Hari Sekhon created HIVE-9768:
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Summary: Hive LLAP Metadata pre-load for low latency, +
cluster-wide metadata refresh/invalidate command
Key: HIVE-9768
URL: https://issues.apache.org/jira/browse/HIVE-9768
Project: Hive
Issue Type: New Feature
Components: Database/Schema
Affects Versions: 0.14.0, llap
Environment: HDP 2.2
Reporter: Hari Sekhon
Feature request for Hive LLAP to preload table metadata across all running
nodes to reduce query latency (this is what Impala does).
The design decision behind this in Impala was to avoid the latency overhead of
fetching the metadata at query time, since that's an extra database query (or
possibly HBase query in future) that must first be completely fullfilled before
the Hive LLAP query even starts to run, which would slow down the response to
the user if not pre-loaded.
This pre-loaded metadata also requires a cluster-wide "refresh metadata"
operation, something Impala added later, and now calls "INVALIDATE METADATA" in
it's SQL dialect. I propose using a more intuitive "REFRESH METADATA" Hive
command instead.
(Fyi I was in the first trio of Impala SMEs at Cloudera in early 2013)
Regards,
Hari Sekhon
ex-Cloudera
http://www.linkedin.com/in/harisekhon
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