Impala Public Jenkins has submitted this change and it was merged. ( 
http://gerrit.cloudera.org:8080/17389 )

Change subject: IMPALA-10680: Replace StringToFloatInternal using 
fast_double_parser library
......................................................................

IMPALA-10680: Replace StringToFloatInternal using fast_double_parser library

StringToFloatInternal is used to parse string into float. It had logic
to ensure it is faster than standard functions like strtod in many
cases, but it was not as accurate. We are replacing it by a third
party library named fast_double_parser which is both fast and doesn't
sacrifise the accuracy for speed. On benchmarking on more than
1 million rows where string is cast to double, it is found that new
patch is on par with the earlier algorithm.

Results:
W/O library: Fetched 1222386 row(s) in 32.10s
With library: Fetched 1222386 row(s) in 31.71s

Testing:
1. Added test to check for accuracy improvement.
2. Ran existing Backend tests for correctness.

Change-Id: Ic105ad38a2fcbf2fb4e8ae8af6d9a8e251a9c141
Reviewed-on: http://gerrit.cloudera.org:8080/17389
Reviewed-by: Impala Public Jenkins <[email protected]>
Tested-by: Impala Public Jenkins <[email protected]>
---
M be/src/exprs/expr-test.cc
M be/src/util/string-parser-test.cc
M be/src/util/string-parser.h
M testdata/workloads/functional-query/queries/QueryTest/values.test
4 files changed, 161 insertions(+), 69 deletions(-)

Approvals:
  Impala Public Jenkins: Looks good to me, approved; Verified

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Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-MessageType: merged
Gerrit-Change-Id: Ic105ad38a2fcbf2fb4e8ae8af6d9a8e251a9c141
Gerrit-Change-Number: 17389
Gerrit-PatchSet: 12
Gerrit-Owner: Amogh Margoor <[email protected]>
Gerrit-Reviewer: Amogh Margoor <[email protected]>
Gerrit-Reviewer: Csaba Ringhofer <[email protected]>
Gerrit-Reviewer: Impala Public Jenkins <[email protected]>
Gerrit-Reviewer: Qifan Chen <[email protected]>
Gerrit-Reviewer: Zoltan Borok-Nagy <[email protected]>

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