David Wayne Birdsall created TRAFODION-2017:
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Summary: Tune HBase row cache sizes so UPDATE STATS completes
Key: TRAFODION-2017
URL: https://issues.apache.org/jira/browse/TRAFODION-2017
Project: Apache Trafodion
Issue Type: Bug
Components: sql-cmp
Affects Versions: 2.0-incubating
Environment: All, though prevalent on clusters with larger tables
and/or heavier loads
Reporter: David Wayne Birdsall
Assignee: David Wayne Birdsall
Fix For: 2.1-incubating
UPDATE STATISTICS often fails with HBase socket timeout exception and/or
scanner timeout exception when run with sampling on larger tables or clusters
with heavy concurrent workloads.
We have experimented in the past with setting various CQDs on large tables to
reduce these failures, however we were loathe to set them all the time due to
fears that this would lengthen elapsed time in non-failure scenarios.
Some recent work by Carol Pearson however shows that the increase in elapsed
time is negligible for smaller tables and in failure scenarios the failure does
not occur quickly, so paying a small penalty in elapsed time to increase the
probability of success seems a better trade-off.
Carol's work involves tables of less than 1 billion rows. The existing CQD
logic is still required for larger tables. But for tables of less than 1
billion rows, she recommends setting HBASE_ROWS_CACHED_MIN and
HBASE_ROWS_CACHED_MAX to '50'. This JIRA is written to cover this change.
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