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https://issues.apache.org/jira/browse/CASSANDRA-4176?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13288495#comment-13288495
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Ahmet AKYOL edited comment on CASSANDRA-4176 at 6/4/12 4:24 PM:
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+1 on 'separation of concerns'. It has nothing to do with composite keys.
On the other hand, as a C* user (a freeloader, not a talented committer like
you guys ), I do not like the sound of any user side (like CQL 3) solution for
sharding wide rows; because, with this approach, users have to think about
"sharding" themselves for many of their CFs.
The problem here is the row size again as in
[CASSANDRA-3929|https://issues.apache.org/jira/browse/CASSANDRA-3929] and IMHO,
the same solution (compaction strategy but maybe with some extras like
chaining) can be used here. I'm sure, it'll make things more complicated on
Cassandra side. However, it's better for users.
In fact, the real problem is the "very very wide rows" as mentioned. Partition
by hash (or any other automatic way) may cause efficiency problems for the
crowd ("not very wide rows") due to unnecessary sharding.
So, please attack the "very very wide rows" problem and if possible, find a
configurable (like "wide row sharding size hint: 10 MB") solution without CQL 3.
P.S.: I'll also admit that, "automated sharding for time series" can be good
enough for some use cases but not all of them. So, this issue still makes sense
but not as "sharding very wide rows" but as "automated sharding for time
series".
was (Author: liqusha):
+1 on 'separation of concerns'. It has nothing to do with composite keys.
On the other hand, as a C* user (a freeloader, not a talented committer like
you guys ), I do not like the sound of any user side (like CQL 3) solution for
sharding wide rows; because, users will have to think about "sharding" for most
of their CFs.
The problem here is the row size again as in
[CASSANDRA-3929|https://issues.apache.org/jira/browse/CASSANDRA-3929] and IMHO,
the same solution (compaction strategy but maybe with some extras like
chaining) can be used here. I'm sure, it'll make things more complicated on
Cassandra side. However, it's better for users.
In fact, the real problem is the "very very wide rows" as mentioned. Partition
by hash (or any other automatic way) may cause efficiency problems for the
crowd ("not very wide rows") due to unnecessary sharding.
So, please attack the "very very wide rows" problem and if possible, find a
configurable (like "wide row sharding size hint: 10 MB") solution without CQL 3.
P.S.: I'll also admit that, "automated sharding for time series" can be good
enough for some use cases but not all of them. So, this issue still makes sense
but not as "sharding very wide rows" but as "automated sharding for time
series".
> Support for sharding wide rows in CQL 3.0
> -----------------------------------------
>
> Key: CASSANDRA-4176
> URL: https://issues.apache.org/jira/browse/CASSANDRA-4176
> Project: Cassandra
> Issue Type: Sub-task
> Components: API
> Reporter: Nick Bailey
> Fix For: 1.1.2
>
>
> CQL 3.0 currently has support for defining wide rows by declaring a composite
> primary key. For example:
> {noformat}
> CREATE TABLE timeline (
> user_id varchar,
> tweet_id uuid,
> author varchar,
> body varchar,
> PRIMARY KEY (user_id, tweet_id)
> );
> {noformat}
> It would also be useful to manage sharding a wide row through the cql schema.
> This would require being able to split up the actual row key in the schema
> definition. In the above example you might want to make the row key a
> combination of user_id and day_of_tweet, in order to shard timelines by day.
> This might look something like:
> {noformat}
> CREATE TABLE timeline (
> user_id varchar,
> day_of_tweet date,
> tweet_id uuid,
> author varchar,
> body varchar,
> PRIMARY KEY (user_id REQUIRED, day_of_tweet REQUIRED, tweet_id)
> );
> {noformat}
> Thats probably a terrible attempt at how to structure that in CQL. But I
> think I've gotten the point across. I tagged this for cql 3.0, but I'm
> honestly not sure how much work it might be. As far as I know built in
> support for composite keys is limited.
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