Zouxxyy opened a new pull request, #8232:
URL: https://github.com/apache/paimon/pull/8232
### Purpose
For a self-referencing Replace Table As Select, e.g. `CREATE OR REPLACE
TABLE t AS SELECT * FROM t`,
the query previously read from the table *after* it had been truncated,
causing all data to be lost.
This PR:
- Pins the snapshot in the query for self-referencing RTAS to the
pre-truncation snapshot, so the
select reads the old data instead of the truncated table.
- Leaves relations with user-specified time travel options (e.g. `VERSION AS
OF`) unchanged, so an
explicitly requested snapshot is still honored.
- Extracts `PaimonTableAsSelectHelper` from
`PaimonReplaceTableStrategyHelper` / `PaimonStrategyHelper`
to share `isV1SaveAsTableOverwrite`, `pinSnapshotInQuery`, and
`rewriteToOverwrite` across Spark
versions without duplication.
### Tests
Added in `DDLTestBase`:
- `REPLACE TABLE AS SELECT from same table preserves data` —
self-referencing RTAS keeps the original rows.
- `REPLACE TABLE AS SELECT with time travel reads specified snapshot` — RTAS
with `VERSION AS OF` reads
the requested snapshot, not the latest.
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