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<@U04SE163WC8> I am running incremental+dedupe rep...
# ask-ai
r
@kapa.ai I am running incremental+dedupe replication dedupe on sql server cdc. If there are multiple updates to a record in the same batch, only the 'insert' record is loaded to the destination. The updates are not applied. What could be the reason?
k
The issue you're experiencing with incremental+dedupe replication on SQL Server CDC, where only the 'insert' record is loaded to the destination and updates are not applied, could be due to the limitations of the cursor field used in the incremental sync mode. ### Explanation 1. Cursor Field Limitation: - The incremental sync mode relies on a cursor field to track changes. If modifications to the underlying records are made without properly updating the cursor field, the updated records won't be picked up by the incremental sync as expected. This is because the source connectors extract delta rows using a SQL query that looks like:
Copy code
sql      select * from table where cursor_field > 'last_sync_max_cursor_field_value'
- If the cursor field is not greater than the last sync's max value, the updated records will not be emitted by the source as new or modified records. This can result in only the initial 'insert' record being loaded to the destination, while subsequent updates are ignored. [Source: Documentation on Incremental Sync - Append + Deduped > Known Limitations](https://docs.airbyte.com/using-airbyte/core-concepts/sync-modes/incremental-append-deduped#known-limitations) 2. Handling Multiple Modifications: - If multiple modifications are made during the same batch and the frequency of the sync is not granular enough, intermediate modifications to the data may not be detected and emitted. Only the state of the data at the time the sync runs will be reflected in the destination. [Source: Documentation on Incremental Sync - Append > Known Limitations](https://docs.airbyte.com/using-airbyte/core-concepts/sync-modes/incremental-append#known-limitations) ### Potential Solutions - Ensure Proper Cursor Field Updates: - Make sure that the cursor field is properly updated with each modification to the records. This will ensure that all changes are captured during the incremental sync. - Increase Sync Frequency: - Increase the frequency of the sync to ensure that intermediate modifications are captured. This can help in detecting and emitting all changes made to the records. - Consider Using CDC: - If the current incremental approach is not sufficient, consider using Change Data Capture (CDC) based on binary logs or Write-Ahead-Logs (WAL). CDC captures all intermediate states for each record and stores them in the destination, ensuring that no updates are lost. [Source: Documentation on Incremental Sync - Append > Known Limitations](https://docs.airbyte.com/using-airbyte/core-concepts/sync-modes/incremental-append#known-limitations) By addressing these potential issues, you can ensure that all updates to your records are properly applied during the incremental+dedupe replication process.
r
@kapa.ai I am already using cdc. Still finding that some updates are not applied
k
A message from kapa.ai
If you are already using CDC and still finding that some updates are not applied, there could be several reasons related to the limitations and configurations of CDC in SQL Server. Here are some potential causes and solutions: ### Potential Causes and Solutions 1. CDC Limitations: - Unsupported Data Types: Ensure that the data types in your tables are supported by CDC. For example, 
hierarchyid
and 
sql_variant
types are not processed in CDC migration type. - SQL Server Version: CDC is only available for SQL Server 2016 Service Pack 1 (SP1) and later. On Linux, CDC is not supported on versions earlier than SQL Server 2017 CU18. - Clustered Columnstore Index: Change data capture cannot be enabled on tables with a clustered columnstore index. [Source: CDC Limitations](https://docs.airbyte.com/integrations/sources/mssql#cdc-limitations) 2. Batch Updates: - If there are batch updates at the source, the CDC connector might struggle to handle large updates. This issue has been reported and is being tracked by the Airbyte team. [Source: Forum Post on MSSQL CDC Incremental Load](https://discuss.airbyte.io/t/4013) 3. Initial Wait Time: - If there are a lot of WAL changes to process for tables that you aren't syncing, increasing the initial wait time might help. However, if there are many tables you will be ignoring, CDC might not be the best choice for syncing this database. [Source: Github Issue on Large WAL](https://github.com/airbytehq/airbyte/issues/31312) 4. Connector Version Compatibility: - Ensure that you are using compatible versions of the Airbyte platform and the connectors. For example, there was a known issue with the Postgres source connector in certain versions that caused incremental state not to be updated. [Source: Forum Post on Postgres CDC](https://discuss.airbyte.io/t/1791) ### Recommended Actions 1. Review CDC Limitations: - Make sure your setup adheres to the limitations listed in the CDC documentation for MSSQL. - [CDC Limitations Documentation](https://docs.airbyte.com/integrations/sources/mssql#cdc-limitations) 2. Check for Known Issues: - Look into any known issues related to the CDC connector for MSSQL and see if there are any updates or patches available. - [Github Issue on MSSQL CDC](https://github.com/airbytehq/airbyte/issues/23658) 3. Increase Initial Wait Time: - If you are experiencing issues with large WAL changes, consider increasing the initial wait time to ensure all changes are captured. 4. Update Connectors and Airbyte Version: - Ensure that you are using the latest versions of the connectors and the Airbyte platform to benefit from any bug fixes and improvements. By addressing these potential issues and following the recommended actions, you should be able to improve the reliability of your CDC replication and ensure that all updates are correctly applied to the destination.
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