*: fix data race in the statsCache (pingcap#37753) (pingcap#37770)

close pingcap#37603

executor/infoschema_reader.go

@@ -229,7 +229,7 @@ func getColLengthAllTables(ctx context.Context, sctx sessionctx.Context) (map[ta
 	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 {
@@ -239,7 +239,7 @@ 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
 		}
 	}
@@ -274,33 +274,44 @@ var tableStatsCache = &statsCache{}
 // TableStatsCacheExpiry is the expiry time for table stats cache.
 var TableStatsCacheExpiry = 3 * time.Second
 
-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.RLock()
 	if time.Since(c.modifyTime) < TableStatsCacheExpiry {
-		tableRows, colLength := c.tableRows, c.colLength
 		c.mu.RUnlock()
-		return tableRows, colLength, nil
+		return nil
 	}
 	c.mu.RUnlock()
 
 	c.mu.Lock()
 	defer c.mu.Unlock()
 	if time.Since(c.modifyTime) < TableStatsCacheExpiry {
-		return c.tableRows, c.colLength, nil
+		return nil
 	}
 	tableRows, err := getRowCountAllTable(ctx, sctx)
 	if err != nil {
-		return nil, nil, err
+		return err
 	}
 	colLength, err := getColLengthAllTables(ctx, sctx)
 	if err != nil {
-		return nil, nil, err
+		return err
 	}
 
 	c.tableRows = tableRows
 	c.colLength = colLength
 	c.modifyTime = time.Now()
-	return tableRows, colLength, nil
+	return nil
 }
 
 func getAutoIncrementID(ctx sessionctx.Context, schema *model.DBInfo, tblInfo *model.TableInfo) (int64, error) {
@@ -505,7 +516,7 @@ 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
 	}
@@ -549,12 +560,13 @@ 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
 					}
@@ -870,7 +882,7 @@ 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
 	}
@@ -886,8 +898,8 @@ 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
@@ -924,8 +936,8 @@ 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 {