fix(clickhouse): [WRA-5] refactor data scan with async streaming #515
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imor
approved these changes
Oct 28, 2025
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What kind of change does this PR introduce?
This PR is to refactor ClickHouse FDW data scan to use async streaming.
What is the current behavior?
Currently, the ClickHouse FDW uses
fetch_all()to read the whole result data set from ClickHouse to local memory, and then convert them to Postgres rows. This approach doesn't limit memory usage and it will exhaust local memory if the result data set is large.What is the new behavior?
Refactored the data scan to use async worker based streaming. The result data set is asynchronously read from ClickHouse by a dedicate thread, and then converted and transmit to Postgres through a buffered sized-limited (1024 by default) channel. By using this streaming approach, the local memory usage will be restricted by the size of channel, thus memory exhaustion will be prevented.
Additional context
N/A