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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 <impala-public-jenkins@cloudera.com>
Tested-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com>
135 lines
3.7 KiB
Plaintext
135 lines
3.7 KiB
Plaintext
====
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---- QUERY
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values(1, 2+1, 1.0, 5.0 + 1.0, 'a')
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---- RESULTS
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1,3,1.0,6.0,'a'
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---- TYPES
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TINYINT, SMALLINT, DECIMAL, DECIMAL, STRING
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====
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---- QUERY
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values(1+1, 2, 5.0, 'a') order by 1 limit 10
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---- RESULTS
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2,2,5.0,'a'
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---- TYPES
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SMALLINT, TINYINT, DECIMAL, STRING
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====
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---- QUERY
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values((1+8, 2, 5.0, 'a'), (2, 3, 6.0, 'b'), (3, 4, 7.0, 'c'))
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---- RESULTS
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9,2,5.0,'a'
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2,3,6.0,'b'
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3,4,7.0,'c'
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---- TYPES
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SMALLINT, TINYINT, DECIMAL, STRING
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====
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---- QUERY
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values((1+8, 2, 5.0, 'a'), (2, 3, 6.0, 'b'), (3, 4, 7.0, 'c')) order by 1 desc limit 2
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---- RESULTS
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9,2,5.0,'a'
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3,4,7.0,'c'
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---- TYPES
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SMALLINT, TINYINT, DECIMAL, STRING
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====
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---- QUERY
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# Test literal casts by inserting into a table that requires a float.
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drop table if exists values_test_float_tbl;
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create table values_test_float_tbl(f float);
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insert overwrite values_test_float_tbl values
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(1), (16), (1024), (65536), (1000000), (1.1), (98.6), (0.07), (33.333);
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select * from values_test_float_tbl;
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---- RESULTS
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1
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16
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1024
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65536
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1000000
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1.100000023841858
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98.59999847412109
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0.07
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33.33300018310547
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---- TYPES
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float
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====
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---- QUERY
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# Test literal casts by inserting into a table that requires a decimal.
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drop table if exists values_test_decimal_tbl;
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create table values_test_decimal_tbl(f decimal(20, 4));
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insert overwrite values_test_decimal_tbl values
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(1), (16), (1024), (65536), (1000000), (1.1), (98.6), (0.07), (33.333);
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select * from values_test_decimal_tbl;
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---- RESULTS
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1.0000
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16.0000
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1024.0000
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65536.0000
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1000000.0000
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1.1000
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98.6000
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0.0700
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33.3330
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---- TYPES
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decimal
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====
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---- QUERY
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# IMPALA-2749: Test that multiplying a DOUBLE and a DECIMAL results in a double
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# value and do not overflow.
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drop table if exists i_2749;
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create table i_2749 (dbl1 double, `dec` decimal(9,4), dbl2 double);
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insert overwrite table i_2749 values
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(0.0017,90,1.0113),
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(0.0342,90,1.0113),
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(0.0128,90,1.0113),
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(0.0163,90,1.0113);
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====
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---- QUERY
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select dbl1 * `dec` * dbl2, dbl1 + `dec`, dbl1 - `dec`, dbl1 / `dec` from i_2749;
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---- RESULTS
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0.1547289,90.0017000000000000,-89.9983000000000000,0.0000188888889
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3.112781400000001,90.0342000000000000,-89.9658000000000000,0.0003800000000
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1.1650176,90.0128000000000000,-89.9872000000000000,0.0001422222222
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1.4835771,90.0163000000000000,-89.9837000000000000,0.0001811111111
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---- TYPES
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DOUBLE,DECIMAL,DECIMAL,DECIMAL
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====
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---- QUERY
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select dbl1 * dbl2 * `dec` from i_2749;
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---- RESULTS
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0.1547289
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3.112781400000001
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1.1650176
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1.4835771
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====
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---- QUERY
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# IMPALA-10350: Test the double precision during inserts.
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# For write path to text files, the default precision of 16
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# is a limitation yet to be fixed so test would not see exact values retained.
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drop table if exists i_10350;
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create table i_10350(dbl1 double, dbl2 double);
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# insert one negative value < -2^53 * 10^(-17)
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# and another negative value > -2^53 * 10^(-17)
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# and corresponding positive values.
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insert into table i_10350 values
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(-0.43149576573887316, -0.231495765738873),
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(0.43149576573887316, 0.231495765738873);
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select * from i_10350;
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---- RESULTS
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-0.4314957657388732,-0.231495765738873
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0.4314957657388732,0.231495765738873
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---- TYPES
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DOUBLE,DOUBLE
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====
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---- QUERY
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# IMPALA-10654: Test accurate conversion from DecimalValue to double.
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# Test below creates DecimalValue for 0.43149576573887316, 0.231495765738873,
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# -0.43149576573887316, -0.231495765738873 and 0.43149576573887315568
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# which has `value_` > 2^53, < 2^53, < -2^53, > -2^53 and > 2^64 correspondingly.
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select cast(1 - 0.56850423426112684 as double),
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cast(1 - 0.768504234261127 as double),
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cast(0.56850423426112684 -1 as double),
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cast(0.768504234261127 -1 as double),
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cast(1 - 0.56850423426112684432 as double)
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---- RESULTS
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0.43149576573887316,0.231495765738873,-0.43149576573887316,-0.231495765738873,0.43149576573887316
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---- TYPES
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DOUBLE,DOUBLE,DOUBLE,DOUBLE,DOUBLE
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==== |