env config: count table use info_schema

Author: ffffwh

internal/client/driver/mysql/extractor.go

@@ -518,16 +518,25 @@ func (e *Extractor) CountTableRows(table *config.Table) (int64, error) {
 	defer atomic.StoreInt64(&e.mysqlContext.CountingRowsFlag, 0)
 	//e.logger.Debugf("mysql.extractor: As instructed, I'm issuing a SELECT COUNT(*) on the table. This may take a while")
 
-	query := fmt.Sprintf(`select count(*) as rows from %s.%s where (%s)`,
-		sql.EscapeName(table.TableSchema), sql.EscapeName(table.TableName), table.Where)
+	var query string
+	var method string
+	if os.Getenv(g.ENV_COUNT_INFO_SCHEMA) != "" {
+		method = "information_schema"
+		query = fmt.Sprintf(`select table_rows from information_schema.tables where table_schema = '%s' and table_name = '%s'`,
+			table.TableSchema, table.TableName)
+	} else {
+		method = "COUNT"
+		query = fmt.Sprintf(`select count(*) as rows from %s.%s where (%s)`,
+			sql.EscapeName(table.TableSchema), sql.EscapeName(table.TableName), table.Where)
+	}
 	var rowsEstimate int64
 	if err := e.db.QueryRow(query).Scan(&rowsEstimate); err != nil {
 		return 0, err
 	}
 	atomic.AddInt64(&e.mysqlContext.RowsEstimate, rowsEstimate)
 
 	e.mysqlContext.Stage = models.StageSearchingRowsForUpdate
-	e.logger.Debugf("mysql.extractor: Exact number of rows(%s.%s) via COUNT: %d", table.TableSchema, table.TableName, rowsEstimate)
+	e.logger.Debugf("mysql.extractor: Exact number of rows(%s.%s) via %v: %d", table.TableSchema, table.TableName, method, rowsEstimate)
 	return rowsEstimate, nil
 }
 

internal/g/g.go

@@ -1,3 +1,4 @@
+// global values
 package g
 
 var (
@@ -11,9 +12,10 @@ const (
 	GtidExecutedTableV2         string = "gtid_executed_v2"
 	GtidExecutedTableV3         string = "gtid_executed_v3"
 
-	ENV_PRINT_TPS        = "UDUP_PRINT_TPS"
-	ENV_DUMP_CHECKSUM    = "DTLE_DUMP_CHECKSUM"
-	ENV_DUMP_OLDWAY      = "DTLE_DUMP_OLDWAY"
-	ENV_TESTSTUB1_DELAY  = "UDUP_TESTSTUB1_DELAY"
-	ENV_FULL_APPLY_DELAY = "DTLE_FULL_APPLY_DELAY"
+	ENV_PRINT_TPS         = "UDUP_PRINT_TPS"
+	ENV_DUMP_CHECKSUM     = "DTLE_DUMP_CHECKSUM"
+	ENV_DUMP_OLDWAY       = "DTLE_DUMP_OLDWAY"
+	ENV_TESTSTUB1_DELAY   = "UDUP_TESTSTUB1_DELAY"
+	ENV_FULL_APPLY_DELAY  = "DTLE_FULL_APPLY_DELAY"
+	ENV_COUNT_INFO_SCHEMA = "DTLE_COUNT_INFO_SCHEMA"
 )