Re: Temporarily very slow planning time after a big delete

On Tue, May 21, 2019 at 8:27 PM Walter Smith <[email protected]> wrote:

> On Tue, May 21, 2019 at 11:17 AM Peter Geoghegan <[email protected]> wrote:
>
>> On Tue, May 21, 2019 at 11:16 AM Walter Smith <[email protected]>
>> wrote:
>> > It occurs to me that is a somewhat unusual index -- it tracks
>> unprocessed notifications so it gets an insert and delete for every row,
>> and is normally almost empty.
>>
>> Is it a very low cardinality index? In other words, is the total
>> number of distinct keys rather low? Not just at any given time, but
>> over time?
>
>
> Very low. Probably less than ten over all time. I suspect the only use of
> the index is to rapidly find the processed=false rows, so the
> notifiable_type value isn’t important, really. It would probably work just
> as well on any other column.
>
> — Walter
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