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