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https://issues.apache.org/jira/browse/HBASE-21476?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16705694#comment-16705694
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Sean Busbey commented on HBASE-21476:
-------------------------------------
{quote}
HBase clients that don’t provide timestamps to their requests, don’t need to
change anything.
The clients looking to write into a table that supports nanoseconds will have
to provide
nanoseconds via “setTimestamp()” using Java 8’s Instant API. Same goes for per
cell TTL and
Get/Scan requests with “setTimeRange()”
{quote}
What happens if a client that doesn't support nanoseconds attempts to write to
a table that is configured for nanoseconds?
> Support for nanosecond timestamps
> ---------------------------------
>
> Key: HBASE-21476
> URL: https://issues.apache.org/jira/browse/HBASE-21476
> Project: HBase
> Issue Type: New Feature
> Affects Versions: 2.1.1
> Reporter: Andrey Elenskiy
> Assignee: Andrey Elenskiy
> Priority: Major
> Labels: features, patch
> Attachments: Apache HBase - Nanosecond Timestamps v1.pdf,
> nanosecond_timestamps_v1.patch, nanosecond_timestamps_v2.patch
>
>
> Introducing a new table attribute "NANOSECOND_TIMESTAMPS" to tell HBase to
> handle timestamps with nanosecond precision. This is useful for applications
> that timestamp updates at the source with nanoseconds and still want features
> like column family TTL and "hbase.hstore.time.to.purge.deletes" to work.
> The attribute should be specified either on new tables or on existing tables
> which have timestamps only with nanosecond precision. There's no migration
> from milliseconds to nanoseconds for already existing tables. We could add
> this migration as part of compaction if you think that would be useful, but
> that would obviously make the change more complex.
> I've added a new EnvironmentEdge method "currentTimeNano()" that uses
> [java.time.Instant|https://docs.oracle.com/javase/8/docs/api/java/time/Instant.html]
> to get time in nanoseconds which means it will only work with Java 8. The
> idea is to gradually replace all places where "EnvironmentEdge.currentTime()"
> is used to have HBase working purely with nanoseconds (which is a
> prerequisite for HBASE-14070). Also, I've refactored ScanInfo and
> PartitionedMobCompactor to expect TableDescriptor as an argument which makes
> code a little cleaner and easier to extend.
> Couple more points:
> - column family TTL (specified in seconds) and
> "hbase.hstore.time.to.purge.deletes" (specified in milliseconds) options
> don't need to be changed, those are adjusted automatically.
> - Per cell TTL needs to be scaled by clients accordingly after
> "NANOSECOND_TIMESTAMPS" table attribute is specified.
> Looking for everyone's feedback to know if that's a worthwhile direction.
> Will add more comprehensive tests in a later patch.
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