[jira] [Created] (ARROW-5536) [JAVA] Leak in JdbcToArrowUtils

["Johannes Luong (JIRA)" <ji...@apache.org>]

Johannes Luong created ARROW-5536:
-------------------------------------

             Summary: [JAVA] Leak in JdbcToArrowUtils
                 Key: ARROW-5536
                 URL: https://issues.apache.org/jira/browse/ARROW-5536
             Project: Apache Arrow
          Issue Type: Bug
          Components: Java
            Reporter: Johannes Luong
            Assignee: Johannes Luong


{{JdbcToArrowUtils::updateVector(VarCharVector, String, boolean, int)}} does not release the memory that it allocates for the {{NullableVarCharHolder}}. This can be verified by changing the first lines of {{JdbcToArrowTest::testJdbcToArrowValues()}} to the following:
{code:java}
RootAllocator allocator = new RootAllocator(Integer.MAX_VALUE);
VectorSchemaRoot root = JdbcToArrow.sqlToArrow(conn, table.getQuery(), allocator, Calendar.getInstance());
testDataSets(root);
root.close();
assertEquals(allocator.getAllocatedMemory(), 0);
{code}
 

The leak can be fixed by closing the buffer in {{updateVector}}. However, I would propose to not use the {{NullableVarCharHolder}} in the first place because it creates an unnecessary copy of the string. Instead, I would use {{BaseVariableWidthVector::setSafe(int index, byte[] value)}} and {{BaseVariableWidthVector::setNull(int index)}} directly.

In addition, I would propose to check for leaks in JdbcToArrowTest.

I am willing to create a patch, so please let me know what approach is preferred.



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