the server process (normally
    the cluster's data directory), not the client's working directory.
   </para>

   <para>
    Executing a command with <literal>PROGRAM</literal> might be restricted
    by the operating system's access control mechanisms, such as SELinux.
   </para>

   <para>
    <command>COPY FROM</command> will invoke any triggers and check
    constraints on the destination table. However, it will not invoke rules.
   </para>

   <para>
    For identity columns, the <command>COPY FROM</command> command will always
    write the column values provided in the input data, like
    the <command>INSERT</command> option <literal>OVERRIDING SYSTEM
    VALUE</literal>.
   </para>

   <para>
    <command>COPY</command> input and output is affected by
    <varname>DateStyle</varname>. To ensure portability to other
    <productname>PostgreSQL</productname> installations that might use
    non-default <varname>DateStyle</varname> settings,
    <varname>DateStyle</varname> should be set to <literal>ISO</literal> before
    using <command>COPY TO</command>.  It is also a good idea to avoid dumping
    data with <varname>IntervalStyle</varname> set to
    <literal>sql_standard</literal>, because negative interval values might be
    misinterpreted by a server that has a different setting for
    <varname>IntervalStyle</varname>.
   </para>

   <para>
    Input data is interpreted according to <literal>ENCODING</literal>
    option or the current client encoding, and output data is encoded
    in <literal>ENCODING</literal> or the current client encoding, even
    if the data does not pass through the client but is read from or
    written to a file directly by the server.
   </para>

   <para>
    The <command>COPY FROM</command> command physically inserts input rows
    into the table as it progresses.  If the command fails, these rows are
    left in a deleted state; these rows will not be visible, but still
    occupy disk space. This might amount to considerable
    wasted disk space if the failure happened well into a large copy
    operation. <command>VACUUM</command> should be used to recover the
    wasted space.
   </para>

   <para>
    <literal>FORCE_NULL</literal> and <literal>FORCE_NOT_NULL</literal> can be used
    simultaneously on the same column. This results in converting quoted
    null strings to null values and unquoted null strings to empty strings.
   </para>

 </refsect1>

 <refsect1 id="sql-copy-file-formats" xreflabel="File Formats">
  <title>File Formats</title>

  <refsect2 id="sql-copy-text-format" xreflabel="Text Format">
   <title>Text Format</title>

   <para>
    When the <literal>text</literal> format is used,
    the data read or written is a text file with one line per table row.
    Columns in a row are separated by the delimiter character.
    The column values themselves are strings generated by the
    output function, or acceptable to the input function, of each
    attribute's data type.  The specified null string is used in
    place of columns that are null.
    <command>COPY FROM</command> will raise an error if any line of the
    input file contains more or fewer columns than are expected.
   </para>

   <para>
    End of data can be represented by a line containing just
    backslash-period (<literal>\.</literal>).  An end-of-data marker is
    not necessary when reading from a file, since the end of file
    serves perfectly well; in that context this provision exists only for
    backward compatibility.  However, <application>psql</application>
    uses <literal>\.</literal> to terminate a <literal>COPY FROM
    STDIN</literal> operation (that is, reading
    in-line <command>COPY</command> data in an SQL script).  In that
    context the rule is needed to be able to end the operation before the
    end of the script.
   </para>

   <para>
    Backslash characters (<literal>\</literal>) can be used in the
    <command>COPY</command> data to quote data characters that might