Re: deferred primary key and logical replication

On Sun, Oct 25, 2020 at 9:39 PM Euler Taveira
<euler(dot)taveira(at)2ndquadrant(dot)com> wrote:
>
> On Mon, 5 Oct 2020 at 08:34, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>>
>> On Mon, May 11, 2020 at 2:41 AM Euler Taveira
>> <euler(dot)taveira(at)2ndquadrant(dot)com> wrote:
>> >
>> > Hi,
>> >
>> > While looking at an old wal2json issue, I stumbled on a scenario that a table
>> > with a deferred primary key is not updatable in logical replication. AFAICS it
>> > has been like that since the beginning of logical decoding and seems to be an
>> > oversight while designing logical decoding.
>> >
>>
>> I am not sure if it is an oversight because we document that the index
>> must be non-deferrable, see "USING INDEX records the old values of the
>> columns covered by the named index, which must be unique, not partial,
>> not deferrable, and include only columns marked NOT NULL." in docs
>> [1].
>>
>
> Inspecting this patch again, I forgot to consider that RelationGetIndexList()
> is called by other backend modules. Since logical decoding deals with finished
> transactions, it is ok to use a deferrable primary key.
>

But starting PG-14, we do support logical decoding of in-progress
transactions as well.

--
With Regards,
Amit Kapila.