mirror of
https://github.com/go-gitea/gitea
synced 2024-12-27 19:14:27 +00:00
55 lines
1.9 KiB
Go
55 lines
1.9 KiB
Go
|
// Copyright (c) 2019 Couchbase, 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 zap
|
||
|
|
|
||
|
|
import (
|
||
|
|
"fmt"
|
||
|
|
)
|
||
|
|
|
||
|
|
// LegacyChunkMode was the original chunk mode (always chunk size 1024)
|
||
|
|
// this mode is still used for chunking doc values.
|
||
|
|
var LegacyChunkMode uint32 = 1024
|
||
|
|
|
||
|
|
// DefaultChunkMode is the most recent improvement to chunking and should
|
||
|
|
// be used by default.
|
||
|
|
var DefaultChunkMode uint32 = 1025
|
||
|
|
|
||
|
|
func getChunkSize(chunkMode uint32, cardinality uint64, maxDocs uint64) (uint64, error) {
|
||
|
|
switch {
|
||
|
|
// any chunkMode <= 1024 will always chunk with chunkSize=chunkMode
|
||
|
|
case chunkMode <= 1024:
|
||
|
|
// legacy chunk size
|
||
|
|
return uint64(chunkMode), nil
|
||
|
|
|
||
|
|
case chunkMode == 1025:
|
||
|
|
// attempt at simple improvement
|
||
|
|
// theory - the point of chunking is to put a bound on the maximum number of
|
||
|
|
// calls to Next() needed to find a random document. ie, you should be able
|
||
|
|
// to do one jump to the correct chunk, and then walk through at most
|
||
|
|
// chunk-size items
|
||
|
|
// previously 1024 was chosen as the chunk size, but this is particularly
|
||
|
|
// wasteful for low cardinality terms. the observation is that if there
|
||
|
|
// are less than 1024 items, why not put them all in one chunk,
|
||
|
|
// this way you'll still achieve the same goal of visiting at most
|
||
|
|
// chunk-size items.
|
||
|
|
// no attempt is made to tweak any other case
|
||
|
|
if cardinality <= 1024 {
|
||
|
|
return maxDocs, nil
|
||
|
|
}
|
||
|
|
return 1024, nil
|
||
|
|
}
|
||
|
|
return 0, fmt.Errorf("unknown chunk mode %d", chunkMode)
|
||
|
|
}
|