windows-function-doc.patch

text/x-patch

Filename: windows-function-doc.patch

Type: text/x-patch

Part: 0

Message: Re: window function count(*) and limit

Patch

Same data as JSON: GET /api/v1/attachments/:id/patch the parsed metadata as JSON — format, series position, per-file stats; never the diff bytes. API reference →

Format: unified

File	+	−
doc/src/sgml/func.sgml	25	0

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 183b72c..7bcbe25 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -10684,6 +10684,30 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
    clause follows the call; otherwise they act as regular aggregates.
   </para>
 
+  <para>
+   The evaluation order may be tricky for Window Functions when used in conjunction 
+   with a <literal>LIMIT</> clause. The <literal>WHERE</> clause is evaluated  
+   first then the Window Function and last the <literal>LIMIT</> is applied.  
+   An example:
+  </para>
+
+<screen>
+# select * from testtable;
+ id | value 
+----+-------
+  1 |     1
+  2 |     2
+  3 |     3
+(3 rows)
+
+# select id,max(id) over () from testtable order by id asc limit 2;
+ id | max 
+----+-----
+  1 |   3
+  2 |   3
+(2 rows)
+</screen>
+
+
   <table id="functions-window-table">
    <title>General-Purpose Window Functions</title>