Am 10.11.19 um 22:39 schrieb John Ralls:

On Nov 10, 2019, at 12:07 PM, Christian Gruber <christian.gru...@posteo.de> 
wrote:


Am 08.11.19 um 23:08 schrieb John Ralls:
On Nov 8, 2019, at 1:58 PM, Christian Gruber <christian.gru...@posteo.de> wrote:

Am 08.11.19 um 04:39 schrieb John Ralls:
Christian,

It's not that it's not prepared for Bayesian matching, it's that older versions 
of GnuCash stored the Bayesian match tokens hierarchically. Aaron Laws (lmat) 
changed it to a flatter structure with somewhat better memory locality for 
faster access. imap_convert_bayes_to_flat should run once to convert the data 
and set the feature, after which check_import_map_data will see the flag and 
return. A file created with 3.x and Baysian maps would already have the feature 
set.


With that background, to your questions:

Why does it take so long? Because it traverses the entire tree of accounts, 
every time. The test book has 1127 accounts. Add to that that there are some 
things inside the loop that shouldn't be and that 
convert_imap_account_bayes_to_flat doesn't use some obvious short circuits and 
you get taking a long time.

Why does it run twice? Because there aren't any accounts with import-map-bayes 
slots, so it does no conversions so it doesn't set the feature.
Why isn't the feature set in any case after conversion is done, whether there 
was any slot to convert or not?

I would expect that, if the hierarchical structure should not be used anymore. 
I wouldn't only set the feature, if there has been any error during conversion. 
But it's not an error, if convert_imap_account_bayes_to_flat() returns false.
The feature isn't set because that would prevent using the file with an older 
version of GnuCash for no good reason: There aren't any import-map-bayes tags 
in the new format so there's nothing for the older version to mess up.

Regards,
John Ralls

Sounds meaningful, but it's not obvious. The conversion process is not much 
transparent to the user. The user is not informed about conversion and 
additionally the conditions, when the GnuCash file is converted and when not, 
are not quite intuitive, I guess. And the second question for me is, if this is 
really a relevant use case to keep the GnuCash file unconverted if possible, 
when it is used with a newer GnuCash version. Maybe it's relevant, if several 
people, who use different GnuCash versions work on the same GnuCash file. But 
what happens, when one with a newer GnuCash version uses the bayesian import 
matcher for the first time, which silently converts the GnuCash file? Will it 
still be usable with an older GnuCash version?

But actually this is another discussion, which is not important for the bug 
ticket. What's more important, I created a new fresh GnuCash file with the 
SKR04 accounts template using my GnuCash version 3.7 and if I checked this 
correctly, even with this GnuCash version the feature 
GNC_FEATURE_GUID_FLAT_BAYESIAN is not set in the GnuCash file. Can you confirm 
this? If yes, then the bug report is relevant not only for migration from older 
to current GnuCash versions but even for current GnuCash versions in general.
No, it's the same discussion. If you don't use the feature then the flag for it 
won't be set. That's how we designed the feature mechanism. The use case is 
straightforward: Some user has two computers, a laptop running Windows and a 
desktop running Ubuntu 16.04. She updates the Windows machine with each release 
but doesn't know how to build GnuCash on her Ubuntu machine so leaves it at 
whatever they shipped on 16.04; 2.6.12 IIRC. As long as she doesn't use any of 
the features supported only in 3.x she can continue to use both systems to keep 
her books and regardless of which machine she uses to create a book.

The "silently" part could be better. It would indeed be a nice enhancement to 
pop a dialog box when GnuCash is about to set a feature flag explaining that it's use 
will preclude using the file on a GnuCash version older than X and giving the user a 
chance to bail out. It would be nicer still to persist that decision so that it need ask 
only once, and if the user assents it could set the feature flag even if the feature 
isn't used, as is the case here. Of course there would then be the need to reset negative 
responses so that when our hypothetical user upgrades her desktop to Ubuntu 20.04 next 
spring she can turn on all of those 3.x only features she'd previously declined.

It occurs to me that another improvement to the existing flat Bayesian 
conversion would be to check the state of the GNC_PREF_USE_BAYES and skip the 
conversion if it's not true.
This is already implemented. Flag GNC_PREF_USE_BAYES is checked in functions matchmap_find_destination() and matchmap_store_destination() and if not set, than functions gnc_account_imap_find_account_bayes() and gnc_account_imap_add_account_bayes() aren't invoked and no conversion will be done.

Regards,
John Ralls

Thanks for the revealing explanation of the feature mechanism. In this case it would be really helpful, if GnuCash would explain itself and interact with the user, when features are changed and conversions are done, which are not backwards compatible. Moreover it would be meaningful, if the user could "enable/disable" backwards compatibility when creating a new GnuCash file to avoid such extensive conversion steps. This means, that all supported features of the used GnuCash version are set by default during creation. Alternatively, if it's possible to significantly speed up searching for (non-existing) bayesian match tokens, this should be preferred.

I'll create an enhancement ticket.

Regards,
Christian


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