Re: ERROR: functions in index expression must be marked IMMUTABLE

On 02/28/2017 01:35 AM, Sven R. Kunze wrote:
> On 27.02.2017 18:17, Adrian Klaver wrote:
>> Yes, but is not about timezone dependency, it is about the other
>> dependencies listed in the second and third points. Namely the
>> datestyle setting and magic strings e.g. 'now'
>
> I am sorry, I still don't understand. to_date and to_timestamp require
> datestyle settings per se and magic strings don't work.

See here:

https://www.postgresql.org/message-id/11190.1488127834%40sss.pgh.pa.us

"There are multiple reasons why the text-to-datetime conversion
functions are not immutable"

Tom was referring to the text --> date cast you where attempting in your
original index definition:

create index docs_birthdate_idx ON docs using btree
(((meta->>'birthdate')::date));

So:

test=> select 'today'::date;
date
------------
2017-02-28
(1 row)

test=> select 'now'::date;
date
------------
2017-02-28
(1 row)

test=> set datestyle = 'SQL, DMY';
SET
test=> select 'today'::date;
date
------------
28/02/2017
(1 row)

test=> select 'now'::date;
date
------------
28/02/2017
(1 row)

Now you tried to work around the casting issue by using to_timestamp:

create index docs_birthdate_idx ON docs using btree
((to_timestamp(meta->>'birthdate', 'YYYY-MM-DD') at time zone 'UTC'));

but that introduced the issue that to_timestamp returns a timestamptz
and so you end up with a dependency on timezones.

>
>
> =# -- required datestyle
> =# select to_date('2000-01-01');
> ERROR: function to_date(unknown) does not exist
> LINE 1: select to_date('2000-01-01');
> ^
> HINT: No function matches the given name and argument types. You might
> need to add explicit type casts.
>
>
> =# -- magic strings don't work
> =# select to_date('');
> ERROR: invalid value "epoc" for "YYYY"
> DETAIL: Value must be an integer.
> =# select to_date('epoch', 'YYYY-MM-DD');
> ERROR: invalid value "epoc" for "YYYY"
> DETAIL: Value must be an integer.
> =# select to_date('infinity', 'YYYY-MM-DD');
> ERROR: invalid value "infi" for "YYYY"
> DETAIL: Value must be an integer.
> =# select to_date('-infinity', 'YYYY-MM-DD');
> ERROR: invalid value "-inf" for "YYYY"
> DETAIL: Value must be an integer.
> =# select to_date('now', 'YYYY-MM-DD');
> ERROR: invalid value "now" for "YYYY"
> DETAIL: Value must be an integer.
> =# select to_date('today', 'YYYY-MM-DD');
> ERROR: invalid value "toda" for "YYYY"
> DETAIL: Value must be an integer.
> =# select to_date('tomorrow', 'YYYY-MM-DD');
> ERROR: invalid value "tomo" for "YYYY"
> DETAIL: Value must be an integer.
> =# select to_date('yesterday', 'YYYY-MM-DD');
> ERROR: invalid value "yest" for "YYYY"
> DETAIL: Value must be an integer.
> =# select to_date('allballs', 'YYYY-MM-DD');
> ERROR: invalid value "allb" for "YYYY"
> DETAIL: Value must be an integer.
>
> Regards,
> Sven

--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com