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error.go
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error.go
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// Copyright 2019 PingCAP, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.
package syncer
import (
"database/sql"
"fmt"
"strings"
"github.com/go-sql-driver/mysql"
"github.com/pingcap/errors"
"github.com/pingcap/tidb-tools/pkg/dbutil"
tddl "github.com/pingcap/tidb/ddl"
"github.com/pingcap/tidb/errno"
"github.com/pingcap/tidb/infoschema"
"github.com/pingcap/tidb/parser"
"github.com/pingcap/tidb/parser/ast"
tmysql "github.com/pingcap/tidb/parser/mysql"
"go.uber.org/zap"
tcontext "github.com/pingcap/tiflow/dm/pkg/context"
"github.com/pingcap/tiflow/dm/pkg/log"
"github.com/pingcap/tiflow/dm/syncer/dbconn"
"github.com/pingcap/tiflow/pkg/errorutil"
)
// ignoreTrackerDDLError is also same with ignoreDDLError, but in order to keep tracker's table structure same as
// upstream's, we can't ignore "already exists" errors because already exists doesn't mean same.
func ignoreTrackerDDLError(err error) bool {
switch {
case infoschema.ErrDatabaseExists.Equal(err), infoschema.ErrDatabaseDropExists.Equal(err),
infoschema.ErrTableDropExists.Equal(err),
tddl.ErrCantDropFieldOrKey.Equal(err):
return true
default:
return false
}
}
func isDropColumnWithIndexError(err error) bool {
mysqlErr, ok := errors.Cause(err).(*mysql.MySQLError)
if !ok {
return false
}
// different version of TiDB has different error message, try to cover most versions
return (mysqlErr.Number == errno.ErrUnsupportedDDLOperation || mysqlErr.Number == tmysql.ErrUnknown) &&
strings.Contains(mysqlErr.Message, "drop column") &&
(strings.Contains(mysqlErr.Message, "with index") ||
strings.Contains(mysqlErr.Message, "with composite index") ||
strings.Contains(mysqlErr.Message, "with tidb_enable_change_multi_schema is disable"))
}
// handleSpecialDDLError handles special errors for DDL execution.
func (s *Syncer) handleSpecialDDLError(tctx *tcontext.Context, err error, ddls []string, index int, conn *dbconn.DBConn) error {
// We use default parser because ddls are came from *Syncer.genDDLInfo, which is StringSingleQuotes, KeyWordUppercase and NameBackQuotes
parser2 := parser.New()
// it only ignore `invalid connection` error (timeout or other causes) for `ADD INDEX`.
// `invalid connection` means some data already sent to the server,
// and we assume that the whole SQL statement has already sent to the server for this error.
// if we have other methods to judge the DDL dispatched but timeout for executing, we can update this method.
// NOTE: we must ensure other PK/UK exists for correctness.
// NOTE: when we are refactoring the shard DDL algorithm, we also need to consider supporting non-blocking `ADD INDEX`.
invalidConnF := func(tctx *tcontext.Context, err error, ddls []string, index int, conn *dbconn.DBConn) error {
// must ensure only the last statement executed failed with the `invalid connection` error
if len(ddls) == 0 || index != len(ddls)-1 || errors.Cause(err) != mysql.ErrInvalidConn {
return err // return the original error
}
ddl2 := ddls[index]
stmt, err2 := parser2.ParseOneStmt(ddl2, "", "")
if err2 != nil {
return err // return the original error
}
handle := func() {
tctx.L().Warn("ignore special error for DDL", zap.String("DDL", ddl2), log.ShortError(err))
err2 := conn.ResetConn(tctx) // also reset the `invalid connection` for later use.
if err2 != nil {
tctx.L().Warn("reset connection failed", log.ShortError(err2))
}
}
switch v := stmt.(type) {
case *ast.AlterTableStmt:
// ddls should be split with only one spec
if len(v.Specs) > 1 {
return err
} else if v.Specs[0].Tp == ast.AlterTableAddConstraint {
// only take effect on `ADD INDEX`, no UNIQUE KEY and FOREIGN KEY
// UNIQUE KEY may affect correctness, FOREIGN KEY should be filtered.
// ref https://github.com/pingcap/tidb/blob/3cdea0dfdf28197ee65545debce8c99e6d2945e3/ddl/ddl_api.go#L1929-L1948.
switch v.Specs[0].Constraint.Tp {
case ast.ConstraintKey, ast.ConstraintIndex:
handle()
return nil // ignore the error
}
}
case *ast.CreateIndexStmt:
handle()
return nil // ignore the error
}
return err
}
// for DROP COLUMN with its single-column index, try drop index first then drop column
// TiDB will support DROP COLUMN with index soon. After its support, executing that SQL will not have an error,
// so this function will not trigger and cause some trouble
dropColumnF := func(tctx *tcontext.Context, originErr error, ddls []string, index int, conn *dbconn.DBConn) error {
if !isDropColumnWithIndexError(originErr) {
return originErr
}
ddl2 := ddls[index]
stmt, err2 := parser2.ParseOneStmt(ddl2, "", "")
if err2 != nil {
return originErr // return the original error
}
var (
schema string
table string
col string
)
n, ok := stmt.(*ast.AlterTableStmt)
switch {
case !ok:
return originErr
case len(n.Specs) != 1:
return originErr
case n.Specs[0].Tp != ast.AlterTableDropColumn:
return originErr
default:
schema = n.Table.Schema.O
table = n.Table.Name.O
col = n.Specs[0].OldColumnName.Name.O
}
tctx.L().Warn("try to fix drop column error", zap.String("DDL", ddl2), log.ShortError(originErr))
// check if dependent index is single-column index on this column
sql2 := "SELECT INDEX_NAME FROM information_schema.statistics WHERE TABLE_SCHEMA = ? and TABLE_NAME = ? and COLUMN_NAME = ?"
var rows *sql.Rows
rows, err2 = conn.QuerySQL(tctx, sql2, schema, table, col)
if err2 != nil {
return originErr
}
var (
idx string
idx2Check []string
idx2Drop []string
count int
)
for rows.Next() {
if err2 = rows.Scan(&idx); err2 != nil {
// nolint:sqlclosecheck
rows.Close()
return originErr
}
idx2Check = append(idx2Check, idx)
}
if rows.Err() != nil {
return rows.Err()
}
// Close is idempotent, we could close in advance to reuse conn
rows.Close()
sql2 = "SELECT count(*) FROM information_schema.statistics WHERE TABLE_SCHEMA = ? and TABLE_NAME = ? and INDEX_NAME = ?"
for _, idx := range idx2Check {
rows, err2 = conn.QuerySQL(tctx, sql2, schema, table, idx)
if err2 != nil || !rows.Next() || rows.Scan(&count) != nil || count != 1 {
tctx.L().Warn("can't auto drop index", zap.String("index", idx))
if rows != nil {
// nolint: sqlclosecheck
rows.Close()
}
return originErr
}
if rows.Err() != nil {
return rows.Err()
}
idx2Drop = append(idx2Drop, idx)
rows.Close()
}
sqls := make([]string, len(idx2Drop))
for i, idx := range idx2Drop {
sqls[i] = fmt.Sprintf("ALTER TABLE %s DROP INDEX %s", dbutil.TableName(schema, table), dbutil.ColumnName(idx))
}
if _, err2 = conn.ExecuteSQL(tctx, sqls); err2 != nil {
tctx.L().Warn("auto drop index failed", log.ShortError(err2))
return originErr
}
tctx.L().Info("drop index success, now try to drop column", zap.Strings("index", idx2Drop))
if _, err2 = conn.ExecuteSQLWithIgnore(tctx, errorutil.IsIgnorableMySQLDDLError, ddls[index:]); err2 != nil {
return err2
}
tctx.L().Info("execute drop column SQL success", zap.String("DDL", ddl2))
return nil
}
// TODO: add support for downstream alter pk without schema
retErr := err
toHandle := []func(*tcontext.Context, error, []string, int, *dbconn.DBConn) error{
dropColumnF,
invalidConnF,
}
for _, f := range toHandle {
retErr = f(tctx, retErr, ddls, index, conn)
if retErr == nil {
break
}
}
return retErr
}