Hello there,
in my code, there is a number of “derived relationships”, defined by Java code
at the EO class level. It works well for years, but now (as part of the “import
another application's database” task I am working on) I would need to move the
behaviour to the model level, so that I can fetch the data as raw rows into
another, essentially unrelated application.
For example, in my application Auction.woa, there is a DBAuction entity; in its
code, there is (essentially) this derived relationship:
===
DBUser auctionOwner() {
for (DBUserAccess ua in userAccess()) // userAccess is a 1:N relationship
from this to DBUserAccess
if (ua.accessAllowed()) { // accessAllowed is a boolean attribute of
DBUserAccess
DBUser user=ua.user() // user is an N:1 relationship from DBUserAccess to
DBUser
if (user.userType()%1000==USER_TYPE_OWNER) // userType is an integer
attribute of DBUser; USER_TYPE_OWNER a constant
return user
}
return null
}
===
Now, the problem is that I would need to fetch data _as raw rows_ through this
relationship into _another application_, say, AuctionImporter.woa, where none
of the entities exist. (Even if I copied the entities there, it would not help
with fetching raw rows.)
For modelled attributes and relationships I have solved the problem by creating
a copy of the Auction model in my AuctionImporter.woa application, having
turned all the model classes to EOGenericRecords. That allows me to fetch raw
rows based on all modelled attributes (and flattened attributes through
modelled :1 relationships) all right: done, tested, works like a charm.
Now, though, I bumped into a need to fetch raw rows based on these complex
“derived” relationships; e.g., I would need to be able to do in
AuctionImporter.woa something like
===
def fs=new EOFetchSpecification("DBAuction",null,null) // DBAuction entity from
the copy of the original model
fs.fetchesRawRows=YES
fs.rawRowKeyPaths=['auctionOwner_login', ... normal modelled (potentially
flattened) attribs, no problem with them ...]
def result=new ERXEC().objectsWithFetchSpecification(fs)
===
Is there a trick to define at the model level a “derived relationship“
auctionOwner, simulating somehow the behaviour described above, through which I
then would be able to flatten the desired attribute (with a definition
"auctionOwner.login")?
If this is not possible, it seems to me I would have to generate the complete
fetch SQL myself, essentially without any help of EOF, and then fetch using
EOUtilities.rawRowsForSQL. Ick. That can get pretty complex pretty quickly[*],
and thus I would rather like to dodge it, if possible. Can you see any easier
way to do this?
Thanks for any advice,
OC
[*] Originally, I have considered it for attributes flattened through modelled
relationships, too. It quickly proved _much_ easier to add appropriate
flattened attributes to the model (syncing appropriately to make sure model
never gets changed by one thread and accessed by another at the same time), and
let EOF to generate the SQL for me :)
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