Reads (get_column) miss data or return stale values if a memtable is being
flushed
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Key: CASSANDRA-98
URL: https://issues.apache.org/jira/browse/CASSANDRA-98
Project: Cassandra
Issue Type: Bug
Affects Versions: trunk
Environment: all
Reporter: Sandeep Tata
Assignee: Sandeep Tata
Fix For: trunk
Reads can return missing values (null/exception) or find stale copies of a
column if the read happens during an SSTable flush.
The get_column can go in, and not find the data in the current memtable. When
it looks in the "historical" memtable, if that CF has already been flushed,
then it gets cleared from the historical memtable. As a result, the read looks
for the column in older SSTables and finds a stale value (if it exists) or
returns with null.
It can be tricky to reproduce this problem, but the reason is pretty easy to
see.
While subsequent reads might return the correct value (from disk), this
behavior makes it very difficult for apps that expect to "read your writes", at
least in the absence of failures.
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