doc: Document factorial function

This has existed for a very long time, equivalent to the ! and !!
operators, but it was never documented.

Reviewed-by: Tom Lane 
Discussion: https://www.postgresql.org/message-id/flat/6ce1df0e-86a3-e544-743a-f357ff663f68%402ndquadrant.com

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index b65aa28f344188eed0ebc97534c676abb919d42b..9d71678029eacc730c0b31a85201709f1c3ec950 100644 (file)
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -1347,6 +1347,23 @@ repeat('Pg', 4) PgPgPgPg
        
       
 
+      
+       
+        
+         factorial
+        
+        factorial ( bigint )
+        numeric
+       
+       
+        Factorial
+       
+       
+        factorial(5)
+        120
+       
+      
+