Hi Mike,
Thanks for the answer.
Yes, I was aware yet hopeful regarding the size.
Regarding the converter, I would be interested to take a look at your py3
work, if you could forward it along.
Thanks.
On Wed, Sep 2, 2020, 00:21 Fred Blaise <fred.bla...@gmail.com> wrote:
> Hi,
>
> I have to migrate a database from mysql to postgresql. Unfortunately,
> there is quite a bit of data in there.
>
> As a strategy, I thought of using Django's ORM feature, dump the data from
> my setup using mysql, and load the fixtures on the other setup using
> postgresql, such as:
>
> # on mysql
> $ docker exec -ti madchap_ddojo_uwsgi_1 bash -c 'python manage.py dumpdata
> --indent=4 -e sessions -e admin --natural-foreign --natural-primary -e
> contenttypes -e auth.permission -v2' > ~/Downloads/datadump_orm_dump_1.json
>
> This yields a 4GB json file.
>
> Reload on the other side, such as:
>
> # on postgresql
> $ docker exec -ti madchap_ddojo_uwsgi_1 bash -c 'python manage.py
> loaddata datadump_orm_dump_small.json'
>
> I let the loaddata run for 4hours, and it eventually returns with no error
> -- but no success either. I actually now think that the message indicating
> "Installed x object(s) from 1 fixture(s)" does not show, I will see again.
>
> Looking at the postgresql side, querying metatables such as:
>
> SELECT nspname || '.' || relname AS "relation",
> pg_size_pretty(pg_total_relation_size(C.oid)) AS "total_size"
> FROM pg_class C
> LEFT JOIN pg_namespace N ON (N.oid = C.relnamespace)
> WHERE nspname NOT IN ('pg_catalog', 'information_schema')
> AND C.relkind <> 'i'
> AND nspname !~ '^pg_toast'
> ORDER BY pg_total_relation_size(C.oid) DESC
> LIMIT 5;
>
> tells me loads of data gets in there. a "\d+" does not agree, however
> (weird, but I don't know enough to get the difference between the two). And
> yet, I cannot see anything through any SELECT statement (hinting to the
> transaction isolation).
>
> All things equal, this strategy works fine when working with small json
> files. I just successfully did it with a file less than 1MB.
>
> I am guessing I have a few questions, I am stuck here.
>
> 1. Are there any hidden args/switches to manage.py loaddata or else that I
> could look at?
> 2. Are there specific django configuration that could help me load the
> data?
> 3. Does a loaddata actually result in a massive single transaction? (looks
> like so, sounds crazy to me :))
> 4. Is there a better way to migrate my data?
>
> Thanks a lot for any pointers!
> Cheers.
>
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