From: Tom Lane <tgl@sss.pgh.pa.us>
To: pgsql-hackers@lists.postgresql.org
Cc: Dean Rasheed <dean.a.rasheed@gmail.com>
Subject: Wrong results from in_range() tests with infinite offset
Date: Thu, 16 Jul 2020 14:58:13 -0400
Message-ID: <3393130.1594925893@sss.pgh.pa.us> (raw)
Dean Rasheed pointed out that in_range for float4/float8 seems to be
doing the wrong thing for infinite offsets, and after some testing
I concur that it is. For example, a sort key of '-infinity' should
be considered to be in-range for a range specified as RANGE BETWEEN
'inf' PRECEDING AND 'inf' PRECEDING; but with the code as it stands,
it isn't. I propose the attached patch, which probably should be
back-patched.
When the current row's value is +infinity, actual computation of
base - offset would yield NaN, making it a bit unclear whether
we should consider -infinity to be in-range. It seems to me that
we should, as that gives more natural-looking results in the test
cases, so that's how the patch does it.
regards, tom lane
Attachments:fix-infinite-in_range-cases.patch (text/x-diff, 7.3K) downloaddiff --git a/src/backend/utils/adt/float.c b/src/backend/utils/adt/float.cindex 50ec3d3dde..5c722d85c3 100644--- a/src/backend/utils/adt/float.c+++ b/src/backend/utils/adt/float.c@@ -1090,11 +1090,18 @@ in_range_float8_float8(PG_FUNCTION_ARGS)
/*
* Deal with infinite offset (necessarily +inf, at this point). We must
* special-case this because if base happens to be -inf, their sum would
- * be NaN, which is an overflow-ish condition we should avoid.+ * be NaN, which is an overflow-ish condition we must avoid. We take that+ * sum to be +inf; that is, we consider base + inf to be +inf for any+ * non-NaN base. Conversely, base - inf is taken to be -inf even if base+ * is +inf. These choices may seem arbitrary, but they give desirable+ * windowing behavior with an infinite offset.
*/
if (isinf(offset))
{
- PG_RETURN_BOOL(sub ? !less : less);+ if (sub)+ sum = -get_float8_infinity();+ else+ sum = get_float8_infinity();
}
/*
@@ -1103,7 +1110,7 @@ in_range_float8_float8(PG_FUNCTION_ARGS)
* produce a suitably signed infinity, which will compare properly against
* val whether or not that's infinity.
*/
- if (sub)+ else if (sub)
sum = base - offset;
else
sum = base + offset;
@@ -1159,11 +1166,18 @@ in_range_float4_float8(PG_FUNCTION_ARGS)
/*
* Deal with infinite offset (necessarily +inf, at this point). We must
* special-case this because if base happens to be -inf, their sum would
- * be NaN, which is an overflow-ish condition we should avoid.+ * be NaN, which is an overflow-ish condition we must avoid. We take that+ * sum to be +inf; that is, we consider base + inf to be +inf for any+ * non-NaN base. Conversely, base - inf is taken to be -inf even if base+ * is +inf. These choices may seem arbitrary, but they give desirable+ * windowing behavior with an infinite offset.
*/
if (isinf(offset))
{
- PG_RETURN_BOOL(sub ? !less : less);+ if (sub)+ sum = -get_float8_infinity();+ else+ sum = get_float8_infinity();
}
/*
@@ -1172,7 +1186,7 @@ in_range_float4_float8(PG_FUNCTION_ARGS)
* produce a suitably signed infinity, which will compare properly against
* val whether or not that's infinity.
*/
- if (sub)+ else if (sub)
sum = base - offset;
else
sum = base + offset;
diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.outindex d5fd4045f9..4cb68ca42f 100644--- a/src/test/regress/expected/window.out+++ b/src/test/regress/expected/window.out@@ -1936,6 +1936,42 @@ window w as (order by f_float4 range between
9 | NaN | 9 | 9
(10 rows)
+select id, f_float4, first_value(id) over w, last_value(id) over w+from numerics+window w as (order by f_float4 range between+ 'inf' preceding and 'inf' preceding);+ id | f_float4 | first_value | last_value +----+-----------+-------------+------------+ 0 | -Infinity | 0 | 0+ 1 | -3 | 0 | 0+ 2 | -1 | 0 | 0+ 3 | 0 | 0 | 0+ 4 | 1.1 | 0 | 0+ 5 | 1.12 | 0 | 0+ 6 | 2 | 0 | 0+ 7 | 100 | 0 | 0+ 8 | Infinity | 0 | 0+ 9 | NaN | 9 | 9+(10 rows)++select id, f_float4, first_value(id) over w, last_value(id) over w+from numerics+window w as (order by f_float4 range between+ 'inf' following and 'inf' following);+ id | f_float4 | first_value | last_value +----+-----------+-------------+------------+ 0 | -Infinity | 8 | 8+ 1 | -3 | 8 | 8+ 2 | -1 | 8 | 8+ 3 | 0 | 8 | 8+ 4 | 1.1 | 8 | 8+ 5 | 1.12 | 8 | 8+ 6 | 2 | 8 | 8+ 7 | 100 | 8 | 8+ 8 | Infinity | 8 | 8+ 9 | NaN | 9 | 9+(10 rows)+
select id, f_float4, first_value(id) over w, last_value(id) over w
from numerics
window w as (order by f_float4 range between
@@ -1995,6 +2031,42 @@ window w as (order by f_float8 range between
9 | NaN | 9 | 9
(10 rows)
+select id, f_float8, first_value(id) over w, last_value(id) over w+from numerics+window w as (order by f_float8 range between+ 'inf' preceding and 'inf' preceding);+ id | f_float8 | first_value | last_value +----+-----------+-------------+------------+ 0 | -Infinity | 0 | 0+ 1 | -3 | 0 | 0+ 2 | -1 | 0 | 0+ 3 | 0 | 0 | 0+ 4 | 1.1 | 0 | 0+ 5 | 1.12 | 0 | 0+ 6 | 2 | 0 | 0+ 7 | 100 | 0 | 0+ 8 | Infinity | 0 | 0+ 9 | NaN | 9 | 9+(10 rows)++select id, f_float8, first_value(id) over w, last_value(id) over w+from numerics+window w as (order by f_float8 range between+ 'inf' following and 'inf' following);+ id | f_float8 | first_value | last_value +----+-----------+-------------+------------+ 0 | -Infinity | 8 | 8+ 1 | -3 | 8 | 8+ 2 | -1 | 8 | 8+ 3 | 0 | 8 | 8+ 4 | 1.1 | 8 | 8+ 5 | 1.12 | 8 | 8+ 6 | 2 | 8 | 8+ 7 | 100 | 8 | 8+ 8 | Infinity | 8 | 8+ 9 | NaN | 9 | 9+(10 rows)+
select id, f_float8, first_value(id) over w, last_value(id) over w
from numerics
window w as (order by f_float8 range between
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sqlindex fe273aa31e..51ec0bac9a 100644--- a/src/test/regress/sql/window.sql+++ b/src/test/regress/sql/window.sql@@ -524,6 +524,14 @@ window w as (order by f_float4 range between
'inf' preceding and 'inf' following);
select id, f_float4, first_value(id) over w, last_value(id) over w
from numerics
+window w as (order by f_float4 range between+ 'inf' preceding and 'inf' preceding);+select id, f_float4, first_value(id) over w, last_value(id) over w+from numerics+window w as (order by f_float4 range between+ 'inf' following and 'inf' following);+select id, f_float4, first_value(id) over w, last_value(id) over w+from numerics
window w as (order by f_float4 range between
1.1 preceding and 'NaN' following); -- error, NaN disallowed
@@ -541,6 +549,14 @@ window w as (order by f_float8 range between
'inf' preceding and 'inf' following);
select id, f_float8, first_value(id) over w, last_value(id) over w
from numerics
+window w as (order by f_float8 range between+ 'inf' preceding and 'inf' preceding);+select id, f_float8, first_value(id) over w, last_value(id) over w+from numerics+window w as (order by f_float8 range between+ 'inf' following and 'inf' following);+select id, f_float8, first_value(id) over w, last_value(id) over w+from numerics
window w as (order by f_float8 range between
1.1 preceding and 'NaN' following); -- error, NaN disallowed
=
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To: pgsql-hackers@postgresql.org
Cc: tgl@sss.pgh.pa.us, pgsql-hackers@lists.postgresql.org, dean.a.rasheed@gmail.com
Subject: Re: Wrong results from in_range() tests with infinite offset
In-Reply-To: <3393130.1594925893@sss.pgh.pa.us>
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