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Design Error (and its Solution) in SQL Query Parser? [message #30230]

Fri, 27 April 2007 08:03

Christian Beckel

Messages: 14
Registered: July 2009

Junior Member

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Hello,

After spending a long time on extending the SQL Query Parser and the
corresponding Lexer I'm quite sure there must be something wrong in the
SQL parser code (package org.eclipse.datatools.sqltools.parsers.sql).

The class SQLParserManager, which is to be extended by each parser
extension, provides an abstract method to create and obtain the
corresponding Lexer before the parsing process. However, it returns an
object of type SQLLexer, being the lpg-generated lexer rather than the
Abstract Lexer which can be used as a base class for custom Lexers.

This fact that an SQLLexer object is needed rather than an
AbstractSQLLexer makes it impossible to use a custom Lexer, since the
lpg-generated class SQLLexer is not extendable. Changing each occurrence
of SQLLexer in the SQLQueryManager to AbstractSQLLexer solves this problem
easily, and has no effect on the rest of the parser (since all the methods
which are called during the lexing process are declared by the abstract
class, anyway.

What's the best way to fix this important problem? Should I provide a
patch to someone?

Greetings,

Christian Beckel

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 Hello,
 
 After spending a long time on extending
the SQL Query Parser and the corresponding Lexer I'm quite sure there must
be something wrong in the SQL parser code (package org.eclipse.datatools.sqltools.parsers.sql).
 
 The class SQLParserManager, which is
to be extended by each parser extension, provides an abstract method to
create and obtain the corresponding Lexer before the parsing process. However,
it returns an object of type SQLLexer, being the lpg-generated lexer rather
than the Abstract Lexer which can be used as a base class for custom Lexers.
 
 This fact that an SQLLexer object is
needed rather than an AbstractSQLLexer makes it impossible to use a custom
Lexer, since the lpg-generated class SQLLexer is not extendable. Changing
each occurrence of SQLLexer in the SQLQueryManager to AbstractSQLLexer
solves this problem easily, and has no effect on the rest of the parser
(since all the methods which are called during the lexing process are declared
by the abstract class, anyway.
 
 What's the best way to fix this important
problem? Should I provide a patch to someone?
 
 Greetings,
 
 Christian Beckel
 
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Re: Design Error (and its Solution) in SQL Query Parser? [message #30446 is a reply to message #30230]

Thu, 03 May 2007 20:31

Brian Payton

Messages: 154
Registered: July 2009

Senior Member

I agree this is a problem. Our example parsers either use the SQLLexer
class directly or extend it, rather than creating a new lexer. Please
open a bug report for Data Tools in Bugzilla, component SQL Query
Parser, and attach a patch file.

Regards,
Brian Payton
DTP SQL Development Tools committer

cbeckel@de.ibm.com wrote:
>
> Hello,
>
> After spending a long time on extending the SQL Query Parser and the
> corresponding Lexer I'm quite sure there must be something wrong in
> the SQL parser code (package org.eclipse.datatools.sqltools.parsers.sql).
>
> The class SQLParserManager, which is to be extended by each parser
> extension, provides an abstract method to create and obtain the
> corresponding Lexer before the parsing process. However, it returns an
> object of type SQLLexer, being the lpg-generated lexer rather than the
> Abstract Lexer which can be used as a base class for custom Lexers.
>
> This fact that an SQLLexer object is needed rather than an
> AbstractSQLLexer makes it impossible to use a custom Lexer, since the
> lpg-generated class SQLLexer is not extendable. Changing each
> occurrence of SQLLexer in the SQLQueryManager to AbstractSQLLexer
> solves this problem easily, and has no effect on the rest of the
> parser (since all the methods which are called during the lexing
> process are declared by the abstract class, anyway.
>
> What's the best way to fix this important problem? Should I provide a
> patch to someone?
>
> Greetings,
>
> Christian Beckel

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Re: Design Error (and its Solution) in SQL Query Parser? [message #585541 is a reply to message #30230]

Thu, 03 May 2007 20:31

Brian Payton

Messages: 154
Registered: July 2009

Senior Member

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