[iceberg] Reject schemas the Iceberg mirror cannot represent before the commit - #9199
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plusplusjiajia wants to merge 1 commit into
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[iceberg] Reject schemas the Iceberg mirror cannot represent before the commit#9199plusplusjiajia wants to merge 1 commit into
plusplusjiajia wants to merge 1 commit into
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Purpose
Some Paimon schemas cannot be represented in the Iceberg metadata this layer emits, and today the mismatch surfaces only after the Paimon snapshot is published: the mirror then publishes metadata Iceberg misreads, or fails on every retry and leaves the manifests it wrote behind. This PR checks before the commit and vetoes it there.
Rejected: nanosecond-precision timestamps on any format version (Paimon writes precision > 6 as Parquet INT96, which Iceberg cannot read back as timestamp_ns), VARIANT on a v2 table, VARIANT partition keys, and manifest.legacy-version on v3. The check runs as a pre-commit callback, so the Paimon snapshot is never published, and the manifests written during preparation are cleaned up exactly like a preparation failure.
Only the schemas a commit newly publishes are gated, so a veto is never permanent: already mirrored schemas stay valid, a schema vetoed at its introduction and since remedied (e.g. the column was dropped) is skipped at emission — with the snapshot entry falling back to the current schema id so no pointer dangles — and a transient read failure is rethrown instead of silently dropping a valid schema.