[CASSANDRA-18078] Consider removing MAXWRITETIME function

• Type: Improvement
• Status: Open
• Priority: Normal
• Resolution: Unresolved
• Fix Version/s: 5.0.x
• Component/s: CQL/Syntax
• Change Category: Semantic
• Complexity: Low Hanging Fruit
• Platform: All

Test and Documentation Plan

The tests for maxwritetime are updated to use collection_max(writetime) instead

• Assignee: Stefan Miklosovic
• Reporter: Andres de la Peña

Authors

Stefan Miklosovic

• Created: 29/Nov/22 12:53
• Updated: 20/Jun/24 19:53

Description

CASSANDRA-17425 added a new MAXWRITETIME function that allows to retrieve the maximum timestamp of a multi-cell column. For example:

> 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

Later, CASSANDRA-8877 added the means to retrieve the write times and TTLs of each of the cells in a multi-cell column:

> SELECT writetime(v) FROM t;

 writetime(v)
-----------------
 [100, 100, 200]

> SELECT writetime(v[1]) FROM t;

 writetime(v[1])
-----------------
             100

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:

> SELECT collection_max(writetime(v)) FROM t;

 system.collection_max(writetime(v))
-------------------------------------
                                 200

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:

SELECT collection_min(writetime(v)) FROM t;
SELECT collection_max(writetime(v)) FROM t;
SELECT collection_avg(writetime(v)) FROM t;
SELECT collection_min(ttl(v)) FROM t;
SELECT collection_max(ttl(v)) FROM t;
SELECT collection_avg(ttl(v)) FROM t;

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.

Issue Links

• depends upon: CASSANDRA-18085 Add support for singletons on CQL collection functions