Stamatis Zampetakis created HIVE-25046:
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Summary: Log CBO plans right after major transformations
Key: HIVE-25046
URL: https://issues.apache.org/jira/browse/HIVE-25046
Project: Hive
Issue Type: Improvement
Components: CBO
Reporter: Stamatis Zampetakis
Assignee: Stamatis Zampetakis
Currently the results of various CBO transformations are logged (in DEBUG mode)
at the end of the optimization
[phase|https://github.com/apache/hive/blob/9f5bd72e908244b2fe915e8dc39f55afa94bbffa/ql/src/java/org/apache/hadoop/hive/ql/parse/CalcitePlanner.java#L2106]
and only if we are not in test mode. This has some disadvantages:
* If there is a failure (exception) in some intermediate step we will miss all
the intermediate plans, possibly losing track of what plan led to the problem.
* Intermediate logs are very useful for identifying plan problems while working
on a patch; unfortunately the logs are explicitly disabled in test mode which
means that in order to appear the respective code needs to change every time we
need to see those logs.
* Logging at the end necessitates keeping additional local variables that make
code harder to read.
The goal of this issue is to place DEBUG logging right after major
transformations and independently if we are running in test mode or not to
alleviate the shortcomings mentioned above.
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