[jira] [Assigned] (SPARK-45449) Cache Invalidation Issue with JDBC Table

["Wenchen Fan (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/SPARK-45449?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Wenchen Fan reassigned SPARK-45449:
-----------------------------------

    Assignee: liangyongyuan

> Cache Invalidation Issue with JDBC Table
> ----------------------------------------
>
>                 Key: SPARK-45449
>                 URL: https://issues.apache.org/jira/browse/SPARK-45449
>             Project: Spark
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 3.5.0
>            Reporter: liangyongyuan
>            Assignee: liangyongyuan
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 4.0.0, 3.5.1
>
>
> We have identified a cache invalidation issue when caching JDBC tables in Spark SQL. The cached table is unexpectedly invalidated when queried, leading to a re-read from the JDBC table instead of retrieving data from the cache.
> Example SQL:
> {code:java}
> CACHE TABLE cache_t SELECT * FROM mysql.test.test1;
> SELECT * FROM cache_t;
> {code}
> Expected Behavior:
> The expectation is that querying the cached table (cache_t) should retrieve the result from the cache without re-evaluating the execution plan.
> Actual Behavior:
> However, the cache is invalidated, and the content is re-read from the JDBC table.
> Root Cause:
> The issue lies in the 'CacheData' class, where the comparison involves 'JDBCTable.' The 'JDBCTable' is a case class:
> {code:java}
> case class JDBCTable(ident: Identifier, schema: StructType, jdbcOptions: JDBCOptions)
> {code}
> The comparison of non-case class components, such as 'jdbcOptions,' involves pointer comparison. This leads to unnecessary cache invalidation.



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