Commit row has no matched prewrite row yet, hold it and stop

Error message

Commit row has no matched prewrite row yet, hold it and stop advancing resolvedTs. commitTs: {}, startTs: {}, key: {}

What it means

When flushing resolved TS events, if a COMMIT row has no matching PREWRITE row in the preWrites buffer (preWrites.remove returned null), the reader cannot pair them. It holds the commit row, lowers safeResolvedTs to commitTs-1 to stop advancing, logs this warning and breaks. This protects against emitting out-of-order/incomplete transactions.

Source

Thrown at seatunnel-connectors-v2/connector-cdc/connector-cdc-tidb/src/main/java/org/apache/seatunnel/connectors/seatunnel/cdc/tidb/source/reader/TiDBSourceReader.java:402

            default:
                log.warn("Unsupported row type:" + row.getType());
        }
        return true;
    }

    protected void flushRows(final long resolvedTs) throws Exception {
        flushRowsAndGetSafeResolvedTs(resolvedTs);
    }

    private long flushRowsAndGetSafeResolvedTs(final long resolvedTs) throws Exception {
        long safeResolvedTs = resolvedTs;
        while (!commits.isEmpty() && commits.firstKey().getTimestamp() <= resolvedTs) {
            final RowKeyWithTs commitKey = commits.firstKey();
            final Cdcpb.Event.Row commitRow = commits.firstEntry().getValue();
            final Cdcpb.Event.Row prewriteRow = preWrites.remove(RowKeyWithTs.ofStart(commitRow));
            if (prewriteRow == null) {
                safeResolvedTs = Math.min(safeResolvedTs, commitKey.getTimestamp() - 1);
                log.warn(
                        "Commit row has no matched prewrite row yet, hold it and stop advancing resolvedTs. "
                                + "commitTs: {}, startTs: {}, key: {}",
                        commitRow.getCommitTs(),
                        commitRow.getStartTs(),
                        commitRow.getKey());
                break;
            }
            commits.pollFirstEntry();
            // if pull cdc event block when region split, cdc event will lose.
            committedEvents.offer(prewriteRow);
            totalCommittedRows++;
        }
        return safeResolvedTs;
    }

    private void logStreamingStats(
            TiDBSourceSplit split,
            long startResolvedTs,

View on GitHub (pinned to cf67b549a7)

Solutions

Check preceding warnings (3192 unsupported row types) that may have dropped the prewrite; upgrade the connector if so.
Restart the CDC job from a checkpoint/snapshot to resync prewrite/commit streams.
If it stalls permanently, verify TiKV cluster health (region balance) and TiCDC protocol version alignment.

Defensive patterns

Strategy: retry

Prevention

Keep checkpoints enabled so a stalled resolvedTs can be recovered by restart
Monitor TiKV region health and avoid frequent rescheduling during CDC runs
Address any 'Unsupported row type' warnings that could drop prewrites

When it happens

Trigger: flushRowsAndGetSafeResolvedTs processes commits whose prewrite event has not yet been received from TiKV (out-of-order delivery across regions, or the prewrite was consumed under a type the connector skipped).

Common situations: TiKV region rescheduling/split-merge causing event reordering; very long-running prewrites; previous 'Unsupported row type' warnings having silently dropped the matching prewrite row.

Understand the failure class

Background: "This is a bug, please report it": internal invariant violations, unreachable panics, and SNH errors explained — this error's family across 47 libraries.

Related errors

AI-assisted analysis of apache/seatunnel@cf67b549a7 (2026-09-10). Data as JSON: /api/errors/b086464e27247f90. Report an issue: GitHub.