Re: BUG #14363: CASE against a literal value produces correct against, same expression against a column null doesn't

Vitaly, thanks for reporting that this is fixed in a more recent version of
Postgres.

And thanks to everyone else for their help.

Best wishes.

On Mon, Oct 10, 2016 at 1:09 PM, Vitaly Burovoy <vitaly(dot)burovoy(at)gmail(dot)com>
wrote:

> On 10/10/16, hcate3(at)gmail(dot)com <hcate3(at)gmail(dot)com> wrote:
> > The following bug has been logged on the website:
> >
> > Bug reference: 14363
> > Logged by: Henry Cate
> > Email address: hcate3(at)gmail(dot)com
> > PostgreSQL version: 9.5.2
> > Operating system: x86_64-pc-linux-gnu
> > Description:
> >
> > With this setup:
> >
> > drop table if exists t2;
> > create table t2 (
> > order_key int,
> > decimal_9_1 decimal(9,1),
> > decimal_18_1 decimal(18,1));
> >
> > insert into t2 values (3, 901.8, null);
> >
> >
> > This query:
> >
> > select decimal_9_1, decimal_18_1, (
> > case decimal_9_1
> > when null then 0
> > when decimal_9_1 then 1 end),
> > case (
> > case decimal_9_1
> > when null then 0
> > when decimal_9_1 then 1 end)
> > when 1 then 2
> > when 0 then 3
> > end,
> > case (
> > case decimal_9_1
> > when decimal_18_1 then 0
> > when decimal_9_1 then 1 end)
> > when 1 then 2
> > when 0 then 3
> > end
> > from t2 ;
> >
> >
> > produces these results:
> >
> > decimal_9_1 | decimal_18_1 | case | case | case
> > -------------+--------------+------+------+--------
> > 901.8 | <null> | 1 | 2 | <null>
> > (1 row)
> >
> >
> > I expect the last two columns to both have a value of 2.
> >
> > The fourth column compares the result of the inner case statement to NULL
> > and produces the correct result. The last column compares to a column
> which
> > does have NULL, but some how Postgres gets confused and returns NULL. It
> > should also be returning 2.
> >
> >
> >
> > Here is the version information:
> >
> > ybd_test=# select version();
> > version
> >
> > ------------------------------------------------------------
> ----------------
> > PostgreSQL 9.5.2 on x86_64-pc-linux-gnu, compiled by clang version
> > 3.8.0-2ubuntu3 (tags/RELEASE_380/final), 64-bit
> > (1 row)
>
> Upgrade to the newest version of 9.5. It works as expected as of 9.5.4
> and 9.6.0:
>
> psql (9.5.4)
> Type "help" for help.
>
> postgres=# create table t2 (
> postgres(# order_key int,
> postgres(# decimal_9_1 decimal(9,1),
> postgres(# decimal_18_1 decimal(18,1));
> CREATE TABLE
> postgres=#
> postgres=# insert into t2 values (3, 901.8, null);
> INSERT 0 1
> postgres=# select decimal_9_1, decimal_18_1, (
> postgres(# case decimal_9_1
> postgres(# when null then 0
> postgres(# when decimal_9_1 then 1 end),
> postgres-# case (
> postgres(# case decimal_9_1
> postgres(# when null then 0
> postgres(# when decimal_9_1 then 1 end)
> postgres-# when 1 then 2
> postgres-# when 0 then 3
> postgres-# end,
> postgres-# case (
> postgres(# case decimal_9_1
> postgres(# when decimal_18_1 then 0
> postgres(# when decimal_9_1 then 1 end)
> postgres-# when 1 then 2
> postgres-# when 0 then 3
> postgres-# end
> postgres-# from t2 ;
> decimal_9_1 | decimal_18_1 | case | case | case
> -------------+--------------+------+------+------
> 901.8 | | 1 | 2 | 2
> (1 row)
>
> postgres=# select version();
> version
> ------------------------------------------------------------
> ----------------------------------------------
> PostgreSQL 9.5.4 on x86_64-pc-linux-gnu, compiled by gcc (Gentoo
> 4.7.3-r1 p1.4, pie-0.5.5) 4.7.3, 64-bit
> (1 row)
>
> --
> Best regards,
> Vitaly Burovoy
>

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