Re: [HACKERS] proposal for 8.3: Simultaneous assignment for PL/pgSQL

2006-08-08 Thread Pavel Stehule 



Tom Lane wrote:
 Pavel Stehule [EMAIL PROTECTED] writes:
 a,b,c := out3fce(1); -- Simultaneous assignment

 I thought we rejected that idea once already, on the grounds that it
 would make it too hard to tell the difference between intended code
 and typos.


In any case, I had some questions:

. is it compatible with PLSQL?
. can the effect be achieved by assigning to a composite?


I looked into SQL2003, and SQL2003 knows it (SQL/PSM):

assignment statement ::=
   singleton variable assignment
 | multiple variable assignment
multiple variable assignment ::=
   SET assignment target list equals operator assigned row
assignment target list ::=
   left paren assignment target [ { comma assignment target }... ] 
right paren

singleton variable assignment ::=
   SET assignment target equals operator assignment source

Regards
Pavel Stehule

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Re: [HACKERS] proposal for 8.3: Simultaneous assignment for PL/pgSQL

2006-08-08 Thread Andrew Dunstan 

Pavel Stehule wrote:



Tom Lane wrote:
 Pavel Stehule [EMAIL PROTECTED] writes:
 a,b,c := out3fce(1); -- Simultaneous assignment

 I thought we rejected that idea once already, on the grounds that it
 would make it too hard to tell the difference between intended code
 and typos.


In any case, I had some questions:

. is it compatible with PLSQL?
. can the effect be achieved by assigning to a composite?


I looked into SQL2003, and SQL2003 knows it (SQL/PSM):

assignment statement ::=
   singleton variable assignment
 | multiple variable assignment
multiple variable assignment ::=
   SET assignment target list equals operator assigned row
assignment target list ::=
   left paren assignment target [ { comma assignment target 
}... ] right paren

singleton variable assignment ::=
   SET assignment target equals operator assignment source



The parentheses are apparently required for multiple variables, so in 
our case it might look like this:


 (a,b,c) := foo(bar);

That might overcome the objection Tom referred to, I guess?


cheers

andrew


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Re: [HACKERS] proposal for 8.3: Simultaneous assignment for PL/pgSQL

2006-08-08 Thread Alvaro Herrera 
Andrew Dunstan wrote:
 Pavel Stehule wrote:

 I looked into SQL2003, and SQL2003 knows it (SQL/PSM):
  [grammar productions]

 The parentheses are apparently required for multiple variables, so in 
 our case it might look like this:
 
  (a,b,c) := foo(bar);
 
 That might overcome the objection Tom referred to, I guess?

Are we intending to support SQL/PSM with PL/pgSQL?

-- 
Alvaro Herrerahttp://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.

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Re: [HACKERS] proposal for 8.3: Simultaneous assignment for PL/pgSQL

2006-08-08 Thread Jonah H. Harris 

On 8/8/06, Alvaro Herrera [EMAIL PROTECTED] wrote:

Are we intending to support SQL/PSM with PL/pgSQL?


I hope not.  While PL/pgSQL and SQL/PSM share some similarities, they
should be totally separate.  IIRC, EnterpriseDB had tried to sponsor
someone to write SQL/PSM support for PostgreSQL a little over a year
ago and no one wanted to do it.

--
Jonah H. Harris, Software Architect | phone: 732.331.1300
EnterpriseDB Corporation| fax: 732.331.1301
33 Wood Ave S, 2nd Floor| [EMAIL PROTECTED]
Iselin, New Jersey 08830| http://www.enterprisedb.com/

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Re: [HACKERS] proposal for 8.3: Simultaneous assignment for PL/pgSQL

2006-08-08 Thread Tom Lane 
Andrew Dunstan [EMAIL PROTECTED] writes:
 Pavel Stehule wrote:
 I looked into SQL2003, and SQL2003 knows it (SQL/PSM):
 
 assignment statement ::=
 singleton variable assignment
 | multiple variable assignment
 multiple variable assignment ::=
 SET assignment target list equals operator assigned row
 assignment target list ::=
 left paren assignment target [ { comma assignment target 
 }... ] right paren
 singleton variable assignment ::=
 SET assignment target equals operator assignment source

 The parentheses are apparently required for multiple variables, so in 
 our case it might look like this:
   (a,b,c) := foo(bar);

More to the point, a SET keyword is required too by that standard.

I concur with the other comment that plpgql is intended to mimic
Oracle PL/SQL, not SQL/PSM.  If we try to follow two different leads
we are likely to find ourselves with a mess.

regards, tom lane

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Re: [HACKERS] proposal for 8.3: Simultaneous assignment for PL/pgSQL

2006-08-08 Thread Josh Berkus 

Tom,


I concur with the other comment that plpgql is intended to mimic
Oracle PL/SQL, not SQL/PSM.  If we try to follow two different leads
we are likely to find ourselves with a mess.


Well, the proposed functionality would be extremely useful in making 
PL/pgSQL a more robust language.   So can we find a syntax that is 
unambiguously assignment?  To be honest, I'm unclear on what's wrong 
with Pavel's suggested syntax.


--Josh


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[HACKERS] proposal for 8.3: Simultaneous assignment for PL/pgSQL

2006-08-07 Thread Pavel Stehule 

Hello

I suggest enhance plpgsq to simultaneous assignment. Main reason is missing 
parameter passing by reference and less readable getting values from 
functions with OUT parameters.


Currently I have to write SELECT: SELECT INTO a,b,c out3fce(1)


a,b,c := out3fce(1); -- Simultaneous assignment

Any comments?

Regards
Pavel Stehule

_
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Re: [HACKERS] proposal for 8.3: Simultaneous assignment for PL/pgSQL

2006-08-07 Thread Tom Lane 
Pavel Stehule [EMAIL PROTECTED] writes:
 a,b,c := out3fce(1); -- Simultaneous assignment

I thought we rejected that idea once already, on the grounds that it
would make it too hard to tell the difference between intended code
and typos.

regards, tom lane

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Re: [HACKERS] proposal for 8.3: Simultaneous assignment for PL/pgSQL

2006-08-07 Thread Pavel Stehule 


Pavel Stehule [EMAIL PROTECTED] writes:
 a,b,c := out3fce(1); -- Simultaneous assignment

I thought we rejected that idea once already, on the grounds that it
would make it too hard to tell the difference between intended code
and typos.



Yes, because wasn't procedures with out params, my arguments wasn't strong. 
Older patch was too liberal. I can test equal type compatibility, count of 
variables and fileds in record compatibility.


Pavel Stehule

_
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http://messenger.msn.cz/



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Re: [HACKERS] proposal for 8.3: Simultaneous assignment for PL/pgSQL

2006-08-07 Thread Pavel Stehule 


Tom Lane wrote:
 Pavel Stehule [EMAIL PROTECTED] writes:
 a,b,c := out3fce(1); -- Simultaneous assignment

 I thought we rejected that idea once already, on the grounds that it
 would make it too hard to tell the difference between intended code
 and typos.


In any case, I had some questions:

. is it compatible with PLSQL?


what I know no, but PLSQL has different mechanism for calling procedures. 
And first of all it knows references to variables.



. can the effect be achieved by assigning to a composite?



yes. I can use record type. But here is problem with less readability

The best of is implementation of CALL statement, where I can transmit values 
by references. But it's not possible in Postgres :-(. I can't to select 
unambiguously called procedure. I can, if I accept SQL Server syntax, where 
caller specify OUT, INOUT, IN flags too. I am unhappy with current 
situation, and I search good solution. Simultaneous assignment  is simplest.


Regards
Pavel Stehule

_
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http://messenger.msn.cz/



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Re: [HACKERS] proposal for 8.3: Simultaneous assignment for PL/pgSQL

2006-08-07 Thread Martijn van Oosterhout 
On Mon, Aug 07, 2006 at 04:11:48PM +0200, Pavel Stehule wrote:
 The best of is implementation of CALL statement, where I can transmit 
 values by references. But it's not possible in Postgres :-(. I can't to 
 select unambiguously called procedure. I can, if I accept SQL Server 
 syntax, where caller specify OUT, INOUT, IN flags too. I am unhappy with 
 current situation, and I search good solution. Simultaneous assignment  is 
 simplest.

Well, you can implement it. After all, the CALL syntax is merely
syntactic sugar. You could (if you wanted to) do the following:

CREATE FUNCTION foo( a TEXT IN, b TEXT INOUT, c TEXT OUT ) as blah...

And in a pl/pgsql function, translate: CALL foo(a,b,c) 
into (b,c) = foo(a,b) internally.

Doesn't seem like that would be too hard.

Have anice day,
-- 
Martijn van Oosterhout   kleptog@svana.org   http://svana.org/kleptog/
 From each according to his ability. To each according to his ability to 
 litigate.


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Re: [HACKERS] proposal for 8.3: Simultaneous assignment for PL/pgSQL

2006-08-07 Thread Tom Lane 
Martijn van Oosterhout kleptog@svana.org writes:
 Well, you can implement it. After all, the CALL syntax is merely
 syntactic sugar. You could (if you wanted to) do the following:

 CREATE FUNCTION foo( a TEXT IN, b TEXT INOUT, c TEXT OUT ) as blah...

 And in a pl/pgsql function, translate: CALL foo(a,b,c) 
 into (b,c) = foo(a,b) internally.

No, Pavel's right: that doesn't work because it's ambiguous.  How do you
tell whether CALL foo(a,b,c) means

a,b,c := foo();
b,c := foo(a);
c := foo(a,b);
select foo(a,b,c);

There could be functions foo matching all four interpretations.

regards, tom lane

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Re: [HACKERS] proposal for 8.3: Simultaneous assignment for PL/pgSQL

2006-08-07 Thread Pavel Stehule 


Martijn van Oosterhout kleptog@svana.org writes:
 Well, you can implement it. After all, the CALL syntax is merely
 syntactic sugar. You could (if you wanted to) do the following:

 CREATE FUNCTION foo( a TEXT IN, b TEXT INOUT, c TEXT OUT ) as blah...

 And in a pl/pgsql function, translate: CALL foo(a,b,c)
 into (b,c) = foo(a,b) internally.

No, Pavel's right: that doesn't work because it's ambiguous.  How do you
tell whether CALL foo(a,b,c) means

a,b,c := foo();
b,c := foo(a);
c := foo(a,b);
select foo(a,b,c);

There could be functions foo matching all four interpretations.


we can do some hints:

CALL foo(a, OUT b, OUT c)

it's better than nothing

comments?

Regards
Pavel Stehule

_
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