Declaring a field that is also an out parameter in a function

Michael Nolan <htfoot@gmail.com> writes:

Shouldn't declaring a field that is also an OUT parameter throw an error?

No. The DECLARE is a block nested within the function,
and the parameter is declared at function scope.
So this is a standard case of an inner declaration masking
an outer one.

Possibly plpgsql_check can be set to complain about such cases,
but they're legal according to the language specification.

regards, tom lane

ne 7. 7. 2024 v 0:14 odesílatel Tom Lane <tgl@sss.pgh.pa.us> napsal:

Michael Nolan <htfoot@gmail.com> writes:

Shouldn't declaring a field that is also an OUT parameter throw an error?

No. The DECLARE is a block nested within the function,
and the parameter is declared at function scope.
So this is a standard case of an inner declaration masking
an outer one.

Possibly plpgsql_check can be set to complain about such cases,
but they're legal according to the language specification.

yes, it does

(2024-07-07 09:27:14) postgres=# select * from
plpgsql_check_function('test_function');
┌───────────────────────────────────────────────────────────────┐
│ plpgsql_check_function │
╞═══════════════════════════════════════════════════════════════╡
│ warning:00000:10:statement block:parameter "d3" is overlapped │
│ Detail: Local variable overlap function parameter. │
│ warning extra:00000:8:DECLARE:never read variable "d3" │
│ warning extra:00000:unused parameter "$1" │
│ warning extra:00000:unused parameter "$2" │
│ warning extra:00000:unused parameter "$3" │
│ warning extra:00000:unmodified OUT variable "d3" │
└───────────────────────────────────────────────────────────────┘
(7 rows)

but looks so there are false alarms related to using an alias. It is
interesting so I have not any report about this issue, so probably using
aliases is not too common today.

Regards

Pavel

ne 7. 7. 2024 v 9:31 odesílatel Pavel Stehule <pavel.stehule@gmail.com>
napsal:

ne 7. 7. 2024 v 0:14 odesílatel Tom Lane <tgl@sss.pgh.pa.us> napsal:

Michael Nolan <htfoot@gmail.com> writes:

Shouldn't declaring a field that is also an OUT parameter throw an

error?

No. The DECLARE is a block nested within the function,
and the parameter is declared at function scope.
So this is a standard case of an inner declaration masking
an outer one.

Possibly plpgsql_check can be set to complain about such cases,
but they're legal according to the language specification.

yes, it does

(2024-07-07 09:27:14) postgres=# select * from
plpgsql_check_function('test_function');
┌───────────────────────────────────────────────────────────────┐
│ plpgsql_check_function │
╞═══════════════════════════════════════════════════════════════╡
│ warning:00000:10:statement block:parameter "d3" is overlapped │
│ Detail: Local variable overlap function parameter. │
│ warning extra:00000:8:DECLARE:never read variable "d3" │
│ warning extra:00000:unused parameter "$1" │
│ warning extra:00000:unused parameter "$2" │
│ warning extra:00000:unused parameter "$3" │
│ warning extra:00000:unmodified OUT variable "d3" │
└───────────────────────────────────────────────────────────────┘
(7 rows)

but looks so there are false alarms related to using an alias. It is
interesting so I have not any report about this issue, so probably using
aliases is not too common today.

I was blind, plpgsql_check is correct

Regards

Pavel

On Sun, Jul 7, 2024 at 4:13 AM Pavel Stehule <pavel.stehule@gmail.com> wrote:

but looks so there are false alarms related to using an alias. It is interesting so I have not any report about this issue, so probably using aliases is not too common today.

I'm not sure why there's a warning about using an alias. 43.3.1 says
to use them for improved readability.

Mike Nolan

Pavel Stehule <pavel.stehule@gmail.com> writes:

(2024-07-07 09:27:14) postgres=# select * from
plpgsql_check_function('test_function');
┌───────────────────────────────────────────────────────────────┐
│ plpgsql_check_function │
╞═══════════════════════════════════════════════════════════════╡
│ warning:00000:10:statement block:parameter "d3" is overlapped │
│ Detail: Local variable overlap function parameter. │

Nice! FWIW, I think the standard terminology is "local variable
shadows function parameter".

regards, tom lane

ne 7. 7. 2024 v 15:01 odesílatel Michael Nolan <htfoot@gmail.com> napsal:

On Sun, Jul 7, 2024 at 4:13 AM Pavel Stehule <pavel.stehule@gmail.com>
wrote:

but looks so there are false alarms related to using an alias. It is

interesting so I have not any report about this issue, so probably using
aliases is not too common today.

I'm not sure why there's a warning about using an alias. 43.3.1 says
to use them for improved readability.

it is obsolete - aliases were used when Postgres doesn't support named
arguments.

I don't know any good reason why one variable can use more than one name.

There can be an exception when argument names are very long, but generally
they are not used.

On Sunday, July 7, 2024, Michael Nolan <htfoot@gmail.com> wrote:

On Sun, Jul 7, 2024 at 4:13 AM Pavel Stehule <pavel.stehule@gmail.com>
wrote:

but looks so there are false alarms related to using an alias. It is

interesting so I have not any report about this issue, so probably using
aliases is not too common today.

I'm not sure why there's a warning about using an alias. 43.3.1 says
to use them for improved readability.

Mostly because you should just name variables correctly the first time. It
improves readability if you use $n parameter names, which you should not.
As noted in 43.3.2, sometimes you don’t have a choice, though new and old
aren’t usually problematic enough to warrant aliasing.

David J.

On 7/7/24 07:42, Pavel Stehule wrote:

I'm not sure why there's a warning about using an alias. 43.3.1 says
to use them for improved readability.

it is obsolete - aliases were used when Postgres doesn't support named
arguments.

Is that was what it was complaining about or the fact they where
declared and never used?

I  don't know any good reason why one variable can use more than one name.

Section 43.3.2. ALIAS provides the pros/cons.

There can be an exception when argument names are very long, but
generally they are not used.

Mike Nolan

--
Adrian Klaver
adrian.klaver@aklaver.com

ne 7. 7. 2024 v 16:48 odesílatel Adrian Klaver <adrian.klaver@aklaver.com>
napsal:

On 7/7/24 07:42, Pavel Stehule wrote:

I'm not sure why there's a warning about using an alias. 43.3.1 says
to use them for improved readability.

it is obsolete - aliases were used when Postgres doesn't support named
arguments.

Is that was what it was complaining about or the fact they where
declared and never used?

I am not sure if I understand the question. My reply was related to
generic usage of aliases.

Report from plpgsql_check was correct - and related variables were not
used.

ne 7. 7. 2024 v 16:37 odesílatel Tom Lane <tgl@sss.pgh.pa.us> napsal:

Pavel Stehule <pavel.stehule@gmail.com> writes:

(2024-07-07 09:27:14) postgres=# select * from
plpgsql_check_function('test_function');
┌───────────────────────────────────────────────────────────────┐
│ plpgsql_check_function │
╞═══════════════════════════════════════════════════════════════╡
│ warning:00000:10:statement block:parameter "d3" is overlapped │
│ Detail: Local variable overlap function parameter. │

Nice! FWIW, I think the standard terminology is "local variable
shadows function parameter".

fixed

On 7/7/24 07:53, Pavel Stehule wrote:

ne 7. 7. 2024 v 16:48 odesílatel Adrian Klaver
<adrian.klaver@aklaver.com <mailto:adrian.klaver@aklaver.com>> napsal:

On 7/7/24 07:42, Pavel Stehule wrote:

     I'm not sure why there's a warning about using an alias.

43.3.1 says

     to use them for improved readability.

it is obsolete - aliases were used when Postgres doesn't support

named

arguments.

Is that was what it was complaining about or the fact they where
declared and never used?

I am not sure if I understand the question. My  reply was related to
generic usage of aliases.

The conversation was:

Mike Nolan

"I'm not sure why there's a warning about using an alias. 43.3.1 says
to use them for improved readability."

Pavel Stehule

"it is obsolete - aliases were used when Postgres doesn't support named
arguments."

I was just trying to confirm that the warning was not for ALIAS being
declared. That it was for what you state below.

Report from plpgsql_check was correct - and related variables were not
used.

I  don't know any good reason why one variable can use more than

one name.

Section 43.3.2. ALIAS provides the pros/cons.

There can be an exception when argument names are very long, but
generally they are not used.

     Mike Nolan

--
Adrian Klaver
adrian.klaver@aklaver.com <mailto:adrian.klaver@aklaver.com>

--
Adrian Klaver
adrian.klaver@aklaver.com

ne 7. 7. 2024 v 17:00 odesílatel Adrian Klaver <adrian.klaver@aklaver.com>
napsal:

On 7/7/24 07:53, Pavel Stehule wrote:

ne 7. 7. 2024 v 16:48 odesílatel Adrian Klaver
<adrian.klaver@aklaver.com <mailto:adrian.klaver@aklaver.com>> napsal:

On 7/7/24 07:42, Pavel Stehule wrote:

I'm not sure why there's a warning about using an alias.

43.3.1 says

to use them for improved readability.

it is obsolete - aliases were used when Postgres doesn't support

named

arguments.

Is that was what it was complaining about or the fact they where
declared and never used?

I am not sure if I understand the question. My reply was related to
generic usage of aliases.

The conversation was:

Mike Nolan

"I'm not sure why there's a warning about using an alias. 43.3.1 says
to use them for improved readability."

Pavel Stehule

"it is obsolete - aliases were used when Postgres doesn't support named
arguments."

I was just trying to confirm that the warning was not for ALIAS being
declared. That it was for what you state below.

ok