Re: [HACKERS] Error in parser with UNIONS.

David Gould <dg@illustra.com>

From: dg@illustra.com (David Gould)
To: lockhart@alumni.caltech.edu (Thomas G. Lockhart)
Cc: chris@topdog.pas1.logicon.com, pgsql-hackers@hub.org
Date: 1998-05-31T05:29:43Z
Lists: pgsql-hackers
Tom Lane he say:
> Made some progress:
> 
> postgres=> select 1.2 as float8 union select 1;
> float8
> ------
>      1
>    1.2
> (2 rows)
> 
> postgres=> select text 'a' as text union select 'b';
> text
> ----
> a
> b
> (2 rows)
> 
> At the moment I'm forcing the types of the union to match the types of
> the first/top clause in the union:
> 
> postgres=> select 1 as all_integers
> postgres-> union select '2.2'::float4 union select 3.3;
> all_integers
> ------------
>            1
>            2
>            3
> (3 rows)
> 
> The better strategy might be to choose the "best" type of the bunch, but
> is more difficult because of the nice recursion technique used in the
> parser. However, it does work OK when selecting _into_ a table:
> 
> postgres=> create table ff (f float);
> CREATE
> postgres=> insert into ff
> postgres-> select 1 union select '2.2'::float4 union select 3.3;
> INSERT 0 3
> postgres=> select * from ff;
>                f
> ----------------
>                1
> 2.20000004768372
>              3.3
> (3 rows)
> 
> Comments??
> 

Great stuff!
-dg