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From "Adriano Crestani (JIRA)" <>
Subject [jira] Updated: (LUCENE-1567) New flexible query parser
Date Tue, 14 Jul 2009 00:24:14 GMT


Adriano Crestani updated LUCENE-1567:

    Attachment: lucene_1567_adriano_crestani_07_13_2009.patch

Hey guys,

Here is a patch containing some changes I did on top of last Luis' patch ( 	lucene_trunk_FlexQueryParser_2009July10_v5.patch):

- javadoc reviewed and improved

- 2 new classes: QueryParserHelper and LuceneQueryParserHelper, they make it easier to use
the new query parser

- added the ability to set the prefix length for fuzzy queries, it was still missing in the
new query parser

- resolved some TODOs

- AnalyzerQueryNodeProcessor is now using only the new TokenStream it required to
be compatible with the old API even if it is in contrib?

- I duplicated the test cases so they run using the query parser API directly, the query parser
helpers and the query parser wrappers, this way we test the three ways the user can actually
use the query parser.

I think that is everything. I will keep reviewing and improving the documentation, I think
there might be some broken javadoc links yet.

I also would like to rename the package and everythiing else that does reference to "lucene2"
to "lucene". I think it does not make sense to have a package name tied to a version. So,
the package org.apache.lucene.queryParser.lucene2 would be renamed to org.apache.lucene.queryParser.lucene.
I know it's kind of weird, because there are 2 "lucene" in the package declararion, but I
think it's better than "lucene2". Anyway, suggestions about this are welcome :) ... if nobody
replies I will feel free to rename it and submit a new patch soon.

I will also work on writing a documentation for Lucene wiki that explains how to easily migrate
from the old query parser to the new one, but I will only add it to the wiki when the code
is committed to the trunk, it doesn't make sense a wiki documentation about something that
is not even committed, agreed?


Adriano Crestani Campos

> New flexible query parser
> -------------------------
>                 Key: LUCENE-1567
>                 URL:
>             Project: Lucene - Java
>          Issue Type: New Feature
>          Components: QueryParser
>         Environment: N/A
>            Reporter: Luis Alves
>            Assignee: Grant Ingersoll
>         Attachments: lucene_1567_adriano_crestani_07_13_2009.patch, lucene_trunk_FlexQueryParser_2009July09_v4.patch,
lucene_trunk_FlexQueryParser_2009July10_v5.patch, lucene_trunk_FlexQueryParser_2009March24.patch,
lucene_trunk_FlexQueryParser_2009March26_v3.patch, new_query_parser_src.tar, QueryParser_restructure_meetup_june2009_v2.pdf
> From "New flexible query parser" thread by Micheal Busch
> in my team at IBM we have used a different query parser than Lucene's in
> our products for quite a while. Recently we spent a significant amount
> of time in refactoring the code and designing a very generic
> architecture, so that this query parser can be easily used for different
> products with varying query syntaxes.
> This work was originally driven by Andreas Neumann (who, however, left
> our team); most of the code was written by Luis Alves, who has been a
> bit active in Lucene in the past, and Adriano Campos, who joined our
> team at IBM half a year ago. Adriano is Apache committer and PMC member
> on the Tuscany project and getting familiar with Lucene now too.
> We think this code is much more flexible and extensible than the current
> Lucene query parser, and would therefore like to contribute it to
> Lucene. I'd like to give a very brief architecture overview here,
> Adriano and Luis can then answer more detailed questions as they're much
> more familiar with the code than I am.
> The goal was it to separate syntax and semantics of a query. E.g. 'a AND
> b', '+a +b', 'AND(a,b)' could be different syntaxes for the same query.
> We distinguish the semantics of the different query components, e.g.
> whether and how to tokenize/lemmatize/normalize the different terms or
> which Query objects to create for the terms. We wanted to be able to
> write a parser with a new syntax, while reusing the underlying
> semantics, as quickly as possible.
> In fact, Adriano is currently working on a 100% Lucene-syntax compatible
> implementation to make it easy for people who are using Lucene's query
> parser to switch.
> The query parser has three layers and its core is what we call the
> QueryNodeTree. It is a tree that initially represents the syntax of the
> original query, e.g. for 'a AND b':
>   AND
>  /   \
> A     B
> The three layers are:
> 1. QueryParser
> 2. QueryNodeProcessor
> 3. QueryBuilder
> 1. The upper layer is the parsing layer which simply transforms the
> query text string into a QueryNodeTree. Currently our implementations of
> this layer use javacc.
> 2. The query node processors do most of the work. It is in fact a
> configurable chain of processors. Each processors can walk the tree and
> modify nodes or even the tree's structure. That makes it possible to
> e.g. do query optimization before the query is executed or to tokenize
> terms.
> 3. The third layer is also a configurable chain of builders, which
> transform the QueryNodeTree into Lucene Query objects.
> Furthermore the query parser uses flexible configuration objects, which
> are based on AttributeSource/Attribute. It also uses message classes that
> allow to attach resource bundles. This makes it possible to translate
> messages, which is an important feature of a query parser.
> This design allows us to develop different query syntaxes very quickly.
> Adriano wrote the Lucene-compatible syntax in a matter of hours, and the
> underlying processors and builders in a few days. We now have a 100%
> compatible Lucene query parser, which means the syntax is identical and
> all query parser test cases pass on the new one too using a wrapper.
> Recent posts show that there is demand for query syntax improvements,
> e.g improved range query syntax or operator precedence. There are
> already different QP implementations in Lucene+contrib, however I think
> we did not keep them all up to date and in sync. This is not too
> surprising, because usually when fixes and changes are made to the main
> query parser, people don't make the corresponding changes in the contrib
> parsers. (I'm guilty here too)
> With this new architecture it will be much easier to maintain different
> query syntaxes, as the actual code for the first layer is not very much.
> All syntaxes would benefit from patches and improvements we make to the
> underlying layers, which will make supporting different syntaxes much
> more manageable.

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