Files
impala/testdata/workloads/functional-query/queries/QueryTest
Tim Armstrong 7843b472f2 IMPALA-5560: always store CHAR(N) inline in tuple
This is done to simplify the CHAR(N) logic. I believe this is overall an
improvement - any benefits of the out-of-line storage that motivated
this optimisation originally were outweighed by the added complexity.

This also avoids IMPALA-5559 (fe/be have different notions of var-len),
which will unblock IMPALA-3200.

Pros:
* Reduce the number of code paths and improve test coverage.
  (e.g. avoids IMPALA-5559: fe/be have different notions of var-len)
* Reduced memory to store non-NULL data (saves 12-byte StringValue)
* Fewer branches in code -> save CPU cycles.
* If CHAR(N) performance is important, reduced complexity makes it
  easier to implement codegen.

Cons:
* Requires N bytes to store a NULL value.
* May hurt cache locality (although this is speculative in my mind).

The change is mostly mechanical - I removed MAX_CHAR_INLINE_LENGTH
and then removed branches that depended on that.

Testing:
Ran exhaustive build.

Change-Id: I9c0b823ccff6b0c37f5267c548d096c29b8caac3
Reviewed-on: http://gerrit.cloudera.org:8080/7303
Reviewed-by: Tim Armstrong <tarmstrong@cloudera.com>
Tested-by: Impala Public Jenkins
2017-06-30 22:49:40 +00:00
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