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filter_fields_iterator.go
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/
filter_fields_iterator.go
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// Copyright (c) 2019 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
package index
import (
"errors"
"github.com/m3db/m3/src/m3ninx/index/segment"
)
var (
errNoFiltersSpecified = errors.New("no fields specified to filter upon")
)
func newFilterFieldsIterator(
reader segment.Reader,
fields AggregateFieldFilter,
) (segment.FieldsIterator, error) {
if len(fields) == 0 {
return nil, errNoFiltersSpecified
}
return &filterFieldsIterator{
reader: reader,
fields: fields,
currentIdx: -1,
}, nil
}
type filterFieldsIterator struct {
reader segment.Reader
fields AggregateFieldFilter
err error
currentIdx int
}
var _ segment.FieldsIterator = &filterFieldsIterator{}
func (f *filterFieldsIterator) Next() bool {
if f.err != nil {
return false
}
f.currentIdx++ // required because we start at -1
for f.currentIdx < len(f.fields) {
field := f.fields[f.currentIdx]
ok, err := f.reader.ContainsField(field)
if err != nil {
f.err = err
return false
}
// i.e. we found a field from the filter list contained in the segment.
if ok {
return true
}
// the current field is unsuitable, so we skip to the next possiblity.
f.currentIdx++
}
return false
}
func (f *filterFieldsIterator) Current() []byte { return f.fields[f.currentIdx] }
func (f *filterFieldsIterator) Err() error { return f.err }
func (f *filterFieldsIterator) Close() error { return nil }