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James Taylor commented on PHOENIX-3860:
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bq. Will the coprocessor update the secondary index table with the shadow cell
information once the post commit procedure adds these to the data table?
Seems like we'd want these secondary index updates to go through a TAL method
or through the Omid-backed HTableInterface (but somehow optimize them such that
no conflict detection takes place). All this logic is in
PhoenixTransactionalIndexer coprocessor. We could create a different
coprocessor for Omid transactional tables. Or we could change
PhoenixTransactionalIndexer to go through the TAL methods. I think perhaps we
may be missing an API in Tephra to have a region server essentially join a
transaction that was started on the client. Unlike with Omid, writing in Tephra
is pretty much like any other HBase write if you use the correct transaction ID
for the timestamp.
bq. I assume that reading always use the tps api? Otherwise, how can we know
that the data was committed? This is also true for reading from the secondary
index?
Yes, for reads we always go through the Tephra-backed HTableInterface. We
serialize the Tephra transaction over the wire when we need to read on the
server-side. Reads from a secondary index are exactly like reads from a data
table from the POV of HBase.
bq. For now I can use Omid's deletion mark to mark deletion. It is a little
different than Tephra's because we are marking the value as opposed to adding a
special qualifier but I guess it has the same semantics.
The semantics are different. We need both a Cell Delete marker and a Family
Delete marker as they have different semantics. When you issue a SQL DELETE
statement, you're deleting entire rows. When you set a column to null, you're
deleting a cell. You can read about the "empty key value" we add to each row
and the purpose of it here:
https://phoenix.apache.org/faq.html#Why_empty_key_value
> Implement TAL functionality for Omid
> ------------------------------------
>
> Key: PHOENIX-3860
> URL: https://issues.apache.org/jira/browse/PHOENIX-3860
> Project: Phoenix
> Issue Type: Sub-task
> Reporter: Ohad Shacham
> Assignee: Ohad Shacham
>
> Implement TAL functionality for Omid in order to be able to use Omid as
> Phoenix's transaction processing engine.
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