Andres de la Peña created CASSANDRA-18078:
---------------------------------------------
Summary: 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
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.
--
This message was sent by Atlassian Jira
(v8.20.10#820010)
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
