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fix: pass the session's batch_size to the Iceberg table scan - #102
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IcebergDataSource::open did not pass execution.batch_size to get_batch_stream, which never called TableScanBuilder::with_batch_size, so scans always read arrow-rs's default 1024-row batches. Add a regression test that sets batch_size above 1024 (smaller sizes pass without the fix because DataFusion splits oversized batches after the scan), and an IcebergTestHarness::query_batches helper that returns unformatted batches. Closes apache#100
gabotechs
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Nov 10, 2026
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Looks good. Thanks @nikkhiil-hadoop!
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Closes #100.
IcebergDataSource::opendidn't passexecution.batch_sizetoget_batch_stream,which never called
TableScanBuilder::with_batch_size. Scans therefore always readarrow-rs's default of 1,024-row batches, and
SET datafusion.execution.batch_sizehad no effect on them. This passes the session's value through, as suggested in
the issue.
Test
crates/datafusion/tests/batch_size.rssetsbatch_size = 2000and checks that thelargest batch from
SELECT pickup_date FROM taxihas 2,000 rows. It fails onmainwith 1,024. The size is deliberately above 1,024: DataFusion splits batches that are
larger than
batch_sizeafter the scan, so a smaller value passes without the fix.The test also snapshots the plan (
CooperativeExecoverDataSourceExec), so anoperator that merges batches above the scan would show up as a snapshot change
instead of silently weakening the assertion.
To get at the batches,
IcebergTestHarnessgainsquery_batches, which returnsthem unformatted;
querynow delegates to it.Checks
cargo fmt --all -- --checkcargo clippy --workspace --locked --all-targets -- -D warningscargo test --workspace --locked