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https://issues.apache.org/jira/browse/CASSANDRA-18078?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17640679#comment-17640679
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Andres de la Peña commented on CASSANDRA-18078:
-----------------------------------------------
Here is a patch showing how the removal of {{maxwritetime}} would look like:
||PR||CI||
|[trunk|https://github.com/apache/cassandra/pull/2032]|[j8|https://app.circleci.com/pipelines/github/adelapena/cassandra/2520/workflows/96c76fe9-95d4-4d4d-9a28-2fa8651b7abe]
[j11|https://app.circleci.com/pipelines/github/adelapena/cassandra/2520/workflows/e19c0258-cd3c-4864-a103-187a2d0a81de]|
I have preserved the original test cases, even when they are also a bit
redundant since we have separate tests for {{writetime}} and {{collection_max}}.
> Consider removing MAXWRITETIME function
> ---------------------------------------
>
> Key: CASSANDRA-18078
> URL: https://issues.apache.org/jira/browse/CASSANDRA-18078
> Project: Cassandra
> Issue Type: Improvement
> Components: CQL/Syntax
> Reporter: Andres de la Peña
> Priority: Normal
> Time Spent: 10m
> Remaining Estimate: 0h
>
> CASSANDRA-17456 added a new {{MAXWRITETIME}} function that allows to retrieve
> the maximum timestamp of a multi-cell column. For example:
> {code:java}
> > CREATE TABLE t (k int PRIMARY KEY, v set<int>);
> > INSERT INTO t (k, v) VALUES (1, {1, 2}) USING TIMESTAMP 100;
> > UPDATE t USING TIMESTAMP 200 SET v += {3} WHERE k=1;
> > SELECT maxwritetime(v) FROM t;
> maxwritetime(v)
> -----------------
> 200
> {code}
> Later, CASSANDRA-8877 added the means to retrieve the write times and TTLs of
> each of the cells in a multi-cell column:
> {code:java}
> > SELECT writetime(v) FROM t;
> writetime(v)
> -----------------
> [100, 100, 200]
> > SELECT writetime(v[1]) FROM t;
> writetime(v[1])
> -----------------
> 100
> {code}
> Quite recently, CASSANDRA-18060 has added generic CQL functions to get the
> min and max items in a collection. Those functions can be used in combination
> with the classic {{writetime}} function to get the same results as the new
> {{maxwritetime}} function:
> {code:java}
> > SELECT collection_max(writetime(v)) FROM t;
> system.collection_max(writetime(v))
> -------------------------------------
> 200
> {code}
> Those new functions can also be used to get the min timestamp, or the min/max
> TTL, for which there isn't a specific function:
> {code:java}
> SELECT collection_min(writetime(v)) FROM t;
> SELECT collection_min(writetime(v)) FROM t;
> SELECT collection_avg(writetime(v)) FROM t;
> SELECT collection_min(ttl(v)) FROM t;
> SELECT collection_min(ttl(v)) FROM t;
> SELECT collection_avg(ttl(v)) FROM t;
> {code}
> I think this makes the new {{maxwritetime}} mostly redundant, since the new
> functions can achieve the same results in a more generic way. Since the new
> {{maxwritetime}} function is only on trunk, we should consider whether we
> want to remove it in favour of the generic functions.
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