start.sgml

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

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 <chapter id="tutorial-start">
  <title>Getting Started</title>

  <sect1 id="tutorial-install">
   <title>Installation</title>

   <para>
    Before you can use <productname>PostgreSQL</productname> you need
    to install it, of course.  It is possible that
    <productname>PostgreSQL</productname> is already installed at your
    site, either because it was included in your operating system
    distribution or because the system administrator already installed
    it.  If that is the case, you should obtain information from the
    operating system documentation or your system administrator about
    how to access <productname>PostgreSQL</productname>.
   </para>

   <para>
    If you are not sure whether <productname>PostgreSQL</productname>
    is already available or whether you can use it for your
    experimentation then you can install it yourself.  Doing so is not
    hard and it can be a good exercise.
    <productname>PostgreSQL</productname> can be installed by any
    unprivileged user; no superuser (<systemitem>root</systemitem>)
    access is required.
   </para>

   <para>
    If you are installing <productname>PostgreSQL</productname>
    yourself, then refer to <xref linkend="installation">
    for instructions on installation, and return to
    this guide when the installation is complete.  Be sure to follow
    closely the section about setting up the appropriate environment
    variables.
   </para>

   <para>
    If your site administrator has not set things up in the default
    way, you may have some more work to do.  For example, if the
    database server machine is a remote machine, you will need to set
    the <envar>PGHOST</envar> environment variable to the name of the
    database server machine.  The environment variable
    <envar>PGPORT</envar> may also have to be set.  The bottom line is
    this: if you try to start an application program and it complains
    that it cannot connect to the database, you should consult your
    site administrator or, if that is you, the documentation to make
    sure that your environment is properly set up.  If you did not
    understand the preceding paragraph then read the next section.
   </para>
  </sect1>


  <sect1 id="tutorial-arch">
   <title>Architectural Fundamentals</title>

   <para>
    Before we proceed, you should understand the basic
    <productname>PostgreSQL</productname> system architecture.
    Understanding how the parts of
    <productname>PostgreSQL</productname> interact will make this
    chapter somewhat clearer.
   </para>

   <para>
    In database jargon, <productname>PostgreSQL</productname> uses a
    client/server model.  A <productname>PostgreSQL</productname>
    session consists of the following cooperating processes
    (programs):

    <itemizedlist>
     <listitem>
      <para>
       A server process, which manages the database files, accepts
       connections to the database from client applications, and
       performs actions on the database on behalf of the clients.  The
       database server program is called
       <filename>postmaster</filename>.
       <indexterm><primary>postmaster</primary></indexterm>
      </para>
     </listitem>

     <listitem>
      <para>
       The user's client (frontend) application that wants to perform
       database operations.  Client applications can be very diverse
       in nature:  a client could be a text-oriented tool, a graphical
       application, a web server that accesses the database to
       display web pages, or a specialized database maintenance tool.
       Some client applications are supplied with the
       <productname>PostgreSQL</productname> distribution; most are
       developed by users.
      </para>
     </listitem>

    </itemizedlist>
   </para>

   <para>
    As is typical of client/server applications, the client and the
    server can be on different hosts.  In that case they communicate
    over a TCP/IP network connection.  You should keep this in mind,
    because the files that can be accessed on a client machine might
    not be accessible (or might only be accessible using a different
    file name) on the database server machine.
   </para>

   <para>
    The <productname>PostgreSQL</productname> server can handle
    multiple concurrent connections from clients.  For that purpose it
    starts (<quote>forks</quote>) a new process for each connection.
    From that point on, the client and the new server process
    communicate without intervention by the original
    <filename>postmaster</filename> process.  Thus, the
    <filename>postmaster</filename> is always running, waiting for
    client connections, whereas client and associated server processes
    come and go.  (All of this is of course invisible to the user.  We
    only mention it here for completeness.)
   </para>
  </sect1>


  <sect1 id="tutorial-createdb">
   <title>Creating a Database</title>

   <indexterm zone="tutorial-createdb">
    <primary>database</primary>
    <secondary>creating</secondary>
   </indexterm>

   <indexterm zone="tutorial-createdb">
    <primary>createdb</primary>
   </indexterm>

   <para>
    The first test to see whether you can access the database server
    is to try to create a database.  A running
    <productname>PostgreSQL</productname> server can manage many
    databases.  Typically, a separate database is used for each
    project or for each user.
   </para>

   <para>
    Possibly, your site administrator has already created a database
    for your use.  He should have told you what the name of your
    database is.  In that case you can omit this step and skip ahead
    to the next section.
   </para>

   <para>
    To create a new database, in this example named
    <literal>mydb</literal>, you use the following command:
<screen>
<prompt>$</prompt> <userinput>createdb mydb</userinput>
</screen>
    This should produce as response:
<screen>
CREATE DATABASE
</screen>
    If so, this step was successful and you can skip over the
    remainder of this section.
   </para>

   <para>
    If you see a message similar to
<screen>
createdb: command not found
</screen>
    then <productname>PostgreSQL</> was not installed properly.  Either it was not
    installed at all or the search path was not set correctly.  Try
    calling the command with an absolute path instead:
<screen>
<prompt>$</prompt> <userinput>/usr/local/pgsql/bin/createdb mydb</userinput>
</screen>
    The path at your site might be different.  Contact your site
    administrator or check back in the installation instructions to
    correct the situation.
   </para>

   <para>
    Another response could be this:
<screen>
createdb: could not connect to database postgres: could not connect to server:
No such file or directory
        Is the server running locally and accepting
        connections on Unix domain socket "/tmp/.s.PGSQL.5432"?
</screen>
    This means that the server was not started, or it was not started
    where <command>createdb</command> expected it.  Again, check the
    installation instructions or consult the administrator.
   </para>

   <para>
    Another response could be this:
<screen>
createdb: could not connect to database postgres: FATAL:  user "joe" does not
exist
</screen>
    where your own login name is mentioned.  This will happen if the
    administrator has not created a <productname>PostgreSQL</> user account
    for you.  (<productname>PostgreSQL</> user accounts are distinct from
    operating system user accounts.)  If you are the administrator, see
    <xref linkend="user-manag"> for help creating accounts.  You will need to
    become the operating system user under which <productname>PostgreSQL</>
    was installed (usually <literal>postgres</>) to create the first user
    account.  It could also be that you were assigned a
    <productname>PostgreSQL</> user name that is different from your
    operating system user name; in that case you need to use the <option>-U</>
    switch or set the <envar>PGUSER</> environment variable to specify your
    <productname>PostgreSQL</> user name.
   </para>

   <para>
    If you have a user account but it does not have the privileges required to
    create a database, you will see the following:
<screen>
createdb: database creation failed: ERROR:  permission denied to create database
</screen>
    Not every user has authorization to create new databases.  If
    <productname>PostgreSQL</productname> refuses to create databases