Thread: Difference between function and procedure?

Difference between function and procedure?

From
Anastasios Hatzis
Date:
Hi,

I'm diving more into depth of the features outside the typical table
stuff, which I usually need.

I wrote a trigger that fires a function written in PL/Python, both works
fine so far.

But as I browsed my database via pgAdmin3 I recognized that there is
also 'Procedures' under 'public' available, but empty yet. Trying to
create a procedure resulted in the same SQL statement like creating a
function (CREATE FUNCTION ...). I couldn't see any difference. Also
didn't find in the PostgreSQL manual if there is a difference between
functions and procedures. Are there any at all?

Anastasios

PS: Using PostgreSQL 8.1.3 on Windows XP development machine.

Re: Difference between function and procedure?

From
"Merlin Moncure"
Date:
On 7/19/06, Anastasios Hatzis <ahatzis@gmx.net> wrote:
> Hi,
>
> I'm diving more into depth of the features outside the typical table
> stuff, which I usually need.
>
> I wrote a trigger that fires a function written in PL/Python, both works
> fine so far.
>
> But as I browsed my database via pgAdmin3 I recognized that there is
> also 'Procedures' under 'public' available, but empty yet. Trying to
> create a procedure resulted in the same SQL statement like creating a
> function (CREATE FUNCTION ...). I couldn't see any difference. Also
> didn't find in the PostgreSQL manual if there is a difference between
> functions and procedures. Are there any at all?

there are differences. PostgreSQL only really supports functions and
on the lists they are used interchangably.  on the -hacker list about
a year back there was a good discussion about implementing true SP and
why they would be needed.

mainly, SP are not externally transactional, making them useful for
maintenance type work, such as vacuum (cant be run from inside a
transaction) or multiple statement data load via 'copy' commands.

i thnk (not sure) that SP can not be inlined into queries like
functions.  this would be an important distinction.

merlin

Re: Difference between function and procedure?

From
Anastasios Hatzis
Date:
Merlin Moncure wrote:
> there are differences. PostgreSQL only really supports functions and
> on the lists they are used interchangably.  on the -hacker list about
> a year back there was a good discussion about implementing true SP and
> why they would be needed.
>
> mainly, SP are not externally transactional, making them useful for
> maintenance type work, such as vacuum (cant be run from inside a
> transaction) or multiple statement data load via 'copy' commands.
>
> i thnk (not sure) that SP can not be inlined into queries like
> functions.  this would be an important distinction.
>
Merlin,

thank you for clarifying this. So, given your hint, I didn't miss SP
until now, but this will probably change in future. ;-)

Anastasios

Re: Difference between function and procedure?

From
"Paul S"
Date:
I saw the same behavior with Functions and Procedures.  At first, I could not tell what made one go into the Function folder and one go into the Procedure one.  The one thing that clearly distinguishes a Procedure (to be placed into the Procedures folder in PgAdminIII) is if you include an OUT parameter.  The first time I wrote a Function with an OUT parameter, I could not find it in the functions folder.  I thought at first that it didn't compile.  Then I noticed it in the Procedures folder.  Probably a lot of other characteristics that make it different, but that is at least one. :)
 
-Paul
 


 
On 7/19/06, Anastasios Hatzis <ahatzis@gmx.net> wrote:
Merlin Moncure wrote:
> there are differences. PostgreSQL only really supports functions and
> on the lists they are used interchangably.  on the -hacker list about
> a year back there was a good discussion about implementing true SP and
> why they would be needed.
>
> mainly, SP are not externally transactional, making them useful for
> maintenance type work, such as vacuum (cant be run from inside a
> transaction) or multiple statement data load via 'copy' commands.
>
> i thnk (not sure) that SP can not be inlined into queries like
> functions.  this would be an important distinction.
>
Merlin,

thank you for clarifying this. So, given your hint, I didn't miss SP
until now, but this will probably change in future. ;-)

Anastasios

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