invalid input json. Contains duplicate record for {"namespa

Error message

invalid input json. Contains duplicate record for  {"namespace":"%s","key":"%s"}. Aborting identifytxs

What it means

generateRecordsMap keys records by (namespace, collection, key); a duplicate (namespace,key) pair in the input JSON makes the map ambiguous (later-height tracking would conflict), so it returns this error naming the duplicated namespace/key and aborts IdentifyTxs.

Source

Thrown at internal/ledgerutil/identifytxs/identifytxs.go:200

			return nil, errors.Errorf("invalid input json. Each record entry must contain both " +
				"a \"namespace\" and a \"key\" field. Aborting identifytxs")
		}
		// Check for hashed data
		var ns, coll string
		if r.Hashed {
			ns, coll, err = decodeHashedNs(r.Namespace)
			if err != nil {
				return nil, err
			}
		} else {
			ns = r.Namespace
		}
		// Record to compKey
		ck := compKey{namespace: ns, collection: coll, key: r.Key}
		// Check for duplicate entry
		_, exists := inputKeyMap[ck]
		if exists {
			return nil, errors.Errorf("invalid input json. Contains duplicate record for "+
				" {\"namespace\":\"%s\",\"key\":\"%s\"}. Aborting identifytxs", r.Namespace, r.Key)
		}
		// New entry, add entry and height
		blockNum, txNum := r.GetLaterHeight()
		// Only namespace and key were provided, record doesn't contain height. Set to "infinite" height to iterate entire block store.
		if blockNum == 0 && txNum == 0 {
			blockNum = math.MaxUint64
			txNum = math.MaxUint64
		}
		// Check for max height
		if blockNum > maxBlock || (blockNum == maxBlock && txNum > maxTx) {
			maxBlock = blockNum
			maxTx = txNum
		}
		// Create output file writer
		filename := fmt.Sprintf("txlist%d.json", i+1)
		ofw, err := jsonrw.NewJSONFileWriter(filepath.Join(outputDirPath, filename))
		if err != nil {

View on GitHub (pinned to 2736b63f8f)

Solutions

Remove duplicate entries with the same namespace/key from the JSON, keeping the one with the latest height if applicable
Regenerate a single diff record list from one compare run instead of merging files
Preprocess with a script that dedupes on (namespace, collection, key) before invoking identifytxs

Example fix

// before
[{"namespace":"ns","key":"k1"},{"namespace":"ns","key":"k1"}]
// after
[{"namespace":"ns","key":"k1"}]

Defensive patterns

Strategy: validation

Validate before calling

// Go: dedupe records on namespace/collection/key before calling IdentifyTxs
seen := map[string]bool{}
var out []models.DiffRecord
for _, r := range records.DiffRecords {
    k := r.Namespace + "|" + r.Key
    if seen[k] { continue }
    seen[k] = true
    out = append(out, r)
}

Try / catch

if _, _, err := ledgerutil.IdentifyTxs(recPath, outDir); err != nil {
    if strings.Contains(err.Error(), "duplicate record") {
        return fmt.Errorf("dedupe namespace/key pairs in the diff JSON: %w", err)
    }
    return err
}

Prevention

Never concatenate diff JSONs from multiple compare runs
Preprocess inputs to dedupe on (namespace, collection, key)
Use one authoritative compare output per identifytxs run

When it happens

Trigger: Running ledgerutil identifytxs with a diff record list that contains two records with the same namespace and key (collection differing may still collide when both are unhashed/empty).

Common situations: Manually merging or concatenating two diff JSON outputs; duplicates introduced while editing the file; combining records from multiple compare runs into one list.

Related errors

AI-assisted analysis of hyperledger/fabric@2736b63f8f (2026-09-04). Data as JSON: /api/errors/9312a00b1b4bf33c. Report an issue: GitHub.