dgraph-io/dgraph · error

Length of facetsMatrix and uidMatrix mismatch: %d vs %d

Error message

Length of facetsMatrix and uidMatrix mismatch: %d vs %d

What it means

While converting query output to RDF (toRDF/preTraverse), each UID in the path must have matching entries in both uidMatrix and facetsMatrix. A non-empty facetsMatrix whose length differs from uidMatrix indicates internal state corruption or a code path that populated facets without corresponding UID rows.

Source

Thrown at query/outputnode.go:1380

		if pc.IsInternal() {
			if pc.Params.Expand != "" {
				continue
			}
			if pc.Params.Normalize && pc.Params.Alias == "" {
				continue
			}
			if err := pc.addInternalNode(enc, uid, dst); err != nil {
				return err
			}
			continue
		}

		if len(pc.uidMatrix) == 0 {
			// Can happen in recurse query.
			continue
		}
		if len(pc.facetsMatrix) > 0 && len(pc.facetsMatrix) != len(pc.uidMatrix) {
			return errors.Errorf("Length of facetsMatrix and uidMatrix mismatch: %d vs %d",
				len(pc.facetsMatrix), len(pc.uidMatrix))
		}

		idx := algo.IndexOf(pc.SrcUIDs, uid)
		if idx < 0 {
			continue
		}
		if pc.Params.IsGroupBy {
			if len(pc.GroupbyRes) <= idx {
				return errors.Errorf("Unexpected length while adding Groupby. Idx: [%v], len: [%v]",
					idx, len(pc.GroupbyRes))
			}
			if err := pc.addGroupby(enc, dst, pc.GroupbyRes[idx], pc.fieldName()); err != nil {
				return err
			}
			continue
		}

View on GitHub (pinned to 759e242be6)

Solutions

1. Upgrade Dgraph — several facet/recurse matrix mismatches were fixed in later releases
2. Remove or isolate the facet portion of the query to confirm it triggers the mismatch, then report with repro
3. Restructure: fetch facets in a separate simpler query without recurse
4. If programmatically building the SubGraph, ensure facetsMatrix rows are appended 1:1 with uidMatrix rows

Example fix

// before
{
  q(func: uid(0x1)) @recurse {
    friend @facets
  }
}
// after (workaround)
{
  q(func: uid(0x1)) {
    friend @facets
  }
}

// avoid the trigger: don't request facets on recurse paths
if (/@recurse/.test(q) && /@facets/.test(q)) throw new Error('facets with recurse unsupported; split query');

try {
  return await dgraph.query(q);
} catch (e) {
  if (String(e).includes('facetsMatrix and uidMatrix mismatch')) {
    return await dgraph.query(stripFacets(q)); // retry without @facets
  }
  throw e;
}

When it happens

Trigger: A facets query path where facetsMatrix was appended but uidMatrix skipped/shortened (the source notes it can happen in recurse queries when len(uidMatrix)==0 is skipped but partial mismatch remains), passed to rdf conversion at outputnode.go:1380.

Common situations: Recurse queries with facets; bugs in specific Dgraph versions' facet handling; mixing facets on reverse edges where the matrix population diverges.

Related errors

• unexpected end of facets
• expected '(' but found %v at facet
• expected key but found %v
• empty facetKeys not allowed
• Unexpected length while adding Groupby. Idx: [%v], len: [%v]

AI-assisted analysis of dgraph-io/dgraph@759e242be6 (2026-09-01). Data as JSON: /api/errors/4e422fbaff4ba40e. Report an issue: GitHub.