/
dense_rank.go
70 lines (57 loc) · 1.86 KB
/
dense_rank.go
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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 function
import (
"context"
)
import (
"github.com/pkg/errors"
)
import (
"github.com/arana-db/arana/pkg/proto"
)
// FuncDenseRank is https://dev.mysql.com/doc/refman/8.0/en/window-function-descriptions.html
const FuncDenseRank = "DENSE_RANK"
var _ proto.Func = (*denserankFunc)(nil)
func init() {
proto.RegisterFunc(FuncDenseRank, denserankFunc{})
}
type denserankFunc struct{}
func (a denserankFunc) Apply(ctx context.Context, inputs ...proto.Valuer) (proto.Value, error) {
first, err := inputs[0].Value(ctx)
if first == nil || err != nil {
return nil, errors.Wrapf(err, "cannot eval %s", FuncDenseRank)
}
firstDec, _ := first.Float64()
secondDec := firstDec
firstNum := 0
for _, it := range inputs[1:] {
val, err := it.Value(ctx)
if val == nil || err != nil {
return nil, errors.Wrapf(err, "cannot eval %s", FuncDenseRank)
}
valDec, _ := val.Float64()
if valDec < firstDec && valDec != secondDec {
firstNum++
secondDec = valDec
}
}
return proto.NewValueInt64(int64(firstNum) + 1), nil
}
func (a denserankFunc) NumInput() int {
return 0
}