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https://issues.apache.org/jira/browse/DERBY-4342?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12759144#action_12759144
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Knut Anders Hatlen commented on DERBY-4342:
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I've had a look at the INNER JOIN case and compared it with a similar, but
working, query where VALUE was replaced by MOD. That is
select * from xyz t1 inner join xyz t2 on t1.c1 = t2.c1 where value(t1.c1,
t1.c2) = 1
vs
select * from xyz t1 inner join xyz t2 on t1.c1 = t2.c1 where mod(t1.c1,
t1.c2) = 1
The node trees for the queries had the exact same structure (except of course
that the CoalesceFunctionNode was replaced by a BinaryArithmeticOperatorNode)
after the parsing phase and the bind phase. After the optimize phase, there was
one difference: The columns under the BinaryArithmeticOperatorNode (for the MOD
query) referenced the base table whereas the columns under the
CoalesceFunctionNode (for the VALUE query) referenced the result columns from
the JoinNode.
At the time when these columns are accessed during execution, no rows have
propagated from the base tables to the join results, so the VALUE query gets
null instead of a row in getColumnFromRow() and fails with NPE.
The difference between CoalesceFunctionNode and BinaryArithmeticOperatorNode
that makes the two queries access the columns differently, is
remapColumnReferencesToExpressions(). CFN inherits the method from ValueNode,
where it is a no-op. BAON inherits it from BinaryOperatorNode, where
remapColumnReferencesToExpressions() is called recursively on the operands.
I tried to add this method to CFN
public ValueNode remapColumnReferencesToExpressions()
throws StandardException
{
for (int i = 0; i < argumentsList.size(); i++) {
ValueNode vn = (ValueNode) argumentsList.elementAt(i);
vn.remapColumnReferencesToExpressions();
}
return this;
}
and then the INNER JOIN did not fail and it returned the expected result.
Unfortunately, the RIGHT OUTER JOIN still raised an assert failure, so either
that's a separate problem, or adding the method was not the right fix. (I did
try to compare the node trees for VALUE vs MOD in the outer join case too, and
there the two queries produced completely different trees.)
> SQLSTATE 38000 (NullPointerException) at inner self join and value(x1, x2...)
> -----------------------------------------------------------------------------
>
> Key: DERBY-4342
> URL: https://issues.apache.org/jira/browse/DERBY-4342
> Project: Derby
> Issue Type: Bug
> Affects Versions: 10.1.1.0, 10.1.2.1, 10.1.3.1, 10.2.1.6, 10.2.2.0,
> 10.3.1.4, 10.3.2.1, 10.3.3.0, 10.4.1.3, 10.4.2.0, 10.5.1.1
> Environment: WINXP
> Reporter: Hubert Garm
>
> create table xyz (c1 int, c2 int);
> insert into xyz values(1,2);
> select * from xyz t1 inner join xyz t2 on t1.c1 = t2.c1 where value(t1.c1,
> t1.c2) = 1;
> causes the following error:
> FEHLER 38000: Bei der Auswertung eines Ausdrucks wurde die Ausnahme
> 'java.lang.NullPointerException' ausgeloest.
> FEHLER XJ001: Java-Ausnahme: ': java.lang.NullPointerException'.
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