github.com/cockroachdb/cockroach@v20.2.0-alpha.1+incompatible/pkg/kv/kvserver/batcheval/cmd_merge.go (about)

     1  // Copyright 2014 The Cockroach Authors.
     2  //
     3  // Use of this software is governed by the Business Source License
     4  // included in the file licenses/BSL.txt.
     5  //
     6  // As of the Change Date specified in that file, in accordance with
     7  // the Business Source License, use of this software will be governed
     8  // by the Apache License, Version 2.0, included in the file
     9  // licenses/APL.txt.
    10  
    11  package batcheval
    12  
    13  import (
    14  	"context"
    15  
    16  	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/batcheval/result"
    17  	"github.com/cockroachdb/cockroach/pkg/roachpb"
    18  	"github.com/cockroachdb/cockroach/pkg/storage"
    19  )
    20  
    21  func init() {
    22  	RegisterReadWriteCommand(roachpb.Merge, DefaultDeclareKeys, Merge)
    23  }
    24  
    25  // Merge is used to merge a value into an existing key. Merge is an
    26  // efficient accumulation operation which is exposed by RocksDB, used
    27  // by CockroachDB for the efficient accumulation of certain
    28  // values. Due to the difficulty of making these operations
    29  // transactional, merges are not currently exposed directly to
    30  // clients. Merged values are explicitly not MVCC data.
    31  func Merge(
    32  	ctx context.Context, readWriter storage.ReadWriter, cArgs CommandArgs, resp roachpb.Response,
    33  ) (result.Result, error) {
    34  	args := cArgs.Args.(*roachpb.MergeRequest)
    35  	h := cArgs.Header
    36  
    37  	return result.Result{}, storage.MVCCMerge(ctx, readWriter, cArgs.Stats, args.Key, h.Timestamp, args.Value)
    38  }