launchpad-dev team mailing list archive

[Jeroen Vermeulen <jtv@xxxxxxxxxxxxx>]

On 2012-03-20 08:02, Francis J. Lacoste wrote:
> My guess is that they are used to work-around some constraints check.
>
> I say if you remove them and the tests pass, leave them out :-)

We've used block_implicit_flushes on several discrete occasions, for 
several reasons.  According to my email archives:

 * To prevent database changes from being flushed during GET requests, 
back when we first had the idea of making GET run read-only.

 * To resolve constraint violations during our migration to Storm. 
Generally we have fixed the order in which we made changes, but of 
course with lazy flushing there's no inherent guarantee that the 
ordering won't go bad again.

 * To maintain integrity of foreign-key relationships in early versions 
of Storm, which would sometimes get flush order wrong.

 * To suppress excessive flushing in security policy code.

So yes, get rid of these where possible; but bear in mind that they may 
be hiding performance problems as well as flush-ordering problems that 
tests may not expose.


Jeroen