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descend_index.go
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descend_index.go
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// Copyright 2020-2021 Dolthub, 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,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package memory
import (
"github.com/Sndav/go-mysql-server/sql"
"github.com/Sndav/go-mysql-server/sql/expression"
)
type DescendIndexLookup struct {
id string
Gt []interface{}
Lte []interface{}
Index ExpressionsIndex
}
var _ memoryIndexLookup = (*DescendIndexLookup)(nil)
var _ sql.IndexLookup = (*DescendIndexLookup)(nil)
func (l *DescendIndexLookup) ID() string { return l.id }
func (l *DescendIndexLookup) String() string { return l.id }
func (l *DescendIndexLookup) Values(p sql.Partition) (sql.IndexValueIter, error) {
return &indexValIter{
tbl: l.Index.MemTable(),
partition: p,
matchExpression: l.EvalExpression(),
}, nil
}
func (l *DescendIndexLookup) EvalExpression() sql.Expression {
var columnExprs []sql.Expression
for i, indexExpr := range l.Index.ColumnExpressions() {
var ltExpr, gtExpr sql.Expression
hasLt := len(l.Lte) > 0
hasGte := len(l.Gt) > 0
if hasLt {
lt, typ := getType(l.Lte[i])
ltExpr = expression.NewLessThanOrEqual(indexExpr, expression.NewLiteral(lt, typ))
}
if hasGte {
gte, typ := getType(l.Gt[i])
gtExpr = expression.NewGreaterThan(indexExpr, expression.NewLiteral(gte, typ))
}
switch {
case hasLt && hasGte:
columnExprs = append(columnExprs, ltExpr, gtExpr)
case hasLt:
columnExprs = append(columnExprs, ltExpr)
case hasGte:
columnExprs = append(columnExprs, gtExpr)
default:
panic("Either Lte or Gt must be set")
}
}
return and(columnExprs...)
}
func (l *DescendIndexLookup) Indexes() []string {
return []string{l.id}
}
func (l *DescendIndexLookup) IsMergeable(lookup sql.IndexLookup) bool {
_, ok := lookup.(MergeableLookup)
return ok
}
func (l *DescendIndexLookup) Union(lookups ...sql.IndexLookup) (sql.IndexLookup, error) {
return union(l.Index, l, lookups...), nil
}
func (l *DescendIndexLookup) Intersection(lookups ...sql.IndexLookup) (sql.IndexLookup, error) {
return intersection(l.Index, l, lookups...), nil
}