Skip to content

util: fix codec for negative zero | tidb-test=pr/2427 #57343

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 5 commits into from
Nov 15, 2024
Merged

util: fix codec for negative zero | tidb-test=pr/2427 #57343

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
5 commits
Select commit Hold shift + click to select a range
1b3ff46
fix
wshwsh12 Nov 13, 2024
9cdb6c0
add issue case
wshwsh12 Nov 13, 2024
2d73a20
fix
wshwsh12 Nov 14, 2024
a74c0f4
address comments
wshwsh12 Nov 15, 2024
cf74ab5
Merge remote-tracking branch 'upstream/master' into negative-zero
wshwsh12 Nov 15, 2024
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
19 changes: 19 additions & 0 deletions pkg/util/codec/codec_test.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1333,3 +1333,22 @@ func TestDatumHashEquals(t *testing.T) {
require.NotEqual(t, hasher1.Sum64(), hasher2.Sum64())
require.False(t, tests[len(tests)-1].d1.Equals(tests[len(tests)-1].d2))
}

func TestEncodeFloatForNegativeZero(t *testing.T) {
floatNum := 0.0
floatNum = -floatNum

b := EncodeFloat(nil, floatNum)
_, v, err := DecodeFloat(b)
require.NoError(t, err)
require.Equal(t, floatNum, v)
require.Equal(t, math.Signbit(floatNum), math.Signbit(v))
require.Equal(t, math.Atan2(0, v), math.Pi)

b = EncodeFloatDesc(nil, floatNum)
_, v, err = DecodeFloatDesc(b)
require.NoError(t, err)
require.Equal(t, floatNum, v)
require.Equal(t, math.Signbit(floatNum), math.Signbit(v))
require.Equal(t, math.Atan2(0, v), math.Pi)
}
10 changes: 9 additions & 1 deletion pkg/util/codec/float.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -22,9 +22,17 @@ import (

func encodeFloatToCmpUint64(f float64) uint64 {
Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Add some comments to make it more readable

func encodeFloatToCmpUint64(f float64) uint64 {
    u := math.Float64bits(f)
    // Check the sign bit (the highest bit in the IEEE 754 representation).
    // If the sign bit is 0, the number is non-negative (+0 is considered non-negative).
    if u&signMask == 0 {
        // For non-negative numbers (+0 included), set the sign bit to 1.
        // This ensures non-negative numbers are ordered after negative numbers
        // when compared as unsigned integers.
        u |= signMask
    } else {
        // For negative numbers (-0 included), invert all bits.
        // This reorders negative numbers so that the smallest (closest to 0)
        // has the smallest encoded value, and the most negative has the largest.
        u = ^u
    }
    return u
}

u := math.Float64bits(f)
if f >= 0 {
// Check the sign bit (the highest bit in the IEEE 754 representation).
// If the sign bit is 0, the number is non-negative (+0 is considered non-negative).
if u&signMask == 0 {
// For non-negative numbers (+0 included), set the sign bit to 1.
// This ensures non-negative numbers are ordered after negative numbers
// when compared as unsigned integers.
u |= signMask
} else {
// For negative numbers (-0 included), invert all bits.
// This reorders negative numbers so that the smallest (closest to 0)
// has the smallest encoded value, and the most negative has the largest.
u = ^u
}
return u
Expand Down
6 changes: 6 additions & 0 deletions tests/integrationtest/r/expression/issues.result
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -3230,3 +3230,9 @@ INSERT INTO test.t VALUES (1234567890123456);
SELECT IFNULL(id, 'abcdef') FROM test.t;
IFNULL(id, 'abcdef')
1234567890123456
DROP TABLE IF EXISTS test.t;
CREATE TABLE test.t (c0 decimal(10,0));
INSERT INTO test.t VALUES (0);
SELECT c0 FROM test.t WHERE CAST(ATAN2(((t.c0) IS NULL), (- (''))) AS TIME);
c0
0
6 changes: 6 additions & 0 deletions tests/integrationtest/t/expression/issues.test
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -2182,3 +2182,9 @@ DROP TABLE IF EXISTS test.t;
CREATE TABLE test.t (id bigint(11) UNSIGNED PRIMARY KEY);
INSERT INTO test.t VALUES (1234567890123456);
SELECT IFNULL(id, 'abcdef') FROM test.t;

# TestIssue41878
DROP TABLE IF EXISTS test.t;
CREATE TABLE test.t (c0 decimal(10,0));
INSERT INTO test.t VALUES (0);
SELECT c0 FROM test.t WHERE CAST(ATAN2(((t.c0) IS NULL), (- (''))) AS TIME);