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https://issues.apache.org/jira/browse/LUCENE-2039?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12776139#action_12776139
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Luis Alves commented on LUCENE-2039:
------------------------------------
{code}
Grant, JavaCC only generates parsers, a flag is a semantic check. You need to
do a lot more work to do those checks. First step would be to build a tree
using jjtree. Then you need to build the symbol table and then you can traverse
the tree to do your checks.
{code}
In the new queryparser we don't use jjtree, but the same concept is implemented
in the new queryparser,
the ouput from the SyntaxParser interface is a syntax tree, this tree is not
related with any lucene objects just like jjtree.
But I think this is a ugly solution.
I think if we use the new queryparser, it allows for multiple SyntaxParsers to
use the same Processors and the Builders.
And with a small implementation of a SyntaxParser(javacc, jflex, antlr, java
tokenizer, etc), you can use the same Processors and Builders to create a
lucene query.
This will avoid duplicate code and allow for multiple syntaxes.
I don't want to be preacher here, but some of these problems are already solved
in the new queryparser framework, we just need to keep improving it, by adding
more syntaxes, extensions and features to it.
I know the new queryparser is not in main, but that can be fixed in 3.1, if the
community thinks is stable we should move it there.
> Regex support and beyond in JavaCC QueryParser
> ----------------------------------------------
>
> Key: LUCENE-2039
> URL: https://issues.apache.org/jira/browse/LUCENE-2039
> Project: Lucene - Java
> Issue Type: Improvement
> Components: QueryParser
> Reporter: Simon Willnauer
> Assignee: Grant Ingersoll
> Priority: Minor
> Fix For: 3.1
>
> Attachments: LUCENE-2039.patch
>
>
> Since the early days the standard query parser was limited to the queries
> living in core, adding other queries or extending the parser in any way
> always forced people to change the grammar file and regenerate. Even if you
> change the grammar you have to be extremely careful how you modify the parser
> so that other parts of the standard parser are affected by customisation
> changes. Eventually you had to live with all the limitation the current
> parser has like tokenizing on whitespaces before a tokenizer / analyzer has
> the chance to look at the tokens.
> I was thinking about how to overcome the limitation and add regex support to
> the query parser without introducing any dependency to core. I added a new
> special character that basically prevents the parser from interpreting any of
> the characters enclosed in the new special characters. I choose the forward
> slash '/' as the delimiter so that everything in between two forward slashes
> is basically escaped and ignored by the parser. All chars embedded within
> forward slashes are treated as one token even if it contains other special
> chars like * []?{} or whitespaces. This token is subsequently passed to a
> pluggable "parser extension" with builds a query from the embedded string. I
> do not interpret the embedded string in any way but leave all the subsequent
> work to the parser extension. Such an extension could be another full
> featured query parser itself or simply a ctor call for regex query. The
> interface remains quiet simple but makes the parser extendible in an easy way
> compared to modifying the javaCC sources.
> The downsides of this patch is clearly that I introduce a new special char
> into the syntax but I guess that would not be that much of a deal as it is
> reflected in the escape method though. It would truly be nice to have more
> than once extension an have this even more flexible so treat this patch as a
> kickoff though.
> Another way of solving the problem with RegexQuery would be to move the JDK
> version of regex into the core and simply have another method like:
> {code}
> protected Query newRegexQuery(Term t) {
> ...
> }
> {code}
> which I would like better as it would be more consistent with the idea of the
> query parser to be a very strict and defined parser.
> I will upload a patch in a second which implements the extension based
> approach I guess I will add a second patch with regex in core soon too.
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