github.com/pingcap/tiflow@v0.0.0-20240520035814-5bf52d54e205/cdc/kv/regionlock/utils.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 regionlock
    15  
    16  import (
    17  	"sort"
    18  
    19  	"github.com/pingcap/kvproto/pkg/metapb"
    20  	"github.com/pingcap/tiflow/cdc/processor/tablepb"
    21  	"github.com/pingcap/tiflow/pkg/spanz"
    22  )
    23  
    24  // CheckRegionsLeftCover checks whether the regions cover the left part of given span
    25  func CheckRegionsLeftCover(regions []*metapb.Region, span tablepb.Span) bool {
    26  	subRegions := CutRegionsLeftCoverSpan(regions, span)
    27  	return len(regions) > 0 && len(subRegions) == len(regions)
    28  }
    29  
    30  // CutRegionsLeftCoverSpan processes a list of regions to remove those that
    31  // do not cover the specified span or are discontinuous with the previous region.
    32  // It returns a new slice containing only the continuous regions that cover the span.
    33  func CutRegionsLeftCoverSpan(regions []*metapb.Region, spanToCover tablepb.Span) []*metapb.Region {
    34  	if len(regions) == 0 {
    35  		return nil
    36  	}
    37  
    38  	sort.Slice(regions, func(i, j int) bool {
    39  		return spanz.StartCompare(regions[i].StartKey, regions[j].StartKey) == -1
    40  	})
    41  
    42  	// If the start key of the first region is after the span's start key,
    43  	// no regions cover the span, return nil.
    44  	if spanz.StartCompare(regions[0].StartKey, spanToCover.StartKey) == 1 {
    45  		return nil
    46  	}
    47  
    48  	nextStartKey := regions[0].StartKey
    49  	for i, region := range regions {
    50  		// If find discontinuous, return the regions up to the current index.
    51  		if spanz.StartCompare(nextStartKey, region.StartKey) != 0 {
    52  			return regions[:i]
    53  		}
    54  		nextStartKey = region.EndKey
    55  	}
    56  	return regions
    57  }