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https://issues.apache.org/jira/browse/LUCENE-1418?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12647446#action_12647446
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Mark Miller commented on LUCENE-1418:
-------------------------------------
bq. And this is also wrong because Lucene query parser syntax allows for
queries without explicit field specification (i.e. "cat AND dog" is a valid
query). From the current docs it is not obvious how to properly construct a
query parser that will correctly parse such queries, not clear what should be
passed as a field in a QueryParser constructor because there is no any
particular field, the same query parser instance is used to parse queries for
different fields. If I'll pass not null and not empty string then AFAIR instead
of "+cat + dog" I'll get as a result "+field:cat +field:doc" and this is not
acceptable as this will cause a creation of a separate query parser instance
for each field - a real overkill I'd say.
Hmmm...it was my understanding that QueryParser supports "cat AND dog" by
allowing you to enter a default field to use, not by letting NULL be any field
or the "" field. If you want each term to match the "" field, I would recommend
thats what you pass as the default field to use. You are doing two things here
- one, you are supplying a default field to use when the query syntax doesn't
contain one, and two, you are supplying the query syntax. I don't see how
passing null to the method as the default field is a parse error - supplying
the field and parsing the query are two distinct pieces.
bq. 1) it should be documented how should be created "fieldless" query parser:
that empty string should be used as a field name, that null is unsupported and
can give undefined results (alternative is to fix this problem with
NullPointerException and document that both ways are supported - null and empty
string);
I don't believe a 'fieldless' query parser is supported...I may be missing
something though...
bq. 2) currently there is no way to use the same query parser instance for
parsing queries for the different fields (except set default field to empty
string and manually add "field:" prefix to each query before parsing).
I think this is by design...perhaps a patch will change peoples minds though...
I think checking for null and throwing an error makes sense, but I'm not
understanding the other changes. Perhaps a patch will help move the issue
forward.
> QueryParser can throw NullPointerException during parsing of some queries in
> case if default field passed to constructor is null
> --------------------------------------------------------------------------------------------------------------------------------
>
> Key: LUCENE-1418
> URL: https://issues.apache.org/jira/browse/LUCENE-1418
> Project: Lucene - Java
> Issue Type: Bug
> Components: QueryParser
> Affects Versions: 2.4
> Environment: CentOS 5.2 (probably any applies)
> Reporter: Alexei Dets
> Priority: Minor
>
> In case if QueryParser was constructed using "QueryParser(String f, Analyzer
> a)" constructor and f equals null then QueryParser can fail with
> NullPointerException during parsing of some queries that _does_ contain field
> name but have unbalanced parenthesis.
> Example 1:
> Query: field:(expr1) expr2)
> Result:
> java.lang.NullPointerException
> at org.apache.lucene.index.Term.<init>(Term.java:50)
> at org.apache.lucene.index.Term.<init>(Term.java:36)
> at
> org.apache.lucene.queryParser.QueryParser.getFieldQuery(QueryParser.java:543)
> at org.apache.lucene.queryParser.QueryParser.Term(QueryParser.java:1324)
> at
> org.apache.lucene.queryParser.QueryParser.Clause(QueryParser.java:1211)
> at
> org.apache.lucene.queryParser.QueryParser.Query(QueryParser.java:1168)
> at
> org.apache.lucene.queryParser.QueryParser.TopLevelQuery(QueryParser.java:1128)
> at org.apache.lucene.queryParser.QueryParser.parse(QueryParser.java:170)
> Example2:
> Query: field:(expr1) "expr2")
> Result:
> java.lang.NullPointerException
> at org.apache.lucene.index.Term.<init>(Term.java:50)
> at org.apache.lucene.index.Term.<init>(Term.java:36)
> at
> org.apache.lucene.queryParser.QueryParser.getFieldQuery(QueryParser.java:543)
> at
> org.apache.lucene.queryParser.QueryParser.getFieldQuery(QueryParser.java:612)
> at org.apache.lucene.queryParser.QueryParser.Term(QueryParser.java:1459)
> at
> org.apache.lucene.queryParser.QueryParser.Clause(QueryParser.java:1211)
> at
> org.apache.lucene.queryParser.QueryParser.Query(QueryParser.java:1168)
> at
> org.apache.lucene.queryParser.QueryParser.TopLevelQuery(QueryParser.java:1128)
> at org.apache.lucene.queryParser.QueryParser.parse(QueryParser.java:170)
> Workaround: pass in constructor empty string as a default field name - in
> this case QueryParser.parse method will throw ParseException (expected result
> because query string is wrong) instead of NullPointerException.
> It is not obvious to me how to fix this so I'll describe my usecase, may be
> I'm doing something completely wrong.
> Basically I have a set of per-field queries entered by user and need to
> programmatically construct (after some preprocessing) one real Lucene query
> combined from these user-entered per-field subqueries.
> To achieve this I basically do the following (simplified a bit):
> QueryParser parser = new QueryParser(null, analyzer); // I'll always provide
> a field name in a query string as it is different each time and I don't have
> any default
> BooleanQuery query = new BooleanQuery();
> Query subQuery1 = parser.parse(field1 + ":(" + queryString1 + ')');
> query.add(subQuery1, operator1); // operator = BooleanClause.Occur.MUST,
> BooleanClause.Occur.MUST_NOT or BooleanClause.Occur.SHOULD
> Query subQuery2 = parser.parse(field2 + ":(" + queryString2 + ')');
> query.add(subQuery2, operator2);
> Query subQuery3 = parser.parse(field3 + ":(" + queryString3 + ')');
> query.add(subQuery3, operator3);
> ...
> IMHO either QueryParser constructor should be changed to throw
> NullPointerException/InvalidArgumentException in case of null field passed
> (and API documentation updated) or QueryParser.parse behavior should be fixed
> to correctly throw ParseException instead of NullPointerException. Also IMHO
> of a great help can be _public_ setField/getField methods of QueryParser
> (that set/get field), this can help in use cases like my:
> QueryParser parser = new QueryParser(null, analyzer); // or add constructor
> with analyzer _only_ for such cases
> BooleanQuery query = new BooleanQuery();
> parser.setField(field1);
> Query subQuery1 = parser.parse(queryString1);
> query.add(subQuery1, operator1);
> parser.setField(field2);
> Query subQuery2 = parser.parse(queryString2);
> query.add(subQuery2, operator2);
> ...
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