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https://issues.apache.org/jira/browse/SPARK-40802?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17618389#comment-17618389
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Hyukjin Kwon commented on SPARK-40802:
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I guess the problem is that {{getMetaData}} doesn't gurantee to work in all
cases or all DBMSes. We could probably introduce a dialect to optimize this
further.
> Enhance JDBC Connector to use PreparedStatement.getMetaData() to resolve
> schema instead of PreparedStatement.executeQuery()
> ---------------------------------------------------------------------------------------------------------------------------
>
> Key: SPARK-40802
> URL: https://issues.apache.org/jira/browse/SPARK-40802
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 2.1.0
> Reporter: Mingli Rui
> Priority: Major
> Original Estimate: 24h
> Remaining Estimate: 24h
>
> Currently, Spark JDBC Connector uses *PreparedStatement.executeQuery()* to
> resolve the JDBCRelation's schema. The schema query is like *s"SELECT * FROM
> $table_or_query WHERE 1=0".*
> But it is not necessary to execute the query. It's enough to *prepare* the
> query. With preparing the statement, the query is parsed and compiled, but is
> not executed. It will be more efficient.
> So, it's better to use PreparedStatement.getMetaData() to resolve schema.
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