Re: How to check if a field exists in NEW in trigger

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От Pavel Stehule
Тема Re: How to check if a field exists in NEW in trigger
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Msg-id CAFj8pRA7XM3SL2Dp9=_SJk6v7Us+4N42HXK7OSEUFrKv-ibV5A@mail.gmail.com
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Ответ на Re: How to check if a field exists in NEW in trigger  (Thomas Kellerer <spam_eater@gmx.net>)
Ответы Re: How to check if a field exists in NEW in trigger  (Thomas Kellerer <spam_eater@gmx.net>)
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po 5. 8. 2019 v 7:55 odesílatel Thomas Kellerer <spam_eater@gmx.net> napsal:
Igal @ Lucee.org schrieb am 05.08.2019 um 00:52:
> I have the following statement in a trigger:
>
>     new.email = lower(new.email);
>
> When I try to update a record without setting the email column however, I get an error:
>
> SQL Error [42703]: ERROR: record "new" has no field "email"
>   Where: SQL statement "SELECT lower(new.email)"
> PL/pgSQL function on_record_modified() line 26 at assignment
>
> I have seen some hacks suggesting TRY/CATCH or converting to a JSON
> and checking if the field exists, but I would think that there's a
> better way to check if the field is in the NEW record, no?


I assume using to_jsonb(new) and then check for the key in the json value
will be faster than checking e.g. information_schema.column
or pg_catalog.pg_attribute

Alternative solution can be using other language than PLpgSQL - PLPythonu or PLPerl (there it is simple task). This language is not designed for too dynamic code. PLpgSQL triggers are designed for stable schema - you should to know if table has email column or not.

Catching errors in PLpgSQL is relative expensive solution due related savepoint overhead in background.

Regards

Pavel


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