Row with 55k deletes timesout scanner lease
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Key: HBASE-946
URL: https://issues.apache.org/jira/browse/HBASE-946
Project: Hadoop HBase
Issue Type: Bug
Reporter: stack
Priority: Blocker
Fix For: 0.18.1, 0.19.0
Made a blocker because it was found by Jon Gray (smile)
So, Jon Gray has a row with 55k deletes all in the same row. When he tries to
scan, his scanner timesout when it gets to this row. The root cause is the
mechanism we use to make sure a delete in a new store file overshadows an entry
at same address in an old file. We accumulate a List of all deletes
encountered. Before adding a delete to the List, we check if already a
deleted. This check is whats killing us. One issue is that its doing super
inefficient check of whether table is root but even fixing this inefficency --
and then removing the check for root since its redundant we're still too slow.
Chatting with Jim K, he suggested that ArrayList check is linear. Changing the
aggregation of deletes to instead use HashSet makes all run an order of
magnitude faster.
Also part of this issue, need to figure why on compaction we are not letting go
of these deletes.
Filing this issue against 0.18.1 so it gets into the RC2 (after chatting w/ J-D
and JK -- J-D is seeing the issue also).
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