Re: Transaction Snapshots and Hot Standby

heikki(dot)linnakangas(at)enterprisedb(dot)com (Heikki Linnakangas) writes:
> Simon Riggs wrote:
>> Taking snapshots from primary has a few disadvantages
>>
>> ...
>> * snapshots on primary prevent row removal (but this was also an
>> advantage of this technique!)
>
> That makes it an awful solution for high availability. A backend hung
> in transaction-in-progress state in the slave will prevent row removal
> on the master. Isolating the master from queries done performed in the
> slave is exactly the reason why people use hot standby. And running
> long reporting queries in the standby is again a very typical use case.

I agree that this is a demerit to this approach.

Whether or not, on balance, it makes it an 'awful solution for high
availability' is much more in the eye of the beholder, and NOT obvious
on the face of it.
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