Update description of timestamp types for 7.3 implementation.

diff --git a/doc/src/sgml/datatype.sgml b/doc/src/sgml/datatype.sgml
index e8a6233277bbb8d3b16b89d06d51fa3bd9a22831..24b169ba6a35128f9107bfc8883af708bc4138d0 100644 (file)
--- a/doc/src/sgml/datatype.sgml
+++ b/doc/src/sgml/datatype.sgml
@@ -1,5 +1,5 @@
 
 
  
@@ -1276,7 +1276,7 @@ SELECT b, char_length(b) FROM test2;
       
       
        
-        timestamp [ (p) ] without time zone
+        timestamp [ (p) ] [ without time zone ]
         both date and time
         8 bytes
         4713 BC
@@ -1284,7 +1284,7 @@ SELECT b, char_length(b) FROM test2;
         1 microsecond / 14 digits
        
        
-        timestamp [ (p) ] [ with time zone ]
+        timestamp [ (p) ] with time zone
         both date and time
         8 bytes
         4713 BC
@@ -1293,7 +1293,7 @@ SELECT b, char_length(b) FROM test2;
        
        
         interval [ (p) ]
-        for time intervals
+        time intervals
         12 bytes
         -178000000 years
         178000000 years
@@ -1334,16 +1334,22 @@ SELECT b, char_length(b) FROM test2;
     optional precision value p which
     specifies the number of fractional digits retained in the seconds
     field. By default, there is no explicit bound on precision.  The
-    effective limit of precision is determined by the underlying double
-    precision floating-point number used to store values (in seconds
-    for interval and
-    in seconds since 2000-01-01 for timestamp).  The
-    useful range of p is from 0 to about
-    6 for timestamp, but may be more for interval.
-    The system will accept p ranging from
-    0 to 13.
+    allowed range of p is from 0 to 6.
    
 
+   
+   
+    When timestamps are stored as double precision floating-point
+    numbers (currently the default), the effective limit of precision
+    may be less than 6, since timestamp values are stored as seconds
+    since 2000-01-01.  Microsecond precision is achieved for dates within
+    a few years of 2000-01-01, but the precision degrades for dates further
+    away.  When timestamps are stored as eight-byte integers (a compile-time
+    option), microsecond precision is available over the full range of
+    values.
+   
+   
+
    
     Time zones, and time-zone conventions, are influenced by
     political decisions, not just earth geometry. Time zones around the