From: Bruce Momjian <bruce@momjian.us>
Date: Sat, 9 Jul 2022 00:23:34 +0000 (-0400)
Subject: doc:  add examples for array_length() and jsonb_array_length()
X-Git-Tag: REL_13_8~50
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=49d296d8e8723b7517ecc074be4694349d6a1cd2;p=thirdparty%2Fpostgresql.git

doc:  add examples for array_length() and jsonb_array_length()

The examples show the output of array_length() and jsonb_array_length()
for empty arrays.

Discussion: https://postgr.es/m/CAKFQuwaoBmRuWdMLzLHDCFDJDX3wvfQ7egAF0bpik_BFgG1KWg@mail.gmail.com

Author: David G. Johnston

Backpatch-through: 13
---

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 98a6b264388..560b6d7d335 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -15261,6 +15261,10 @@ table2-mapping
        <para>
         <literal>json_array_length('[1,2,3,{"f1":1,"f2":[5,6]},4]')</literal>
         <returnvalue>5</returnvalue>
+       </para>
+       <para>
+        <literal>jsonb_array_length('[]')</literal>
+        <returnvalue>0</returnvalue>
        </para></entry>
       </row>
 
@@ -17756,10 +17760,19 @@ SELECT NULLIF(value, '(none)') ...
        </para>
        <para>
         Returns the length of the requested array dimension.
+        (Produces NULL instead of 0 for empty or missing array dimensions.)
        </para>
        <para>
         <literal>array_length(array[1,2,3], 1)</literal>
         <returnvalue>3</returnvalue>
+       </para>
+       <para>
+        <literal>array_length(array[]::int[], 1)</literal>
+        <returnvalue>NULL</returnvalue>
+       </para>
+       <para>
+        <literal>array_length(array['text'], 2)</literal>
+        <returnvalue>NULL</returnvalue>
        </para></entry>
       </row>