converted into a named struct for every
      variable. A declaration like:
<programlisting>
bytea var[180];
</programlisting>
     is converted into:
<programlisting>
struct bytea_var { int len; char arr[180]; } var;
</programlisting>
      The member <structfield>arr</structfield> hosts binary format
      data. It can also handle <literal>'\0'</literal> as part of
      data, unlike <type>VARCHAR</type>.
      The data is converted from/to hex format and sent/received by
      ecpglib.
     </para>

     <note>
      <para>
       <type>bytea</type> variable can be used only when
       <xref linkend="guc-bytea-output"/> is set to <literal>hex</literal>.
      </para>
     </note>
    </sect4>
   </sect3>

   <sect3 id="ecpg-variables-nonprimitive-c">
    <title>Host Variables with Nonprimitive Types</title>

    <para>
     As a host variable you can also use arrays, typedefs, structs, and
     pointers.
    </para>

    <sect4 id="ecpg-variables-arrays">
     <title>Arrays</title>

     <para>
      There are two use cases for arrays as host variables.  The first
      is a way to store some text string in <type>char[]</type>
      or <type>VARCHAR[]</type>, as
      explained in <xref linkend="ecpg-char"/>.  The second use case is to
      retrieve multiple rows from a query result without using a
      cursor.  Without an array, to process a query result consisting
      of multiple rows, it is required to use a cursor and
      the <command>FETCH</command> command.  But with array host
      variables, multiple rows can be received at once.  The length of
      the array has to be defined to be able to accommodate all rows,
      otherwise a buffer overflow will likely occur.
     </para>

     <para>
      Following example scans the <literal>pg_database</literal>
      system table and shows all OIDs and names of the available
      databases:
<programlisting>
int
main(void)
{
EXEC SQL BEGIN DECLARE SECTION;
    int dbid[8];
    char dbname[8][16];
    int i;
EXEC SQL END DECLARE SECTION;

    memset(dbname, 0, sizeof(char)* 16 * 8);
    memset(dbid, 0, sizeof(int) * 8);

    EXEC SQL CONNECT TO testdb;
    EXEC SQL SELECT pg_catalog.set_config('search_path', '', false); EXEC SQL COMMIT;

    /* Retrieve multiple rows into arrays at once. */
    EXEC SQL SELECT oid,datname INTO :dbid, :dbname FROM pg_database;

    for (i = 0; i &lt; 8; i++)
        printf("oid=%d, dbname=%s\n", dbid[i], dbname[i]);

    EXEC SQL COMMIT;
    EXEC SQL DISCONNECT ALL;
    return 0;
}
</programlisting>

    This example shows following result. (The exact values depend on
    local circumstances.)
<screen>
oid=1, dbname=template1
oid=11510, dbname=template0
oid=11511, dbname=postgres
oid=313780, dbname=testdb
oid=0, dbname=
oid=0, dbname=
oid=0, dbname=
</screen>
     </para>
    </sect4>

    <sect4 id="ecpg-variables-struct">
     <title>Structures</title>

     <para>
      A structure whose member names match the column names of a query
      result, can be used to retrieve multiple columns at once.  The
      structure enables handling multiple column values in a single
      host variable.
     </para>

     <para>
      The following example retrieves OIDs, names, and sizes of the
      available databases from the <literal>pg_database</literal>
      system table and using
      the <function>pg_database_size()</function> function.  In this
      example, a structure variable <varname>dbinfo_t</varname> with
      members whose names match each column in
      the <literal>SELECT</literal> result is used to retrieve one
      result row without putting multiple host variables in
      the <literal>FETCH</literal> statement.
<programlisting>
EXEC SQL BEGIN DECLARE SECTION;
    typedef struct
    {
       int oid;
       char datname[65];
       long long int size;
    } dbinfo_t;

    dbinfo_t dbval;
EXEC SQL END DECLARE SECTION;

    memset(&amp;dbval, 0, sizeof(dbinfo_t));

    EXEC SQL DECLARE cur1 CURSOR FOR SELECT oid, datname,