Question 1

Does PostgreSQL change data capture work into MotherDuck?

Accepted Answer

Yes, and it merges rather than appends. Changes stream out through logical replication using a publication and a replication slot, then load into MotherDuck via its Parquet staging path. Staging is transport only: records land in a staging table and are reconciled against the destination with update and insert statements, so a table with a primary key stays correct rather than accumulating duplicate versions of each row.

Question 2

How are PostgreSQL arrays and JSONB handled?

Accepted Answer

JSON and JSONB come through as values you can query in DuckDB. The caveat worth knowing is native PostgreSQL array columns, which currently normalize to generic JSON rather than becoming typed DuckDB LIST columns. Nothing is lost, but if you were expecting a typed list on the MotherDuck side you will need to cast it. Worth checking before you model against array heavy tables.

Question 3

Can I run capture against a replica instead of the primary?

Accepted Answer

Yes, on PostgreSQL 16 and later, and it is one of the better reasons to choose this pairing. Running logical replication from a replica keeps the additional read load away from the primary serving your application, which matters when the source is production. Watch replication slot lag either way, since a slot holds write ahead log segments until they have been consumed and can consume disk if a sync falls behind.

Question 4

Can MotherDuck write back into PostgreSQL?

Accepted Answer

Yes, with create, update, create or update, and replace modes. Teams use this to push a computed score or an aggregate built in MotherDuck back into the application database the product reads, without adding that logic to the application. Note that MotherDuck STRUCT, MAP, JSON, and LIST values generally arrive in PostgreSQL as JSON rather than as native PostgreSQL arrays.

Connect MotherDuck with PostgreSQL

Connect MotherDuck and PostgreSQL with Polytomic

Logical replication capture

Capture from a replica

JSON carried through

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