Saksham Gangwar created PHOENIX-6273:
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Summary: All the map tasks should operate on the same restored
snapshot
Key: PHOENIX-6273
URL: https://issues.apache.org/jira/browse/PHOENIX-6273
Project: Phoenix
Issue Type: Bug
Components: core
Affects Versions: 4.14.3, 5.0.0
Reporter: Saksham Gangwar
Assignee: Saksham Gangwar
Fix For: 4.x, 4.16.1
Recently we switched an MR application from scanning live tables to scanning
snapshots (PHOENIX-3744). We ran into a severe performance issue, which turned
out to a correctness issue due to over-lapping scan splits generation. After
some debugging we figured that it has been fixed via PHOENIX-4997.
We also *need not restore the snapshot per map task*. Currently, we restore the
snapshot once per map task into a temp directory. For large tables on big
clusters, this creates a storm of NN RPCs. We can do this once per job and let
all the map tasks operate on the same restored snapshot. HBase already did this
via HBASE-18806, we can do something similar.
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