mirror of https://github.com/go-gitea/gitea
Git with a cup of tea, painless self-hosted git service
Mirror for internal git.with.parts use
https://git.with.parts
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
67 lines
2.5 KiB
67 lines
2.5 KiB
// 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 = 1026
|
|
|
|
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
|
|
|
|
case chunkMode == 1026:
|
|
// improve upon the ideas tested in chunkMode 1025
|
|
// the observation that the fewest number of dense chunks is the most
|
|
// desirable layout, given the built-in assumptions of chunking
|
|
// (that we want to put an upper-bound on the number of items you must
|
|
// walk over without skipping, currently tuned to 1024)
|
|
//
|
|
// 1. compute the number of chunks needed (max 1024/chunk)
|
|
// 2. convert to chunkSize, dividing into maxDocs
|
|
numChunks := (cardinality / 1024) + 1
|
|
chunkSize := maxDocs / numChunks
|
|
return chunkSize, nil
|
|
}
|
|
return 0, fmt.Errorf("unknown chunk mode %d", chunkMode)
|
|
}
|
|
|