It's been a holiday here in the UK, hence the delay, but thank you for your far
more prompt response.
It makes sense that the filter is removing the punctuation-only term, and that
it only looks odd when alongside the original with preserveOriginal=true.
Fortunately it was just a curio that came up while I was testing a downstream
(and typically flaky) custom filter I'm working on that gets it's own
positional increments in a twist, otherwise I don't think I'd have noticed it.
We don't - or shouldn't - actually send punctuation-only tokens, so its not
really a production concern.
Thanks for the reminder about FlattenGraphFilterFactory too btw.
-Original Message-
From: Shawn Heisey [mailto:apa...@elyograg.org]
Sent: 29 March 2018 22:59
To: solr-user@lucene.apache.org
Subject: Re: WordDelimiterGraphFilter expected behaviour ?
On 3/29/2018 1:48 PM, Kelvyn Scrupps wrote:
> I'm using WordDelimiterGraphFilter on a field and came across a curious
> additional positional "hole" generated by the filter while playing with the
> analysis tool.
> For input "wibble , wobble" (space either side of the comma so it's a
> separate token), the output introduces an additional positional hole after
> the comma, i.e.
>
> Term position
> Wibble 1
> , 2
> Wobble 4 *
>
> The positionlength for each is 1, so no obvious graph-span going on.
>
> Its not just comma, any punctuation would do, e.g. "wibble ! wobble"
The wrinkle here is enabling preserveOriginal at the same time that you have a
term which is completely removed by the filter (in this case, the comma). If
preserveOriginal is disabled, they both behave the same. I don't know if this
is a bug or not. My instinct is to say it's a bug, but it's possible that this
is expected.
Having a term that's just a punctuation character in the index is generally not
very useful ... but there are OTHER situations with this filter where
preserveOriginal *is* the behavior you want. I would imagine that as long as
you don't have terms that completely disappear when the filter runs, it would
behave correctly. Try replacing the ","
with "x," to see what I mean.
Also, FYI, when using a Graph filter, the index analysis chain must also have
this filter (but not the query analysis):
Adding that didn't seem to fix the behavior that concerns you, but the docs do
say it's required on the index analysis whenever using a Graph filter.
Thanks,
Shawn
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