Thanks Alan, I agree we should open an issue and iterate.

Mike McCandless

http://blog.mikemccandless.com


On Wed, Jan 11, 2017 at 5:41 AM, Alan Woodward <a...@flax.co.uk> wrote:
> The problem here is mainly with the Sorted*DocValues APIs, which return a
> TermsEnum but don’t have a Terms instance to call intersect on.  So maybe
> the thing to do is to add a termsEnum(CompiledAutomaton) method to
> SortedDocValue and SortedSetDocValues?  That should avoid the trap of
> bypassing Terms.intersect() when it’s available.  I’ll try and work up a
> patch.
>
> Alan Woodward
> www.flax.co.uk
>
>
> On 6 Jan 2017, at 21:44, Michael McCandless <luc...@mikemccandless.com>
> wrote:
>
> Unfortunately I think that's somewhat dangerous because it creates an
> ambiguous API with a nasty performance trap?
>
> I.e. this new method won't invoke the fast Terms.intersect in the
> default terms dict?
>
> Mike McCandless
>
> http://blog.mikemccandless.com
>
>
> On Fri, Jan 6, 2017 at 3:20 PM, Alan Woodward <a...@flax.co.uk> wrote:
>
> Hm, how about something like this, on CompiledAutomaton:
>
> public TermsEnum getTermsEnum(TermsEnum te) throws IOException {
>  switch (type) {
>    case NONE:
>      return TermsEnum.EMPTY;
>    case ALL:
>      return te;
>    case SINGLE:
>      return new SingleTermsEnum(te, term);
>    case NORMAL:
>      return new AutomatonTermsEnum(te, this);
>    default:
>      // unreachable
>      throw new RuntimeException("unhandled case");
>  }
> }
>
>
> Alan Woodward
> www.flax.co.uk
>
>
> On 6 Jan 2017, at 19:16, Michael McCandless <luc...@mikemccandless.com>
> wrote:
>
> These automaton intersection APIs are frustrating with all the special
> case handling... Ideas welcome!
>
> We've had similar challenges with them in the past, when a user
> invoked Terms.intersect directly instead of via CompiledAutomaton:
> https://issues.apache.org/jira/browse/LUCENE-7576
>
> The problem is CompiledAutomaton specializes certain cases (all
> strings match, no strings match, single term) and sidesteps
> Terms.intersect for those cases.
>
> We should fix AutomatonTermsEnum public ctor w/ the same checks
> (insist on a NORMAL case) so you don't hit assert failures, or, worse
> ... I'll do that.
>
> I think a new CompiledAutomaton.intersect taking TermsEnum would be
> tricky in general because it relies on the (efficient) Terms.intersect
> to handle the NORMAL case well, but we can't invoke that from a
> TermsEnum.
>
> In the SINGLE case, could you use SingleTermsEnum, passing the
> TermsEnum from your doc values, and the term from the
> CompiledAutomaton?  Would that suffice as a workaround?
>
> Mike McCandless
>
> http://blog.mikemccandless.com
>
> On Fri, Jan 6, 2017 at 11:17 AM, Alan Woodward <a...@flax.co.uk> wrote:
>
> We’ve hit an issue while developing marple, where we want to have the
> ability to filter the values from a SortedDocValues terms dictionary.
> Normally you’d create a CompiledAutomaton from the filter string, and then
> call #getTermsEnum(Terms) on it; but for docvalues, we don’t have a Terms
> instance, we instead have a TermsEnum.
>
> Using AutomatonTermsEnum to wrap the TermsEnum works in most cases here, but
> if the CompiledAutomaton in question is a fixed string, then we get
> assertion failures, because ATE uses the  compiled automaton’s internal
> ByteRunAutomaton for filtering, and fixed-string automata don’t have one.
>
> Is there a work-around that I’m missing here?  Or should I maybe open a JIRA
> to add a #getTermsEnum(TermsEnum) method to CompiledAutomaton?
>
> Alan Woodward
> www.flax.co.uk
>
>
>
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