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508f67554d
With TableFileStore.WriteTableFile() being used on the clone path, we want to turn chunk sources into an io.ReadCloser. In the past, store/nbs always did this by using the ReaderAt to emulate an io.Reader. For files this maybe has OK performance, but for AWS/Blobstore remotes it causes a serial sequence of lots of small reads against blob storage as the io.Copy() implementation copies a few dozen KBs at a time. This change makes it so a chunkSource can return an actual Reader. file_table_reader leaves the reader at emulation in place for now. One reason to potentially get rid of even that layer is to enable something like .WriteTo() -> sendfile() translations. Those are not currently directly in place because we currently instrument the returned Reader with byte counting, for example, so we can report on Clone progress. One reason to leave the ReaderAt implementation in place, on the other hand, is interactions with file descriptors and the file descriptor cache. This is an investigation for later; it seemed most prudent to leave it for now since it's not currently causing pain.
96 lines
2.6 KiB
Go
96 lines
2.6 KiB
Go
// Copyright 2019 Dolthub, Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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// This file incorporates work covered by the following copyright and
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// permission notice:
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//
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// Copyright 2016 Attic Labs, Inc. All rights reserved.
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// Licensed under the Apache License, version 2.0:
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// http://www.apache.org/licenses/LICENSE-2.0
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package nbs
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import (
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"bytes"
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"context"
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"io"
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"golang.org/x/sync/errgroup"
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"github.com/dolthub/dolt/go/store/chunks"
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"github.com/dolthub/dolt/go/store/hash"
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)
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type emptyChunkSource struct{}
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func (ecs emptyChunkSource) has(h addr) (bool, error) {
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return false, nil
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}
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func (ecs emptyChunkSource) hasMany(addrs []hasRecord) (bool, error) {
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return true, nil
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}
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func (ecs emptyChunkSource) get(ctx context.Context, h addr, stats *Stats) ([]byte, error) {
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return nil, nil
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}
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func (ecs emptyChunkSource) getMany(ctx context.Context, eg *errgroup.Group, reqs []getRecord, found func(context.Context, *chunks.Chunk), stats *Stats) (bool, error) {
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return true, nil
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}
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func (ecs emptyChunkSource) getManyCompressed(ctx context.Context, eg *errgroup.Group, reqs []getRecord, found func(context.Context, CompressedChunk), stats *Stats) (bool, error) {
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return true, nil
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}
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func (ecs emptyChunkSource) count() (uint32, error) {
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return 0, nil
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}
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func (ecs emptyChunkSource) uncompressedLen() (uint64, error) {
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return 0, nil
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}
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func (ecs emptyChunkSource) hash() addr {
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return addr{}
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}
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func (ecs emptyChunkSource) index() (tableIndex, error) {
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return onHeapTableIndex{}, nil
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}
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func (ecs emptyChunkSource) reader(context.Context) (io.ReadCloser, uint64, error) {
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return io.NopCloser(&bytes.Buffer{}), 0, nil
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}
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func (ecs emptyChunkSource) getRecordRanges(lookups []getRecord) (map[hash.Hash]Range, error) {
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return map[hash.Hash]Range{}, nil
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}
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func (ecs emptyChunkSource) currentSize() uint64 {
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return 0
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}
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func (ecs emptyChunkSource) calcReads(reqs []getRecord, blockSize uint64) (reads int, remaining bool, err error) {
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return 0, true, nil
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}
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func (ecs emptyChunkSource) close() error {
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return nil
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}
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func (ecs emptyChunkSource) clone() (chunkSource, error) {
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return ecs, nil
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}
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