vitessio/vitess · error

cannot reshard streams with a mix of reference and sharded t

Error message

cannot reshard streams with a mix of reference and sharded tables: %v

What it means

blsIsReference determines the stream type (Reference vs Sharded) from the table filters inside a stream's BinlogSource. If different tables (or different streams) resolve to conflicting types — some reference, some sharded — the resharding code cannot handle the mix and errors, printing the offending BinlogSource.

Source

Thrown at go/vt/wrangler/resharder.go:269

		return nil
	})
	return err
}

// blsIsReference is partially copied from streamMigrater.templatize.
// It reuses the constants from that function also.
func (rs *resharder) blsIsReference(bls *binlogdatapb.BinlogSource) (bool, error) {
	streamType := workflow.StreamTypeUnknown
	for _, rule := range bls.Filter.Rules {
		typ, err := rs.identifyRuleType(rule)
		if err != nil {
			return false, err
		}

		switch typ {
		case workflow.StreamTypeSharded:
			if streamType == workflow.StreamTypeReference {
				return false, fmt.Errorf("cannot reshard streams with a mix of reference and sharded tables: %v", bls)
			}
			streamType = workflow.StreamTypeSharded
		case workflow.StreamTypeReference:
			if streamType == workflow.StreamTypeSharded {
				return false, fmt.Errorf("cannot reshard streams with a mix of reference and sharded tables: %v", bls)
			}
			streamType = workflow.StreamTypeReference
		}
	}
	return streamType == workflow.StreamTypeReference, nil
}

func (rs *resharder) identifyRuleType(rule *binlogdatapb.Rule) (workflow.StreamType, error) {
	vtable, ok := rs.vschema.Tables[rule.Match]
	if !ok && !schema.IsInternalOperationTableName(rule.Match) {
		return 0, fmt.Errorf("table %v not found in vschema", rule.Match)
	}
	if vtable != nil && vtable.Type == vindexes.TypeReference {

View on GitHub (pinned to 01a25a7d17)

Solutions

1. Inspect the stream's filter (print the BinlogSource from `_vt.vreplication`) and identify which rules are KeyRange-based vs reference-style.
2. Split the workflow: move reference-table streams into a separate workflow/keyspace configuration from the sharded-table streams, then reshard each separately.
3. Fix the filter rules so all tables in the stream are consistently typed (remove the keyrange on reference tables or drop them from this stream).
4. Re-run the reshard after the stream configuration is homogeneous.

Example fix

// before: filter mixes rules
{"rules":[{"match":"ref_t"},{"match":"sharded_t","keyrange":"-80"}]}
// after: only sharded rules in this stream; move ref_t to a reference stream
{"rules":[{"match":"sharded_t","keyrange":"-80"}]}

for _, rule := range bls.Filter.Rules {
    isSharded := rule.GetKeyrange() != ""
    if lastSeen != nil && isSharded != *lastSeen {
        return fmt.Errorf("filter mixes reference and sharded tables")
    }
    lastSeen = &isSharded
}

func isUniformStreamType(bls *binlogdatapb.BinlogSource) bool {
    seenSharded, seenRef := false, false
    for _, r := range bls.Filter.Rules {
        if r.GetKeyrange() != "" { seenSharded = true } else { seenRef = true }
    }
    return !(seenSharded && seenRef)
}

if err := wr.Reshard(...); err != nil {
    if strings.Contains(err.Error(), "mix of reference and sharded tables") {
        return splitReferenceAndShardedWorkflows(ctx, bls)
    }
    return err
}

When it happens

Trigger: Resharding a keyspace whose VReplication streams' filter rules mix `KeyRange`-sharded table rules with reference-table rules (no keyrange) within the same workflow's streams.

Common situations: A workflow was edited over time so some rules became reference tables while others stayed sharded; combining MoveTables output with reference-table streams manually; misconfigured filter JSON where a table intended to be reference got a keyrange assigned.

Related errors

• unsupported mix of '*' and columns
• unsupported qualifier for '*' expression
• unsupported non-select statement
• unsupported distinct clause
• unsupported select from dual

AI-assisted analysis of vitessio/vitess@01a25a7d17 (2026-09-01). Data as JSON: /api/errors/c435dd448f509fee. Report an issue: GitHub.