doc: add docs for age(xid) and mxid_age(xid)

Reported-by: David Rowley
Discussion: https://postgr.es/m/CAKJS1f_OQpz7rpe-KJmskVxbU06buiXbfonxG3JLB+nGCJ5E=g@mail.gmail.com

Backpatch-through: 16

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 9f17cbd5806a652a5f0e7a3f47877158fb9c433c..13ce7f856a35dea5dded476099411fc114b6d566 100644 (file)
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -25800,6 +25800,34 @@ SELECT collation for ('foo' COLLATE "de_DE");
      
 
      
+      
+       
+        
+         age
+        
+        age  ( xid )
+        integer
+       
+       
+        Returns the number of transactions between the supplied
+        transaction id and the current transaction counter.
+       
+      
+
+      
+       
+        
+         mxid_age
+        
+        mxid_age  ( xid )
+        integer
+       
+       
+        Returns the number of multixacts IDs between the supplied
+        multixact ID and the current multixacts counter.
+       
+      
+