Re: "unexpected" query behaviour after i change parser code

On Sat, May 22, 2010 at 9:33 PM, Mohammad Heykal Abdillah
<heykal(dot)abdillah(at)gmail(dot)com> wrote:
>> > My question :
>> > 1) Can someone explain why my last test it's work?
>>
>> In standard PostgreSQL, "select item from item" is valid SQL.  It
>> returns a single column whose value is a record containing all the
>> columns from the item table.  I suspect something similar is happening
>> in your case.
>>
>
> Hmm.., i know that "select item from item" is valid SQL. But since in my
> case "from cause" was deleted. Shouldnt "select item.id_item,item;"
> failed? Since "select id_item,name;" was also failed.

Well, it's hard for me to speculate about what your code might do. I
think your best bet is to fire up gdb and maybe stick in some
debugging printfs and see if you can figure out what's happening.

>> Which brings me to another point: I'm not really sure what
>> you're trying to accomplish with this modification, considering that
>> adding_missing_from sounds like it does about what you want, but
>> without breaking nearly as much stuff.
>>
>
> I am trying to make some kind automate join relation without have to
> explicitly declare the join relation key.
>
> Example :
> "select item_id,fname;" in my modified query will be eqivalen with SQL
> query.
>
> "select item.id_item,customer.fname from item,fname where
> item.id_item=customer.id"
>
> Ah, yes my "conversion" will be do after raw_parsertree was forming by
> lex and yacc.

It's probably not possible to do this well in general. You might want
to think about writing some kind of preprocessor or query generator
that would rewrite your queries like this for you before sending them
to the database, rather than modifying PostgreSQL itself.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise Postgres Company