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From "Mamta A. Satoor (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-4439) NullPointerException at bind time when selecting from VALUES NULL
Date Mon, 09 Nov 2009 19:13:32 GMT

    [ https://issues.apache.org/jira/browse/DERBY-4439?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12775081#action_12775081

Mamta A. Satoor commented on DERBY-4439:

I looked through the code and experimented with some changes. Basically, during the bind phase,
CursorNode does binding in following order

			// bind the query expression

			// this rejects any untyped nulls in the select list
			// pass in null to indicate that we don't have any
			// types for this node
In other words, untyped nulls are bound at the end. 

In case of our query, where we are using a binary operator node, while we are going through
the resultSet.bindResultColumns(fromList) code in CursorNode, we call BinaryOperatorNode.bindExpression()
and towards the end of this method, there is following call
		return genSQLJavaSQLTree();
This piece of code assumes that everything is bound by now but since call to untyped nulls
has not been made, we run into NPE.

I tried putting in call to binding untyped nulls in FromSubquery.bindExpression and that fixed
the query in question but that is not the right thing to do exactly. For following query,
with my changes, we end up throwing exception that Null is only allowed in a VALUES clause
within an INSERT statement.
create table u (c1 integer);
insert into u select * from (values null) as X;
We need to be able to differentiate the fact that we are dealing with a CursorNode at the
top and hence only for that case, we should try to bind untyped nulls. I will work on this
more. If anyone has any suggestions on a fix, please share them here

> NullPointerException at bind time when selecting from VALUES NULL
> -----------------------------------------------------------------
>                 Key: DERBY-4439
>                 URL: https://issues.apache.org/jira/browse/DERBY-4439
>             Project: Derby
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions:,
>            Reporter: Knut Anders Hatlen
>            Priority: Minor
> I see a NullPointerException when I try the following query:
> ij> select x*2 from (values null) v(x);
> ERROR XJ001: Java exception: ': java.lang.NullPointerException'.
> It should fail gracefully instead, like this similar query:
> ij> select x from (values null) v(x);
> ERROR 42X07: Null is only allowed in a VALUES clause within an INSERT statement.

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