Re: How can I look at a recursive table dependency tree?

Ivan Sergio Borgonovo wrote:
> On Mon, 19 Jan 2009 14:41:12 +0000
> Richard Huxton <dev@archonet.com> wrote:
>
>> Ivan Sergio Borgonovo wrote:
>>> On Mon, 19 Jan 2009 14:19:51 +0000
>>> Richard Huxton <dev@archonet.com> wrote:
>>>
>>>> Igor Katson wrote:
>>>>> Is there a way to watch all dependencies recursively without
>>>>> doing a drop?
>>>> BEGIN;
>>>> DROP CASCADE...
>>>> -- check things
>>>> ROLLBACK;
>>> Isn't it going to be a pretty expensive way to see?
>
>> Not necessarily - you're not likely to have a lot of concurrency
>> on a backup database. And we are all testing this sort of stuff on
>> a backup database, aren't we?
>
> Isn't it going to be expensive even if there is no concurrency?

Not particularly. If you DELETE a lot of rows that can be expensive, but
dropping a table doesn't need to track each record individually.

> mvcc should be pretty efficient to rollback transactions but... well
> it should have a cost anyway... and you add deleting to rolling
> back, not just traversing some schema somehow.

No deletion, just removes the table (and its indexes) from catalogues
and deletes the relevant file(s) on commit.

> Surely recursively traversing a schema may be expensive in termos of
> programming time if there is no pre-build function.

Well, it shouldn't take more than an hour or so to write and test a
function. Never done so myself, since I tend to know what my schemas
look like.

--
  Richard Huxton
  Archonet Ltd