Re: Why extract( ... from timestamp ) is not immutable?

On 2012-01-25, hubert depesz lubaczewski <depesz@depesz.com> wrote:
> On Wed, Jan 25, 2012 at 02:07:40PM -0800, Adrian Klaver wrote:
>> Finally dawned on me. When you use 'at time zone' on a timestamp
>> with tz it strips the tz which then allows the value to be indexed
>> because:
>>
>> -[ RECORD 5 ]-------+-------------------------------------------------------------------------
>> Schema              | pg_catalog
>> Name                | date_part
>> Result data type    | double precision
>> Argument data types | text, timestamp without time zone
>> Type                | normal
>> Volatility          | immutable
>> Owner               | postgres
>> Language            | internal
>> Source code         | timestamp_part
>> Description         | extract field from timestamp
>
> yes, but it is not correct - the value is actually stable, and not
> immutable.

it's immutable for all date parts except "epoch".

epoch is backwards to the other date parts.
immutable for timestamptz and stable for timestamp

--
⚂⚃ 100% natural