Joe McDonnell created IMPALA-14121:
--------------------------------------
Summary: Allow tuple caching for valid locations with variability
Key: IMPALA-14121
URL: https://issues.apache.org/jira/browse/IMPALA-14121
Project: IMPALA
Issue Type: Task
Components: Frontend
Affects Versions: Impala 5.0.0
Reporter: Joe McDonnell
Tuple caching currently eliminates locations with variability: limits, variable
functions, etc.
Some of those locations are valid to cache. Even though the result is variable,
it is a valid result for the query, and there is no requirement that it vary
from execution to execution. For example, a limit without a sort means that
there can be many acceptable answers to a query. As long as the cached result
is one of those valid answers, it is acceptable.
There are locations where this is not possible. For example, if the variable
result feeds into an exchange, then the consumer fragments may have a mixture
of cache hits and misses. The variability can result in invalid results if it
mixes some fragments using one set of rows and other fragments using a
different set of rows.
A more sophisticated algorithm can determine which locations can handle
variability and allow caching in those circumstances.
--
This message was sent by Atlassian Jira
(v8.20.10#820010)
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
