[Phpmyadmin-devel] Parser support for virtual columns

[Dan Ungureanu]

On 13.07.2015 18:09, Madhura Jayaratne wrote:
> Hi Dan,
>
> MariaDB (5.2.0+) supports virtual columns and the syntax is
> <type>  [GENERATED ALWAYS]  AS   ( <expression> ) [VIRTUAL | 
> PERSISTENT]  [UNIQUE] [UNIQUE KEY] [COMMENT <text>]
>
> While implementing [1], to add parser support for virtual columns, I 
> tried to model this syntax using $FIELD_OPTIONS [2]. Even though I am 
> able to retrieve the expression this way, all the brackets and spaces 
> of the expression are gone. As I understand, this due to the 
> tokenization.
>
> Do you have any suggestion for an alternative approach?
>
> [1] https://sourceforge.net/p/phpmyadmin/feature-requests/1517/
> [2] 
> https://github.com/madhuracj/phpmyadmin/commit/b287aae9d56c4ae15d850b47a5f76d49f4f155ba
>
> -- 
> Thanks and Regards,
>
> Madhura Jayaratne
>
>
>
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Hello Madhura,

The way you approached this was the correct solution, however, there was 
a bug in my code which skipped white-spaces. I am not sure what exactly 
you want to extract from that expression and I implemented here [2] a 
new type of option "expr" that should make your job easier and parse an 
expression directly.

You can find here [1] a snippet of code I used to parse a CREATE 
statement that contains virtual fields and the result of the parsing. As 
you can see, the fact that I used the `Expression` component to parse 
the expression extracted the function name as well. Anyway, you can 
continue using the "var" option which will only format the expression, 
without extracting any information.

[1] https://gist.github.com/udan11/4b6eaee2a1fb7fa315c2
[2] 
https://github.com/udan11/sql-parser/commit/68ad40b4f30c0ff55d662413729fec4a535a3fec

Best regards,
Dan Ungureanu
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