Depending on my interpreting (and programming) skills, this might solve

anywhere from zero to two TODO items.

* Allow flag to control COPY input/output of NULLs

I got this:
COPY table .... [ WITH NULL AS 'string' ]
which does what you'd expect. The default is \N, otherwise you can use
empty strings, etc. On Copy In this acts like a filter: every data item
that looks like 'string' becomes a NULL. Pretty straightforward.

This also seems to be related to

* Make postgres user have a password by default

If I recall this discussion correctly, the problem was actually that the
default password for the postgres (or any) user is in fact "\N", because
of the way copy is used. With this change, the file pg_pwd is copied out
with nulls as empty strings, so if someone doesn't have a password, the
password is just '', which one would expect from a new account. I don't
think anyone really wants a hard-coded default password.

Peter Eisentraut                  Sernanders väg 10:115

1 files changed, 27 insertions, 5 deletions

diff --git a/doc/src/sgml/ref/copy.sgml b/doc/src/sgml/ref/copy.sgml
index 3653ae9ef60..adbaa4c8e91 100644
--- a/doc/src/sgml/ref/copy.sgml
+++ b/doc/src/sgml/ref/copy.sgml
@@ -1,5 +1,5 @@
 <!--
-$Header: /cvsroot/pgsql/doc/src/sgml/ref/copy.sgml,v 1.10 1999/10/29 23:52:20 momjian Exp $
+$Header: /cvsroot/pgsql/doc/src/sgml/ref/copy.sgml,v 1.11 1999/12/14 00:08:12 momjian Exp $
 Postgres documentation
 -->
 
@@ -20,15 +20,17 @@ Postgres documentation
  </refnamediv>
  <refsynopsisdiv>
   <refsynopsisdivinfo>
-   <date>1999-07-20</date>
+   <date>1999-12-11</date>
   </refsynopsisdivinfo>
   <synopsis>
 COPY [ BINARY ] <replaceable class="parameter">table</replaceable> [ WITH OIDS ]
     FROM { '<replaceable class="parameter">filename</replaceable>' | <filename>stdin</filename> }
     [ [USING] DELIMITERS '<replaceable class="parameter">delimiter</replaceable>' ]
+    [ WITH NULL AS '<replaceable class="parameter">null string</replaceable>' ]
 COPY [ BINARY ] <replaceable class="parameter">table</replaceable> [ WITH OIDS ]
     TO { '<replaceable class="parameter">filename</replaceable>' | <filename>stdout</filename> }
     [ [USING] DELIMITERS '<replaceable class="parameter">delimiter</replaceable>' ]
+    [ WITH NULL AS '<replaceable class="parameter">null string</replaceable>' ]
   </synopsis>
   
   <refsect2 id="R2-SQL-COPY-1">
@@ -104,6 +106,25 @@ COPY [ BINARY ] <replaceable class="parameter">table</replaceable> [ WITH OIDS ]
        </para>
       </listitem>
      </varlistentry>
+
+     <varlistentry>
+      <term><replaceable class="parameter">null print</replaceable></term>
+      <listitem>
+       <para>
+        A string to represent NULL values. The default is
+        <quote><literal>\N</literal></quote> (backslash-N), for historical
+        reasons. You might prefer an empty string, for example.
+       </para>
+       <note>
+        <para>
+         On a copy in, any data item that matches this string will be stored as
+         a NULL value, so you should make sure that you use the same string
+         as you used on copy out.
+        </para>
+       </hote>
+      </listitem>
+     </varlistentry>
+
     </variablelist>
    </para>
   </refsect2>
@@ -287,15 +308,16 @@ ERROR: <replaceable>reason</replaceable>
     encountered before this special end-of-file pattern is found.
    </para>
    <para>
-    The backslash character has other special meanings.  NULL attributes are
-    represented as "\N".  A literal backslash character is represented as two
+    The backslash character has other special meanings.  A literal backslash
+    character is represented as two
     consecutive backslashes ("\\").  A literal tab character is represented
     as a backslash and a tab.  A literal newline character is
     represented as a backslash and a newline.  When loading text data
     not generated by <acronym>Postgres</acronym>,
     you will need to convert backslash
     characters ("\") to double-backslashes ("\\") to ensure that they are loaded
-    properly.
+    properly. (The sequence "\N" will always be interpreted as a backslash and
+    an "N", for compatibility. The more general solution is "\\N".)
    </para>
   </refsect2>