Date: Fri, 20 Jan 2023 15:42:10 +0100
From: hubert depesz lubaczewski <depesz@depesz.com>
Sender: depesz@depesz.com
To: Liang Shen <shenzhuxi@gmail.com>
Cc: pgsql-bugs@lists.postgresql.org
Subject: Re: ST_Union(rast, uniontype) treat bands with different classes as
 the same as first band
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On Fri, Jan 20, 2023 at 01:56:51PM +0000, Liang Shen wrote:
> Related to https://trac.osgeo.org/postgis/ticket/2200 support multiple
> bands issue
> 
> If the $RASTER has bands like ARRAY['8BUI', '16BUI'], the result of
> ```
>             ST_Union(
>               $RASTER,
>               ARRAY[
>                 ROW(1, 'SUM'),
>                 ROW(2, 'MAX')
>               ]::unionarg[]
>             )
> ```
> will be like ARRAY['8BUI', ' 8BUI'].
> 
> ST_Union always uses the first band class to process the 2nd band and
> ignore the original class.

You might want to report this bug to postgis devs, as it's clearly not
postgresql bug.

Their page (https://postgis.net/support/) lists
https://trac.osgeo.org/postgis as their bug tracker.

depesz