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https://issues.apache.org/jira/browse/SOLR-5093?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13724446#comment-13724446
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Hoss Man commented on SOLR-5093:
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I can see the argument for making "field:*" parse as equivalent to "field:[* TO
*]" if the later is in fact more efficient, but i agree with rob that we
shouldn't try make the parser pull out individual clauses and construct special
query objects that are baked by the filterCache. If i have an fq in my
solrconfig that looks like this...
{noformat}
<str name="fq">X AND Y AND Z</str>
{noformat}
...that entire BooleanQuery should be cached as a single entity in the
filterCache regardless of what X, Y, and Z really are -- because that's what i
asked for: a single filter query.
it would suck if the Query Parser looked at the specifics of what each of those
clauses are and said "I'm going to try and be smart and make each of these
clauses be special query backed by the filterCache" because now i have 4
queries in my filterCache instead of just 1, and 3 of them will never be used.
> Rewrite field:* to use the filter cache
> ---------------------------------------
>
> Key: SOLR-5093
> URL: https://issues.apache.org/jira/browse/SOLR-5093
> Project: Solr
> Issue Type: New Feature
> Components: query parsers
> Reporter: David Smiley
>
> Sometimes people writes a query including something like {{field:*}} which
> matches all documents that have an indexed value in that field. That can be
> particularly expensive for tokenized text, numeric, and spatial fields. The
> expert advise is to index a separate boolean field that is used in place of
> these query clauses, but that's annoying to do and it can take users a while
> to realize that's what they need to do.
> I propose that Solr's query parser rewrite such queries to return a query
> backed by Solr's filter cache. The underlying query happens once (and it's
> slow this time) and then it's cached after which it's super-fast to reuse.
> Unfortunately Solr's filter cache is currently index global, not per-segment;
> that's being handled in a separate issue.
> Related to this, it may be worth considering if Solr should behind the scenes
> index a field that records which fields have indexed values, and then it
> could use this indexed data to power these queries so they are always fast to
> execute. Likewise, {{\[\* TO \*\]}} open-ended range queries could similarly
> use this.
> For an example of how a user bumped into this, see:
> http://lucene.472066.n3.nabble.com/Performance-question-on-Spatial-Search-tt4081150.html
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