[GNC] Import Matcher Comments and Questions

[David Cousens]

Dale, 

The assignment of an internal GnuCash account to an external account during
import has a couple of levels. If a transfer account is specified in the import
record, then the first time that account description is encountered the external
name has to be assigned to a specific internal GnuCash account. 

If there is no explicit specification of an account in the import record, then a
probabalistic (Bayesian) procedure tries to assign an account on the basis of
what information is present in the import record and how well it matches
information in reords where the second account was manually assigned during the
import of previous similar records. There is also an older non-Bayesian matching
procedure (Edit->Preferences->Import->use bayesian matching) which is optionally
available but is generally less successful at providing a good match than the
Bayesian procedure.

Where an account structure is changed, the Bayesian procedure will "remember"
any assignment made prior to the restructure as the probability tables it has
accumulated and used to make the assignment will only change very slowly as
records with assignments to the new account structure are made manually during
import. If you import records without manually changing the assigned account
during the import matching process and change the account assigned after import
in the register, the probability tables do not change at all as that data is
only stored during the final stage of the import procedure.

It is possible to edit the data on which the account assignment on import is
made using Tools->Import Map Editor but this requires some considerable
understanding of the import matching process to avoid changing the wrong data.
There is not a lot of guidance about how to do this however. There have been
some historical posts in the user list which may help if you search for them

Alternatively you can remove all the data used by the matching procedure and
retrain the matcher on subsequent imports but that is a drastic solution and
will affect all accounts that are matched on import not just the ones which
changed in the restructure.

David Cousens


On Sat, 2023-12-30 at 12:17 -0600, Dale Alspach wrote:
> Recently there was some restructuring of some of my retirement accounts
> (still under control of my former employer). This caused problems with
> importing because the parent accounts of the securities were altered.
> This led to a lot of questions from the importer. This entailed a tedious
> process of selecting the correct "new" account. One particular difficulty
> is that the same security may be used in more than one branch of the
> account tree. Fortunately the importer actually supplies some detailed
> information which greatly helps identify the correct branch.
> 
> 1. I discovered that the importer does not require uniqueness. That is,
> multiple accounts in the import file can be mapped to the same gnucash
> account. My accounting is strictly personal so the restructuring just meant
> creating an appropriate branch for each investment and reparenting the
> account. The nonuniqueness allowed me to point transactions corresponding
> to the old and new versions of the investment to the new one. *Thus for me
> the nonuniqueness is a desirable feature.*
> 
> 2. The account selection process seems to make some unwarranted assumptions
> that resulted in extra steps and in some cases a difficult to resolve
> ambiguity.
> i. After I selected one branch for a matching account, the importer kept
> suggesting that same branch for all subsequent selections. This resulted in
> extra steps to select the correct branch. It  would have been better for
> the importer to suggest the branch of the last selection and not the very
> first one.
> ii. The ambiguity arose when the importer asked what income account to
> associate with a security. In my setup, the assignment of any income
> attributable to an investment depends on which branch of the accounts this
> particular investment occurs. (taxable or not?, IRA, 403b, brokerage?) The
> name/symbol of the security does not uniquely determine the branch. What I
> needed was that more detailed information that appears when the account
> corresponding to the investment is selected.
> 
> Before I add a formal request for enhancement, I would be interested in
> knowing whether others have the same or similar concerns. I checked
> bugzilla and did not find anything.
> Dale
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