Tweak parser so that there is a defined representation for datatypes

bpchar, bit, numeric with typmod -1.  Alter format_type so that this
representation is printed when the typmod is -1.  This ensures that
tables having such columns can be pg_dump'd and reloaded correctly.
Also, remove the rather useless and non-SQL-compliant default
precision and scale for type NUMERIC.  A numeric column declared as
such (with no precision/scale) will now have typmod -1 which means
that numeric values of any precision/scale can be stored in it,
without conversion to a uniform scale.  This seems significantly
more useful than the former behavior.  Part of response to bug #513.

1 files changed, 19 insertions, 11 deletions

diff --git a/doc/src/sgml/datatype.sgml b/doc/src/sgml/datatype.sgml
index 83ffcca2750..5a9e9277457 100644
--- a/doc/src/sgml/datatype.sgml
+++ b/doc/src/sgml/datatype.sgml
@@ -1,5 +1,5 @@
 <!--
-$Header: /cvsroot/pgsql/doc/src/sgml/datatype.sgml,v 1.68 2001/11/08 23:36:55 petere Exp $
+$Header: /cvsroot/pgsql/doc/src/sgml/datatype.sgml,v 1.69 2001/11/12 21:04:45 tgl Exp $
 -->
 
  <chapter id="datatype">
@@ -533,14 +533,18 @@ NUMERIC(<replaceable>precision</replaceable>, <replaceable>scale</replaceable>)
 <programlisting>
 NUMERIC(<replaceable>precision</replaceable>)
 </programlisting>
-     selects a scale of 0.  Merely specifying
+     selects a scale of 0.  Specifying
 <programlisting>
 NUMERIC
 </programlisting>
-     uses a default precision and scale, which is currently (30,6).
-     (The SQL standard requires a default scale of 0.  We find this a
-     bit useless.  If you're concerned about portability, always
-     specify the precision and scale explicitly.)
+     without any precision or scale creates a column in which numeric
+     values of any precision and scale can be stored, up to the implementation
+     limit on precision.  A column of this kind will not coerce input
+     values to any particular scale, whereas <type>numeric</type> columns
+     with a declared scale will coerce input values to that scale.
+     (The SQL standard requires a default scale of 0, ie, coercion to
+     integer accuracy.  We find this a bit useless.  If you're concerned about
+     portability, always specify the precision and scale explicitly.)
     </para>
 
     <para>
@@ -852,13 +856,17 @@ CREATE TABLE <replaceable class="parameter">tablename</replaceable> (<replaceabl
    <para>
     The storage requirement for data of these types is 4 bytes plus
     the actual string, and in case of <type>character</type> plus the
-    padding.  Long strings will actually be compressed by the system
-    automatically.  In any case, the longest possible character string
+    padding.  Long strings will be compressed by the system
+    automatically, so the physical requirement on-disk may be less.
+    In any case, the longest possible character string
     that can be stored is about 1 GB.  (The maximum value that will be
     allowed for <replaceable>n</> in the data type declaration is
-    actually larger than that.  It wouldn't be very useful to change
+    less than that.  It wouldn't be very useful to change
     this because with multibyte character encodings the number of
-    characters and bytes can be quite different anyway.)
+    characters and bytes can be quite different anyway.  If you desire
+    to store long strings with no specific upper limit, use <type>text</type>
+    or <type>character varying</type> without a length specifier,
+    rather than making up an arbitrary length limit.)
    </para>
 
    <tip>
@@ -916,7 +924,7 @@ SELECT b, char_length(b) FROM test2;
     <productname>Postgres</productname>.  The <type>name</type> type
     exists <emphasis>only</emphasis> for storage of internal catalog
     names and is not intended for use by the general user.  Its length
-    is currently defined as 32 bytes (31 characters plus terminator)
+    is currently defined as 32 bytes (31 usable characters plus terminator)
     but should be referenced using the macro
     <symbol>NAMEDATALEN</symbol>.  The length is set at compile time
     (and is therefore adjustable for special uses); the default