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From "C. Scott Andreas (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (CASSANDRA-9966) Option to apply statements within a batch sequentially
Date Sun, 18 Nov 2018 18:09:01 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-9966?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

C. Scott Andreas updated CASSANDRA-9966:
----------------------------------------
    Component/s: CQL

> Option to apply statements within a batch sequentially
> ------------------------------------------------------
>
>                 Key: CASSANDRA-9966
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-9966
>             Project: Cassandra
>          Issue Type: New Feature
>          Components: CQL
>            Reporter: Sam Overton
>            Priority: Major
>              Labels: LWT
>             Fix For: 4.x
>
>
> It is possible to batch CAS statements such that their outcome is different to the outcome
were they executed sequentially outside of a batch.
> eg.
> a | b | c
> a | 1 | 1
> BEGIN BATCH
> UPDATE foo SET b=2 WHERE a='a' iF c=1
> UPDATE foo SET c=2 WHERE a='a' IF b=1
> APPLY BATCH
> results in 
> a | b | c
> a | 2 | 2
> If these statements were not batched, the outcome would be 
> UPDATE foo SET b=2 WHERE a='a' iF c=1
> a | b | c
> a | 2 | 1
> UPDATE foo SET c=2 WHERE a='a' IF b=1
> applied=false (pre-condition b=1 not met)
> Cassandra already checks for incompatible preconditions within a batch (eg one statement
with IF c=1 and another statement with IF c=2). It should also check for mutations to columns
in one statement that affect the pre-conditions of another statement, or it should evaluate
the statement pre-conditions sequentially after applying the mutations of the previous statement
to an in-memory model of the partition.
> For backwards compatibility this would have to be a new "strict" batch mode, eg.
> BEGIN STRICT BATCH



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