f8518988e4
* ddl: always try a better algorithm * ddl: adapt the test * ddl: fix TestAlterAlgorithm * ddl: better test fix * ddl: typo * ddl: update comment Co-authored-by: bb7133 <bb7133@gmail.com> * executor: typo Co-authored-by: djshow832 <zhangming@pingcap.com> Co-authored-by: bb7133 <bb7133@gmail.com> Co-authored-by: djshow832 <zhangming@pingcap.com> Co-authored-by: ti-srebot <66930949+ti-srebot@users.noreply.github.com>
81 lines
2.9 KiB
Go
81 lines
2.9 KiB
Go
// Copyright 2018 PingCAP, Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package ddl
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import (
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"fmt"
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"github.com/pingcap/parser/ast"
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)
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// AlterAlgorithm is used to store supported alter algorithm.
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// For now, TiDB only support AlterAlgorithmInplace and AlterAlgorithmInstant.
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// The most alter operations are using instant algorithm, and only the add index is using inplace(not really inplace,
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// because we never block the DML but costs some time to backfill the index data)
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// See https://dev.mysql.com/doc/refman/8.0/en/alter-table.html#alter-table-performance.
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type AlterAlgorithm struct {
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// supported MUST store algorithms in the order 'INSTANT, INPLACE, COPY'
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supported []ast.AlgorithmType
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// If the alter algorithm is not given, the defAlgorithm will be used.
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defAlgorithm ast.AlgorithmType
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}
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var (
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instantAlgorithm = &AlterAlgorithm{
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supported: []ast.AlgorithmType{ast.AlgorithmTypeInstant},
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defAlgorithm: ast.AlgorithmTypeInstant,
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}
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inplaceAlgorithm = &AlterAlgorithm{
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supported: []ast.AlgorithmType{ast.AlgorithmTypeInplace},
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defAlgorithm: ast.AlgorithmTypeInplace,
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}
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)
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func getProperAlgorithm(specify ast.AlgorithmType, algorithm *AlterAlgorithm) (ast.AlgorithmType, error) {
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if specify == ast.AlgorithmTypeDefault {
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return algorithm.defAlgorithm, nil
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}
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r := ast.AlgorithmTypeDefault
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for _, a := range algorithm.supported {
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if specify <= a {
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r = a
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break
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}
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}
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var err error
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if specify != r {
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err = ErrAlterOperationNotSupported.GenWithStackByArgs(fmt.Sprintf("ALGORITHM=%s", specify), fmt.Sprintf("Cannot alter table by %s", specify), fmt.Sprintf("ALGORITHM=%s", algorithm.defAlgorithm))
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}
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return r, err
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}
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// ResolveAlterAlgorithm resolves the algorithm of the alterSpec.
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// If specify is the ast.AlterAlgorithmDefault, then the default algorithm of the alter action will be returned.
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// If specify algorithm is not supported by the alter action, it will try to find a better algorithm in the order `INSTANT > INPLACE > COPY`, errAlterOperationNotSupported will be returned.
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// E.g. INSTANT may be returned if specify=INPLACE
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// If failed to choose any valid algorithm, AlgorithmTypeDefault and errAlterOperationNotSupported will be returned
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func ResolveAlterAlgorithm(alterSpec *ast.AlterTableSpec, specify ast.AlgorithmType) (ast.AlgorithmType, error) {
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switch alterSpec.Tp {
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// For now, TiDB only support inplace algorithm and instant algorithm.
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case ast.AlterTableAddConstraint:
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return getProperAlgorithm(specify, inplaceAlgorithm)
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default:
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return getProperAlgorithm(specify, instantAlgorithm)
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}
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}
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