Impala Public Jenkins has submitted this change and it was merged. (
http://gerrit.cloudera.org:8080/17303 )
Change subject: IMPALA-10654: Fix precision loss in DecimalValue to double
conversion.
......................................................................
IMPALA-10654: Fix precision loss in DecimalValue to double conversion.
Original approach to convert DecimalValue(internal representation
of decimals) to double was not accurate.
It was:
static_cast<double>(value_) / pow(10.0, scale).
However only integers from −2^53 to 2^53 can be represented
accurately by double precision without any loss.
Hence, it would not work for numbers like -0.43149576573887316.
For DecimalValue representing -0.43149576573887316, value_ would be
-43149576573887316 and scale would be 17. As value_ < -2^53,
result would not be accurate. In newer approach we are using third
party library https://github.com/lemire/fast_double_parser, which
handles above scenario in a performant manner.
Testing:
1. Added End to End Tests covering following scenarios:
a. Test to show precision limitation of 16 in the write path
b. DecimalValue's value_ between -2^53 and 2^53.
b. value_ outside above range but abs(value_) < UINT64_MAX
c. abs(value_) > UINT64_MAX -covers DecimalValue<__int128_t>
2. Ran existing backend and end-to-end tests completely
Change-Id: I56f0652cb8f81a491b87d9b108a94c00ae6c99a1
Reviewed-on: http://gerrit.cloudera.org:8080/17303
Reviewed-by: Impala Public Jenkins <[email protected]>
Tested-by: Impala Public Jenkins <[email protected]>
---
M be/src/runtime/decimal-value.inline.h
A be/src/thirdparty/fast_double_parser/LICENSE
A be/src/thirdparty/fast_double_parser/LICENSE.BSL
A be/src/thirdparty/fast_double_parser/README.md
A be/src/thirdparty/fast_double_parser/fast_double_parser.h
M bin/rat_exclude_files.txt
M testdata/workloads/functional-query/queries/QueryTest/values.test
M tests/query_test/test_insert_parquet.py
8 files changed, 1,579 insertions(+), 1 deletion(-)
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: I56f0652cb8f81a491b87d9b108a94c00ae6c99a1
Gerrit-Change-Number: 17303
Gerrit-PatchSet: 8
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: Zoltan Borok-Nagy <[email protected]>
