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Skip copying the table metadata when a transaction has nothing staged - #4302
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Fokko merged 1 commit intoNov 12, 2026
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Transaction.table_metadata deep-copied the whole metadata on every read, even with nothing staged, so appends slowed down as the snapshot history grew.
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Closes #4294
Rationale for this change
Transaction.table_metadatareplays the staged updates on every read:iceberg-python/pyiceberg/table/__init__.py
Lines 276 to 278 in 718c790
and
update_table_metadataalways ends in a deep copy:iceberg-python/pyiceberg/table/update/__init__.py
Line 763 in 718c790
An append reads the property about 20 times before staging anything, so every read deep copies the full snapshot history. This returns the table's metadata directly when nothing is staged, as @geruh suggested on #3302.
Table.metadataalready shares that object uncopied.The reproduction script from #4294, on
mainwith and without this change (one timed append per depth):update_table_metadatacallsAre these changes tested?
Yes. Two tests in
tests/table/test_init.pycheck that with nothing staged the property returns the table's own metadata object and that staged updates are still applied without changing the table's metadata.test_snapshot_producer_bounded_metadata_accesscountsupdate_table_metadatacalls as a stand-in for reads of the property, so it now stages an update first, otherwise every read would skip the call. It still fails if a read is added back to the snapshot producer.Are there any user-facing changes?
No.