Re: Caching and Blobs in PG? Was: Can PG replace redis, amqp, s3 in the future?

On 03.05.2017 12:57, Thomas Güttler wrote:
> Am 02.05.2017 um 05:43 schrieb Jeff Janes:
>> On Sun, Apr 30, 2017 at 4:37 AM, Thomas Güttler
>> <guettliml(at)thomas-guettler(dot)de <mailto:guettliml(at)thomas-guettler(dot)de>>
>> wrote:
>>
>> Is is possible that PostgreSQL will replace these building blocks
>> in the future?
>>
>> - redis (Caching)
>>
>>
>> PostgreSQL has its own caching. It might not be quite as effective
>> as redis', but you can us it if you are willing to
>> take those trade offs.
>
> What kind of caching does PG offer?
>
> I would use a table with a mtime-column and delete the content after N
> days.

After searching the web, it seems to me that PostgreSQL doesn't offer a
cron-like background job for cleanup tasks.

http://stackoverflow.com/questions/18187490/postgresql-delete-old-rows-on-a-rolling-basis

But there's an extension - pg_cron:
https://www.citusdata.com/blog/2016/09/09/pgcron-run-periodic-jobs-in-postgres/

>
>> No. You can certainly use PostgreSQL to store blobs. But then, you
>> need to store the PostgreSQL data **someplace**.
>> If you don't store it in S3, you have to store it somewhere else.
>
> I don't understand what you mean here. AFAIK storing blobs in PG is
> not recommended since it is not very efficient.

Seems like several people here disagree with this conventional wisdom.

I think what he was talking about the data itself. You have to store the
bits and bytes somewhere (e.g. on S3).

Sven