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

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.

Best regards,

depesz

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