Hi Alvaro,
Thanks for the feedback!
On 3/27/21 3:13 PM, Alvaro Herrera wrote:
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> On 2021-Feb-02, Drouvot, Bertrand wrote:
>
>> On 12/18/20 12:26 AM, Tom Lane wrote:
>>> But any of these options lead to the same question: why stop there?
>>> An approach that would actually be defensible, perhaps, is to incorporate
>>> this functionality into the dependency mechanism: any time we're about to
>>> create a pg_depend or pg_shdepend entry, take out an AccessShareLock on
>>> the referenced object, and then check to make sure it still exists.
>>> This would improve the dependency mechanism so it prevents creation-time
>>> race conditions, not just attempts to drop dependencies of
>>> already-committed objects.
>> Agree that working with pg_depend and pg_shdepend is the way to go.
>>
>> Instead of using the locking machinery (and then make the one that
>> would currently produce the orphaned object waiting), Jim proposed
>> another approach: make use of special snapshot (like a dirty one
>> depending of the case).
>>
>> That way instead of locking we could instead report an error,
>> something like this:
>>
>> postgres=# drop schema tobeorph;
>> ERROR: cannot drop schema tobeorph because other objects that are currently under creation depend on it
>> DETAIL: function under creation tobeorph.bdttime() depends on schema tobeorph
> Sounds like an idea worth trying.
Great, if no objections is coming then I'll work on a patch proposal.
> What are the semantics of that
> special snapshot? Why do we need a special snapshot at all -- doesn't
> CatalogSnapshot serve?
Yes, the CatalogSnapshot should serve the need.
By "special" I meant "dirty" for example.
>
> This item is classified as a bug-fix in the commitfest, but it doesn't
> sound like something we can actually back-patch.
Why couldn't it be back-patchable?
Thanks
Bertrand
