Re: Wrong results from in_range() tests with infinite offset - Mailing list pgsql-hackers

I wrote:
> 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.

Actually, after staring at those results awhile longer, I decided
they were wrong.  The results shown here seem actually sane ---
for instance, -Infinity shouldn't "infinitely precede" itself,
I think.  (Maybe if you got solipsistic enough you could argue
that that is valid, but it seems pretty bogus.)

            regards, tom lane

diff --git a/src/backend/utils/adt/float.c b/src/backend/utils/adt/float.c
index 50ec3d3dde..7333ec667a 100644
--- a/src/backend/utils/adt/float.c
+++ b/src/backend/utils/adt/float.c
@@ -1089,17 +1089,45 @@ 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.
+     * special-case this when base is also infinite, first because we must
+     * avoid subtracting inf from inf (the result would be NaN), and second
+     * because we'd like to consider inf + inf to be "greater than inf"
+     * (otherwise we'd have oddities like inf being considered to infinitely
+     * precede itself).  That leads to the following code.
      */
-    if (isinf(offset))
+    if (isinf(offset) && isinf(base))
     {
-        PG_RETURN_BOOL(sub ? !less : less);
+        if (sub)
+        {
+            if (less)
+            {
+                /* val <= base - inf: true if base is +inf and val isn't */
+                PG_RETURN_BOOL(base > 0 && (!isinf(val) || val < 0));
+            }
+            else
+            {
+                /* val >= base - inf: true for all val & either sign of base */
+                PG_RETURN_BOOL(true);
+            }
+        }
+        else
+        {
+            if (less)
+            {
+                /* val <= base + inf: true for all val & either sign of base */
+                PG_RETURN_BOOL(true);
+            }
+            else
+            {
+                /* val >= base + inf: true if base is -inf and val isn't */
+                PG_RETURN_BOOL(base < 0 && (!isinf(val) || val > 0));
+            }
+        }
     }

     /*
      * Otherwise it should be safe to compute base +/- offset.  We trust the
-     * FPU to cope if base is +/-inf or the true sum would overflow, and
+     * FPU to cope if one input is +/-inf or the true sum would overflow, and
      * produce a suitably signed infinity, which will compare properly against
      * val whether or not that's infinity.
      */
@@ -1158,17 +1186,45 @@ 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.
+     * special-case this when base is also infinite, first because we must
+     * avoid subtracting inf from inf (the result would be NaN), and second
+     * because we'd like to consider inf + inf to be "greater than inf"
+     * (otherwise we'd have oddities like inf being considered to infinitely
+     * precede itself).  That leads to the following code.
      */
-    if (isinf(offset))
+    if (isinf(offset) && isinf(base))
     {
-        PG_RETURN_BOOL(sub ? !less : less);
+        if (sub)
+        {
+            if (less)
+            {
+                /* val <= base - inf: true if base is +inf and val isn't */
+                PG_RETURN_BOOL(base > 0 && (!isinf(val) || val < 0));
+            }
+            else
+            {
+                /* val >= base - inf: true for all val & either sign of base */
+                PG_RETURN_BOOL(true);
+            }
+        }
+        else
+        {
+            if (less)
+            {
+                /* val <= base + inf: true for all val & either sign of base */
+                PG_RETURN_BOOL(true);
+            }
+            else
+            {
+                /* val >= base + inf: true if base is -inf and val isn't */
+                PG_RETURN_BOOL(base < 0 && (!isinf(val) || val > 0));
+            }
+        }
     }

     /*
      * Otherwise it should be safe to compute base +/- offset.  We trust the
-     * FPU to cope if base is +/-inf or the true sum would overflow, and
+     * FPU to cope if one input is +/-inf or the true sum would overflow, and
      * produce a suitably signed infinity, which will compare properly against
      * val whether or not that's infinity.
      */
diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index d5fd4045f9..8043fccbb2 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 |             |
+  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 |          7
+  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 |           1 |          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 |             |
+  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 |             |
+  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 |          7
+  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 |           1 |          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 |             |
+  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.sql
index 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