github.com/pingcap/ticdc@v0.0.0-20220526033649-485a10ef2652/cdc/sink/dispatcher/index_value.go (about)

     1  // Copyright 2020 PingCAP, Inc.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // See the License for the specific language governing permissions and
    12  // limitations under the License.
    13  
    14  package dispatcher
    15  
    16  import (
    17  	"github.com/pingcap/ticdc/cdc/model"
    18  	"github.com/pingcap/ticdc/pkg/hash"
    19  )
    20  
    21  type indexValueDispatcher struct {
    22  	partitionNum int32
    23  	hasher       *hash.PositionInertia
    24  }
    25  
    26  func newIndexValueDispatcher(partitionNum int32) *indexValueDispatcher {
    27  	return &indexValueDispatcher{
    28  		partitionNum: partitionNum,
    29  		hasher:       hash.NewPositionInertia(),
    30  	}
    31  }
    32  
    33  func (r *indexValueDispatcher) Dispatch(row *model.RowChangedEvent) int32 {
    34  	r.hasher.Reset()
    35  	r.hasher.Write([]byte(row.Table.Schema), []byte(row.Table.Table))
    36  	// FIXME(leoppro): if the row events includes both pre-cols and cols
    37  	// the dispatch logic here is wrong
    38  
    39  	// distribute partition by rowid or unique column value
    40  	dispatchCols := row.Columns
    41  	if len(row.Columns) == 0 {
    42  		dispatchCols = row.PreColumns
    43  	}
    44  	for _, col := range dispatchCols {
    45  		if col == nil {
    46  			continue
    47  		}
    48  		if col.Flag.IsHandleKey() {
    49  			r.hasher.Write([]byte(col.Name), []byte(model.ColumnValueString(col.Value)))
    50  		}
    51  	}
    52  	return int32(r.hasher.Sum32() % uint32(r.partitionNum))
    53  }