Extend CREATE DATABASE to allow selection of a template database to be

cloned, rather than always cloning template1.  Modify initdb to generate
two identical databases rather than one, template0 and template1.
Connections to template0 are disallowed, so that it will always remain
in its virgin as-initdb'd state.  pg_dumpall now dumps databases with
restore commands that say CREATE DATABASE foo WITH TEMPLATE = template0.
This allows proper behavior when there is user-added data in template1.
initdb forced!

1 files changed, 88 insertions, 22 deletions

diff --git a/doc/src/sgml/ref/create_database.sgml b/doc/src/sgml/ref/create_database.sgml
index d9e371b1be8..0bae8450c16 100644
--- a/doc/src/sgml/ref/create_database.sgml
+++ b/doc/src/sgml/ref/create_database.sgml
@@ -1,5 +1,5 @@
 <!--
-$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_database.sgml,v 1.15 2000/10/05 19:48:17 momjian Exp $
+$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_database.sgml,v 1.16 2000/11/14 18:37:40 tgl Exp $
 Postgres documentation
 -->
 
@@ -23,7 +23,10 @@ Postgres documentation
    <date>1999-12-11</date>
   </refsynopsisdivinfo>
   <synopsis>
-CREATE DATABASE <replaceable class="PARAMETER">name</replaceable> [ WITH LOCATION = '<replaceable class="parameter">dbpath</replaceable>' ]
+CREATE DATABASE <replaceable class="PARAMETER">name</replaceable>
+    [ WITH [ LOCATION = '<replaceable class="parameter">dbpath</replaceable>' ]
+           [ TEMPLATE = <replaceable class="parameter">template</replaceable> ]
+           [ ENCODING = <replaceable class="parameter">encoding</replaceable> ] ]
   </synopsis>
 
   <refsect2 id="R2-SQL-CREATEDATABASE-1">
@@ -48,8 +51,30 @@ CREATE DATABASE <replaceable class="PARAMETER">name</replaceable> [ WITH LOCATIO
       <term><replaceable class="parameter">dbpath</replaceable></term>
       <listitem>
        <para>
-	An alternate location where to store the new database in the filesystem.
-        See below for caveats.
+	An alternate filesystem location in which to store the new database,
+	specified as a string literal;
+	or <literal>DEFAULT</literal> to use the default location.
+       </para>
+      </listitem>
+     </varlistentry>
+     <varlistentry>
+      <term><replaceable class="parameter">template</replaceable></term>
+      <listitem>
+       <para>
+        Name of template from which to create the new database,
+	or <literal>DEFAULT</literal> to use the default template
+	(<literal>template1</literal>).
+       </para>
+      </listitem>
+     </varlistentry>
+     <varlistentry>
+      <term><replaceable class="parameter">encoding</replaceable></term>
+      <listitem>
+       <para>
+        Multibyte encoding method to use in the new database.  Specify
+	a string literal name (e.g., <literal>'SQL_ASCII'</literal>),
+	or an integer encoding number, or <literal>DEFAULT</literal>
+	to use the default encoding.
        </para>
       </listitem>
      </varlistentry>
@@ -98,11 +123,10 @@ CREATE DATABASE <replaceable class="PARAMETER">name</replaceable> [ WITH LOCATIO
      </varlistentry>
 
      <varlistentry>
-      <term><computeroutput>ERROR:  Single quotes are not allowed in database names.</computeroutput></term>
-      <term><computeroutput>ERROR:  Single quotes are not allowed in database paths.</computeroutput></term>
+      <term><computeroutput>ERROR:  database path may not contain single quotes</computeroutput></term>
       <listitem>
        <para>
-	The database <replaceable class="parameter">name</replaceable> and
+	The database location
         <replaceable class="parameter">dbpath</replaceable> cannot contain
         single quotes. This is required so that the shell commands that
         create the database directory can execute safely.
@@ -111,18 +135,7 @@ CREATE DATABASE <replaceable class="PARAMETER">name</replaceable> [ WITH LOCATIO
      </varlistentry>
 
      <varlistentry>
-      <term><computeroutput>ERROR:  The path 'xxx' is invalid.</computeroutput></term>
-      <listitem>
-       <para>
-        The expansion of the specified <replaceable class="parameter">dbpath</replaceable>
-        (see below) failed. Check the path you entered or make sure that the
-        environment variable you are referencing does exist.
-       </para>
-      </listitem>
-     </varlistentry>
-
-     <varlistentry>
-      <term><computeroutput>ERROR:  createdb: May not be called in a transaction block.</computeroutput></term>
+      <term><computeroutput>ERROR:  CREATE DATABASE: may not be called in a transaction block</computeroutput></term>
       <listitem>
        <para>
         If you have an explicit transaction block in progress you cannot call
@@ -133,6 +146,9 @@ CREATE DATABASE <replaceable class="PARAMETER">name</replaceable> [ WITH LOCATIO
 
      <varlistentry>
       <term><computeroutput>ERROR:  Unable to create database directory '<replaceable>path</replaceable>'.</computeroutput></term>
+     </varlistentry>
+
+     <varlistentry>
       <term><computeroutput>ERROR:  Could not initialize database directory.</computeroutput></term>
       <listitem>
        <para>
@@ -169,10 +185,10 @@ CREATE DATABASE <replaceable class="PARAMETER">name</replaceable> [ WITH LOCATIO
    command.
   </para>
   <para>
-   If the path contains a slash, the leading part is interpreted
-   as an environment variable, which must be known to the
+   If the path name does not contain a slash, it is interpreted
+   as an environment variable name, which must be known to the
    server process. This way the database administrator can
-   exercise control over at which locations databases can be created.
+   exercise control over locations in which databases can be created.
    (A customary choice is, e.g., '<envar>PGDATA2</envar>'.)
    If the server is compiled with <literal>ALLOW_ABSOLUTE_DBPATHS</literal>
    (not so by default), absolute path names, as identified by
@@ -181,6 +197,29 @@ CREATE DATABASE <replaceable class="PARAMETER">name</replaceable> [ WITH LOCATIO
    are allowed as well.
   </para>
 
+  <para>
+   By default, the new database will be created by cloning the standard
+   system database <literal>template1</>.  A different template can be
+   specified by writing <literal>TEMPLATE =</>
+   <replaceable class="parameter">name</replaceable>.  In particular,
+   by writing <literal>TEMPLATE = template0</>, you can create a virgin
+   database containing only the standard objects predefined by your
+   version of Postgres.  This is useful if you wish to avoid copying
+   any installation-local objects that may have been added to template1.
+  </para>
+
+  <para>
+   The optional encoding parameter allows selection of the database encoding,
+   if your server was compiled with multibyte encoding support.  When not
+   specified, it defaults to the encoding used by the selected template
+   database.
+  </para>
+
+  <para>
+   Optional parameters can be written in any order, not only the order
+   illustrated above.
+  </para>
+
   <refsect2 id="R2-SQL-CREATEDATABASE-3">
    <refsect2info>
     <date>1999-12-11</date>
@@ -221,6 +260,33 @@ comment from Olly; response from Thomas...
    Not sure if the dump/reload would guarantee that
    the alternate data area gets refreshed though...
 -->
+
+  <para>
+   Although it is possible to copy a database other than template1 by
+   specifying its name as the template, this is not (yet) intended as
+   a general-purpose COPY DATABASE facility.  In particular, it is
+   essential that the source database be idle (no data-altering transactions
+   in progress)
+   for the duration of the copying operation.  CREATE DATABASE will check
+   that no backend processes (other than itself) are connected to
+   the source database at the start of the operation, but this does not
+   guarantee that changes cannot be made while the copy proceeds.  Therefore,
+   we recommend that databases used as templates be treated as read-only.
+  </para>
+
+  <para>
+   Two useful flags exist in <literal>pg_database</literal> for each
+   database: <literal>datistemplate</literal> and
+   <literal>datallowconn</literal>.  <literal>datistemplate</literal>
+   may be set to indicate that a database is intended as a template for
+   CREATE DATABASE.  If this flag is set, the database may be cloned by
+   any user with CREATEDB privileges; if it is not set, only superusers
+   and the owner of the database may clone it.
+   If <literal>datallowconn</literal> is false, then no new connections
+   to that database will be allowed (but existing sessions are not killed
+   simply by setting the flag false).  The <literal>template0</literal>
+   database is normally marked this way to prevent modification of it.
+  </para>
   </refsect2>
  </refsect1>