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From "Flavio Palumbo" <f.palu...@silmasoftware.com>
Subject R: Using derby to parse an SQL statement
Date Thu, 13 Nov 2008 12:14:48 GMT
Hi guys,

I followed this post finding it very exciting, cause I post a similar
question a while ago.

Now I'd like to test the work submitted by Rick but I'm not so inside Derby
to catch he whole job I have to do.

I understood that I have to :

- download Derby sources (from where ?)
- apply the patch suggested by Rich (seen the classes but not catch the
lines of code)
- recompile Derby (what libraries/jars I need to)
- use ASTParser as suggested

Can somebody give me a hint ?

Thanks a lot

Flavio

> -----Messaggio originale-----
> Da: news [mailto:news@ger.gmane.org]Per conto di Christian Riedel
> Inviato: giovedì 13 novembre 2008 6.37
> A: derby-user@db.apache.org
> Oggetto: Re: Using derby to parse an SQL statement
>
>
> Hi Rick,
>
> at first thank you very much for your efforts so far. At a first glance
> your changes to the code seem to be exactly what we want. I will try if
> it works asap.
>
> To test it with the derby libs I'd have to work on the current trunk and
> apply the patch an then compile derby manually, right?
>
> I'll keep you updated
>
> Thanks for your help
>
> Christian
>
> Rick Hillegas schrieb:
> > Hi Christian,
> >
> > I have created a JIRA to track this issue:
> > https://issues.apache.org/jira/browse/DERBY-3946
> >
> > I have attached to the JIRA a small patch which exposes the AST
> produced
> > by the parser. I have also attached a simple program, ASTParser, which
> > shows how to retrieve the AST from Derby. I am inclined to check this
> > patch in to the trunk. Please let me know if you find this
> useful and if
> > you would like me to port this patch to another Derby branch.
> >
> > Hope this helps,
> > -Rick
> >
> > Christian Riedel wrote:
> >> Hi Rick,
> >>
> >> first of all thanks for your answer ... now the relations have become
> >> a lot clearer ...
> >>
> >> Your are right, there is a lot of things to be done that we probably
> >> don't want to go through. You asked why we cannot take the whole derby
> >> engine and use it ... well there is nor real reason not to do so. The
> >> only "problem" I see is, that derby is a dbms - if I am not mistaken -
> >> and we only have an SQL statement that we extract from a text file and
> >> want tot analyze it to extract some metadata from it.
> >>
> >> So if we take the derby engine as it is, how can I prevent that we
> >> have to set up a "dummy" DB in order to be able to actually use thje
> >> parsing feature ....
> >>
> >> I hope you see my point.
> >>
> >> We could live with setting up a dummy DB ... and I do think that the
> >> derby AST offers all information we need. It's just that I don't see
> >> how we can set this thing up. So having a dummy DB is necessary to be
> >> able to intercept the parsing process to get hold of the AST? Can we
> >> actually access the AST if we choose to set up a dummy DB? I think
> >> that would be something we could live with ;-)
> >>
> >>
> >> Thanks for your support
> >>
> >> Christian
> >>
> >>
> >> Rick Hillegas schrieb:
> >>> Hi Christian,
> >>>
> >>> I think you will have difficulty isolating the Parser from the rest
> >>> of the SQL interpreter. In theory, you should be able to isolate the
> >>> compiler from the execution engine and the storage layer--but that is
> >>> an untested theory.
> >>>
> >>> The Parser wants to turn out abstract syntax trees (AST). Ideally,
> >>> the Parser would just need to ask a NodeFactory for AST nodes and you
> >>> could supply your own NodeFactory. But I think that there is a fair
> >>> amount of coupling between the Parser and Derby's concrete
> >>> implementation of NodeFactory. I think that you could uncouple the
> >>> two, but you may not want to spend your time on that.
> >>>
> >>> So the Parser is going to force you to pull in the AST nodes. Once
> >>> you do that, you will end up with the whole compiler. In particular,
> >>> the AST nodes (and the Parser itself) expect that you will supply an
> >>> implementation of LanguageConnectionContext, the master state
> >>> variable for the whole SQL interpreter. Untangling that requirement
> >>> is another chunk of work you may not want to do.
> >>>
> >>> Then there is the Monitor. It has been a while since I was in that
> >>> code but I seem to recall that fairly early on the Monitor wants to
> >>> fault in a storage layer. In theory you ought to be able to supply
> >>> the Monitor a list of modules that doesn't include a storage layer.
> >>> But since no-one runs in this configuration, there are probably a lot
> >>> of undocumented surprises that you may not want to fix either.
> >>>
> >>> Can I ask you what breaks if you just pull in the whole Derby engine?
> >>> Are you concerned that you will fault in too much code that you
> >>> barely use? Are you concerned that you'll end up with a dummy
> >>> database that you don't need? Are Derby's AST nodes not a usable
> >>> representation of statement syntax?
> >>>
> >>> Thanks,
> >>> -Rick
> >>>
> >>> Christian Riedel wrote:
> >>>> Hi there,
> >>>>
> >>>> we are working on a small project where we need to analyze an SQL
> >>>> statement that can be of any kind: very simple, with inner selects,
> >>>> complex join etc.
> >>>>
> >>>> We figured it inappropriate to start to write our own parser when
> >>>> there are other projects, like derby, out there that can do it much
> >>>> better than we would possibly do ... so this was our idea:
> >>>>
> >>>> Can we use derby to create an instance of Parser
> >>>> (org.apache.derby.iapi.sql.compile.Parser.class) and let our SQL
> >>>> statement be parsed by calling the parse() method on this instance?
> >>>> What we want to have is a syntax tree of the statement that allows
> >>>> us to see which tables and which fields are accessed / included in
> >>>> the statement (including any possibly done "renames" á la SELECT
> >>>> street AS "ADDRESS" FROM USER_DATA ).
> >>>>
> >>>> The problem is, that we are stuck ... we spent several days now to
> >>>> try to find the proper way to create an instance of the Parser. Is
> >>>> it possible at all without having to set up a running derby system?
> >>>>
> >>>> Is the Monitor class the right entry point? How can we create a
> >>>> CompilerContext so that a Parser instance can be created?
> >>>>
> >>>>
> >>>> This sure is off-topic but we don't see any way through all this.
> >>>> Can you help us?
> >>>>
> >>>>
> >>>> Thanks in advance
> >>>>
> >>>> Christian
> >>>>
> >>>
> >>>
> >>
> >
> >
>
> --
> To reply to this posting directly use the following address and
> remove the 'NO-SPAM' part: Riedel.Christian.NO-SPAM@gmx.net
>


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