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https://issues.apache.org/jira/browse/CASSANDRA-19546?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17842437#comment-17842437
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Brad Schoening commented on CASSANDRA-19546:
--------------------------------------------
[~smiklosovic] I like the intent here and think this will be a nice
enhancement. More direct function names instead of a generic catch-all would
be preferable in my view. I looked at some other DBs which support something
like this:
[format_bytes()|https://dev.mysql.com/doc/refman/5.7/en/sys-format-bytes.html]
{quote}Given a byte count, converts it to human-readable format and returns a
string consisting of a value and a units indicator. Depending on the size of
the value, the units part is {{{}bytes{}}}, {{KiB}} (kibibytes), {{MiB}}
(mebibytes), {{GiB}} (gibibytes), {{TiB}} (tebibytes), or {{PiB}} (pebibytes).
{quote}
[format_time()|https://dev.mysql.com/doc/refman/8.0/en/sys-format-time.html]
{quote}Depending on the size of the value, the units part is {{ps}}
(picoseconds), {{ns}} (nanoseconds), {{us}} (microseconds), {{ms}}
(milliseconds), {{s}} (seconds), {{m}} (minutes), {{h}} (hours), {{d}} (days),
or {{w}} (weeks).
{quote}
[format()|https://dev.mysql.com/doc/refman/8.0/en/string-functions.html#function_format]
{quote}Formats the number _{{X}}_ to a format like {{{}'#,###,###.##'{}}},
rounded to _{{D}}_ decimal places, and returns the result as a string.
{quote}
MySQL, [Big
Query|https://cloud.google.com/bigquery/docs/reference/standard-sql/format-elements]
and [Azure Data
Explorer|https://learn.microsoft.com/en-us/azure/data-explorer/kusto/query/format-bytes-function]
use the format_\{type} approach.
Oracle, Postgres and DataBricks uses a single function
[to_char()|https://www.postgresql.org/docs/current/functions-formatting.html]
One could envision formatting percentages and currency at some future point.
Instead of to_human_size, using either the explicit type naming (format_bytes)
or to_char() would be a good convention to follow.
Would the time / duration format apply to both Cassandra's integer and duration
types? The code otherwise looks fine.
> Add to_human_size and to_human_duration function
> ------------------------------------------------
>
> Key: CASSANDRA-19546
> URL: https://issues.apache.org/jira/browse/CASSANDRA-19546
> Project: Cassandra
> Issue Type: New Feature
> Components: Legacy/CQL
> Reporter: Stefan Miklosovic
> Assignee: Stefan Miklosovic
> Priority: Normal
> Fix For: 5.x
>
> Time Spent: 20m
> Remaining Estimate: 0h
>
> There are cases (e.g in our system_views tables but might be applicable for
> user tables as well) when a column is of a type which represents number of
> bytes. However, it is quite hard to parse a value for a human to have some
> estimation what that value is.
> I propose this:
> {code:java}
> cqlsh> select * from myks.mytb ;
> id | col1 | col2 | col3 | col4
> ----+------+------+------+----------
> 1 | 100 | 200 | 300 | 32432423
> (1 rows)
> cqlsh> select to_human_size(col4) from myks.mytb where id = 1;
> system.to_human_size(col4)
> ----------------------
> 30.93 MiB
> (1 rows)
> cqlsh> select to_human_size(col4,0) from myks.mytb where id = 1;
> system.to_human_size(col4, 0)
> -------------------------
> 31 MiB
> (1 rows)
> cqlsh> select to_human_size(col4,1) from myks.mytb where id = 1;
> system.to_human_size(col4, 1)
> -------------------------
> 30.9 MiB
> (1 rows)
> {code}
> The second argument is optional and represents the number of decimal places
> (at most) to use. Without the second argument, it will default to
> FileUtils.df which is "#.##" format.
> {code}
> cqlsh> DESCRIBE myks.mytb ;
> CREATE TABLE myks.mytb (
> id int PRIMARY KEY,
> col1 int,
> col2 smallint,
> col3 bigint,
> col4 varint,
> )
> {code}
> I also propose that this to_human_size function (name of it might be indeed
> discussed and it is just a suggestion) should be only applicable for int,
> smallint, bigint and varint types. I am not sure how to apply this to e.g.
> "float" or similar. As I mentioned, it is meant to convert just number of
> bytes, which is just some number, to a string representation of that and I do
> not think that applying that function to anything else but these types makes
> sense.
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