perl bindings to Xapian::Query

[Alex Aminoff]

On 9/12/2017 5:41 PM, Olly Betts wrote:
> On Tue, Sep 12, 2017 at 04:47:52PM -0400, Alex Aminoff wrote:
>>          my $filterepoch = time() - ($datefilter * 60 * 60 * 24);
>>          my $filterquery =
>> Xapian::Query->new(OP_VALUE_GE,I_DATE,$filterepoch);
> I think your issue here is that $filterepoch is a number rather than
> a string (a Perl scalar can have different representations internally).
> In t/valuerange.t this testcase works:
>
> | ok( $query = Xapian::Query->new(OP_VALUE_GE, 0, "two") );
>
> But if I change that "two" to 2 then I get the same error you report.
>
> While such sensitivity to the actual current representation of a scalar
> isn't very Perl-ish, it does actually indicate a problem with your code -
> OP_VALUE_GE performs a *string* >= (like Perl's own "ge"), so if you give it
> variable width integers (like the above would if $filterepoch were silently
> coerced to a string) then you won't in general get the correct filtering
> - for example, "100" < "99".
>
> I'd suggest formatting as a fixed width string value (left padded with
> zeros or spaces) or packing into a big-endian binary value (e.g.
> pack("N", $filterepoch)) or using Xapian::sortable_serialise().
Huh. I was even vaguely aware of this problem, but expected to work on 
that later, after I got the code working first - I was figuring I would 
quickly see problematic search results (as you say, "100" < "99" and 
similar) once it was running. I guess it would be nice if the error 
message was more of a pointer to the problem.

Xapian::Query has no perldoc. If I were to write some, and pass it in 
through a git pull request or some such mechanism, would that be helpful?

  - Alex

> Xapian::sortable_serialise() is particularly useful with floating
> point values, but even with integers it produces fairly compact output
> (much better than a fixed width string).
>
>> I should say that I am using xapian-bindings-1.4.4 which I compiled and
>> installed myself.
> In case you missed the warning in the README:
>
> | Perl            These Perl bindings are generated by SWIG, and are intended
> |                 to replace the hand-written Search::Xapian XS bindings.
> |                 The current API should be regarded as experimental - we plan
> |                 to review it, possibly make some changes and then declare it
> |                 stable early in the 1.4.x release series.  [...]
>
> Sadly I've still not found time to sort that out.
>
> If you're happy to potentially have to tweak your code, the SWIG-based
> Perl bindings in 1.4.x certainly aren't a bad choice.
>
> But if you prefer something that's got a stable API, then Search::Xapian
> 1.2.x should work with xapian-core 1.4.x (its main downside is that it
> doesn't wrap the C++ API as completely as the SWIG-based bindings do).
>
> Cheers,
>      Olly