github.com/vescale/zgraph@v0.0.0-20230410094002-959c02d50f95/storage/batch_getter.go (about)

     1  // Copyright 2022 zGraph Authors. All rights reserved.
     2  //
     3  // Copyright 2016 PingCAP, Inc.
     4  //
     5  // Licensed under the Apache License, Version 2.0 (the "License");
     6  // you may not use this file except in compliance with the License.
     7  // You may obtain a copy of the License at
     8  //
     9  //     http://www.apache.org/licenses/LICENSE-2.0
    10  //
    11  // Unless required by applicable law or agreed to in writing, software
    12  // distributed under the License is distributed on an "AS IS" BASIS,
    13  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    14  // See the License for the specific language governing permissions and
    15  // limitations under the License.
    16  
    17  package storage
    18  
    19  import (
    20  	"context"
    21  
    22  	"github.com/vescale/zgraph/storage/kv"
    23  )
    24  
    25  // BatchBufferGetter is the interface for BatchGet.
    26  type BatchBufferGetter interface {
    27  	kv.Getter
    28  	Len() int
    29  }
    30  
    31  // BufferBatchGetter is the type for BatchGet with MemBuffer.
    32  type BufferBatchGetter struct {
    33  	buffer   BatchBufferGetter
    34  	snapshot kv.BatchGetter
    35  }
    36  
    37  // NewBufferBatchGetter creates a new BufferBatchGetter.
    38  func NewBufferBatchGetter(buffer BatchBufferGetter, snapshot kv.BatchGetter) *BufferBatchGetter {
    39  	return &BufferBatchGetter{buffer: buffer, snapshot: snapshot}
    40  }
    41  
    42  // BatchGet gets a batch of values.
    43  func (b *BufferBatchGetter) BatchGet(ctx context.Context, keys []kv.Key) (map[string][]byte, error) {
    44  	if b.buffer.Len() == 0 {
    45  		return b.snapshot.BatchGet(ctx, keys)
    46  	}
    47  	bufferValues := make([][]byte, len(keys))
    48  	shrinkKeys := make([]kv.Key, 0, len(keys))
    49  	for i, key := range keys {
    50  		val, err := b.buffer.Get(ctx, key)
    51  		if err == nil {
    52  			bufferValues[i] = val
    53  			continue
    54  		}
    55  		if !kv.IsErrNotFound(err) {
    56  			return nil, err
    57  		}
    58  		shrinkKeys = append(shrinkKeys, key)
    59  	}
    60  	storageValues, err := b.snapshot.BatchGet(ctx, shrinkKeys)
    61  	if err != nil {
    62  		return nil, err
    63  	}
    64  	for i, key := range keys {
    65  		if len(bufferValues[i]) == 0 {
    66  			continue
    67  		}
    68  		storageValues[string(key)] = bufferValues[i]
    69  	}
    70  	return storageValues, nil
    71  }