Backend Interface (BKI) files are scripts in a
special language that are input to the
PostgreSQL backend running in the special
"bootstrap" mode that allows it to perform database
functions without a database system already existing.
BKI files can therefore be used to create the
database system in the first place. (And they are probably not
useful for anything else.)
initdb uses a BKI file
to do part of its job when creating a new database cluster. The
input file used by initdb is created as
part of building and installing PostgreSQL
by a program named genbki.sh from some
specially formatted C header files in the source tree. The created
BKI file is called postgres.bki and is
normally installed in the
share subdirectory of the installation tree.
Related information may be found in the documentation for
initdb.
This section describes how the PostgreSQL
backend interprets BKI files. This description
will be easier to understand if the postgres.bki
file is at hand as an example. You should also study the source
code of initdb to get an idea of how the
backend is invoked.
BKI input consists of a sequence of commands. Commands are made up
of a number of tokens, depending on the syntax of the command.
Tokens are usually separated by whitespace, but need not be if
there is no ambiguity. There is no special command separator; the
next token that syntactically cannot belong to the preceding
command starts a new one. (Usually you would put a new command on
a new line, for clarity.) Tokens can be certain key words, special
characters (parentheses, commas, etc.), numbers, or double-quoted
strings. Everything is case sensitive.
Lines starting with a # are ignored.
