[Xapian-tickets] [Xapian] #677: OP_WILDCARD with multidb (was: OP_WILDCARD and OP_ELITE_SET with multidb)

[Xapian]

#677: OP_WILDCARD with multidb
-------------------------+------------------------------
 Reporter:  olly         |             Owner:  olly
     Type:  defect       |            Status:  new
 Priority:  normal       |         Milestone:  1.4.x
Component:  Library API  |           Version:  SVN trunk
 Severity:  normal       |        Resolution:
 Keywords:               |        Blocked By:
 Blocking:               |  Operating System:  All
-------------------------+------------------------------
Changes (by olly):

 * milestone:  1.3.x => 1.4.x


Old description:

> Currently the limits for both of these are applied separately for each
> subdatabase in the multidatabase case - really they should both work the
> same as for a single database containing the same documents as all the
> subdatabases.
>
> `OP_ELITE_SET` and `QueryParser`'s wildcard expansion limits do work that
> way in 1.2.x, so this seems like it ought to be fixed before 1.4.0.

New description:

 Currently the limits ~~~for both of these~~~ are applied separately for
 each subdatabase in the multidatabase case - really they should both work
 the same as for a single database containing the same documents as all the
 subdatabases.

 ~~~`OP_ELITE_SET` and~~~ `QueryParser`'s wildcard expansion limits do work
 that way in 1.2.x, so this seems like it ought to be fixed before 1.4.0.

--

Comment:

 Turns out `OP_ELITE_SET` is easy to fix - we just remove the special case
 check for `termfreq_max()` being zero!  That's done in
 [6f3ff69b87bf50390c09c4f0f31740857c241109].

 The fix for `OP_WILDCARD` is unfortunately not just a matter of deleting a
 couple of lines of code.

 The reason for the wildcard limits is to improve performance so we want
 the implementation to be efficient, and perhaps that's more important than
 it being exact.  Care is certainly needed to make sure any fix isn't a lot
 slower.

 As I noted in the description, 1,2's `QueryParser` wildcard expansion
 limits work differently, but the current behaviour isn't entirely
 unreasonable, and `OP_WILDCARD` and these limits are new features.

 So I think for 1.4.0 we document what currently happens, and note that
 these details may change - done in
 [a6cbcf9ee8c091adef1547571ac502f8c78343c2].

--
Ticket URL: <http://trac.xapian.org/ticket/677#comment:2>
Xapian <http://xapian.org/>
Xapian