From: Leif Biberg Kristensen <leif@solumslekt.org>
To: pgsql-sql@postgresql.org
Subject: Re: Subselects not allowed?
Date: Sat, 11 Jun 2011 17:39:04 +0200
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On Saturday 11. June 2011 17.23.40 Andreas Kretschmer wrote:
> Leif Biberg Kristensen <leif@solumslekt.org> wrote:
> > Can anybody tell me why this doesn't work?
> > 
> > pgslekt=> CREATE SEQUENCE sources_source_id_seq START WITH (SELECT
> > MAX(source_id) FROM sources);
> > ERROR:  syntax error at or near "("
> > LINE 1: CREATE SEQUENCE sources_source_id_seq START WITH (SELECT MAX...
> > 
> >                                                          ^
> > 
> > pgslekt=>
> > 
> > regards, Leif
> 
> You can't do that, but you can do this:
> 
> test=# select * from foo;
>  i
> ----
>  98
>  99
> (2 rows)
> 
> Time: 0,146 ms
> test=*# \ds seq_foo;
> No matching relations found.
> test=*# do $$ declare m int; begin select into m max(i) from foo; execute
> 'create sequence seq_foo start with ' || m; end; $$; DO
> Time: 1,115 ms
> test=*# \ds seq_foo;
>             List of relations
>  Schema |  Name   |   Type   |   Owner
> --------+---------+----------+------------
>  public | seq_foo | sequence | kretschmer
> (1 row)
> 
> test=*# select * from seq_foo;
>  sequence_name | last_value | start_value | increment_by |      max_value  
>    | min_value | cache_value | log_cnt | is_cycled | is_called
> ---------------+------------+-------------+--------------+----------------
> -----+-----------+-------------+---------+-----------+----------- seq_foo  
>     |         99 |          99 |            1 | 9223372036854775807 |     
>    1 |           1 |       1 | f         | f (1 row)
> 
> 
> 
> I'm using 9.1Beta, but it works since 9.0, see:
> http://www.depesz.com/index.php/2009/11/01/waiting-for-8-5-do/#more-1535

Yes it works like a charm with 9.x, but it's not backwards compatible.

That looks like a problem waiting to happen. But of course I can create a one-
shot function and drop it afterwards.

regards, Leif