pan3793 opened a new pull request, #56092:
URL: https://github.com/apache/spark/pull/56092
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### What changes were proposed in this pull request?
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This PR contains 3 parts:
1. `JdbcDialects` API change - deprecate `def supportsTableSample: Boolean`
and `def getTableSample(sample: TableSampleInfo): String`, introduce a `def
compileTableSample(sample: TableSampleInfo): Option[String]` as the suggested
replacement.
1.1. this is a correctness fix - PostgreSQL does not support
`withReplacement = true`, but the current implementation ignores
`withReplacement` and always treats it as `withReplacement = false`, which is
incorrect.
1.2. it's a pre-step to support `TABLESAMPLE SYSTEM` as some RDBMSs may
only support `TABLESAMPLE BERNOULLI` but not `TABLESAMPLE SYSTEM`.
2. Mark the old `pushTableSample` method as deprecated and suggest the new
API, connectors are suggested to only implement the new `pushTableSample` that
has a `sampleMethod` parameter.
3. Extend the built-in JDBC connector to support pushdown `TABLESAMPLE
SYSTEM`, for now, this is only applicable to the PostgreSQL dialect.
### Why are the changes needed?
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Correctness fix - TABLESAMPLE `withReplacement = true` should not push down
to PostgreSQL and Databricks JDBC connector.
Make `JdbcDialects` API more flexible - RDBMS may partially support
TABLESAMPLE, now they can answer whether the expression can be pushed down by
testing the real pushed TABLESAMPLE expression instead of blindly answering
yes/no without knowing the real pushed expression.
Extend the built-in JDBC connector feature.
### Does this PR introduce _any_ user-facing change?
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Yes, see the above section for details.
### How was this patch tested?
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New UT/IT cases are added.
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The code contains content generated-by: MiMo-V2.5-Pro
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