ikarol opened a new pull request #35283:
URL: https://github.com/apache/spark/pull/35283
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### What changes were proposed in this pull request?
I've added a DB2 specific truncate implementation that adds an IMMEDIATE
statement at the end of the query.
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### Why are the changes needed?
I've encountered this issue myself while working with DB2 and trying to use
truncate functionality.
A quick google search shows that some people have also encountered this
issue before:
https://stackoverflow.com/questions/70027567/overwrite-mode-does-not-work-in-spark-sql-while-adding-data-in-db2
https://issues.apache.org/jira/browse/SPARK-30062
By looking into DB2 docs it becomes apparent that the IMMEDIATE statement is
only optional if the table is column organized(though I'm not sure if it
applies to all DB2 versions). So for the cases(such as mine) where the table is
not column organized adding an IMMEDIATE statement becomes essential for the
query to work.
https://www.ibm.com/support/knowledgecenter/en/SSEPGG_11.5.0/com.ibm.db2.luw.sql.ref.doc/doc/r0053474.html
Also, that might not be the best example, but I've found that DbVisualizer
does add an IMMEDIATE statement at the end of the truncate command. Though,
does it only for versions that are >=9.7
https://fossies.org/linux/dbvis/resources/profiles/db2.xml (please look at
line number 473)
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### Does this PR introduce _any_ user-facing change?
It should not, as even though the docs mention that if the TRUNCATE
statement is executed in conjunction with IMMEDIATE, it has to be the first
statement in the transaction, the JDBC connection that is established to
execute the TRUNCATE statement has the auto-commit mode turned on. This means
that there won't be any other query/statement executed prior within the same
transaction.
https://www.ibm.com/docs/en/db2/11.5?topic=statements-truncate (see the
description for IMMEDIATE)
https://github.com/apache/spark/blob/master/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/jdbc/JdbcRelationProvider.scala#L49
https://github.com/apache/spark/blob/master/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/jdbc/JdbcRelationProvider.scala#L57
https://github.com/apache/spark/blob/master/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/jdbc/JdbcUtils.scala#L108
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### How was this patch tested?
Existing test case with slightly adjusted logic.
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