[Impala-CR](cdh5-trunk) IMPALA-3168: replace HashTable parameters with constants

["Tim Armstrong (Code Review)" <ge...@cloudera.org>]

Tim Armstrong has uploaded a new patch set (#3).

Change subject: IMPALA-3168: replace HashTable parameters with constants
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IMPALA-3168: replace HashTable parameters with constants

This addresses the regression for small-ndv aggs resulting from
prefetching. The idea is that for small-ndv aggs prefetching
increases the # of instructions and memory references, but
doesn't provide any compensating benefit. This change replaces
constant values in the hash-table code, which reduces the
instruction count and # of memory references in aggregations.

Preliminary perf results show that a low-NDV decimal agg is
around 20% faster (2.1s -> 1.7s) and a high-NDV decimal agg
is around 7% faster (15s -> 14s). I haven't investigated
how much of the speedup is reduced codegen time.

TODO: rebase onto final version of PHJ prefetch patch.

Change-Id: I483a19662c90ca54bc21d60fd6ba97dbed93eaef
---
M be/src/codegen/llvm-codegen.cc
M be/src/codegen/llvm-codegen.h
M be/src/exec/hash-table-test.cc
M be/src/exec/hash-table.cc
M be/src/exec/hash-table.h
M be/src/exec/hash-table.inline.h
M be/src/exec/partitioned-aggregation-node.cc
M be/src/exec/partitioned-hash-join-node.cc
8 files changed, 246 insertions(+), 83 deletions(-)


  git pull ssh://gerrit.cloudera.org:29418/Impala refs/changes/88/3088/3
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Gerrit-MessageType: newpatchset
Gerrit-Change-Id: I483a19662c90ca54bc21d60fd6ba97dbed93eaef
Gerrit-PatchSet: 3
Gerrit-Project: Impala
Gerrit-Branch: cdh5-trunk
Gerrit-Owner: Tim Armstrong <ta...@cloudera.com>
Gerrit-Reviewer: Dan Hecht <dh...@cloudera.com>
Gerrit-Reviewer: Michael Ho
Gerrit-Reviewer: Tim Armstrong <ta...@cloudera.com>