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Date: Wed, 14 Sep 2016 12:41:20 +0000 (UTC)
From: "Alex Petrov (JIRA)" <jira@apache.org>
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Subject: [jira] [Commented] (CASSANDRA-12060) Establish consistent
 distinction between non-existing partition and NULL value for LWTs on
 static columns
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archived-at: Wed, 14 Sep 2016 12:41:22 -0000


    [ https://issues.apache.org/jira/browse/CASSANDRA-12060?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15490342#comment-15490342 ] 

Alex Petrov commented on CASSANDRA-12060:
-----------------------------------------

I agree that having the behaviour consistent with the regular columns makes most sense. 

bq. I'm not sure I understand the reason for the change in CQL3CasRequest.columnsToRead() 

This was added to make sure that output in 3.x is same as in 2.x: 

{code}
assertRows(execute("BEGIN BATCH " +
                           "UPDATE %1$s SET v='foobar' WHERE id=0 AND k='k1'; " +
                           "UPDATE %1$s SET v='barfoo' WHERE id=0 AND k='k2'; " +
                           "UPDATE %1$s SET version=3 WHERE id=0 IF version=1; " +
                           "APPLY BATCH "),
                   row(false, 0, "k1", 2));
// vs
//                 row(false, 0, null, 2));
{code}

bq. I'm not fond of using null for empty partitions since we can just test with isEmpty() directly.

Agree. This makes it much cleaner. 

bq. I think the code would be easier to follow if we separated static conditions in CQL3CasRequest

True, it is much easier to follow now. Special-casing static clause was quite counter-intuitive.

I've ran the dtests locally and they're failing, but they're mostly cosmetic (condition is being applied correctly, just returned results differ a bit). Do we want to keep the resultset format for LWTs completely same as it was in 2.x?..

> Establish consistent distinction between non-existing partition and NULL value for LWTs on static columns
> ---------------------------------------------------------------------------------------------------------
>
>                 Key: CASSANDRA-12060
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-12060
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: Alex Petrov
>            Assignee: Alex Petrov
>
> When executing following CQL commands: 
> {code}
> CREATE KEYSPACE test WITH replication = {'class': 'NetworkTopologyStrategy', 'datacenter1': '1' };
> USE test;
> CREATE TABLE testtable (a int, b int, s1 int static, s2 int static, v int, PRIMARY KEY (a, b));
> INSERT INTO testtable (a,b,s1,s2,v) VALUES (2,2,2,null,2);
> DELETE s1 FROM testtable WHERE a = 2 IF s2 IN (10,20,30);
> {code}
> The output is different between {{2.x}} and {{3.x}}:
> 2.x:
> {code}
> cqlsh:test> DELETE s1 FROM testtable WHERE a = 2 IF s2 = 5;
>  [applied] | s2
> -----------+------
>      False | null
> {code}
> 3.x:
> {code}
> cqlsh:test> DELETE s1 FROM testtable WHERE a = 2 IF s2 = 5;
>  [applied]
> -----------
>      False
> {code}
> {{2.x}} would although return same result if executed on a partition that does not exist at all:
> {code}
> cqlsh:test> DELETE s1 FROM testtable WHERE a = 5 IF s2 = 5;
>  [applied]
> -----------
>      False
> {code}
> It _might_ be related to static column LWTs, as I could not reproduce same behaviour with non-static column LWTs. The most recent change was [CASSANDRA-10532], which enabled LWT operations on static columns with partition keys only. -Another possible relation is [CASSANDRA-9842], which removed distinction between {{null}} column and non-existing row.- (striked through since same happens on pre-[CASSANDRA-9842] code.


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