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133 lines
4.2 KiB
133 lines
4.2 KiB
// Copyright 2019 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 util
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import (
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"github.com/pingcap/parser/ast"
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"github.com/pingcap/parser/model"
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"github.com/pingcap/tidb/expression"
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"github.com/pingcap/tidb/kv"
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"github.com/pingcap/tidb/sessionctx"
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"github.com/pingcap/tidb/types"
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"github.com/pingcap/tidb/util/collate"
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"github.com/pingcap/tidb/util/ranger"
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)
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// AccessPath indicates the way we access a table: by using single index, or by using multiple indexes,
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// or just by using table scan.
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type AccessPath struct {
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Index *model.IndexInfo
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FullIdxCols []*expression.Column
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FullIdxColLens []int
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IdxCols []*expression.Column
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IdxColLens []int
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Ranges []*ranger.Range
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// CountAfterAccess is the row count after we apply range seek and before we use other filter to filter data.
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CountAfterAccess float64
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// CountAfterIndex is the row count after we apply filters on index and before we apply the table filters.
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CountAfterIndex float64
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AccessConds []expression.Expression
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EqCondCount int
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EqOrInCondCount int
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IndexFilters []expression.Expression
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TableFilters []expression.Expression
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// PartialIndexPaths store all index access paths.
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// If there are extra filters, store them in TableFilters.
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PartialIndexPaths []*AccessPath
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StoreType kv.StoreType
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IsDNFCond bool
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// IsTablePath indicates whether this path is table path.
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IsTablePath bool
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// IsTiFlashGlobalRead indicates whether this path is a remote read path for tiflash
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IsTiFlashGlobalRead bool
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// Forced means this path is generated by `use/force index()`.
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Forced bool
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PkCol *expression.Column
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}
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// SplitCorColAccessCondFromFilters move the necessary filter in the form of index_col = corrlated_col to access conditions.
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func (path *AccessPath) SplitCorColAccessCondFromFilters(ctx sessionctx.Context, eqOrInCount int) (access, remained []expression.Expression) {
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access = make([]expression.Expression, len(path.IdxCols)-eqOrInCount)
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used := make([]bool, len(path.TableFilters))
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for i := eqOrInCount; i < len(path.IdxCols); i++ {
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matched := false
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for j, filter := range path.TableFilters {
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if used[j] || !isColEqCorColOrConstant(ctx, filter, path.IdxCols[i]) {
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continue
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}
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matched = true
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access[i-eqOrInCount] = filter
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if path.IdxColLens[i] == types.UnspecifiedLength {
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used[j] = true
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}
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break
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}
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if !matched {
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access = access[:i-eqOrInCount]
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break
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}
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}
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for i, ok := range used {
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if !ok {
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remained = append(remained, path.TableFilters[i])
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}
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}
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return access, remained
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}
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// isColEqCorColOrConstant checks if the expression is a eq function that one side is constant or correlated column
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// and another is column.
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func isColEqCorColOrConstant(ctx sessionctx.Context, filter expression.Expression, col *expression.Column) bool {
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f, ok := filter.(*expression.ScalarFunction)
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if !ok || f.FuncName.L != ast.EQ {
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return false
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}
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_, collation := f.CharsetAndCollation(ctx)
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if c, ok := f.GetArgs()[0].(*expression.Column); ok {
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if c.RetType.EvalType() == types.ETString && !collate.CompatibleCollate(collation, c.RetType.Collate) {
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return false
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}
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if _, ok := f.GetArgs()[1].(*expression.Constant); ok {
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if col.Equal(nil, c) {
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return true
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}
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}
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if _, ok := f.GetArgs()[1].(*expression.CorrelatedColumn); ok {
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if col.Equal(nil, c) {
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return true
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}
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}
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}
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if c, ok := f.GetArgs()[1].(*expression.Column); ok {
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if c.RetType.EvalType() == types.ETString && !collate.CompatibleCollate(collation, c.RetType.Collate) {
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return false
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}
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if _, ok := f.GetArgs()[0].(*expression.Constant); ok {
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if col.Equal(nil, c) {
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return true
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}
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}
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if _, ok := f.GetArgs()[0].(*expression.CorrelatedColumn); ok {
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if col.Equal(nil, c) {
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return true
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}
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}
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}
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return false
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}
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