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Donald Smith commented on CASSANDRA-6611:
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I see. But setting gc_grace_seconds to zero will affect deletes other than TTL
expirations, won't it? So, I want something in the TABLE declaration that
states this more declaratively.
> Allow for FINAL ttls and FINAL inserts or TABLEs to eliminate the need for
> tombstones
> -------------------------------------------------------------------------------------
>
> Key: CASSANDRA-6611
> URL: https://issues.apache.org/jira/browse/CASSANDRA-6611
> Project: Cassandra
> Issue Type: New Feature
> Reporter: Donald Smith
>
> Suppose you're not allowed to update the TTL of a column (cell) -- either
> because CQL is extended to allow syntax like "USING *FINAL* TTL 86400" or
> because there were a table option saying that TTL is immutable.
> If you never update the TTL of a column, then there should be no need for
> tombstones at all: any replicas will have the same TTL. So there’d be no
> risk of missed deletes. You wouldn’t even need GCable tombstones. The
> purpose of a tombstone is to cover the case where a different node was down
> and it didn’t notice the delete and it still had the column and tried to
> replicate it back; but that won’t happen if it too had the TTL.
> So, if – and it’s a big if – a table disallowed updates to TTL, then you
> could really optimize deletion of TTLed columns: you could do away with
> tombstones entirely. If a table allows updates to TTL then it’s possible a
> different node will have the row without the TTL and the tombstone would be
> needed.
> Or am I missing something?
> Disallowing updates to rows would seem to enable optimizations in general.
> Write-once, non-updatable rows are a common use case. If cassandra had FINAL
> tables (or FINAL INSERTS) then it could eliminate tombstones for those too.
> Probably other optimizations would be enabled too.
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