[
https://issues.apache.org/jira/browse/CASSANDRA-13127?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16079873#comment-16079873
]
ZhaoYang commented on CASSANDRA-13127:
--------------------------------------
[~tjake] yes, it will have to read existing data more often.
the extra cases are: when updating base's columns which are not used in view.
If a user has multiple views on a base, read-before-write is very likely to
happen, the original optimization won't help too much.
another naive way is totally disable TTL on table with MV. because it may not
make sense to denormalize a short-life data..
> Materialized Views: View row expires too soon
> ---------------------------------------------
>
> Key: CASSANDRA-13127
> URL: https://issues.apache.org/jira/browse/CASSANDRA-13127
> Project: Cassandra
> Issue Type: Bug
> Components: Local Write-Read Paths, Materialized Views
> Reporter: Duarte Nunes
> Assignee: ZhaoYang
>
> Consider the following commands, ran against trunk:
> {code}
> echo "DROP MATERIALIZED VIEW ks.mv; DROP TABLE ks.base;" | bin/cqlsh
> echo "CREATE TABLE ks.base (p int, c int, v int, PRIMARY KEY (p, c));" |
> bin/cqlsh
> echo "CREATE MATERIALIZED VIEW ks.mv AS SELECT p, c FROM base WHERE p IS NOT
> NULL AND c IS NOT NULL PRIMARY KEY (c, p);" | bin/cqlsh
> echo "INSERT INTO ks.base (p, c) VALUES (0, 0) USING TTL 10;" | bin/cqlsh
> # wait for row liveness to get closer to expiration
> sleep 6;
> echo "UPDATE ks.base USING TTL 8 SET v = 0 WHERE p = 0 and c = 0;" | bin/cqlsh
> echo "SELECT p, c, ttl(v) FROM ks.base; SELECT * FROM ks.mv;" | bin/cqlsh
> p | c | ttl(v)
> ---+---+--------
> 0 | 0 | 7
> (1 rows)
> c | p
> ---+---
> 0 | 0
> (1 rows)
> # wait for row liveness to expire
> sleep 4;
> echo "SELECT p, c, ttl(v) FROM ks.base; SELECT * FROM ks.mv;" | bin/cqlsh
> p | c | ttl(v)
> ---+---+--------
> 0 | 0 | 3
> (1 rows)
> c | p
> ---+---
> (0 rows)
> {code}
> Notice how the view row is removed even though the base row is still live. I
> would say this is because in ViewUpdateGenerator#computeLivenessInfoForEntry
> the TTLs are compared instead of the expiration times, but I'm not sure I'm
> getting that far ahead in the code when updating a column that's not in the
> view.
--
This message was sent by Atlassian JIRA
(v6.4.14#64029)
---------------------------------------------------------------------
To unsubscribe, e-mail: commits-unsubscr...@cassandra.apache.org
For additional commands, e-mail: commits-h...@cassandra.apache.org
