.\" This is -*-nroff-*-
.\" XXX standard disclaimer belongs here....
.\" $Header: /cvsroot/pgsql/doc/src/sgml/ref/postgres-ref.sgml,v 1.1 1999/05/26 17:25:38 thomas Exp $
.TH POSTGRESQL UNIX 05/19/99 PostgreSQL PostgreSQL
.SH NAME
postgres - the Postgres backend server
.SH SYNOPSIS
.BR "postgres"
[\c
.BR "-B"
n_buffers]
[\c
.BR "-C"
]
[\c
.BR "-D"
data_directory]
[\c
.BR "-E"
]
[\c
.BR "-F"
]
[\c
.BR "-O"
]
[\c
.BR "-Q"
]
[\c
.BR "-S kbytes"
]
[\c
.BR "-d"
debug_level]
[\c
.BR "-e"
]
[\c
.BR "-o"
output_file]
[\c
.BR "-s"
]
[\c
.BR "-v protocol"
]
[dbname]
.in -5n
.SH DESCRIPTION
The Postgres backend server can be executed directly from the user shell.
This should be done only while debugging by the DBA, and should not be
done while other Postgres backends are being managed by a
.IR postmaster
on this set of databases.
.PP
Some of the switches explained in this man page can be passed to the backend
through the "database options" field of a connection request, and thus can be
set for a particular backend without going to the trouble of restarting the
postmaster.  This is particularly handy for debugging-related switches.
.PP
The optional argument
.IR dbname
specifies the name of the database to be accessed.
.IR Dbname
defaults to the value of the
.SM USER
environment variable.
.PP
The 
.IR postgres
server understands the following command-line options:
.TP
.BR "-B" " n_buffers"
If the backend is running under the 
.IR postmaster ,
.IR "n_buffers"
is the number of shared-memory buffers that the
.IR "postmaster"
has allocated for the backend server processes that it starts.  If the
backend is running standalone, this specifies the number of buffers to
allocate.  This value defaults to 64 buffers, where each buffer is 8k bytes
(or whatever BLCKSZ is set to in config.h).
.TP
.BR "-C"
Do not show server version number.
.TP
.BR "-D" " data_directory"
This option specifies the pathname of the directory that contains the
database system data (the tables, the catalogs, etc.).  If you don't 
specify this option, Postgres uses the value of the PGDATA environment
variable.  You must either specify a -D option or set PGDATA.
 
The data directory pathname for a database system is normally determined when
the database system is created with
.IR initdb ,
with a --pgdata option to
.IR initdb .
.TP
.BR "-E"
Echo all queries.
.TP
.BR "-F"
Disable automatic fsync() call after each transaction.
This option improves performance, but an operating system crash
while a transaction is in progress will probably cause data loss.
.TP
.BR "-O"
Override restrictions, so system table structures can be modified(pg_*).
.TP
.BR "-Q"
Specifies \*(lqquiet\*(rq mode.
.TP
.BR "-S" " kbytes"
Specifies the amount of memory to be used by internal sorts and hashes
before resorting to temporary disk files.  The value is specified in
kilobytes, and defaults to 512 kilobytes.  Note that for a complex query,
several sorts and/or hashes might be running in parallel, and each one
will be allowed to use as much as -S kilobytes before it starts to put
data into temporary files.
.TP
.BR "-e"
The
.IR "-e"
option controls how dates are input to and output from the database.
.IP
If the
.IR "-e"
option is supplied, then all dates passed to and from the frontend
processes will be assumed to be in
.IR "European"
format ie.
.IR "DD-MM-YYYY"
otherwise dates are input and output in
.IR "American"
format ie.
.IR "MM-DD-YYYY"
.TP
.BR "-d" " debug_level"
Turns on debugging at the numeric level
.IR "debug_level" .
Turning on debugging will cause query, parse trees, and query plans to
be displayed.
.TP
.BR "-o" " output_file"
Sends all debugging and error output to 
.IR output_file .
If the backend is running under the 
.IR postmaster ,
error messages are still sent to the frontend process as well as to
.IR output_file ,
but debugging output is sent to the controlling tty of the
.IR postmaster
(since only one file descriptor can be sent to an actual file).
.TP
.BR "-s"
Print time information and other statistics at the end of each query.
This is useful for benchmarking or for use in tuning the number of
buffers.
.TP
.BR "-v" " protocol"
Specifies the number of the frontend/backend protocol to be used for this
particular session.
.SH "DEVELOPER COMMAND OPTIONS"
There are several other options that may be specified, used mainly
for debugging purposes.  These are listed here only for the use by
Postgres system developers.
.BR "Use of any of these options is highly discouraged" .
Furthermore, any of these options may disappear or change at any time.
.TP
.BR "-A" "n|r|b|Q\fIn\fP|X\fIn\fP"
.IP
This option generates a tremendous amount of output.
.TP
.BR "-L"
Turns off the locking system.
.TP
.BR "-N"
Disables use of newline as a query delimiter.
.TP
.BR "-f"
Forbids the use of particular scan and join methods:
.IR s " and " i
disable sequential and index scans respectively, while
.IR n ", " m " and " h
disable nested-loop, merge and hash joins respectively.
(Neither sequential scans nor nested-loop joins can be disabled completely;
the -fs and -fn options simply discourage the optimizer from using those
plan types if it has any other alternative.)
.TP
.BR "-i"
Prevents query execution, but shows the plan tree.
.TP
.BR "-p" " databasename"
Indicates to the backend server that it has been started by a 
.IR postmaster
and make different assumptions about buffer pool management, file
descriptors, etc.  Switches following -p are restricted to those
considered "secure".
.TP
.BR "-t" "pa[rser]|pl[anner]|e[xecutor]"
Print timing statistics for each query relating to each of the major
system modules.  This option cannot be used with
.BR "-s" .
.SH "SEE ALSO"
ipcclean(1),
psql(1), 
postmaster(1).
.SH "DIAGNOSTICS"
Of the nigh-infinite number of error messages you may see when you
execute the backend server directly, the most common will probably be:
.TP
.BR "semget: No space left on device"
If you see this message, you should run the
.IR ipcclean
command.  After doing this, try starting
.IR postgres
again.  If this still doesn't work, you probably need to configure
your kernel for shared memory and semaphores as described in the
installation notes.
