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Understanding CDC/LOG_BASED replication method
We use logical replication of the Postgres write-ahead log (WAL) to incrementally capture updates and deletes using a replication plugin.
We use wal2json as a default plugin, which is included in most Postgres deployments and available from Postgres 9.4+

Should I use CDC for Postgres?

  • If you need a record of deletions and can accept the limitations posted below, you should to use CDC for Postgres.
  • If your data set is small and you just want snapshot of your table in the destination, consider using FULL_TABLE Refresh replication for your database instead of CDC.

CDC Limitations

  • Make sure to read our CDC docs to see limitations that impact all databases using CDC replication.
  • CDC is not available with Heroku Postgres.
  • Whaly requires a replication slot configured only for its use. Only one source should be configured that uses this replication slot. Instructions on how to set up a replication slot can be found below.
  • Log-based replication only works for master instances of Postgres.
  • Using logical replication increases disk space used on the database server. The additional data is stored until it is consumed.
    • We recommend setting frequent syncs for CDC in order to ensure that this data doesn't fill up your disk space.
    • If you stop syncing a CDC-configured Postgres instance to Whaly, you should delete the replication slot. Otherwise, it may fill up your disk space.
Last modified 17d ago