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From "ZhaoYang (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (CASSANDRA-13409) Materialized Views: View cells are resurrected
Date Wed, 03 May 2017 12:44:04 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-13409?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15994766#comment-15994766
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ZhaoYang edited comment on CASSANDRA-13409 at 5/3/17 12:43 PM:
---------------------------------------------------------------

Thanks.

deleted cell + shadowable row tombstone:   deleted cells should be kept even if there is more
recent shadowable row-tombstones, this could be done without changing storage format

regular row tombstone + shadowable row tombstone: if shadowable is newer, only most recent
regular row tombstone plus shadowable should be kept. maybe have to change storage format.
eg. extra flag to indicate extra deletion.


was (Author: jasonstack):
Thanks.

deleted cell + shadowable row tombstone:   deleted cells should be kept even if there is more
recent shadowable row-tombstones, this could be done without changing storage format

regular row tombstone + shadowable row tombstone: if shadowable is newer, only most recent
regular row tombstone should be kept. maybe have to change storage format. eg. extra flag
to indicate extra deletion.

> Materialized Views: View cells are resurrected
> ----------------------------------------------
>
>                 Key: CASSANDRA-13409
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-13409
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Local Write-Read Paths, Materialized Views
>            Reporter: Duarte Nunes
>            Assignee: ZhaoYang
>
> Consider the following commands, ran against trunk@0f054fee5c:
> {code:xml}
> echo "create keyspace ks WITH replication = {'class': 'SimpleStrategy', 'replication_factor':
1};" | bin/cqlsh
> echo "create table ks.base (p int primary key, v1 int, v2 int) with gc_grace_seconds
= 1;" | bin/cqlsh
> echo "create materialized view ks.my_view as select * from ks.base where p is not null
and v1 is not null primary key (v1, p);" | bin/cqlsh
> echo "insert into ks.base (p, v1, v2) values (3, 1, 3) using timestamp 1;" | bin/cqlsh
> bin/nodetool flush ks my_view base
> echo "delete from ks.base using timestamp 2 where p = 3;" | bin/cqlsh
> bin/nodetool flush ks my_view base
> echo "insert into ks.base (p, v1) values (3, 1) using timestamp 3;" | bin/cqlsh
> bin/nodetool flush ks my_view base
> echo "select * from ks.my_view;" | bin/cqlsh
>  v1 | p | v2
> ----+---+----
>   1 | 3 |  3
> (1 rows)
> echo "select * from ks.base;" | bin/cqlsh
>  p | v1 | v2
> ---+----+------
>  3 |  1 | null
> (1 rows)
> {code}
> As you can see, this incorrectly brings back cell v2=3. 
> There is one definitive problem and a potential one:
> * Merging rows must be commutative. If a shadowable tombstone is applied after a row
tombstone, it will replace that tombstone; if a row marker shadows the shadowable tombstone
before the row containing the original data is applied, then any dead cells in said data will
be resurrected;
> * Shadowable tombstones shouldn't compact away previous row tombstones or even deleted
cells; if the relevant tombstones have been GCed from the base table, then a base table update
won't carry them anymore (alongside a newer row marker).



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