[
https://issues.apache.org/jira/browse/LUCENE-7276?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15318332#comment-15318332
]
Michael McCandless commented on LUCENE-7276:
--------------------------------------------
I'm going to break this up into separate steps ... the current patch combines
too many things: changing {{MatchNoDocsQuery.toString}}, adding a reason to it,
changing it to return its own {{Weight}} instead of rewriting to BQ, changing
BQ to rewrite to it when there are no clauses.
I'll start by fixing {{MatchNoDocsQuery.toString()}} to simply return
"MatchNoDocsQuery". But even that small change is not easy: it is something of
a break in our normal policy for a {{Query.toString}} in that today queries try
to have a {{.toString}} which when sent back through a query parser would parse
back to an equivalent query instance. E.g., a {{PhraseQuery}} instance's
{{toString}} would be {{"foo bar"}}, which most query parsers would parse back
into an equivalent query.
The Python world handles this situation nicely, by having two separate
functions: {{repr}} makes a string which when eval'd (parsed and executed by
Python) turns back into the same object, whereas {{str}} makes a pretty thing
that humans can understand. But Lucene has no such separation ... and our
{{Query.toString}} is more like {{repr}} now.
Is anyone besides me worried about this? Do we have other queries that return
a "human but not query-parser consumable" string?
> Add an optional reason to the MatchNoDocsQuery
> ----------------------------------------------
>
> Key: LUCENE-7276
> URL: https://issues.apache.org/jira/browse/LUCENE-7276
> Project: Lucene - Core
> Issue Type: Improvement
> Components: core/search
> Reporter: Ferenczi Jim
> Priority: Minor
> Labels: patch
> Attachments: LUCENE-7276.patch, LUCENE-7276.patch, LUCENE-7276.patch,
> LUCENE-7276.patch
>
>
> It's sometimes difficult to debug a query that results in a MatchNoDocsQuery.
> The MatchNoDocsQuery is always rewritten in an empty boolean query.
> This patch adds an optional reason and implements a weight in order to keep
> track of the reason why the query did not match any document. The reason is
> printed on toString and when an explanation for noMatch is asked.
> For instance the query:
> new MatchNoDocsQuery("Field not found").toString()
> => 'MatchNoDocsQuery["field 'title' not found"]'
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
