Commands

This chapter discusses the usage of the available console scripts.

pg_python

The pg_python command provides a simple way to write Python scripts against a single target database. It acts like the regular Python console command, but takes standard PostgreSQL options as well to specify the client parameters to make establish connection with. The Python environment is then augmented with the following built-ins:

db
The PG-API connection object.
xact
db.xact, the transaction creator.
settings
db.settings
prepare
db.prepare, the statement creator.
proc
db.proc
sqlexec
db.execute, execute multiple SQL statements (None is always returned)

pg_python Usage

Usage: pg_python.py [connection options] [script] ...

Options:
--unix=UNIX path to filesystem socket
--ssl-mode=SSLMODE
 SSL requirement for connectivity: require, prefer, allow, disable
-s SETTINGS, --setting=SETTINGS
 run-time parameters to set upon connecting
-I PQ_IRI, --iri=PQ_IRI
 database locator string [pq://user:password@host:port/database?setting=value]
-h HOST, --host=HOST
 database server host
-p PORT, --port=PORT
 database server port
-U USER, --username=USER
 user name to connect as
-W, --password prompt for password
-d DATABASE, --database=DATABASE
 database’s name
--pq-trace=PQ_TRACE
 trace PQ protocol transmissions
-C PYTHON_CONTEXT, --context=PYTHON_CONTEXT
 Python context code to run[file://,module:,<code>]
-m PYTHON_MAIN Python module to run as script(__main__)
-c PYTHON_MAIN Python expression to run(__main__)
--version show program’s version number and exit
--help show this help message and exit

Interactive Console Backslash Commands

Inspired by psql:

>>> \?
Backslash Commands:

  \?      Show this help message.
  \E      Edit a file or a temporary script.
  \e      Edit and Execute the file directly in the context.
  \i      Execute a Python script within the interpreter's context.
  \set    Configure environment variables. \set without arguments to show all
  \x      Execute the Python command within this process.

pg_python Examples

Module execution taking advantage of the new built-ins:

$ pg_python -h localhost -W -m timeit "prepare('SELECT 1').first()"
Password for pg_python[pq://jwp@localhost:5432]:
1000 loops, best of 3: 1.35 msec per loop

$ pg_python -h localhost -W -m timeit -s "ps=prepare('SELECT 1')" "ps.first()"
Password for pg_python[pq://jwp@localhost:5432]:
1000 loops, best of 3: 442 usec per loop

Simple interactive usage:

$ pg_python -h localhost -W
Password for pg_python[pq://jwp@localhost:5432]:
>>> ps = prepare('select 1')
>>> ps.first()
1
>>> c = ps()
>>> c.read()
[(1,)]
>>> ps.close()
>>> import sys
>>> sys.exit(0)

pg_dotconf

pg_dotconf is used to modify a PostgreSQL cluster’s configuration file. It provides a means to apply settings specified from the command line and from a file referenced using the -f option.

Warning

include directives in configuration files are completely ignored. If modification of an included file is desired, the command must be applied to that specific file.

pg_dotconf Usage

Usage: pg_dotconf.py [–stdout] [-f filepath] postgresql.conf ([param=val]|[param])*

Options:
--version show program’s version number and exit
-h, --help show this help message and exit
-f SETTINGS, --file=SETTINGS
 A file of settings to apply to the given “postgresql.conf”
--stdout Redirect the product to standard output instead of writing back to the “postgresql.conf” file

Examples

Modifying a simple configuration file:

$ echo "setting = value" >pg.conf

# change 'setting'
$ pg_dotconf pg.conf setting=newvalue

$ cat pg.conf
setting = 'newvalue'

# new settings are appended to the file
$ pg_dotconf pg.conf another_setting=value
$ cat pg.conf
setting = 'newvalue'
another_setting = 'value'

# comment a setting
$ pg_dotconf pg.conf another_setting

$ cat pg.conf
setting = 'newvalue'
#another_setting = 'value'

When a setting is given on the command line, it must been seen as one argument to the command, so it’s very important to avoid invocations like:

$ pg_dotconf pg.conf setting = value
ERROR: invalid setting, '=' after 'setting'
HINT: Settings must take the form 'setting=value' or 'setting_name_to_comment'. Settings must also be received as a single argument.

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