JNSimba opened a new pull request, #4453:
URL: https://github.com/apache/flink-cdc/pull/4453
## What is the purpose of the change
The Postgres incremental source uses the Debezium connector config's snapshot
fetch size (`connectorConfig.getSnapshotFetchSize()`, default `10240`) for
the
snapshot split read, instead of the Flink CDC option
`scan.snapshot.fetch.size`
(default `1024`). As a result:
1. `scan.snapshot.fetch.size` has no effect for the Postgres source.
2. When a snapshot chunk's row count is `<=` the fetch size, the JDBC
server-side cursor returns the whole chunk in a single batch, loading
every
row of the chunk into memory at once. On wide tables (many columns / large
rows) this can exhaust the heap and OOM.
The MySQL source already reads `sourceConfig.getFetchSize()` for its snapshot
read. This PR makes the Postgres snapshot read task do the same, so that
`scan.snapshot.fetch.size` is honored consistently across connectors.
## Brief change log
- `PostgresSnapshotSplitReadTask` now takes the `PostgresSourceConfig` and
uses
`sourceConfig.getFetchSize()` for the snapshot select statement, instead of
`connectorConfig.getSnapshotFetchSize()`.
## Verifying this change
This change is covered by existing Postgres source tests; the snapshot fetch
size now follows the `scan.snapshot.fetch.size` option.
## Does this pull request potentially affect one of the following parts:
- Dependencies (does it add or upgrade a dependency): no
- The public API: no
- The serializers: no
- The runtime per-record code paths (performance sensitive): no
- Anything that affects deployment or recovery: no
- The S3 file system connector: no
## Documentation
- Does this pull request introduce a new feature? no
- If yes, how is the feature documented? not applicable
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