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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 5/4/17 10:59 AM:
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Thanks. I didn't think about compaction with sub-group
1. 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
since it's after gc_grace_seconds, it's less critical.
2. 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.
it's critical..
was (Author: jasonstack):
Thanks. I didn't think about compaction with sub-group
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.
> 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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