Обсуждение: format() function with string_agg

Raj Gandhi wrote

> I'm trying to use format() function with string_agg with Postgres 9.1.9
> but
> getting error - "too few arguments for format"
>
> I have two tables t_message and t_message_args. Table t_message   has
> 'message' column with text in the format 'Test message first arg is %1$s
> and second arg  %2$s end-of-message'
>
>               id             | integer           |
>               message | character varying |
>
>
> And the second table t_message_args contains message argument and values
>               id           | integer           |
>              arg          | integer           |
>              argvalue  | character varying |
>
>
> Here is the SQL that uses format() function to retrieve formatted message
> by replacing arg value in the message:
> =
> select m.id, format(m.message, string_agg(a.argvalue, ',' order by a.arg)
> from t_message m, t_message_args a
> where m.id = a.id
> group by m.id, m.message
>
>
> ERROR:  too few arguments for format
>
> ********** Error **********
>
> ERROR: too few arguments for format
> SQL state: 22023

format('%s %s', '1', '2'); --works
format('%s %s, array['1','2']) -- doesn't work

http://www.postgresql.org/docs/9.3/interactive/xfunc-sql.html

(arguably this is not SQL language specific and should be relocated to a
more generic part of the documentation...)


> You can't actually write that, though — or at least, it will not match
> this function definition. A parameter marked VARIADIC matches one or more
> occurrences of its element type, not of its own type.
>
> Sometimes it is useful to be able to pass an already-constructed array to
> a variadic function; this is particularly handy when one variadic function
> wants to pass on its array parameter to another one. You can do that by
> specifying VARIADIC in the call:

select format('%s %s', VARIADIC array_agg(val)) from (values ('1'),('2'))
src (val) -- works

Note the use of array_agg(); string_agg() returns text, not an array, so its
not going to be of use here - unless you want to build up the specifier
portion on the fly too:

select format(string_agg(fmt_prt, ';'), array_agg(val))
from (values ('%s','1'),('%s','2')) src (fmt_prt, val) --works

David J.





--
View this message in context: http://postgresql.1045698.n5.nabble.com/format-function-with-string-agg-tp5820247p5820251.html
Sent from the PostgreSQL - admin mailing list archive at Nabble.com.


--
Sent via pgsql-admin mailing list (pgsql-admin@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-admin

Note that the second query you noted has an error - i left out the VARIADIC modifier before the array_agg()

The 9.1 and 9.3 documentation match with respect to the above so it should work in theory...

You should supply the exact queries you attempted; and at the moment I cannot test anything except 9.0 and 9.3 so maybe someone else can confirm.

David J.

On Wed, Sep 24, 2014 at 9:26 AM, Raj Gandhi <raj01gandhi@gmail.com> wrote:

I tried both SQLs in Postgres 9.1 but they failed with same error - "ERROR: too few arguments for format"

select format('%s %s', VARIADIC array_agg(val)) from (values ('1'),('2'))
src (val) 

select format(string_agg(fmt_prt, ';'), array_agg(val))
from (values ('%s','1'),('%s','2')) src (fmt_prt, val) 

==

ERROR:  too few arguments for format

********** Error **********

ERROR: too few arguments for format

SQL state: 22023

It looks like the error is specific to 9.1 since it worked for you in 9.3.  

I can't upgrade to 9.3 soon. Is there any workaround  or another way to achieve the formatting of message?

On Tue, Sep 23, 2014 at 11:09 PM, David G Johnston <david.g.johnston@gmail.com> wrote:

Raj Gandhi wrote

> I'm trying to use format() function with string_agg with Postgres 9.1.9
> but
> getting error - "too few arguments for format"
>
> I have two tables t_message and t_message_args. Table t_message   has
> 'message' column with text in the format 'Test message first arg is %1$s
> and second arg  %2$s end-of-message'
>
>               id             | integer           |
>               message | character varying |
>
>
> And the second table t_message_args contains message argument and values
>               id           | integer           |
>              arg          | integer           |
>              argvalue  | character varying |
>
>
> Here is the SQL that uses format() function to retrieve formatted message
> by replacing arg value in the message:
> =
> select m.id, format(m.message, string_agg(a.argvalue, ',' order by a.arg)
> from t_message m, t_message_args a
> where m.id = a.id
> group by m.id, m.message
>
>
> ERROR:  too few arguments for format
>
> ********** Error **********
>
> ERROR: too few arguments for format
> SQL state: 22023

format('%s %s', '1', '2'); --works
format('%s %s, array['1','2']) -- doesn't work

http://www.postgresql.org/docs/9.3/interactive/xfunc-sql.html

(arguably this is not SQL language specific and should be relocated to a
more generic part of the documentation...)


> You can't actually write that, though — or at least, it will not match
> this function definition. A parameter marked VARIADIC matches one or more
> occurrences of its element type, not of its own type.
>
> Sometimes it is useful to be able to pass an already-constructed array to
> a variadic function; this is particularly handy when one variadic function
> wants to pass on its array parameter to another one. You can do that by
> specifying VARIADIC in the call:

select format('%s %s', VARIADIC array_agg(val)) from (values ('1'),('2'))
src (val) -- works

Note the use of array_agg(); string_agg() returns text, not an array, so its
not going to be of use here - unless you want to build up the specifier
portion on the fly too:

select format(string_agg(fmt_prt, ';'), array_agg(val))
from (values ('%s','1'),('%s','2')) src (fmt_prt, val) --works

David J.





--
View this message in context: http://postgresql.1045698.n5.nabble.com/format-function-with-string-agg-tp5820247p5820251.html
Sent from the PostgreSQL - admin mailing list archive at Nabble.com.


--
Sent via pgsql-admin mailing list (pgsql-admin@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-admin

On Wednesday, September 24, 2014, Tom Lane <tgl@sss.pgh.pa.us> wrote:

Raj Gandhi <raj01gandhi@gmail.com> writes:
> SQL with VARIADIC also gives the same error in 9.1:
> select format('%s %s', VARIADIC array_agg(val))
> from (values ('1'),('2')) src (val)
> ==
> ERROR:  too few arguments for format

You need 9.3 or later for that to work.  Per the 9.3 release notes:

    * Allow concat() and format() to properly expand VARIADIC-labeled arguments (Pavel Stehule)

                        regards, tom lane

Found it.

 http://www.postgresql.org/docs/9.3/interactive/functions-string.html

In the comments after table 9.6

This whole feature could maybe be made more visible in the 9.3 documentation but (arguably) since it was a feature and not a bug fix back patching was not possible.  Specifically it seems like it was too invasive a change to make it work properly in the back branches.

David J.