cassandra-commits mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "graham sanderson (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (CASSANDRA-7449) Variation of SELECT DISTINCT to find clustering keys with only static columns
Date Thu, 26 Jun 2014 02:03:25 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-7449?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14044242#comment-14044242
] 

graham sanderson edited comment on CASSANDRA-7449 at 6/26/14 2:02 AM:
----------------------------------------------------------------------

Attaching a sample implementation I was just playing around with (patch against cassandra-2.0)
- it has no tests yet, since I have no idea if this is something you guys even want.

Also I am not familiar enough with the code to know how to fix this, but it is very similar
to DISTINCT but STATICONLY breaks the count == 1 relied upon to make CQL row count == live
column count relied upon in two places in the paging code

I need a little advice on that one


was (Author: graham sanderson):
Attaching a sample implementation I was just playing around with - it has no tests yet, since
I have no idea if this is something you guys even want.

Also I am not familiar enough with the code to know how to fix this, but it is very similar
to DISTINCT but STATICONLY breaks the count == 1 relied upon to make CQL row count == live
column count relied upon in two places in the paging code

I need a little advice on that one

> Variation of SELECT DISTINCT to find clustering keys with only static columns
> -----------------------------------------------------------------------------
>
>                 Key: CASSANDRA-7449
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-7449
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: API, Core
>            Reporter: graham sanderson
>         Attachments: paging_broken_no_tests_v0.patch
>
>
> A possible use case for static columns involves (per partition) multiple small TTL time
series data values combined with a potentially much larger static piece of data.
> While the TTL time series data will go away on its own, there is no way to TTL the static
data (and keep it updated with the latest TTL) without re-inserting it every time to reset
the TTL (which is undesirable since it is large and unchanged)
> The use case looks something like this:
> {code}
> CREATE KEYSPACE test WITH replication = {
>   'class': 'SimpleStrategy',
>   'replication_factor': '1'
> };
> USE test;
> CREATE TABLE expiring_series (
> 	id text,
> 	series_order int,
> 	small_data text,
> 	large_data text static,
> 	PRIMARY KEY (id, series_order)
> );
> INSERT INTO expiring_series (id, large_data) VALUES ('123', 'this is large and should
not be inserted every time');
> INSERT INTO expiring_series (id, series_order, small_data) VALUES ('123', 1, 'antelope')
USING TTL 120;
> // time passes (point A)
> INSERT INTO expiring_series (id, series_order, small_data) VALUES ('123', 2, 'gibbon')
USING TTL 120;
> // time passes (point B)
> INSERT INTO expiring_series (id, series_order, small_data) VALUES ('123', 3, 'firebucket')
USING TTL 120;
> // time passes (point C)
> // time passes and the first row expires (point D)
> // more time passes and eventually all the "rows" expire (point E)
> {code}
> GIven the way the storage engine works, there is no trivial way to make the static column
expire when the last row expires, however if there was an easy way to find partitions with
no regular rows (just static columns), then that would make manual clean up easy
> The possible implementation of such a feature is very similar to SELECT DISTINCT, so
I'm suggesting SELECT STATICONLY
> Looking at the points again
> h4. Point A
> {code}
> cqlsh:test> SELECT id, series_order, small_data, large_data, ttl(small_data) from
expiring_series;
>  id  | series_order | small_data | large_data                                       
  | ttl(small_data)
> -----+--------------+------------+-----------------------------------------------------+-----------------
>  123 |            1 |   antelope | this is large and should not be inserted every time
|             108
> (1 rows)
> cqlsh:test> SELECT id FROM expiring_series;
>  id
> -----
>  123
> (1 rows)
> cqlsh:test> SELECT DISTINCT id FROM expiring_series;
>  id
> -----
>  123
> (1 rows)
> cqlsh:test> SELECT STATICONLY id FROM expiring_series;
> (0 rows)
> {code}
> h4. Point B
> {code}
> cqlsh:test> SELECT id, series_order, small_data, large_data, ttl(small_data) from
expiring_series;
>  id  | series_order | small_data | large_data                                       
  | ttl(small_data)
> -----+--------------+------------+-----------------------------------------------------+-----------------
>  123 |            1 |   antelope | this is large and should not be inserted every time
|              87
>  123 |            2 |     gibbon | this is large and should not be inserted every time
|             111
> (2 rows)
> cqlsh:test> SELECT id FROM expiring_series;
>  id
> -----
>  123
>  123
> (2 rows)
> cqlsh:test> SELECT DISTINCT id FROM expiring_series;
>  id
> -----
>  123
> (1 rows)
> cqlsh:test> SELECT STATICONLY id FROM expiring_series;
> (0 rows)
> {code}
> h4. Point C
> {code}
> cqlsh:test> SELECT id, series_order, small_data, large_data, ttl(small_data) from
expiring_series;
>  id  | series_order | small_data | large_data                                       
  | ttl(small_data)
> -----+--------------+------------+-----------------------------------------------------+-----------------
>  123 |            1 |   antelope | this is large and should not be inserted every time
|              67
>  123 |            2 |     gibbon | this is large and should not be inserted every time
|              91
>  123 |            3 | firebucket | this is large and should not be inserted every time
|             110
> (3 rows)
> cqlsh:test> SELECT id FROM expiring_series;
>  id
> -----
>  123
>  123
>  123
> (3 rows)
> cqlsh:test> SELECT DISTINCT id FROM expiring_series;
>  id
> -----
>  123
> (1 rows)
> cqlsh:test> SELECT STATICONLY id FROM expiring_series;
> (0 rows)
> {code}
> h4. Point D
> {code}
> cqlsh:test> SELECT id, series_order, small_data, large_data, ttl(small_data) from
expiring_series;
>  id  | series_order | small_data | large_data                                       
  | ttl(small_data)
> -----+--------------+------------+-----------------------------------------------------+-----------------
>  123 |            2 |     gibbon | this is large and should not be inserted every time
|              22
>  123 |            3 | firebucket | this is large and should not be inserted every time
|              41
> (2 rows)
> cqlsh:test> SELECT id FROM expiring_series;
>  id
> -----
>  123
>  123
> (2 rows)
> cqlsh:test> SELECT DISTINCT id FROM expiring_series;
>  id
> -----
>  123
> (1 rows)
> cqlsh:test> SELECT STATICONLY id FROM expiring_series;
> (0 rows)
> {code}
> h4. Point E
> {code}
> cqlsh:test> SELECT id, series_order, small_data, large_data, ttl(small_data) from
expiring_series;
>  id  | series_order | small_data | large_data                                       
  | ttl(small_data)
> -----+--------------+------------+-----------------------------------------------------+-----------------
>  123 |         null |       null | this is large and should not be inserted every time
|            null
> (1 rows)
> cqlsh:test> SELECT id FROM expiring_series;
> (0 rows)
> cqlsh:test> SELECT DISTINCT id FROM expiring_series;
>  id
> -----
>  123
> (1 rows)
> cqlsh:test> SELECT STATICONLY id FROM expiring_series;
>  id
> -----
>  123
> (1 rows)
> {code}
> Notice that after the last id has expired SELECT STATICONLY id returns the row, and it
can be deleted (under whatever concurrency rules the application needs)
> {code}
> cqlsh:test> DELETE FROM expiring_series where id = '123';
> cqlsh:test> SELECT id, series_order, small_data, large_data, ttl(small_data) from
expiring_series;
> (0 rows)
> cqlsh:test> SELECT id FROM expiring_series;
> (0 rows)
> cqlsh:test> SELECT DISTINCT id FROM expiring_series;
> (0 rows)
> cqlsh:test> SELECT STATICONLY id FROM expiring_series;
> (0 rows)
> {code}



--
This message was sent by Atlassian JIRA
(v6.2#6252)

Mime
View raw message