AI / Apache Paimon Interview questions
What is the purpose of the changelog-producer table property?
changelog-producer controls what shape of change stream a primary key table's writer generates for downstream streaming readers. By default (none), Paimon only exposes merged changes across snapshots — it can tell you a key's new value, but not its old one.
Some streaming consumers, such as ones computing a running sum over a grouping key, genuinely need the old value to know whether to add or subtract from a running result. Setting changelog-producer to input, lookup, or full-compaction makes Paimon generate a complete before/after changelog instead, at the cost of extra write-side work.
CREATE TABLE my_table ( ... ) WITH ( 'changelog-producer' = 'lookup' );
With the default changelog-producer setting (none), a streaming consumer can see:
A consumer computing a running sum over a grouping key generally needs:
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