Re: Question about commit consistency level for Lightweight Transactions in Paxos v2

[Weng, Justin via user]

So for upgrading Paxos to v2, the non-serial consistency level should be set to 
ANY or LOCAL_QUORUM, and the serial consistency level should still be SERIAL or 
LOCAL_SERIAL. Got it, thanks!

From: Laxmikant Upadhyay 
Date: Tuesday, 12 March 2024 at 7:33 am
To: user@cassandra.apache.org 
Cc: Weng, Justin 
Subject: Re: Question about commit consistency level for Lightweight 
Transactions in Paxos v2
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You need to set both in case of lwt. your regular non -serial consistency level 
will only applied during commit phase of lwt.


On Wed, 6 Mar, 2024, 03:30 Weng, Justin via user, 
mailto:user@cassandra.apache.org>> wrote:
Hi Cassandra Community,

I’ve been investigating Cassandra Paxos v2 (as implemented in 
CEP-14<https://cwiki.apache.org/confluence/display/CASSANDRA/CEP-14%3A+Paxos+Improvements>)
 which improves the performance of lightweight transaction (LWT). But I’ve got 
a question about setting the commit consistency level for LWT after upgrading 
Paxos.

In 
cqlsh<https://docs.datastax.com/en/cql-oss/3.3/cql/cql_reference/cqlshSerialConsistency.html>,
 gocql<https://github.com/gocql/gocql/blob/master/session.go#L1247> and Python 
driver<https://docs.datastax.com/en/developer/python-driver/3.29/api/cassandra/query/#cassandra.query.Statement.serial_consistency_level>,
 there are two settings for consistency levels: normal Consistency Level and 
Serial Consistency Level. As mentioned in the cqlsh 
documentation<https://docs.datastax.com/en/cql-oss/3.3/cql/cql_reference/cqlshSerialConsistency.html>,
 Serial Consistency Level is only used for LWT and can only be set to either 
SERIAL or LOCAL_SERIAL. However, the Steps for Upgrading 
Paxos<https://github.com/apache/cassandra/blob/trunk/NEWS.txt#L532> and 
CEP-14<https://cwiki.apache.org/confluence/display/CASSANDRA/CEP-14%3A+Paxos+Improvements>
 mention that ANY or LOCAL_QUOROM can be used as the commit consistency level 
for LWT after upgrading Paxos to v2. Therefore, I have a question about how to 
correctly set the commit consistency level to ANY or LOCAL_QUORUM for LWT. 
Namely, which consistency level should I set, the normal Consistency Level or 
Serial Consistency Level?

Any help would be really appreciated.

Thanks,
Justin

Re: Question about commit consistency level for Lightweight Transactions in Paxos v2

[Laxmikant Upadhyay]

You need to set both in case of lwt. your regular non -serial consistency
level will only applied during commit phase of lwt.


On Wed, 6 Mar, 2024, 03:30 Weng, Justin via user, 
wrote:

> Hi Cassandra Community,
>
>
>
> I’ve been investigating Cassandra Paxos v2 (as implemented in CEP-14
> )
> which improves the performance of lightweight transaction (LWT). But I’ve
> got a question about setting the commit consistency level for LWT after
> upgrading Paxos.
>
>
>
> In cqlsh
> ,
> gocql  and Python
> driver
> ,
> there are two settings for consistency levels: normal Consistency Level and
> Serial Consistency Level. As mentioned in the cqlsh documentation
> ,
> Serial Consistency Level is only used for LWT and can only be set to either
> SERIAL or LOCAL_SERIAL. However, the Steps for Upgrading Paxos
>  and CEP-14
> 
> mention that ANY or LOCAL_QUOROM can be used as the commit consistency
> level for LWT after upgrading Paxos to v2. Therefore, I have a question
> about how to correctly set the commit consistency level to ANY or
> LOCAL_QUORUM for LWT. Namely, which consistency level should I set, the
> normal Consistency Level or Serial Consistency Level?
>
>
>
> Any help would be really appreciated.
>
>
>
> Thanks,
>
> Justin
>