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Sylvain Lebresne commented on CASSANDRA-5514:
---------------------------------------------
bq. We should be able to eliminate sstables based on the entire column name,
even if it is a composite one right?
That won't work as well as we want unfortunately. Say your table is something
like:
{noformat}
CREATE TABLE timeline (
key int,
category string,
time timestamp,
value1 int,
value2 text,
PRIMARY KEY (key, category, time);
)
{noformat}
i.e. the (internal) column names are a composite with a category first and then
a timeline for each category (not saying that model is smart, it's just an
example to illustrate :)).
Now say in one sstable you only have entries whose {{time}} is <= 10, but for
{{category}} "a" through "z". So the min/max column names might be
"a:0"/"z:10". So if you do a query like:
{noformat}
SELECT * FROM timeline WHERE key = 3 AND category = "c" AND time > 100
{noformat}
then we cannot eliminate the sstable above, because "a:0" < "c:100" < "z:10".
However, if we keep each component separately, we would keep: for {{category}},
min/max = "a"/"z" and for {{time}}, min/max = 0/10. And from that we can
eliminate the sstable for the query above since the time queried is not in the
min/max range for {{time}}.
> Allow timestamp hints
> ---------------------
>
> Key: CASSANDRA-5514
> URL: https://issues.apache.org/jira/browse/CASSANDRA-5514
> Project: Cassandra
> Issue Type: New Feature
> Components: API, Core
> Reporter: Jonathan Ellis
> Assignee: Marcus Eriksson
> Fix For: 2.0
>
> Attachments: 0001-CASSANDRA-5514-v1.patch
>
>
> Slice queries can't optimize based on timestamp except for rare cases
> (CASSANDRA-4116). However, many common queries involve an implicit time
> component, where the application author knows that he is only interested in
> data more recent than X, or older than Y.
> We could use the per-sstable max and min timestamps we track to avoid
> touching cold data if we could pass a hint to Cassandra about the time range
> we care about.
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