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Floating-point negative zero doesn't match positive zero in the index [CORE3547] #3903

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firebird-issue-importer opened this issue Jul 7, 2011 · 11 comments

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@firebird-issue-importer firebird-issue-importer commented Jul 7, 2011

Submitted by: John Kilin (johnkilin)

Is related to QA487

The IEEE representation of single- and double-precision floating point values distinguish between positive and negative zeros. When they're compared naturally (using compiler generated code), everything is okay. But if they're stored in the index, they get compared byte-wise. As a result, searching for the negative zero cannot find the positive zero, and vice versa.

Test case:

select count(*) from rdb$relations where rdb$relation_id = 0
-- result = 1

select count(*) from rdb$relations where rdb$relation_id = 0e0
-- result = 1

select count(*) from rdb$relations where rdb$relation_id = (1e0 - 1e0)
-- result = 1

select count(*) from rdb$relations where rdb$relation_id = -0e0
-- result = 0

select count(*) from rdb$relations where rdb$relation_id = -(1e0 - 1e0)
-- result = 0

In dialect 1 it could be reproduced without explicit floating point values:

select count(*) from rdb$relations where rdb$relation_id = (1 - 1)
-- result = 1

select count(*) from rdb$relations where rdb$relation_id = -(1 - 1)
-- result = 0

At the same time:

select count(*) from rdb$database where 0e0 = -0e0
-- result = 1, as no index is involved

Commits: eb546d9 52cfec0 c27550a FirebirdSQL/fbt-repository@4650554

====== Test Details ======

:: NB ::: Problematic key representaion for 0e0 differ in Windows vs Linux!
NIX: -Problematic key value is ("COL" = 0.000000000000000) -- 15 digits
WIN: -Problematic key value is ("COL" = 0.0000000000000000) -- 16 digits

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@firebird-issue-importer firebird-issue-importer commented Jul 7, 2011

Modified by: @dyemanov

assignee: Dmitry Yemanov [ dimitr ]

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@firebird-issue-importer firebird-issue-importer commented Jul 7, 2011

Modified by: @dyemanov

reporter: Dmitry Yemanov [ dimitr ] => John Kilin [ johnkilin ]

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@firebird-issue-importer firebird-issue-importer commented Jul 7, 2011

Commented by: @dyemanov

Another test case (PK violation):

create table t (col double precision primary key);
commit;

insert into t (col) values (0e0);
insert into t (col) values (-0e0);
commit;

select col, count(*) from t group by col;
-- result = {0.000, 2}

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@firebird-issue-importer firebird-issue-importer commented Jul 7, 2011

Modified by: @dyemanov

status: Open [ 1 ] => In Progress [ 3 ]

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@firebird-issue-importer firebird-issue-importer commented Jul 7, 2011

Commented by: @dyemanov

And finally:

create table t (col float);
commit;

insert into t (col) values (0e0);
insert into t (col) values (-0e0);
commit;

select count(distinct col) from t;
-- result = 2

i.e. the sorting module is also affected.

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@firebird-issue-importer firebird-issue-importer commented Jul 7, 2011

Modified by: @dyemanov

status: In Progress [ 3 ] => Open [ 1 ]

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@firebird-issue-importer firebird-issue-importer commented Jul 7, 2011

Modified by: @dyemanov

Fix Version: 2.5.1 [ 10333 ]

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@firebird-issue-importer firebird-issue-importer commented Jul 13, 2011

Modified by: @dyemanov

status: Open [ 1 ] => Resolved [ 5 ]

resolution: Fixed [ 1 ]

Fix Version: 3.0 Alpha 1 [ 10331 ]

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@firebird-issue-importer firebird-issue-importer commented Mar 27, 2014

Modified by: @pcisar

Link: This issue is related to QA487 [ QA487 ]

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@firebird-issue-importer firebird-issue-importer commented Apr 9, 2014

Modified by: @pmakowski

status: Resolved [ 5 ] => Closed [ 6 ]

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@firebird-issue-importer firebird-issue-importer commented May 29, 2015

Modified by: @pavel-zotov

status: Closed [ 6 ] => Closed [ 6 ]

QA Status: Done successfully

Test Details: :: NB ::: Problematic key representaion for 0e0 differ in Windows vs Linux!
NIX: -Problematic key value is ("COL" = 0.000000000000000) -- 15 digits
WIN: -Problematic key value is ("COL" = 0.0000000000000000) -- 16 digits

Test Specifics: [Platform (Windows/Linux) specific]

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