RE: [EXT] Re: Read-only connectios optimizatios

Just a thought if you are moving to AWS Aurora Postgres. You can point the read queries/transaction/long running read queries to the reader node. That will not block the autovacuum process.

-----Original Message-----
From: peter plachta <pplachta(at)gmail(dot)com>
Sent: Saturday, January 25, 2025 4:12 PM
To: Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at>
Cc: Edson Richter <edsonrichter(at)hotmail(dot)com>; pgsql-performance(at)lists(dot)postgresql(dot)org
Subject: [EXT] Re: Read-only connectios optimizatios

External Email: Use caution with links and attachments.

You can still block vacuum from running if you have long running (or very aggressive) read transactions. I don’t think they are very helpful or performant from a Postgres engine perspective.
They can be helpful in application development because they will fail if devs attempt any mutations inside read only (from what I recall).

Sent from my iPhone

> On Jan 25, 2025, at 10:01 AM, Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at> wrote:
>
> On Sat, 2025-01-25 at 14:55 +0000, Edson Richter wrote:
>> -Connections are established using the jdbc "readonly" attribute.
>>
>> Does PostgreSQL perform any optimization on queries in this scenario
>> to avoid establishing locks? Or are these queries treated like any other?
>
> The only difference that I am aware of is that read-only transactions
> at the SERIALIZABLE isolation level can release predicate locks
> earlier, which can benefit performance.
>
> But I don't think that you need to worry: reading transactions only
> take an ACCESS SHARE lock on tables, which won't conflict with data modifications.
>
> Yours,
> Laurenz Albe
>
>