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Subsections
postgres
postgres -- Run a Postgres single-user backend
postgres [ dbname ]
postgres [ -B nBuffers ] [ -C ] [ -D DataDir ] [
-E ] [ -F ] [ -O ] [ -P ] [ -Q ] [ -S SortSize ]
[ -d [ DebugLevel ] ] [ -e ] [ -o ] [ OutputFile
] [ -s ] [ -v protocol ] [ dbname ]
postgres accepts the following command line arguments:
- dbname
- The optional argument dbname specifies the name of the
database to be accessed. dbname defaults to the value of the USER environment
variable.
- -B nBuffers
- If the backend is running under the postmaster, nBuffers
is the number of shared-memory buffers that the postmaster has allocated for
the backend server processes that it starts. If the backend is running stand-alone,
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).
- -C
- Do not show the server version number.
- -D DataDir
- Specifies the directory to use as the root of the tree of
database directories. If -D is not given, the default data directory name is
the value of the environment variable PGDATA. If PGDATA is not set, then the
directory used is $POSTGRESHOME/data. If neither environment variable is set
and this command-line option is not specified, the default directory that was
set at compile-time is used.
- -E
- Echo all queries.
- -F
- Disable an automatic fsync() call after each transaction. This option improves
performance, but an operating system crash while a transaction is in progress
may cause the loss of the most recently entered data. Without the fsync() call
the data is buffered by the operating system, and written to disk sometime later.
- -O
- Override restrictions, so system table structures can be modified. These
tables are typically those with a leading pg_ in the table name.
- -P
- Ignore system indexes to scan/update system tuples. The REINDEX
for system tables/indexes requires this option. System tables are typically
those with a leading pg_ in the table name.
- -Q
- Specifies "quiet" mode.
- -S SortSize
- 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 SortSize kilobytes before it starts to put
data into temporary files.
- -d [ DebugLevel ]
- The optional argument DebugLevel determines
the amount of debugging output the backend servers will produce. If DebugLevel
is one, the postmaster will trace all connection traffic, and nothing else.
For levels two and higher, debugging is turned on in the backend process and
the postmaster displays more information, including the backend environment
and process traffic. Note that if no file is specified for backend servers to
send their debugging output then this output will appear on the controlling
tty of their parent postmaster.
- -e
- This option controls how dates are interpreted upon input to and output
from the database. If the -e option is supplied, then dates passed to and from
the frontend processes will be assumed to be in "European"
format (DD-MM-YYYY), otherwise dates are assumed to be in "American"
format (MM-DD-YYYY). Dates are accepted by the backend in a wide variety of
formats, and for input dates this switch mostly affects the interpretation for
ambiguous cases. See the PostgreSQL User's Guide for more information.
- -o OutputFile
- Sends all debugging and error output to OutputFile.
If the backend is running under the postmaster, error messages are still sent
to the frontend process as well as to OutputFile, but debugging output
is sent to the controlling tty of the postmaster (since only one file descriptor
can be sent to an actual file).
- -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.
- -v protocol
- Specifies the number of the frontend/backend protocol to
be used for this particular session.
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.
Use of any of these options is highly discouraged. Furthermore, any of
these options may disappear or change at any time.
These special-case options are:
- -A [ n r b Q X ]
- This option
generates a tremendous amount of output.
- -L
- Turns off the locking system.
- -N
- Disables use of newline as a query delimiter.
- -f [ s i m n h ]
- Forbids the
use of particular scan and join methods: s and i disable sequential
and index scans respectively, while n, m, and h disable nested-loop,
merge and hash joins respectively. Note: 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.
- -i
- Prevents query execution, but shows the plan tree.
- -p dbname
- Indicates to the backend server that it has been started by
a postmaster and makes different assumptions about buffer pool management, file
descriptors, etc. Switches following -p are restricted to those considered
"secure".
- -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 -s.
Of the nigh-infinite number of error messages you may see when you execute the
backend server directly, the most common will probably be:
- semget: No space left on device
- If you see this message, you should run the
ipcclean command. After doing this, try starting postmaster 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. If you have a kernel with
particularly small shared memory and/or semaphore limits, you may have to reconfigure
your kernel to increase its shared memory or semaphore parameters. Tip:
You may be able to postpone reconfiguring your kernel by decreasing -B to reduce
Postgres' shared memory consumption.
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 postmaster on this set of databases.
Some of the switches explained here 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.
The optional argument dbname specifies the name of the database to be
accessed. dbname defaults to the value of the USER environment variable.
Useful utilities for dealing with shared memory problems include ipcs(1), ipcrm(1),
and ipcclean(1). See also postmaster.
Next: postmaster
Up: Reference Manual
Previous: pgtksh
Bruce Momjian
2001-05-09