[ARROW-5536] [JAVA] Leak in JdbcToArrowUtils

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Component/s: Java
• External issue URL: https://github.com/apache/arrow/issues/21983
• Assignee: Unassigned
• Reporter: Johannes Luong
• Created: 09/Jun/19 10:39
• Updated: 11/Jan/23 07:41

Description

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:

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);

 

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.