partition.go

// Copyright 2018 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 ddl

import (
	"bytes"
	"fmt"
	"strconv"
	"strings"

	"github.com/pingcap/errors"
	"github.com/pingcap/parser/ast"
	"github.com/pingcap/parser/model"
	"github.com/pingcap/parser/mysql"
	"github.com/pingcap/parser/opcode"
	"github.com/pingcap/tidb/expression"
	"github.com/pingcap/tidb/meta"
	"github.com/pingcap/tidb/sessionctx"
	"github.com/pingcap/tidb/table"
	"github.com/pingcap/tidb/types"
	"github.com/pingcap/tidb/util/chunk"
)

const (
	partitionMaxValue = "MAXVALUE"
	primarykey        = "PRIMARY KEY"
)

// buildTablePartitionInfo builds partition info and checks for some errors.
func buildTablePartitionInfo(ctx sessionctx.Context, d *ddl, s *ast.CreateTableStmt) (*model.PartitionInfo, error) {
	if s.Partition == nil {
		return nil, nil
	}

	// force-discard the unsupported types, even when @@tidb_enable_table_partition = 'on'
	switch s.Partition.Tp {
	case model.PartitionTypeKey:
		// can't create a warning for KEY partition, it will fail an integration test :/
		return nil, nil
	case model.PartitionTypeList, model.PartitionTypeSystemTime:
		ctx.GetSessionVars().StmtCtx.AppendWarning(errUnsupportedCreatePartition)
		return nil, nil
	}

	var enable bool
	switch ctx.GetSessionVars().EnableTablePartition {
	case "on":
		enable = true
	case "off":
		enable = false
	default:
		// When tidb_enable_table_partition = 'auto',
		if s.Partition.Tp == model.PartitionTypeRange {
			// Partition by range expression is enabled by default.
			if s.Partition.ColumnNames == nil {
				enable = true
			}
			// Partition by range columns and just one column.
			if len(s.Partition.ColumnNames) == 1 {
				enable = true
			}
		}
		// Partition by hash is enabled by default.
		// Note that linear hash is not enabled.
		if s.Partition.Tp == model.PartitionTypeHash {
			enable = true
		}
	}
	if !enable {
		ctx.GetSessionVars().StmtCtx.AppendWarning(errUnsupportedCreatePartition)
	}

	pi := &model.PartitionInfo{
		Type:   s.Partition.Tp,
		Enable: enable,
		Num:    s.Partition.Num,
	}
	if s.Partition.Expr != nil {
		buf := new(bytes.Buffer)
		s.Partition.Expr.Format(buf)
		pi.Expr = buf.String()
	} else if s.Partition.ColumnNames != nil {
		// TODO: Support multiple columns for 'PARTITION BY RANGE COLUMNS'.
		if len(s.Partition.ColumnNames) != 1 {
			pi.Enable = false
			ctx.GetSessionVars().StmtCtx.AppendWarning(ErrUnsupportedPartitionByRangeColumns)
		}
		pi.Columns = make([]model.CIStr, 0, len(s.Partition.ColumnNames))
		for _, cn := range s.Partition.ColumnNames {
			pi.Columns = append(pi.Columns, cn.Name)
		}
	}

	if s.Partition.Tp == model.PartitionTypeRange {
		if err := buildRangePartitionDefinitions(ctx, d, s, pi); err != nil {
			return nil, errors.Trace(err)
		}
	} else if s.Partition.Tp == model.PartitionTypeHash {
		if err := buildHashPartitionDefinitions(ctx, d, s, pi); err != nil {
			return nil, errors.Trace(err)
		}
	}
	return pi, nil
}

func buildHashPartitionDefinitions(ctx sessionctx.Context, d *ddl, s *ast.CreateTableStmt, pi *model.PartitionInfo) error {
	genIDs, err := d.genGlobalIDs(int(pi.Num))
	if err != nil {
		return errors.Trace(err)
	}
	defs := make([]model.PartitionDefinition, pi.Num)
	for i := 0; i < len(defs); i++ {
		defs[i].ID = genIDs[i]
		if len(s.Partition.Definitions) == 0 {
			defs[i].Name = model.NewCIStr(fmt.Sprintf("p%v", i))
		} else {
			def := s.Partition.Definitions[i]
			defs[i].Name = def.Name
			defs[i].Comment, _ = def.Comment()
		}
	}
	pi.Definitions = defs
	return nil
}

func buildRangePartitionDefinitions(ctx sessionctx.Context, d *ddl, s *ast.CreateTableStmt, pi *model.PartitionInfo) error {
	genIDs, err := d.genGlobalIDs(len(s.Partition.Definitions))
	if err != nil {
		return err
	}
	for ith, def := range s.Partition.Definitions {
		comment, _ := def.Comment()
		piDef := model.PartitionDefinition{
			Name:    def.Name,
			ID:      genIDs[ith],
			Comment: comment,
		}

		buf := new(bytes.Buffer)
		// Range columns partitions support multi-column partitions.
		for _, expr := range def.Clause.(*ast.PartitionDefinitionClauseLessThan).Exprs {
			expr.Format(buf)
			piDef.LessThan = append(piDef.LessThan, buf.String())
			buf.Reset()
		}
		pi.Definitions = append(pi.Definitions, piDef)
	}
	return nil
}

func checkPartitionNameUnique(tbInfo *model.TableInfo, pi *model.PartitionInfo) error {
	partNames := make(map[string]struct{})
	if tbInfo.Partition != nil {
		oldPars := tbInfo.Partition.Definitions
		for _, oldPar := range oldPars {
			partNames[oldPar.Name.L] = struct{}{}
		}
	}
	newPars := pi.Definitions
	for _, newPar := range newPars {
		if _, ok := partNames[newPar.Name.L]; ok {
			return ErrSameNamePartition.GenWithStackByArgs(newPar.Name)
		}
		partNames[newPar.Name.L] = struct{}{}
	}
	return nil
}

// See https://github.com/mysql/mysql-server/blob/5.7/sql/item_func.h#L387
func hasTimestampField(ctx sessionctx.Context, tblInfo *model.TableInfo, expr ast.ExprNode) (bool, error) {
	partCols, err := partitionColumns(ctx, tblInfo, expr)
	if err != nil {
		return false, err
	}

	for _, c := range partCols {
		if c.GetType().Tp == mysql.TypeTimestamp {
			return true, nil
		}
	}

	return false, nil
}

// See https://github.com/mysql/mysql-server/blob/5.7/sql/item_func.h#L399
func hasDateField(ctx sessionctx.Context, tblInfo *model.TableInfo, expr ast.ExprNode) (bool, error) {
	partCols, err := partitionColumns(ctx, tblInfo, expr)
	if err != nil {
		return false, err
	}

	for _, c := range partCols {
		if c.GetType().Tp == mysql.TypeDate || c.GetType().Tp == mysql.TypeDatetime {
			return true, nil
		}
	}

	return false, nil
}

// See https://github.com/mysql/mysql-server/blob/5.7/sql/item_func.h#L412
func hasTimeField(ctx sessionctx.Context, tblInfo *model.TableInfo, expr ast.ExprNode) (bool, error) {
	partCols, err := partitionColumns(ctx, tblInfo, expr)
	if err != nil {
		return false, err
	}

	for _, c := range partCols {
		if c.GetType().Tp == mysql.TypeDatetime || c.GetType().Tp == mysql.TypeDuration {
			return true, nil
		}
	}

	return false, nil
}

// We assume the result of any function that has a TIMESTAMP argument to be
// timezone-dependent, since a TIMESTAMP value in both numeric and string
// contexts is interpreted according to the current timezone.
// The only exception is UNIX_TIMESTAMP() which returns the internal
// representation of a TIMESTAMP argument verbatim, and thus does not depend on
// the timezone.
// See https://github.com/mysql/mysql-server/blob/5.7/sql/item_func.h#L445
func defaultTimezoneDependent(ctx sessionctx.Context, tblInfo *model.TableInfo, expr ast.ExprNode) (bool, error) {
	v, err := hasTimestampField(ctx, tblInfo, expr)
	if err != nil {
		return false, err
	}

	return !v, nil
}

// checkPartitionFuncValid checks partition function validly.
func checkPartitionFuncValid(ctx sessionctx.Context, tblInfo *model.TableInfo, expr ast.ExprNode) error {
	switch v := expr.(type) {
	case *ast.FuncCastExpr, *ast.CaseExpr:
		return errors.Trace(ErrPartitionFunctionIsNotAllowed)
	case *ast.FuncCallExpr:
		// check function which allowed in partitioning expressions
		// see https://dev.mysql.com/doc/mysql-partitioning-excerpt/5.7/en/partitioning-limitations-functions.html
		switch v.FnName.L {
		// Mysql don't allow creating partitions with expressions with non matching
		// arguments as a (sub)partitioning function,
		// but we want to allow such expressions when opening existing tables for
		// easier maintenance. This exception should be deprecated at some point in future so that we always throw an error.
		// See https://github.com/mysql/mysql-server/blob/5.7/sql/sql_partition.cc#L1072
		case ast.Day, ast.DayOfMonth, ast.DayOfWeek, ast.DayOfYear, ast.Month, ast.Quarter, ast.ToDays, ast.ToSeconds,
			ast.Weekday, ast.Year, ast.YearWeek:
			return checkPartitionFunc(hasDateField(ctx, tblInfo, expr))
		case ast.Hour, ast.MicroSecond, ast.Minute, ast.Second, ast.TimeToSec:
			return checkPartitionFunc(hasTimeField(ctx, tblInfo, expr))
		case ast.UnixTimestamp:
			return checkPartitionFunc(hasTimestampField(ctx, tblInfo, expr))
		case ast.Abs, ast.Ceiling, ast.DateDiff, ast.Extract, ast.Floor, ast.Mod:
			return checkPartitionFunc(defaultTimezoneDependent(ctx, tblInfo, expr))
		default:
			return errors.Trace(ErrPartitionFunctionIsNotAllowed)
		}
	case *ast.BinaryOperationExpr:
		// The DIV operator (opcode.IntDiv) is also supported; the / operator ( opcode.Div ) is not permitted.
		// see https://dev.mysql.com/doc/refman/5.7/en/partitioning-limitations.html
		switch v.Op {
		case opcode.Or, opcode.And, opcode.Xor, opcode.LeftShift, opcode.RightShift, opcode.BitNeg, opcode.Div:
			return errors.Trace(ErrPartitionFunctionIsNotAllowed)
		}
		return nil
	case *ast.UnaryOperationExpr:
		if v.Op == opcode.BitNeg {
			return errors.Trace(ErrPartitionFunctionIsNotAllowed)
		}
		return nil
	}

	// check constant.
	_, err := partitionColumns(ctx, tblInfo, expr)
	return err
}

// For partition tables, mysql do not support Constant, random or timezone-dependent expressions
// Based on mysql code to check whether field is valid, every time related type has check_valid_arguments_processor function.
// See https://github.com/mysql/mysql-server/blob/5.7/sql/item_timefunc.
func checkPartitionFunc(isTimezoneDependent bool, err error) error {
	if err != nil {
		return err
	}

	if !isTimezoneDependent {
		return errors.Trace(errWrongExprInPartitionFunc)
	}

	return nil
}

func partitionColumns(ctx sessionctx.Context, tblInfo *model.TableInfo, expr ast.ExprNode) ([]*expression.Column, error) {
	buf := new(bytes.Buffer)
	expr.Format(buf)
	partCols, err := extractPartitionColumns(ctx, buf.String(), tblInfo)
	if err != nil {
		return nil, errors.Trace(err)
	}

	if len(partCols) == 0 {
		return nil, errors.Trace(errWrongExprInPartitionFunc)
	}

	return partCols, nil
}

// checkPartitionFuncType checks partition function return type.
func checkPartitionFuncType(ctx sessionctx.Context, s *ast.CreateTableStmt, cols []*table.Column, tblInfo *model.TableInfo) error {
	if s.Partition.Expr == nil {
		return nil
	}
	buf := new(bytes.Buffer)
	s.Partition.Expr.Format(buf)
	exprStr := buf.String()
	if s.Partition.Tp == model.PartitionTypeRange || s.Partition.Tp == model.PartitionTypeHash {
		// if partition by columnExpr, check the column type
		if _, ok := s.Partition.Expr.(*ast.ColumnNameExpr); ok {
			for _, col := range cols {
				name := strings.Replace(col.Name.String(), ".", "`.`", -1)
				// Range partitioning key supported types: tinyint, smallint, mediumint, int and bigint.
				if !validRangePartitionType(col) && fmt.Sprintf("`%s`", name) == exprStr {
					return errors.Trace(ErrNotAllowedTypeInPartition.GenWithStackByArgs(exprStr))
				}
			}
		}
	}

	e, err := expression.ParseSimpleExprWithTableInfo(ctx, exprStr, tblInfo)
	if err != nil {
		return errors.Trace(err)
	}
	if e.GetType().EvalType() == types.ETInt {
		return nil
	}
	if s.Partition.Tp == model.PartitionTypeHash {
		if _, ok := s.Partition.Expr.(*ast.ColumnNameExpr); ok {
			return ErrNotAllowedTypeInPartition.GenWithStackByArgs(exprStr)
		}
	}

	return ErrPartitionFuncNotAllowed.GenWithStackByArgs("PARTITION")
}

// checkCreatePartitionValue checks whether `less than value` is strictly increasing for each partition.
// Side effect: it may simplify the partition range definition from a constant expression to an integer.
func checkCreatePartitionValue(ctx sessionctx.Context, tblInfo *model.TableInfo, pi *model.PartitionInfo, cols []*table.Column) error {
	defs := pi.Definitions
	if len(defs) <= 1 {
		return nil
	}

	if strings.EqualFold(defs[len(defs)-1].LessThan[0], partitionMaxValue) {
		defs = defs[:len(defs)-1]
	}
	isUnsignedBigint := isRangePartitionColUnsignedBigint(cols, pi)
	var prevRangeValue interface{}
	for i := 0; i < len(defs); i++ {
		if strings.EqualFold(defs[i].LessThan[0], partitionMaxValue) {
			return errors.Trace(ErrPartitionMaxvalue)
		}

		currentRangeValue, fromExpr, err := getRangeValue(ctx, tblInfo, defs[i].LessThan[0], isUnsignedBigint)
		if err != nil {
			return errors.Trace(err)
		}
		if fromExpr {
			// Constant fold the expression.
			defs[i].LessThan[0] = fmt.Sprintf("%d", currentRangeValue)
		}

		if i == 0 {
			prevRangeValue = currentRangeValue
			continue
		}

		if isUnsignedBigint {
			if currentRangeValue.(uint64) <= prevRangeValue.(uint64) {
				return errors.Trace(ErrRangeNotIncreasing)
			}
		} else {
			if currentRangeValue.(int64) <= prevRangeValue.(int64) {
				return errors.Trace(ErrRangeNotIncreasing)
			}
		}
		prevRangeValue = currentRangeValue
	}
	return nil
}

// getRangeValue gets an integer from the range value string.
// The returned boolean value indicates whether the input string is a constant expression.
func getRangeValue(ctx sessionctx.Context, tblInfo *model.TableInfo, str string, unsignedBigint bool) (interface{}, bool, error) {
	// Unsigned bigint was converted to uint64 handle.
	if unsignedBigint {
		if value, err := strconv.ParseUint(str, 10, 64); err == nil {
			return value, false, nil
		}

		if e, err1 := expression.ParseSimpleExprWithTableInfo(ctx, str, tblInfo); err1 == nil {
			res, isNull, err2 := e.EvalInt(ctx, chunk.Row{})
			if err2 == nil && !isNull {
				return uint64(res), true, nil
			}
		}
	} else {
		if value, err := strconv.ParseInt(str, 10, 64); err == nil {
			return value, false, nil
		}
		// The range value maybe not an integer, it could be a constant expression.
		// For example, the following two cases are the same:
		// PARTITION p0 VALUES LESS THAN (TO_SECONDS('2004-01-01'))
		// PARTITION p0 VALUES LESS THAN (63340531200)
		if e, err1 := expression.ParseSimpleExprWithTableInfo(ctx, str, tblInfo); err1 == nil {
			res, isNull, err2 := e.EvalInt(ctx, chunk.Row{})
			if err2 == nil && !isNull {
				return res, true, nil
			}
		}
	}
	return 0, false, ErrNotAllowedTypeInPartition.GenWithStackByArgs(str)
}

// validRangePartitionType checks the type supported by the range partitioning key.
func validRangePartitionType(col *table.Column) bool {
	switch col.FieldType.EvalType() {
	case types.ETInt:
		return true
	default:
		return false
	}
}

// checkDropTablePartition checks if the partition exists and does not allow deleting the last existing partition in the table.
func checkDropTablePartition(meta *model.TableInfo, partName string) error {
	pi := meta.Partition
	if pi.Type != model.PartitionTypeRange && pi.Type != model.PartitionTypeList {
		return errOnlyOnRangeListPartition.GenWithStackByArgs("DROP")
	}
	oldDefs := pi.Definitions
	for _, def := range oldDefs {
		if strings.EqualFold(def.Name.L, strings.ToLower(partName)) {
			if len(oldDefs) == 1 {
				return errors.Trace(ErrDropLastPartition)
			}
			return nil
		}
	}
	return errors.Trace(ErrDropPartitionNonExistent.GenWithStackByArgs(partName))
}

// removePartitionInfo each ddl job deletes a partition.
func removePartitionInfo(tblInfo *model.TableInfo, partName string) int64 {
	oldDefs := tblInfo.Partition.Definitions
	newDefs := make([]model.PartitionDefinition, 0, len(oldDefs)-1)
	var pid int64
	for i := 0; i < len(oldDefs); i++ {
		if !strings.EqualFold(oldDefs[i].Name.L, strings.ToLower(partName)) {
			continue
		}
		pid = oldDefs[i].ID
		newDefs = append(oldDefs[:i], oldDefs[i+1:]...)
		break
	}
	tblInfo.Partition.Definitions = newDefs
	return pid
}

// onDropTablePartition deletes old partition meta.
func onDropTablePartition(t *meta.Meta, job *model.Job) (ver int64, _ error) {
	var partName string
	if err := job.DecodeArgs(&partName); err != nil {
		job.State = model.JobStateCancelled
		return ver, errors.Trace(err)
	}
	tblInfo, err := getTableInfoAndCancelFaultJob(t, job, job.SchemaID)
	if err != nil {
		return ver, errors.Trace(err)
	}
	// If an error occurs, it returns that it cannot delete all partitions or that the partition doesn't exist.
	err = checkDropTablePartition(tblInfo, partName)
	if err != nil {
		job.State = model.JobStateCancelled
		return ver, errors.Trace(err)
	}
	physicalTableID := removePartitionInfo(tblInfo, partName)
	ver, err = updateVersionAndTableInfo(t, job, tblInfo, true)
	if err != nil {
		return ver, errors.Trace(err)
	}

	// Finish this job.
	job.FinishTableJob(model.JobStateDone, model.StateNone, ver, tblInfo)
	// A background job will be created to delete old partition data.
	job.Args = []interface{}{physicalTableID}
	return ver, nil
}

// onDropTablePartition truncates old partition meta.
func onTruncateTablePartition(t *meta.Meta, job *model.Job) (int64, error) {
	var ver int64
	var oldID int64
	if err := job.DecodeArgs(&oldID); err != nil {
		job.State = model.JobStateCancelled
		return ver, errors.Trace(err)
	}
	tblInfo, err := getTableInfoAndCancelFaultJob(t, job, job.SchemaID)
	if err != nil {
		return ver, errors.Trace(err)
	}
	pi := tblInfo.GetPartitionInfo()
	if pi == nil {
		return ver, errors.Trace(ErrPartitionMgmtOnNonpartitioned)
	}

	var find bool
	for i := 0; i < len(pi.Definitions); i++ {
		def := &pi.Definitions[i]
		if def.ID == oldID {
			pid, err1 := t.GenGlobalID()
			if err != nil {
				return ver, errors.Trace(err1)
			}
			def.ID = pid
			find = true
			break
		}
	}
	if !find {
		return ver, table.ErrUnknownPartition.GenWithStackByArgs("drop?", tblInfo.Name.O)
	}

	ver, err = updateVersionAndTableInfo(t, job, tblInfo, true)
	if err != nil {
		return ver, errors.Trace(err)
	}

	// Finish this job.
	job.FinishTableJob(model.JobStateDone, model.StateNone, ver, tblInfo)
	// A background job will be created to delete old partition data.
	job.Args = []interface{}{oldID}
	return ver, nil
}

func checkAddPartitionTooManyPartitions(piDefs uint64) error {
	if piDefs > uint64(PartitionCountLimit) {
		return errors.Trace(ErrTooManyPartitions)
	}
	return nil
}

func checkNoHashPartitions(ctx sessionctx.Context, partitionNum uint64) error {
	if partitionNum == 0 {
		return ast.ErrNoParts.GenWithStackByArgs("partitions")
	}
	return nil
}

func checkNoRangePartitions(partitionNum int) error {
	if partitionNum == 0 {
		return ast.ErrPartitionsMustBeDefined.GenWithStackByArgs("RANGE")
	}
	return nil
}

func getPartitionIDs(table *model.TableInfo) []int64 {
	if table.GetPartitionInfo() == nil {
		return []int64{}
	}
	physicalTableIDs := make([]int64, 0, len(table.Partition.Definitions))
	for _, def := range table.Partition.Definitions {
		physicalTableIDs = append(physicalTableIDs, def.ID)
	}
	return physicalTableIDs
}

// checkRangePartitioningKeysConstraints checks that the range partitioning key is included in the table constraint.
func checkRangePartitioningKeysConstraints(sctx sessionctx.Context, s *ast.CreateTableStmt, tblInfo *model.TableInfo, constraints []*ast.Constraint) error {
	// Returns directly if there is no constraint in the partition table.
	// TODO: Remove the test 's.Partition.Expr == nil' when we support 'PARTITION BY RANGE COLUMNS'
	if len(constraints) == 0 || s.Partition.Expr == nil {
		return nil
	}

	// Parse partitioning key, extract the column names in the partitioning key to slice.
	buf := new(bytes.Buffer)
	s.Partition.Expr.Format(buf)
	partCols, err := extractPartitionColumns(sctx, buf.String(), tblInfo)
	if err != nil {
		return err
	}

	// Checks that the partitioning key is included in the constraint.
	// Every unique key on the table must use every column in the table's partitioning expression.
	// See https://dev.mysql.com/doc/refman/5.7/en/partitioning-limitations-partitioning-keys-unique-keys.html
	for _, constraint := range constraints {
		switch constraint.Tp {
		case ast.ConstraintPrimaryKey, ast.ConstraintUniq, ast.ConstraintUniqKey, ast.ConstraintUniqIndex:
			if !checkUniqueKeyIncludePartKey(partCols, constraint.Keys) {
				if constraint.Tp == ast.ConstraintPrimaryKey {
					return ErrUniqueKeyNeedAllFieldsInPf.GenWithStackByArgs("PRIMARY KEY")
				}
				return ErrUniqueKeyNeedAllFieldsInPf.GenWithStackByArgs("UNIQUE INDEX")
			}
		}
	}
	return nil
}

func checkPartitionKeysConstraint(sctx sessionctx.Context, partExpr string, idxColNames []*ast.IndexColName, tblInfo *model.TableInfo) error {
	// Parse partitioning key, extract the column names in the partitioning key to slice.
	partCols, err := extractPartitionColumns(sctx, partExpr, tblInfo)
	if err != nil {
		return err
	}

	// Every unique key on the table must use every column in the table's partitioning expression.
	// See https://dev.mysql.com/doc/refman/5.7/en/partitioning-limitations-partitioning-keys-unique-keys.html
	if !checkUniqueKeyIncludePartKey(partCols, idxColNames) {
		return ErrUniqueKeyNeedAllFieldsInPf.GenWithStackByArgs("UNIQUE INDEX")
	}
	return nil
}

func extractPartitionColumns(sctx sessionctx.Context, partExpr string, tblInfo *model.TableInfo) ([]*expression.Column, error) {
	e, err := expression.ParseSimpleExprWithTableInfo(sctx, partExpr, tblInfo)
	if err != nil {
		return nil, errors.Trace(err)
	}
	return expression.ExtractColumns(e), nil
}

// checkUniqueKeyIncludePartKey checks that the partitioning key is included in the constraint.
func checkUniqueKeyIncludePartKey(partCols []*expression.Column, idxCols []*ast.IndexColName) bool {
	for _, partCol := range partCols {
		if !findColumnInIndexCols(partCol, idxCols) {
			return false
		}
	}
	return true
}

// isRangePartitionColUnsignedBigint returns true if the partitioning key column type is unsigned bigint type.
func isRangePartitionColUnsignedBigint(cols []*table.Column, pi *model.PartitionInfo) bool {
	for _, col := range cols {
		isUnsigned := col.Tp == mysql.TypeLonglong && mysql.HasUnsignedFlag(col.Flag)
		if isUnsigned && strings.Contains(strings.ToLower(pi.Expr), col.Name.L) {
			return true
		}
	}
	return false
}

// truncateTableByReassignPartitionIDs reassigns new partition ids.
func truncateTableByReassignPartitionIDs(t *meta.Meta, tblInfo *model.TableInfo) error {
	newDefs := make([]model.PartitionDefinition, 0, len(tblInfo.Partition.Definitions))
	for _, def := range tblInfo.Partition.Definitions {
		pid, err := t.GenGlobalID()
		if err != nil {
			return errors.Trace(err)
		}
		newDef := def
		newDef.ID = pid
		newDefs = append(newDefs, newDef)
	}
	tblInfo.Partition.Definitions = newDefs
	return nil
}