Doc: improve documentation about width_bucket().

Specify whether the bucket bounds are inclusive or exclusive,
and improve some other vague language.  Explain the behavior that
occurs when the "low" bound is greater than the "high" bound.
Make width_bucket_numeric's comment more like that for
width_bucket_float8, in particular noting that infinite
bounds are rejected (since they became possible in v14).

Reported-by: Ben Peachey Higdon <bpeacheyhigdon@gmail.com>
Author: Robert Treat <rob@xzilla.net>
Co-authored-by: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Dean Rasheed <dean.a.rasheed@gmail.com>
Discussion: https://postgr.es/m/2BD74F86-5B89-4AC1-8F13-23CED3546AC1@gmail.com
Backpatch-through: 13

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 8d7d9a2f3e8e88a06b83864c22b1ac121f05ab21..a6d79765c1a73bcea14ee4ee2a370f1da1e8d4aa 100644 (file)
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -1824,13 +1824,23 @@ SELECT NOT(ROW(table.*) IS NOT NULL) FROM TABLE; -- detect at least one null in
         which <parameter>operand</parameter> falls in a histogram
         having <parameter>count</parameter> equal-width buckets spanning the
         range <parameter>low</parameter> to <parameter>high</parameter>.
-        Returns <literal>0</literal>
+        The buckets have inclusive lower bounds and exclusive upper bounds.
+        Returns <literal>0</literal> for an input less
+        than <parameter>low</parameter>,
         or <literal><parameter>count</parameter>+1</literal> for an input
-        outside that range.
+        greater than or equal to <parameter>high</parameter>.
+        If <parameter>low</parameter> &gt; <parameter>high</parameter>,
+        the behavior is mirror-reversed, with bucket <literal>1</literal>
+        now being the one just below <parameter>low</parameter>, and the
+        inclusive bounds now being on the upper side.
        </para>
        <para>
         <literal>width_bucket(5.35, 0.024, 10.06, 5)</literal>
         <returnvalue>3</returnvalue>
+       </para>
+       <para>
+        <literal>width_bucket(9, 10, 0, 10)</literal>
+        <returnvalue>2</returnvalue>
        </para></entry>
       </row>
 
@@ -1842,8 +1852,8 @@ SELECT NOT(ROW(table.*) IS NOT NULL) FROM TABLE; -- detect at least one null in
        <para>
         Returns the number of the bucket in
         which <parameter>operand</parameter> falls given an array listing the
-        lower bounds of the buckets.  Returns <literal>0</literal> for an
-        input less than the first lower
+        inclusive lower bounds of the buckets.
+        Returns <literal>0</literal> for an input less than the first lower
         bound.  <parameter>operand</parameter> and the array elements can be
         of any type having standard comparison operators.
         The <parameter>thresholds</parameter> array <emphasis>must be

diff --git a/src/backend/utils/adt/float.c b/src/backend/utils/adt/float.c
index 6d20ae07ae7b08a69a54762e3fa52841ed03b7b6..ba66a9c4ce63affca0a7cc026aec397f60eeac7b 100644 (file)
--- a/src/backend/utils/adt/float.c
+++ b/src/backend/utils/adt/float.c
@@ -4065,8 +4065,8 @@ float84ge(PG_FUNCTION_ARGS)
  * in the histogram. width_bucket() returns an integer indicating the
  * bucket number that 'operand' belongs to in an equiwidth histogram
  * with the specified characteristics. An operand smaller than the
- * lower bound is assigned to bucket 0. An operand greater than the
- * upper bound is assigned to an additional bucket (with number
+ * lower bound is assigned to bucket 0. An operand greater than or equal
+ * to the upper bound is assigned to an additional bucket (with number
  * count+1). We don't allow "NaN" for any of the float8 inputs, and we
  * don't allow either of the histogram bounds to be +/- infinity.
  */

diff --git a/src/backend/utils/adt/numeric.c b/src/backend/utils/adt/numeric.c
index 40dcbc7b6710b37a781a5b9543243c06a4aaaf07..58ad1a65ef7b109b73860c4945661921632a596e 100644 (file)
--- a/src/backend/utils/adt/numeric.c
+++ b/src/backend/utils/adt/numeric.c
@@ -1958,9 +1958,10 @@ generate_series_numeric_support(PG_FUNCTION_ARGS)
  * in the histogram. width_bucket() returns an integer indicating the
  * bucket number that 'operand' belongs to in an equiwidth histogram
  * with the specified characteristics. An operand smaller than the
- * lower bound is assigned to bucket 0. An operand greater than the
- * upper bound is assigned to an additional bucket (with number
- * count+1). We don't allow "NaN" for any of the numeric arguments.
+ * lower bound is assigned to bucket 0. An operand greater than or equal
+ * to the upper bound is assigned to an additional bucket (with number
+ * count+1). We don't allow "NaN" for any of the numeric inputs, and we
+ * don't allow either of the histogram bounds to be +/- infinity.
  */
 Datum
 width_bucket_numeric(PG_FUNCTION_ARGS)