[jira] [Comment Edited] (CASSANDRA-18078) Consider removing MAXWRITETIME function

["Yifan Cai (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-18078?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17642102#comment-17642102 ] 

Yifan Cai edited comment on CASSANDRA-18078 at 12/1/22 6:21 PM:
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Thank you for adding the capability! I also checked the case of map, `collection_*` now works with the data type. As noted in the doc, it now accepts 'any type'. So `collection_max` is equivalent to `maxwritetime`. 

{code:sql}
cqlsh> SELECT a, d, collection_max(writetime(d)) FROM test.max_ts WHERE a = 2;

 a | d            | system.collection_max(writetime(d))
---+--------------+-------------------------------------
 2 | {1: 1, 2: 2} |                    1669918636589727
{code}

What do you think about splitting into 2 patches? One to make `collection_*` functions to work with non-collections, and the other one to remove `maxwritetime`. This way it is a bit more clear in the changes. 


was (Author: yifanc):
Thank you for adding the capability! I also checked the case of map, `collection_*` now works with the data type. As noted in the doc, it now accepts 'any type'. So `collection_max` is equivalent to `maxwritetime`. 

{code:sql}
// code placeholder
cqlsh> SELECT a, d, collection_max(writetime(d)) FROM test.max_ts WHERE a = 2;

 a | d            | system.collection_max(writetime(d))
---+--------------+-------------------------------------
 2 | {1: 1, 2: 2} |                    1669918636589727
{code}

What do you think about splitting into 2 patches? One to make `collection_*` functions to work with non-collections, and the other one to remove `maxwritetime`. This way it is a bit more clear in the changes. 

> 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
>             Fix For: 4.2
>
>          Time Spent: 50m
>  Remaining Estimate: 0h
>
> CASSANDRA-17425 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_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;
> {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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