From efcecd9eca884776137b156a3f1f93c23b98a648 Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <peter_e@gmx.net>
Date: Tue, 22 May 2001 16:37:17 +0000
Subject: Make bit and bit varying types reject too long input.  (They already
 tried to do that, but inconsistently.)  Make bit type reject too short input,
 too, per SQL.  Since it no longer zero pads, 'zpbit*' has been renamed to
 'bit*' in the source, hence initdb.

---
 doc/src/sgml/datatype.sgml | 50 +++++++++++++++++++++++++++++++++-------------
 1 file changed, 36 insertions(+), 14 deletions(-)

(limited to 'doc/src')

diff --git a/doc/src/sgml/datatype.sgml b/doc/src/sgml/datatype.sgml
index bbbc85197bb..e86614f2ef7 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 1.54 2001/05/21 16:54:45 petere Exp $
+$Header: /cvsroot/pgsql/doc/src/sgml/datatype.sgml,v 1.55 2001/05/22 16:37:15 petere Exp $
 -->
 
  <chapter id="datatype">
@@ -2276,30 +2276,52 @@ SELECT * FROM test1 WHERE a;
     Bit strings are strings of 1's and 0's.  They can be used to store
     or visualize bit masks.  There are two SQL bit types:
     <type>BIT(<replaceable>x</replaceable>)</type> and <type>BIT
-    VARYING(<replaceable>x</replaceable>)</type>; the
-    <replaceable>x</replaceable> specifies the maximum length.
-    <type>BIT</type> type data is automatically padded with 0's on the
-    right to the maximum length, <type>BIT VARYING</type> is of
-    variable length.  <type>BIT</type> without length is equivalent
-    to <literal>BIT(1)</literal>, <type>BIT VARYING</type> means
-    unlimited length.  Input data that is longer than the allowed
-    length will be truncated.  Refer to <xref
+    VARYING(<replaceable>x</replaceable>)</type>; where
+    <replaceable>x</replaceable> is a positive integer.
+   </para>
+
+   <para>
+    <type>BIT</type> type data must match the length
+    <replaceable>x</replaceable> exactly; it is an error to attempt to
+    store shorter or longer bit strings.  <type>BIT VARYING</type> is
+    of variable length up to the maximum length
+    <replaceable>x</replaceable>; longer strings will be rejected.
+    <type>BIT</type> without length is equivalent to
+    <literal>BIT(1)</literal>, <type>BIT VARYING</type> without length
+    specification means unlimited length.
+   </para>
+
+   <note>
+    <para>
+     Prior to PostgreSQL 7.2, <type>BIT</type> type data was
+     zero-padded on the right.  This was changed to comply with the
+     SQL standard.  To implement zero-padded bit strings, a
+     combination of the concatenation operator and the
+     <function>substring</function> function can be used.
+    </para>
+   </note>
+
+   <para>
+    Refer to <xref
     linkend="sql-syntax-bit-strings"> for information about the syntax
     of bit string constants.  Bit-logical operators and string
     manipulation functions are available; see <xref
     linkend="functions">.
    </para>
 
-   <informalexample>
-    <para>
-     Some examples:
+   <example>
+    <title>Using the bit string types</title>
+
 <programlisting>
 CREATE TABLE test (a BIT(3), b BIT VARYING(5));
 INSERT INTO test VALUES (B'101', B'00');
+INSERT INTO test VALUES (B'10', B'101');
+<computeroutput>
+ERROR:  bit string length does not match type bit(3)
+</computeroutput>
 SELECT SUBSTRING(b FROM 1 FOR 2) FROM test;
 </programlisting>
-    </para>
-   </informalexample>
+   </example>
 
   </sect1>
 
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