Wt

In the DBO tutorial it mentions that queries for a collection will attempt to use the same internal prepared statement. Because these are usually not reentrant that using the same query at the same time is going to cause problems.

Link to the tutorial: http://www.webtoolkit.eu/wt/doc/tutorial/dbo.html#_querying_objects

Actual quote: Because a prepared statement is usually not reentrant

Despite this being easy to work around and documented, it must cost newcomers some grief when intermittent bugs crop up in their apparently correct code. Koen informs me that this is caused by a design decision inside Wt and that correcting this might not be hard because "the implementation is not that complex".