moomindani opened a new pull request #28953:
URL: https://github.com/apache/spark/pull/28953
### What changes were proposed in this pull request?
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This pull request is to support query execution before/after reading/writing
over JDBC.
There are two new options; `preActions` and `postActions` in DataFrame's
JDBC configuration.
SQL statements specified in `preActions` will be executed before
reading/writing DataFrame via JDBC.
SQL statements specified in `postActions` will be executed after writing
DataFrame via JDBC.
Note: `postActions` is only supported in JDBC writer, not in JDBC reader. It
is because it won't be needed so often and I was not able to find good places
to implement this.
### Why are the changes needed?
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For ETL workload, there is a common requirement to perform SQL statement
before/after reading/writing over JDBC.
Here's examples;
- Create a view with specific conditions
- Delete/Update some records
- Truncate a table (it is already possible in `truncate` option)
- Execute stored procedure (it is also requested in SPARK-32014)
### Does this PR introduce _any_ user-facing change?
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Yes.
With this feature, users can run any SQL statements before/after
reading/writing DataFrame over JDBC.
It does not affect any existing behavior. It just adds new options to use
this new feature.
### How was this patch tested?
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I added test cases into `JDBCSuite.scala` and `JDBCWriteSuite.scala`, and
confirmed all the tests have been passed.
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