Michael and Forum,-
Thanks for thegreat explanations.
one question please:
why is PrefixQuery used instead of WildCardQuery in the below snippet?
Best regards
> On Feb 17, 2020, at 3:01 PM, Michael Froh <msf...@gmail.com> wrote:
>
> Hi Baris,
>
> The idea with PhraseWildcardQuery is that you can mix literal "exact" terms
> with "MultiTerms" (i.e. any subclass of MultiTermQuery). Using addTerm is
> for exact terms, while addMultiTerm is for things that may match a number
> of possible terms in the given position.
>
> If you want to search for term1 followed by any term that starts with a
> given character, I would suggest using:
>
> int maxMultiTermExpansions = ...; // Discussed below
> PhraseWildCardQuery.Builder builder = new PhraseWildcardQuery("field",
> maxMultiTermExpansions);
> builder.addTerm(new BytesRef("term1")); // Add fixed term in position 0
> builder.addMultiTerm(new PrefixQuery(new Term("field", "term2FirstChar")));
> // Add multiterm in position 1
> Query q = builder.build();
>
> The PrefixQuery effectively gets expanded into a bunch of possible terms,
> based on the term dictionary on each index segment. To avoid expanding to
> cover too many terms (say, if you added a bunch of WildcardQuery),
> maxMultiTermExpansions serves as a guard rail, to put a rough bound on
> memory consumption and query execution time. If you're interested in
> details of how the maxMultiTermExpansions budget is distributed across
> MultiTerms, check out PhraseWildcardQuery.createWeight. If you're just
> running an experiment in your IDE, you could probably set
> maxMultiTermExpansions to Integer.MAX_VALUE. (If you're running in a
> production environment, it's likely a good idea to tune it down based on
> your memory/latency constraints.)
>
> Incidentally, for tracking down the source code for anything in Lucene,
> it's probably better to go to GitHub for the most up-to-date source:
> https://urldefense.com/v3/__https://github.com/apache/lucene-solr/blob/master/lucene/sandbox/src/java/org/apache/lucene/search/PhraseWildcardQuery.java__;!!GqivPVa7Brio!ONqQgLIltNBUuSo5Cn_Fz7-wuR1LQv68YS_z-6g7X-S86PHQtT9tKl7VbIq9tVLYyw$
>
> .
>
> Hope that helps,
> Michael
>
>> On Thu, 13 Feb 2020 at 12:29, <baris.ka...@oracle.com> wrote:
>>
>> Hi,-
>>
>> i hope everyone is doing great.
>>
>> if i want to do the following search with PhraseWildCardQuery and
>> thanks to this forum for letting me know about this class (Especially to
>> David and Bruno)
>>
>> term1 term2FirstChar*
>>
>> i need to do two ways: (i found the source code at
>>
>> https://urldefense.com/v3/__https://fossies.org/linux/lucene/sandbox/src/java/org/apache/lucene/search/PhraseWildcardQuery.java__;!!GqivPVa7Brio!ONqQgLIltNBUuSo5Cn_Fz7-wuR1LQv68YS_z-6g7X-S86PHQtT9tKl7VbIpV8n29nQ$
>>
>> )
>>
>> /*
>>
>> maxMultiTermExpansions - The maximum number of expansions across all
>> multi-terms and across all segments. It counts expansions for each
>> segments individually, that allows optimizations per segment and unused
>> expansions are credited to next segments. This is different from
>> MultiPhraseQuery and SpanMultiTermQueryWrapper which have an expansion
>> limit per multi-term.
>>
>> segmentOptimizationEnabled - Whether to enable the segment optimization
>> which consists in ignoring a segment for further analysis as soon as a
>> term is not present inside it. This optimizes the query execution
>> performance but changes the scoring. The result ranking is preserved.
>>
>> */
>>
>>
>> 1st way:
>>
>> PhraseWildCardQuery.Builder builder = PharseWildCardQuery.Builder(field,
>> 2 _*/<<< i dont know what number to use here for
>> maxMultiTermExpansions>>>/*_, true/*boolean segmentOptimizationEnabled*/)
>>
>> pwcqBuilder.addTerm(field, new Term(field, "term1"));
>>
>> pwcqBuilder.addTerm(field,new Term(field, "term2FirstChar"));
>>
>> PhraseWildCardQuery pwcq = pwcqBuilder.build();
>>
>> or
>>
>> 2nd way:
>>
>> pwcqBuilder.addMultiTerm(MultiTermQuery object here contaning {field,
>> "term1"} and {field ,"term2FirstChar"});
>>
>> PhraseWildCardQuery pwcq = pwcqBuilder.build();
>>
>>
>> Then this pwcq object will be fed into IndexSearcher's as the query
>> parameter.
>>
>>
>> Now, it looks like the first way will not consider expansions or in
>> other words wildcard? Am i right?
>>
>> i also need to understand this maxMultiTermExpansions parameter better.
>> For instance if first way is used, will maxMultiTermExpansions be
>> meaningful?
>>
>>
>> Thanks
>>
>>
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