Re: pg_dump --data-only: is dump ordered to keep foreign-key-relations

Harald Armin Massa wrote:
> [snipped text]
> pg_dump --data-only -U user database
>
> and tried to reload the data. But it fails on foreign keys: depending tables
> are being dumped before the tables they depend on.
>
> I solved it by manually dumping the relevant tables and reloading them,
>
> Now I cannot find documentation
> - if pg_dump is supposed to produce a "ordered dump" so that not doing is a
> bug and I need to present a showcase
> - or if it is simply not implemented and an enhancement request;
> - or if it is even on a theoretical basis impossible to derive the correct
> order. [circular foreign keys came to my mind]

Hi

There are three possibilities to solve this
1) Use pg_dump (or pg_restore, if you are using custom-format dumps)
with the --disable-trigger option (check the man-page for the exact
syntax). This will disable all triggers, including those which check the
foreign-key contraints during the restore

2) If all your foreign keys are defined as "deferrable", you can
wrap the data-loading in a transaction, and do "set contraints all
deferred" before loading the data. This will defer the constraint-checks
until you issue commit.

3) If you have a schema and data-dump in seperate files, you could
manually split the schema dump into two files, one containing all
table definitions, the other containing the f-k definitions. You
can then first restore the schema, then your data, and finally your
foreign keys.

The ordering of the three options in terms of speed is 1 < 3 < 2, I
believe - but 2 and 3 give you additional security, because they check
the foreign keys during the import. 1) relies on the fact the the
dump doesn't containt foreign-key violations.

greetings, Florian Pflug