[pg_restore] Triggers handling

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От Kevin Le Gouguec
Тема [pg_restore] Triggers handling
Дата
Msg-id 2127914125.9520629.1412759915016.JavaMail.zimbra@insa-lyon.fr
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Ответы Re: Triggers handling  (Albe Laurenz <laurenz.albe@wien.gv.at>)
Список pgsql-novice
Hi all,

On 9.1, the doc[1] says that --disable-triggers is only relevant when processing data-only dumps. What about when it's
*not*data-only? 

Say I have a table T (id, column1, column2, ...) and another table T_integrity (id, hash), where "hash" corresponds to
md5(correspondingrow in T). T_integrity is updated by a trigger watching T for insertions/updates/deletions. 
Now I dump (pg_dump -Fc) the base, i.e. a set of tables like T, each with its corresponding T_integrity. My question
is,if the dump is not data-only, is there a formal definition somewhere of pg_restore's behaviour regarding triggers? 

Initially, I thought pg_restore would recreate the tables, register the triggers, and then fill the tables as a series
ofINSERT INTO statements, so the restored T_integrity would end up with duplicated rows (one row from the dump, another
fromthe trigger). As it happened, that wasn't the case. Empirically, pg_restore seems to copy/paste the tables'
contents,and THEN enable triggers (meaning updating T after pg_restore causes an update in T_integrity). 

That's great, since that fits my intended use case (check the hashes after restoring, which would be tautological
and/orconfusing if pg_restore executed triggers). However, I'd like to see it written somewhere that this behaviour is
intendedrather than coincidental, i.e. : 

1) I can expect pg_restore to not execute triggers on regular (not data-only) dumps, without specifying
--without-triggers;
2) This behaviour is consistent with future PostgreSQL versions.


Thanks in advance to anyone who can point the relevant part of the documentation!


[1] http://www.postgresql.org/docs/9.1/static/app-pgrestore.html


--
Kévin Le Gouguec


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