[hibernate-issues] [Hibernate-JIRA] Commented: (HHH-2207) Suggested fix for HQL - MySQL setMaxResults issue

[Toby Moore (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HHH-2207?page=comments#action_25110 ] 

Toby Moore commented on HHH-2207:
---------------------------------

I'm not sure how to go about creating a test case for this as the method is in a chain of other methods to convert the HQL to the prepared statement sql, and we only have scope to test it on our MySql implementation. If you look at the only method that calls the one I've changed, it's clear to see that it's expecting the parameter count added, not the new position. Any other questions please ask.  

> Suggested fix for HQL - MySQL setMaxResults issue
> -------------------------------------------------
>
>          Key: HHH-2207
>          URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-2207
>      Project: Hibernate3
>         Type: Bug

>   Components: query-hql
>     Versions: 3.2.0.ga
>  Environment: Hi 3.2.0.ga MySQL
>     Reporter: Toby Moore
>  Attachments: querloaderdiff.patch
>
> Original Estimate: 0 minutes
>         Remaining: 0 minutes
>
> Hi,
> After some experimentation, we'd like to suggest an easy fix to a problem we encountered.
> When using HQL with the Hibernate 3 entity manager to limit the number of records returned ( at the database level, via generated SQL, not in memory) we were getting an exception due to the query builder trying to attach a parameter to the prepared statement that was out of bounds :
> by: java.sql.SQLException: Parameter index out of range (4 > number of parameters, which is 3).
>    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:910)
>    at com.mysql.jdbc.PreparedStatement.setInternal(PreparedStatement.java:2556)
>    at com.mysql.jdbc.PreparedStatement.setInternal(PreparedStatement.java:2584)
>    at com.mysql.jdbc.PreparedStatement.setInt(PreparedStatement.java:2540)
>    at com.mchange.v2.c3p0.impl.NewProxyPreparedStatement.setInt(NewProxyPreparedStatement.java:677)
>    at org.hibernate.loader.Loader.bindLimitParameters(Loader.java:1616)
>    at org.hibernate.loader.Loader.prepareQueryStatement(Loader.java:1560)
>    at org.hibernate.loader.Loader.doQuery(Loader.java:661)
>    at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:224)
>    at org.hibernate.loader.Loader.doList(Loader.java:2156)
>    ... 10 more
> On looking at the code in the method bindParameterValues in org.hibernate.loader.hql.QueryLoader ( line 491 ) the method returns the next parameter position that needs to be set, not the amount of parameters it has added, which is expected in Loader.java on the line
>          col += bindParameterValues( st, queryParameters, col, session );
> This causes the parameter count to get out of sync and thus throw the expcetion saying that it can't add a parameter out of range.
> A simple fix for this is to change the return line in QueryLoader to be
> return position - startPosition;
> which will return the amount of parameters this method added.
> We've tested this on our mysql implementation and it works, and run the unit tests to check that no extra errors are generated. If this seems like a good fix then i'll submit it as a patch via the JIRA, but would like to hear any thoughts first?
> Kind regards,
> TobyM - MindCandyDesign London

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