<!--
$Header: /cvsroot/pgsql/doc/src/sgml/bki.sgml,v 1.2 1998/12/29 02:24:13 thomas Exp $

Transcribed from the original bki.man.5 documentation
- Thomas Lockhart 1998-08-03
-->

<chapter id="bki">
<title>Backend Interface</title>

<para>
Backend Interface (<acronym>BKI</acronym>) files are scripts that are input 
to the <productname>Postgres</productname>
backend running in the special "bootstrap" mode that allows it to perform
database functions without a database system already existing.  <acronym>BKI</acronym> files
can therefore be used to create the database system in the first place.
<application>initdb</application>
uses <acronym>BKI</acronym> files to do just that: to create a database system.  However,
<application>initdb</application>'s
<acronym>BKI</acronym> files are generated internally.  It generates them using the files
<filename>global1.bki.source</filename> and <filename>local1.template1.bki.source</filename>, which it finds in the
<productname>Postgres</productname> "library" directory.  They get installed there as part of installing
<productname>Postgres</productname>.  These .source files get build as part of the <productname>Postgres</productname> build
process, by a build program called 
  <application>genbki</application>.
  <application>genbki</application>
takes as input <productname>Postgres</productname> source files that double as
  <application>genbki</application>
input that builds tables and C header files that describe those
tables.
</para>

<para>
Related information may be found in documentation for 
<application>initdb</application>,
<application>createdb</application>,
and the <acronym>SQL</acronym> command <command>CREATE DATABASE</command>.
</para>

<sect1>
<title><acronym>BKI</acronym> File Format</title>

<para>
The <productname>Postgres</productname> backend interprets <acronym>BKI</acronym> files as described below.  This
description will be easier to understand if the <filename>global1.bki.source</filename> file is
at hand as an example.  (As explained above, this .source file isn't quite
a <acronym>BKI</acronym> file, but you'll be able to guess what the resulting <acronym>BKI</acronym> file would be
anyway).
</para>

<para>
Commands are composed of a command name followed by space separated
arguments.  Arguments to a command which begin with a <quote>$</quote> are
treated specially.  If <quote>$$</quote> are the first two characters, then
the first <quote>$</quote> is ignored and the argument is then processed
normally.  If the <quote>$</quote> is followed by space, then it is treated
as a NULL
value.  Otherwise, the characters following the <quote>$</quote> are
interpreted as the name of a macro causing the argument to be replaced
with the macro's value.  It is an error for this macro to be
undefined.
</para>

<para>
Macros are defined using
<programlisting>
define macro macro_name = macro_value
</programlisting>
and are undefined using 
<programlisting>
undefine macro macro_name
</programlisting>
and redefined using the same syntax as define.
</para>

<para>
Lists of general commands and macro commands
follow.
</para>
</sect1>

<sect1>
<title>General Commands</title>

<variablelist>
<varlistentry>
<term>
OPEN <replaceable class="parameter">classname</replaceable>
</term>
<listitem>
<para>
Open the class called
<replaceable class="parameter">classname</replaceable>
for further manipulation.
</para>
</listitem>
</varlistentry>

<varlistentry>
<term>
CLOSE [<replaceable class="parameter">classname</replaceable>]
</term>
<listitem>
<para>
Close the open class called
<replaceable class="parameter">classname</replaceable>.
It is an error if 
<replaceable class="parameter">classname</replaceable>
is not already opened.   If no
<replaceable class="parameter">classname</replaceable>
is given, then the currently open class is closed.
</para>
</listitem>
</varlistentry>

<varlistentry>
<term>
PRINT
</term>
<listitem>
<para>
Print the currently open class.
</para>
</listitem>
</varlistentry>

<varlistentry>
<term>
INSERT [OID=<replaceable class="parameter">oid_value</replaceable>] (<replaceable class="parameter">value1</replaceable> <replaceable class="parameter">value2</replaceable> ...)
</term>
<listitem>
<para>
Insert a new instance to the open class using
<replaceable class="parameter">value1</replaceable>,
<replaceable class="parameter">value2</replaceable>,
etc., for its attribute values and 
<replaceable class="parameter">oid_value</replaceable>
for its OID.  If
<replaceable class="parameter">oid_value</replaceable>
is not <quote>0</quote>, then this value will be used as the instance's
object identifier.  Otherwise, it is an error.
</para>
</listitem>
</varlistentry>

<varlistentry>
<term>
INSERT (<replaceable class="parameter">value1</replaceable> <replaceable class="parameter">value2</replaceable> ...)
</term>
<listitem>
<para>
As above, but the system generates a unique object identifier.
</para>
</listitem>
</varlistentry>

<varlistentry>
<term>
CREATE <replaceable class="parameter">classname</replaceable> (<replaceable class="parameter">name1</replaceable> = <replaceable class="parameter">type1</replaceable> [,<replaceable class="parameter">name2</replaceable> = <replaceable class="parameter">type2</replaceable>[,...]])
</term>
<listitem>
<para>
Create a class named
<replaceable class="parameter">classname</replaceable>
with the attributes given in parentheses.
</para>
</listitem>
</varlistentry>

<varlistentry>
<term>
OPEN (<replaceable class="parameter">name1</replaceable> = <replaceable class="parameter">type1</replaceable> [,<replaceable class="parameter">name2</replaceable> = <replaceable class="parameter">type2</replaceable>[,...]]) AS <replaceable class="parameter">classname</replaceable>
</term>
<listitem>
<para>
Open a class named
<replaceable class="parameter">classname</replaceable>
for writing but do not record its existence in the system catalogs.
(This is primarily to aid in bootstrapping.)
</para>
</listitem>
</varlistentry>

<varlistentry>
<term>
DESTROY <replaceable class="parameter">classname</replaceable>
</term>
<listitem>
<para>
Destroy the class named
<replaceable class="parameter">classname</replaceable>.
</para>
</listitem>
</varlistentry>

<varlistentry>
<term>
DEFINE INDEX <replaceable class="parameter">indexname</replaceable> ON <replaceable class="parameter">class_name</replaceable> USING <replaceable class="parameter">amname</replaceable>
  (<replaceable class="parameter">opclass</replaceable> <replaceable class="parameter">attr</replaceable> | (<replaceable class="parameter">function</replaceable>(<replaceable class="parameter">attr</replaceable>))
</term>
<listitem>
<para>
Create an index named
<replaceable class="parameter">indexname</replaceable>
on the class named
<replaceable class="parameter">classname</replaceable>
using the
<replaceable class="parameter">amname</replaceable>
access method.  The fields to index are called
<replaceable class="parameter">name1</replaceable>,
<replaceable class="parameter">name2</replaceable>
etc., and the operator collections to use are
<replaceable class="parameter">collection_1</replaceable>,
<replaceable class="parameter">collection_2</replaceable>
etc., respectively.
</para>
</listitem>
</varlistentry>

</variablelist>

<note>
<para>
This last sentence doesn't reference anything in the example. Should be changed to make sense. - Thomas 1998-08-04
</para>
</note>
</sect1>

<sect1>
<title>Macro Commands</title>

<para>
<variablelist>
<varlistentry>
<term>
DEFINE FUNCTION <replaceable class="parameter">macro_name</replaceable> AS <replaceable class="parameter">rettype</replaceable> <replaceable class="parameter">function_name</replaceable>(<replaceable class="parameter">args</replaceable>)
</term>
<listitem>
<para>
Define a function prototype for a function named
<replaceable class="parameter">macro_name</replaceable>
which has its value of type
<replaceable class="parameter">rettype</replaceable>
computed from the execution
<replaceable class="parameter">function_name</replaceable>
with the arguments
<replaceable class="parameter">args</replaceable>
declared in a C-like manner.
</para>
</listitem>
</varlistentry>

<varlistentry>
<term>
DEFINE MACRO <replaceable class="parameter">macro_name</replaceable> FROM FILE <replaceable class="parameter">filename</replaceable>
</term>
<listitem>
<para>
Define a macro named
<replaceable class="parameter">macro_name</replaceable>
which has its value 
read from the file called
<replaceable class="parameter">filename</replaceable>.
</para>
</listitem>
</varlistentry>

</variablelist>
</para>
</sect1>

<sect1>
<title>Debugging Commands</title>

<para>
<note>
<para>
This section on debugging commands was commented-out in the original documentation. Thomas 1998-08-05
</para>
</note>

<variablelist>
<varlistentry>
<term>
r
</term>
<listitem>
<para>
Randomly print the open class.
</para>
</listitem>
</varlistentry>

<varlistentry>
<term>
m -1
</term>
<listitem>
<para>
Toggle display of time information.
</para>
</listitem>
</varlistentry>

<varlistentry>
<term>
m 0
</term>
<listitem>
<para>
Set retrievals to now.
</para>
</listitem>
</varlistentry>

<varlistentry>
<term>
m 1 Jan 1 01:00:00 1988
</term>
<listitem>
<para>
Set retrievals to snapshots of the specfied time.
</para>
</listitem>
</varlistentry>

<varlistentry>
<term>
m 2 Jan 1 01:00:00 1988, Feb 1 01:00:00 1988
</term>
<listitem>
<para>
Set retrievals to ranges of the specified times.
Either time may be replaced with space
if an unbounded time range is desired.
</para>
</listitem>
</varlistentry>

<varlistentry>
<term>
&amp;A <replaceable class="parameter">classname</replaceable> <replaceable class="parameter">natts</replaceable> <replaceable class="parameter">name1</replaceable> <replaceable class="parameter">type1</replaceable> <replaceable class="parameter">name2</replaceable> <replaceable class="parameter">type2</replaceable> <replaceable class="parameter">...</replaceable>
</term>
<listitem>
<para>
Add 
<replaceable class="parameter">natts</replaceable>
attributes named
<replaceable class="parameter">name1</replaceable>,
<replaceable class="parameter">name2</replaceable>,
etc. of
types
<replaceable class="parameter">type1</replaceable>,
<replaceable class="parameter">type2</replaceable>,
etc. to the class
<replaceable class="parameter">classname</replaceable>.
</para>
</listitem>
</varlistentry>

<varlistentry>
<term>
&amp;RR <replaceable class="parameter">oldclassname</replaceable> <replaceable class="parameter">newclassname</replaceable>
</term>
<listitem>
<para>
Rename the
<replaceable class="parameter">oldclassname</replaceable>
class to
<replaceable class="parameter">newclassname</replaceable>.
</para>
</listitem>
</varlistentry>

<varlistentry>
<term>
&amp;RA	classname oldattname newattname
<replaceable class="parameter">classname</replaceable>
<replaceable class="parameter">oldattname</replaceable>
<replaceable class="parameter">newattname</replaceable>
</term>
<listitem>
<para>
Rename the
<replaceable class="parameter">oldattname</replaceable>
attribute in the class named
<replaceable class="parameter">classname</replaceable>
to
<replaceable class="parameter">newattname</replaceable>.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</sect1>

<sect1>
<title>Example</title>

<para>
The following set of commands will create the <quote>pg_opclass</quote>
class containing the
<parameter>int_ops</parameter>
collection as an object with an OID of
<parameter>421</parameter>,
print out the class, and then close it.
<programlisting>
create pg_opclass (opcname=name)
open pg_opclass
insert oid=421 (int_ops)
print
close pg_opclass
</programlisting>
</para>
</sect1>
</chapter>
