vitessio/vitess · error

same keyrange is present in source and target: %v

Error message

same keyrange is present in source and target: %v

What it means

ValidateForReshard verifies that a set of source shards can be resharded into a set of target shards. If any source shard has a KeyRange exactly equal to any target shard's KeyRange, resharding would be a no-op/dangerous overlap and this error is returned, naming the offending keyrange.

Source

Thrown at go/vt/topotools/split.go:34

package topotools

import (
	"errors"
	"fmt"

	"vitess.io/vitess/go/vt/key"
	topodatapb "vitess.io/vitess/go/vt/proto/topodata"
	"vitess.io/vitess/go/vt/topo"
)

// ValidateForReshard returns an error if sourceShards cannot reshard into
// targetShards.
func ValidateForReshard(sourceShards, targetShards []*topo.ShardInfo) error {
	for _, source := range sourceShards {
		for _, target := range targetShards {
			if key.KeyRangeEqual(source.KeyRange, target.KeyRange) {
				return fmt.Errorf("same keyrange is present in source and target: %v", key.KeyRangeString(source.KeyRange))
			}
		}
	}
	sourcekr, err := combineKeyRanges(sourceShards)
	if err != nil {
		return err
	}
	targetkr, err := combineKeyRanges(targetShards)
	if err != nil {
		return err
	}
	if !key.KeyRangeEqual(sourcekr, targetkr) {
		return fmt.Errorf("source and target keyranges don't match: %v vs %v", key.KeyRangeString(sourcekr), key.KeyRangeString(targetkr))
	}
	return nil
}

func combineKeyRanges(shards []*topo.ShardInfo) (*topodatapb.KeyRange, error) {

View on GitHub (pinned to 01a25a7d17)

Solutions

1. Remove the identical keyrange from either the source or the target list — every target keyrange must differ from every source keyrange.
2. If splitting a shard, define non-overlapping new keyranges covering the full range of the removed source shards (e.g. split 0- into -80,80- and exclude 0- from sources).
3. Re-run ValidateForReshard after correcting the shard plan to confirm no overlaps remain.

Example fix

// before: target includes the original shard
sourceShards := []string{"0-"}
targetShards := []string{"0-", "..."} // wrong
// after
targetShards := []string{"-80", "80-"}

for _, s := range sourceShards {
    for _, t := range targetShards {
        if key.KeyRangeEqual(s.KeyRange, t.KeyRange) {
            return fmt.Errorf("shard %v appears in both source and target", s.ShardName())
        }
    }
}

func hasIdenticalKeyRange(source, target []*topo.ShardInfo) bool {
    for _, s := range source {
        for _, t := range target {
            if key.KeyRangeEqual(s.KeyRange, t.KeyRange) {
                return true
            }
        }
    }
    return false
}

if err := topotools.ValidateForReshard(sourceShards, targetShards); err != nil {
    if strings.Contains(err.Error(), "same keyrange is present") {
        return fmt.Errorf("fix shard plan: remove unchanged shard from one side: %w", err)
    }
    return err
}

When it happens

Trigger: Calling ValidateForReshard (via vtctld reshard setup / buildResharder) with target shard lists that still include an original source shard — e.g. resharding keyspace shard '0-' into targets where one target is '0-' unchanged, or passing the same ShardInfo list as both source and target.

Common situations: Specifying target shards by copying the source shard list and forgetting to remove the shard being split; planning a reshard where one of the new shards retains the identical keyrange of a source shard; copy-paste errors in shard name/keyrange definitions.

Related errors

• source and target keyranges don't match: %v vs %v
• non-contiguous KeyRange values for %v in cell %v at shard %v
• shard %v/%v has a different KeyRange: %v != %v
• can't rebuild serving keyspace while a migration is on going
• %w: uid %v is already in use

AI-assisted analysis of vitessio/vitess@01a25a7d17 (2026-09-01). Data as JSON: /api/errors/08ce8f3d93f9a1a1. Report an issue: GitHub.