Evergreen needs the ability for comparison of columns in in-db circ/holds

[Chris Sharp]

Currently Evergreen circ and hold rules do not include the ability to compare the values of fields in assessing whether a circ or hold is allowed or denied. This leads to a proliferation (using Bill's term from our IRC discussion) of hold and circ rules that say something like "if the user's home library is Branch A and the hold pickup library is Branch A, then allow the hold". In PINES's case, we have about a dozen rules based on circulation modifier that if we were to apply the logic in my example rule, it would have to be applied to all 54 of our systems.

12 "restricted" circ modifiers x 54 systems = 648 rules

Editing and maintaining such a complex rule set through upgrades, etc. creates a huge administrative burden.

I propose that we implement some bit of logic that allows for the creation of rules that can compare these values.

Example:

"if the user's home library is the same as the pickup library, allow the hold"

I won't attempt to propose how that implementation would happen in this initial request, but I hope others can chime in!

We had IRC discussion about this too: http://irc.evergreen-ils.org/evergreen/2013-10-21#i_41305