GDA: Status

[Phil Longstaff]

I'll leave the specific detail of "CREATE IF NOT EXIST" aside.

I think gda is a general solution that will allow us to meet the
requirement of supporting sqlite, mysql and postgresql.  Gnucash is
currently at 2.2.5 moving towards 2.4.  If I could work full time on it,
the gda backend might be fully integrated into gc in 3 months.  Given I
only have evenings and weekends (if that), make it 6-9 months.

Re dropping GDA: rather than drop it, I think it would be better to pull
it into the tree.  That would at least give us the assurance that
everyone who wants to use the gda backend has a consistent set of fixes
and functionality.

Phil

Derek Atkins wrote:
> Can't you just use "CREATE IF NOT EXIST" ?  Or is that not portable enough
> across various SQL implementations?
> 
> Part of me is really thinking that GDA is more trouble than it's worth.
> I'm sure Esodan will vociferously argue against this, but perhaps we
> should drop GDA and choose something that actually works?
> 
> -derek
> 
> Quoting Phil Longstaff <plongstaff at rogers.com>:
> 
>> Graham Leggett wrote:
>>> Phil Longstaff wrote:
>>>
>>>> Well, V4 basically works with the sqlite provider.  There were a number
>>>> of memory leaks and other small issues.  However, there are a number of
>>>> problems with the V4 mysql provider - it's not ready for use.
>>>>
>>>> I've decided to switch back to V3 for now.  I'll continue to supply
>>>> patches and if I have to, I'll pull it into the tree under 'lib'.
>>>
>>> Considering that V3 is not being actively developed, and that bugfixes
>>> to v3 won't be accepted, is it not safer to develop for V4, and get the
>>> upstream project to fix any problems involved? How far away is the V4
>>> mysql provider?
>>
>>
>> I don't know how far away the V4 provider is.  They have a
>> meta-information system which allows you to access info about the db
>> structure (e.g. which tables exist) and the meta-information system has
>> been redesigned for V4.  It hasn't been implemented for mysql yet, so
>> when gc starts, it tries to create all of the tables, even if they
>> already exist.  Note that it was a meta-information bug which was
>> causing a problem in the gc-V3 code which was not accepted.  The bug is
>> that if you delete all db tables and then ask libgda to update the
>> meta-information, it still thinks that the 2nd table exists (usually,
>> billterms) so that it won't be created.  This could happen when you are
>> trying to save-as to a db, so billterms won't be saved, and lots of
>> business objects will be screwed up.
>>
>> I see 3 possibilities:
>> 1) Do libgda V3 maintenance ourselves by sending in patches and asking
>> for them to be applied.  For the particular bug I found, I didn't send
>> in a patch, but asked for the bug to be fixed.  Maybe they won't fix
>> bugs but will apply patches.  They would probably not create new
>> tarballs, so anyone who wanted to use gc-libgda would need to check out
>> the V3 trunk from svn and build from source.
>> 2) Pull the libgda-V3 branch into the gc tree under lib.  The GC team
>> would maintain it.  This has the advantage that it would not be an
>> external dependency any longer, so anyone who wanted to try the gda
>> backend could.  The obvious disadvantage is a mess of code that nobody
>> knows but that we need to maintain.  Once libgda-V4 is further along, I
>> can switch back to V4.
>> 3) Change my decision and switch back to V4.  I have basic operation
>> with sqlite working.  There is at least 1 regression (I can't create the
>> index on the slots table) which would have performance implications.  I
>> don't know where the problem with index creation is.  However, there are
>> some improvements.  The libgda-V4 statement structures can represent SQL
>> operations which were not possible in V3, and which would improve
>> performance.  However, as I said above, the mysql provider is missing
>> some major functionality.  I don't know about postgresql.
>>
>> There are other issues with the whole gda backend which I need to work
>> on and which are independent of which version of libgda is used:
>> 1) some of the dialogs (e.g. price editor) create an object when the
>> dialog is opened and then modify it as the dialog is used.  This can
>> cause commit requests for objects which break db constraints (a price
>> must have a commodity, but a save request may come before the commodity
>> is set).  Fixing this requires a change to db logic to only create the
>> object when 'OK' is pressed.
>> 2) versions for tables and handling of version updates
>>
>> I had decided to stay with V3 because it would not be a step backwards
>> in functionality.  I wanted to try V4 to see what shape it was in, to
>> get some experience with it, and to provide some feedback to the
>> developers before they release.
>>
>> I think I'll stay with V3 for now and monitor V4.  When they implement
>> the V4 mysql meta-info code, I'll reconsider switching.  I'll also do a
>> bit of testing to see how postgresql looks.
>>
>> Phil
>>
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> 
> 
>