Re: [RFC] CREATE QUEUE (log-only table) for londiste/pgQ ccompatibility

On 10/23/2012 04:13 PM, Tom Lane wrote:
> [ hadn't been following this thread, sorry ]
>
> Hannu Krosing <hannu(at)2ndQuadrant(dot)com> writes:
>> My RFC was for a proposal to skip writing the unneeded info in local
>> tables and put it _only_ in WAL.
> This concept seems fundamentally broken. What will happen if the master
> crashes immediately after emitting the WAL record? It will replay it
> locally, that's what, and thus you have uncertainty about whether the
> master will contain the data or not.
I agree that emitting a record indistinguishable from current insert
record would probably be a bad idea as it would require the WAL
replay to examine the table description to find that the corresponding
table does not accept local data .

It surely would be better to use a special record type so crash
recovery on the master knows not to replay it.

The syntax and mechanics of what would essentially be a simple QUEUEing
feature being declared and defined in a similar way to a table were chosen
for 2 reasons -
* familiarity - easy to adapt
* most structure can be shared with tables & views - easy to implement

--------------------
Hannu

> regards, tom lane
>
>