Support empty GTID set

[ilidemi]

Happens when the MySQL instance didn't execute any GTID transactions (restored from a backup or GTID recently enabled) or got reset. Was supported before, regressed in #4051

Validated on the real mirror that was failing

Closes DBI-685

[codecov]

❌ 2 Tests Failed:

Tests completed	Failed	Passed	Skipped
2197	2	2195	187

View the top 2 failed test(s) by shortest run time

github.com/PeerDB-io/peerdb/flow/e2e::TestPeerFlowE2ETestSuiteMySQL_CH_Cluster

Stack Traces | 0.01s run time

=== RUN   TestPeerFlowE2ETestSuiteMySQL_CH_Cluster
=== PAUSE TestPeerFlowE2ETestSuiteMySQL_CH_Cluster
=== CONT  TestPeerFlowE2ETestSuiteMySQL_CH_Cluster
--- FAIL: TestPeerFlowE2ETestSuiteMySQL_CH_Cluster (0.01s)
2026/04/17 04:28:41 INFO Received AWS credentials from peer for connector: ci x-peerdb-additional-metadata={Operation:FLOW_OPERATION_UNKNOWN}
2026/04/17 04:28:41 INFO Received AWS credentials from peer for connector: clickhouse x-peerdb-additional-metadata={Operation:FLOW_OPERATION_UNKNOWN}
2026/04/17 04:28:41 INFO Executing and processing query x-peerdb-additional-metadata={Operation:FLOW_OPERATION_UNKNOWN} partitionId=testpart query="SELECT id,t,t_nullable,t_nullable_2 FROM e2e_test_pgch_afhtknaj.\"test_time\" ORDER BY id"
2026/04/17 04:28:41 INFO Executing and processing query stream x-peerdb-additional-metadata={Operation:FLOW_OPERATION_UNKNOWN} partitionId=testpart query="SELECT id,t,t_nullable,t_nullable_2 FROM e2e_test_pgch_afhtknaj.\"test_time\" ORDER BY id"
2026/04/17 04:28:41 INFO [pg_query_executor] declared cursor x-peerdb-additional-metadata={Operation:FLOW_OPERATION_UNKNOWN} partitionId=testpart cursorQuery="DECLARE peerdb_cursor_11199122163911924876 CURSOR FOR SELECT id,t,t_nullable,t_nullable_2 FROM e2e_test_pgch_afhtknaj.\"test_time\" ORDER BY id" args=[]
2026/04/17 04:28:41 INFO [pg_query_executor] fetching rows start x-peerdb-additional-metadata={Operation:FLOW_OPERATION_UNKNOWN} partitionId=testpart query="SELECT id,t,t_nullable,t_nullable_2 FROM e2e_test_pgch_afhtknaj.\"test_time\" ORDER BY id" channelLen=0
2026/04/17 04:28:41 INFO [pg_query_executor] fetching from cursor x-peerdb-additional-metadata={Operation:FLOW_OPERATION_UNKNOWN} partitionId=testpart cursor=peerdb_cursor_11199122163911924876
2026/04/17 04:28:41 INFO processed row stream x-peerdb-additional-metadata={Operation:FLOW_OPERATION_UNKNOWN} partitionId=testpart cursor=peerdb_cursor_11199122163911924876 records=2 bytes=40 channelLen=1
2026/04/17 04:28:41 INFO [pg_query_executor] fetched rows x-peerdb-additional-metadata={Operation:FLOW_OPERATION_UNKNOWN} partitionId=testpart query="SELECT id,t,t_nullable,t_nullable_2 FROM e2e_test_pgch_afhtknaj.\"test_time\" ORDER BY id" rows=2 bytes=40 channelLen=1
2026/04/17 04:28:41 INFO [pg_query_executor] fetching from cursor x-peerdb-additional-metadata={Operation:FLOW_OPERATION_UNKNOWN} partitionId=testpart cursor=peerdb_cursor_11199122163911924876
2026/04/17 04:28:41 INFO processed row stream x-peerdb-additional-metadata={Operation:FLOW_OPERATION_UNKNOWN} partitionId=testpart cursor=peerdb_cursor_11199122163911924876 records=0 bytes=0 channelLen=0
2026/04/17 04:28:41 INFO [pg_query_executor] fetched rows x-peerdb-additional-metadata={Operation:FLOW_OPERATION_UNKNOWN} partitionId=testpart query="SELECT id,t,t_nullable,t_nullable_2 FROM e2e_test_pgch_afhtknaj.\"test_time\" ORDER BY id" rows=0 bytes=0 channelLen=0
2026/04/17 04:28:41 INFO [pg_query_executor] committing transaction x-peerdb-additional-metadata={Operation:FLOW_OPERATION_UNKNOWN} partitionId=testpart
2026/04/17 04:28:41 INFO [pg_query_executor] committed transaction for query x-peerdb-additional-metadata={Operation:FLOW_OPERATION_UNKNOWN} partitionId=testpart query="SELECT id,t,t_nullable,t_nullable_2 FROM e2e_test_pgch_afhtknaj.\"test_time\" ORDER BY id" rows=2 bytes=40 channelLen=0

github.com/PeerDB-io/peerdb/flow/e2e::TestPeerFlowE2ETestSuiteMySQL_CH_Cluster/Test_UnsignedMySQL

Stack Traces | 5.09s run time

=== RUN   TestPeerFlowE2ETestSuiteMySQL_CH_Cluster/Test_UnsignedMySQL
=== PAUSE TestPeerFlowE2ETestSuiteMySQL_CH_Cluster/Test_UnsignedMySQL
=== CONT  TestPeerFlowE2ETestSuiteMySQL_CH_Cluster/Test_UnsignedMySQL
2026/04/17 04:27:21 INFO Received AWS credentials from peer for connector: ci x-peerdb-additional-metadata={Operation:FLOW_OPERATION_UNKNOWN}
2026/04/17 04:27:21 INFO Received AWS credentials from peer for connector: clickhouse x-peerdb-additional-metadata={Operation:FLOW_OPERATION_UNKNOWN}
    clickhouse_mysql_test.go:61: Failed to connect temporal client: failed reaching server: context deadline exceeded
--- FAIL: TestPeerFlowE2ETestSuiteMySQL_CH_Cluster/Test_UnsignedMySQL (5.09s)

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[github-actions]

❌ Test Failure

Analysis: The test TestReplicationMechanismInUseFromOffsetText/empty fails deterministically because the PR's changes to replicationMechanismInUseFromOffsetText now return MYSQL_GTID for an empty offset string, but the test (line 67) asserts the result must be empty.
Confidence: 0.9

⚠️ This appears to be a real bug - manual intervention needed

View workflow run

[github-actions]

🔄 Flaky Test Detected

Analysis: Test TestPeerFlowE2ETestSuiteMySQL_CH_Cluster/Test_UnsignedMySQL failed due to a Temporal server connection timeout ("context deadline exceeded") — a transient infrastructure issue in CI, not a code bug.
Confidence: 0.93

✅ Automatically retrying the workflow

View workflow run