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https://issues.apache.org/jira/browse/FLINK-36561?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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ASF GitHub Bot updated FLINK-36561:
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Labels: pull-request-available (was: )
> ResultSet.wasNull() does not reflect null values in Flink JDBC Driver
> ---------------------------------------------------------------------
>
> Key: FLINK-36561
> URL: https://issues.apache.org/jira/browse/FLINK-36561
> Project: Flink
> Issue Type: Bug
> Components: Table SQL / JDBC
> Affects Versions: 1.18.1, 1.20.0, 1.19.1
> Reporter: Ilya Soin
> Priority: Major
> Labels: pull-request-available
>
> As per JDBC
> [standard|https://docs.oracle.com/en/java/javase/17/docs/api/java.sql/java/sql/ResultSet.html#wasNull()],
> {{ResultSet.wasNull()}}
> {quote}Reports whether the last column read had a value of SQL NULL. Note
> that you must first call one of the getter methods on a column to try to read
> its value and then call the method wasNull to see if the value read was SQL
> NULL.
> {quote}
> However, Flink JDBC driver currently does not update the {{wasNull}} flag
> within the {{FlinkResultSet.get*()}} methods. Instead, it only sets this flag
> during [iteration over
> rows|https://github.com/apache/flink/blob/release-2.0-preview1-rc1/flink-table/flink-sql-jdbc-driver/src/main/java/org/apache/flink/table/jdbc/FlinkResultSet.java#L106]
> fetched from the gateway endpoint. This behavior leads to {{wasNull}}
> returning true only if the entire row is null, not when individual column
> values are null. Consequently, reading a null value using
> {{FlinkResultSet.get*()}} incorrectly results in {{wasNull()}} returning
> false, which is not compliant with the JDBC specification.
> h4. Proposed solution
> Check if the underlying value accessed with {{FlinkResultSet.get*()}} method
> is null, and update wasNull accordingly.
> h4. For discussion
> Can we skip null rows in FlinkResultSet.next()?
> h4. Steps to reproduce:
> Add
> {code:java}
> assertTrue(resultSet.wasNull());
> {code}
> after any call to resultSet.get*() in
> [testStringResultSetNullData()|https://github.com/apache/flink/blob/release-2.0-preview1-rc1/flink-table/flink-sql-jdbc-driver/src/test/java/org/apache/flink/table/jdbc/FlinkResultSetTest.java#L115].
> Run the test and see the failed check.
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