[
https://issues.apache.org/jira/browse/PHOENIX-2909?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15437596#comment-15437596
]
Andrew Purtell commented on PHOENIX-2909:
-----------------------------------------
You might consider implementing counters as simple puts of deltas as Increments
with SELECT time aggregation of deltas into the current value rather than use
checkAndPut. The semantics won't be quite the same but could satisfy the
majority of counter use cases and my intuition says that will perform much
better on writes and competitively on reads.
> Surface checkAndPut through UPDATE statement
> --------------------------------------------
>
> Key: PHOENIX-2909
> URL: https://issues.apache.org/jira/browse/PHOENIX-2909
> Project: Phoenix
> Issue Type: Bug
> Reporter: James Taylor
> Assignee: James Taylor
> Fix For: 4.9.0
>
>
> We can surface atomic checkAndPut like functionality through support of the
> SQL UPSERT statement.
> For example, the following could use do a get under row lock to perform the
> row update atomically
> {code}
> UPDATE my_table SET counter=coalesce(counter,0) + 1
> FROM my_table WHERE pk1 = 1 AND pk2 = 2;
> {code}
> To force prior MVCC transactions to complete (making it serializable as an
> Increment is), we'd have code like this:
> {code}
> mvcc = region.getMVCC();
> mvcc.completeMemstoreInsert(mvcc.beginMemstoreInsert());
> {code}
> By users setting auto commit to true and issuing an UPDATE statement over a
> non transactional table, they'd get a way for row updates to be atomic. This
> would work especially well to support counters.
> An UPDATE statement would simply be translated to an equivalent UPSERT SELECT
> with a flag being passed to the server such that the row lock and read occurs
> when executed. For example, the above statement would become:
> {code}
> UPSERT INTO my_table(pk1,pk2,counter) SELECT pk1, pk2, coalesce(counter,0) +
> 1
> FROM my_table WHERE pk1 = 1 AND pk2 = 2;
> {code}
> Note that the coalesce call above handles the case where counter is null.
> This could be made prettier with support for the DEFAULT clause at CREATE
> TABLE time (PHOENIX-476).
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
