
+	err := tableStatsCache.update(ctx, sctx)
 	if err != nil {
 		return err
 	}
@@ -660,12 +670,13 @@ func (e *memtableRetriever) setDataFromTables(ctx context.Context, sctx sessionc
 
 				var rowCount, dataLength, indexLength uint64
 				if table.GetPartitionInfo() == nil {
-					rowCount = tableRowsMap[table.ID]
-					dataLength, indexLength = getDataAndIndexLength(table, table.ID, rowCount, colLengthMap)
+					rowCount = tableStatsCache.GetTableRows(table.ID)
+					dataLength, indexLength = getDataAndIndexLength(table, table.ID, rowCount)
 				} else {
 					for _, pi := range table.GetPartitionInfo().Definitions {
-						rowCount += tableRowsMap[pi.ID]
-						parDataLen, parIndexLen := getDataAndIndexLength(table, pi.ID, tableRowsMap[pi.ID], colLengthMap)
+						piRowCnt := tableStatsCache.GetTableRows(pi.ID)
+						rowCount += piRowCnt
+						parDataLen, parIndexLen := getDataAndIndexLength(table, pi.ID, piRowCnt)
 						dataLength += parDataLen
 						indexLength += parIndexLen
 					}
@@ -993,7 +1004,7 @@ func calcCharOctLength(lenInChar int, cs string) int {
 }
 
 func (e *memtableRetriever) setDataFromPartitions(ctx context.Context, sctx sessionctx.Context, schemas []*model.DBInfo) error {
-	tableRowsMap, colLengthMap, err := tableStatsCache.get(ctx, sctx)
+	err := tableStatsCache.update(ctx, sctx)
 	if err != nil {
 		return err
 	}
@@ -1009,8 +1020,8 @@ func (e *memtableRetriever) setDataFromPartitions(ctx context.Context, sctx sess
 
 			var rowCount, dataLength, indexLength uint64
 			if table.GetPartitionInfo() == nil {
-				rowCount = tableRowsMap[table.ID]
-				dataLength, indexLength = getDataAndIndexLength(table, table.ID, rowCount, colLengthMap)
+				rowCount = tableStatsCache.GetTableRows(table.ID)
+				dataLength, indexLength = getDataAndIndexLength(table, table.ID, rowCount)
 				avgRowLength := uint64(0)
 				if rowCount != 0 {
 					avgRowLength = dataLength / rowCount
@@ -1047,8 +1058,8 @@ func (e *memtableRetriever) setDataFromPartitions(ctx context.Context, sctx sess
 				rows = append(rows, record)
 			} else {
 				for i, pi := range table.GetPartitionInfo().Definitions {
-					rowCount = tableRowsMap[pi.ID]
-					dataLength, indexLength = getDataAndIndexLength(table, pi.ID, tableRowsMap[pi.ID], colLengthMap)
+					rowCount = tableStatsCache.GetTableRows(pi.ID)
+					dataLength, indexLength = getDataAndIndexLength(table, pi.ID, rowCount)
 
 					avgRowLength := uint64(0)
 					if rowCount != 0 {