Re: [PATCH] Add --syntax to postgres for SQL syntax checking

=?UTF-8?B?Sm9zZWYgxaBpbcOhbmVr?=  writes:
> I'm not sure everyone in this thread understands the reason for this
> patch, which is clearly my fault, since I have failed to explain. Main
> idea is to make a tool to validate query can be parsed, that's all.
> Similar to running "EXPLAIN query", but not caring about the result
> and not caring about the DB structure (ignoring missing tables, ...),
> just checking it was successfully executed. This definitely belongs to
> the server side and not to the client side, it is just a tool to
> validate that for this running PostgreSQL backend it is a "parseable"
> query.

The thing that was bothering me most about this is that I don't
understand why that's a useful check.  If I meant to type

	UPDATE mytab SET mycol = 42;

and instead I type

	UPDATEE mytab SET mycol = 42;

your proposed feature would catch that; great.  But if I type

	UPDATE mytabb SET mycol = 42;

it won't.  How does that make sense?  I'm not entirely sure where
to draw the line about what a "syntax check" should catch, but this
seems a bit south of what I'd want in a syntax-checking editor.

BTW, if you do feel that a pure grammar check is worthwhile, you
should look at the ecpg preprocessor, which does more or less that
with the SQL portions of its input.  ecpg could be a better model
to follow because it doesn't bring all the dependencies of the server
and so is much more likely to appear in a client-side installation.
It's kind of an ugly, unmaintained mess at the moment, sadly.

The big knock on doing this client-side is that there might be
version skew compared to the server you're using --- but if you
are not doing anything beyond a grammar-level check then your
results are pretty approximate anyway, ISTM.  We've not heard
anything suggesting that version skew is a huge problem for
ecpg users.

			regards, tom lane