Re: Proposal: USING clause for DO statement

On Sat, Nov 21, 2009 at 3:32 PM, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> wrote:
> 2009/11/21 Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>:
>> Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> writes:
>>> Hypothetically - when we are able to pass any value to DO script, then
>>> I don't see problem. If I use Andrew's design - ${shellvar} and add it
>>> to psql parser, then I could to write
>>
>>> \set par1 world
>>
>>> do $$
>>>   begin
>>>     raise notice 'Helo, % and %', $1, $2;
>>>   end;
>>> $$ using :par1, ${USER};
>>
>> Ick.  Double, triple ick.  It is astonishing to me how many people think
>> that the solution to today's problem is always to invent some weird new
>> syntax to plaster over SQL.  Which for some reason invariably involves
>> dollar signs and/or curly braces ... there isn't even any originality
>> involved :-(.
>>
>> Maybe we should accept one of these proposals, just so that it usurps
>> that part of the syntax space forever and we can reject the next ten bad
>> ideas out-of-hand.  Of course, if the SQL committee ever gets around to
>> defining curly braces as doing something, we'll be screwed.
>>
>> colon-foo is bad enough.  Let's not add more.
>
> I have a no problem. Syntax should be defined later. there is simple
> workaround (using shellvariables):
>
> psql ... -v user = $USER
>
>
> I repeat it again and finish:
>
> proposal is related only to DO statement (what is Pg specific).
> Doesn't propose psql changes, doesn't propose PL changes.

I code all day long by editing various text files and pasting some/all
of them into psql. Once in a while I \i a file from psql or cat foo |
psql. Only the last method is addressed by using a wrapper script or
"bash/psql -c"...wrappers aren't really a general solution. If psql
could introduce variables into arbitrary sql somehow, I could load a
bunch of variables in .psqlrc, have constants set up, etc.

For example, when I have a constant (let's say, and advisory lock#) I
want to define in a plpgsql function, I have a choice between three
not very pleasant options:
*) simply hard code the value
*) look it up every time from a global control table
*) wrap it in an immutable sql function

I don't care much about the syntax, but it would be absolutely
wonderful if psql could operate on a function body in some sort of
regular way before it gets to the backend. if it solves
parameterizing 'do' statements, so much the better.

merlin