search_path
(string
)
This variable specifies the order in which schemas are searched when an object (table, data type, function, etc.) is referenced by a simple name with no schema component. When there are objects of identical names in different schemas, the one found first in the search path is used. An object that is not in any of the schemas in the search path can only be referenced by specifying its containing schema with a qualified (dotted) name.
The value for search_path
has to be a comma-separated
list of schema names. If one of the list items is
the special value $user
, then the schema
having the name returned by SESSION_USER
is substituted, if there
is such a schema. (If not, $user
is ignored.)
The system catalog schema, pg_catalog
, is always
searched, whether it is mentioned in the path or not. If it is
mentioned in the path then it will be searched in the specified
order. If pg_catalog
is not in the path then it will
be searched before searching any of the path items.
It should also be noted that the temporary-table schema,
pg_temp_
, is implicitly searched before any of
these.
nnn
When objects are created without specifying a particular target schema, they will be placed in the first schema listed in the search path. An error is reported if the search path is empty.
The default value for this parameter is
'"$user", public'
(where the second part will be
ignored if there is no schema named public
).
This supports shared use of a database (where no users
have private schemas, and all share use of public
),
private per-user schemas, and combinations of these. Other
effects can be obtained by altering the default search path
setting, either globally or per-user.
The current effective value of the search path can be examined
via the SQL function
current_schemas()
. This is not quite the same as
examining the value of search_path
, since
current_schemas()
shows how the requests
appearing in search_path
were resolved.
For more information on schema handling, see Section 5.7, “Schemas”.
default_tablespace
(string
)
This variable specifies the default tablespace in which to create
objects (tables and indexes) when a CREATE
command does
not explicitly specify a tablespace.
The value is either the name of a tablespace, or an empty string to specify using the default tablespace of the current database. If the value does not match the name of any existing tablespace, PostgreSQL will automatically use the default tablespace of the current database.
For more information on tablespaces, see Section 19.6, “Tablespaces”.
check_function_bodies
(boolean
)
This parameter is normally on. When set to off
, it
disables validation of the function body string during CREATE FUNCTION. Disabling validation is
occasionally useful to avoid problems such as forward references
when restoring function definitions from a dump.
default_transaction_isolation
(string
)
Each SQL transaction has an isolation level, which can be either “read uncommitted”, “read committed”, “repeatable read”, or “serializable”. This parameter controls the default isolation level of each new transaction. The default is “read committed”.
Consult Chapter 12, Concurrency Control and SET TRANSACTION for more information.
default_transaction_read_only
(boolean
)
A read-only SQL transaction cannot alter non-temporary tables.
This parameter controls the default read-only status of each new
transaction. The default is off
(read/write).
Consult SET TRANSACTION for more information.
statement_timeout
(integer
)
Abort any statement that takes over the specified number of
milliseconds, starting from the time the command arrives at the server
from the client. If log_min_error_statement
is set to
ERROR
or lower, the statement that timed out will also be
logged. A value of zero (the default) turns off the
limitation.
vacuum_freeze_min_age
(integer
)
Specifies the cutoff age (in transactions) that VACUUM
should use to decide whether to replace transaction IDs with
FrozenXID
while scanning a table.
The default is 100 million transactions. Although
users can set this value anywhere from zero to one billion,
VACUUM
will silently limit the effective value to half
the value of autovacuum_freeze_max_age, so
that there is not an unreasonably short time between forced
autovacuums. For more information see Section 22.1.3, “Preventing transaction ID wraparound failures”.
DateStyle
(string
)
Sets the display format for date and time values, as well as the
rules for interpreting ambiguous date input values. For
historical reasons, this variable contains two independent
components: the output format specification (ISO
,
Postgres
, SQL
, or German
)
and the input/output specification for year/month/day ordering
(DMY
, MDY
, or YMD
). These
can be set separately or together. The keywords Euro
and European
are synonyms for DMY
; the
keywords US
, NonEuro
, and
NonEuropean
are synonyms for MDY
. See
Section 8.5, “Date/Time Types” for more information. The
built-in default is ISO, MDY
, but
initdb will initialize the
configuration file with a setting that corresponds to the
behavior of the chosen lc_time
locale.
timezone
(string
)
Sets the time zone for displaying and interpreting time stamps.
The default is 'unknown'
, which means to use whatever
the system environment specifies as the time zone. See Section 8.5, “Date/Time Types” for more
information.
timezone_abbreviations
(string
)
Sets the collection of time zone abbreviations that will be accepted
by the server for datetime input. The default is 'Default'
,
which is a collection that works in most of the world; there are
also 'Australia' and 'India', and other collections can be defined
for a particular installation. See Appendix B, Date/Time Support for more information.
extra_float_digits
(integer
)
This parameter adjusts the number of digits displayed for
floating-point values, including float4
, float8
,
and geometric data types. The parameter value is added to the
standard number of digits (FLT_DIG
or DBL_DIG
as appropriate). The value can be set as high as 2, to include
partially-significant digits; this is especially useful for dumping
float data that needs to be restored exactly. Or it can be set
negative to suppress unwanted digits.
client_encoding
(string
)
Sets the client-side encoding (character set). The default is to use the database encoding.
lc_messages
(string
)
Sets the language in which messages are displayed. Acceptable values are system-dependent; see Section 21.1, “Locale Support” for more information. If this variable is set to the empty string (which is the default) then the value is inherited from the execution environment of the server in a system-dependent way.
On some systems, this locale category does not exist. Setting this variable will still work, but there will be no effect. Also, there is a chance that no translated messages for the desired language exist. In that case you will continue to see the English messages.
Only superusers can change this setting, because it affects the messages sent to the server log as well as to the client.
lc_monetary
(string
)
Sets the locale to use for formatting monetary amounts, for
example with the to_char
family of
functions. Acceptable values are system-dependent; see Section 21.1, “Locale Support” for more information. If this variable is
set to the empty string (which is the default) then the value
is inherited from the execution environment of the server in a
system-dependent way.
lc_numeric
(string
)
Sets the locale to use for formatting numbers, for example
with the to_char
family of
functions. Acceptable values are system-dependent; see Section 21.1, “Locale Support” for more information. If this variable is
set to the empty string (which is the default) then the value
is inherited from the execution environment of the server in a
system-dependent way.
lc_time
(string
)
Sets the locale to use for formatting date and time values. (Currently, this setting does nothing, but it may in the future.) Acceptable values are system-dependent; see Section 21.1, “Locale Support” for more information. If this variable is set to the empty string (which is the default) then the value is inherited from the execution environment of the server in a system-dependent way.
explain_pretty_print
(boolean
)
Determines whether EXPLAIN VERBOSE
uses the
indented or non-indented format for displaying detailed
query-tree dumps. The default is on
.
dynamic_library_path
(string
)
If a dynamically loadable module needs to be opened and the
file name specified in the CREATE FUNCTION
or
LOAD
command
does not have a directory component (i.e. the
name does not contain a slash), the system will search this
path for the required file.
The value for dynamic_library_path
has to be a
list of absolute directory paths separated by colons (or semi-colons
on Windows). If a list element starts
with the special string $libdir
, the
compiled-in PostgreSQL package
library directory is substituted for $libdir
. This
is where the modules provided by the standard
PostgreSQL distribution are installed.
(Use pg_config --pkglibdir
to find out the name of
this directory.) For example:
dynamic_library_path = '/usr/local/lib/postgresql:/home/my_project/lib:$libdir'
or, in a Windows environment:
dynamic_library_path = 'C:\tools\postgresql;H:\my_project\lib;$libdir'
The default value for this parameter is
'$libdir'
. If the value is set to an empty
string, the automatic path search is turned off.
This parameter can be changed at run time by superusers, but a
setting done that way will only persist until the end of the
client connection, so this method should be reserved for
development purposes. The recommended way to set this parameter
is in the postgresql.conf
configuration
file.
gin_fuzzy_search_limit
(integer
)
Soft upper limit of the size of the set returned by GIN index. For more information see Section 51.4, “GIN tips and tricks”.
local_preload_libraries
(string
)
This variable specifies one or more shared libraries that are to be preloaded at connection start. If more than one library is to be loaded, separate their names with commas. This parameter cannot be changed after the start of a particular session.
Because this is not a superuser-only option, the libraries
that can be loaded are restricted to those appearing in the
plugins
subdirectory of the installation's
standard library directory. (It is the database administrator's
responsibility to ensure that only “safe” libraries
are installed there.) Entries in local_preload_libraries
can specify this directory explicitly, for example
$libdir/plugins/mylib
, or just specify
the library name — mylib
would have
the same effect as $libdir/plugins/mylib
.
There is no performance advantage to loading a library at session
start rather than when it is first used. Rather, the intent of
this feature is to allow debugging or performance-measurement
libraries to be loaded into specific sessions without an explicit
LOAD
command being given. For example, debugging could
be enabled for all sessions under a given user name by setting
this parameter with ALTER USER SET
.
If a specified library is not found, the connection attempt will fail.
Every PostgreSQL-supported library has a “magic block” that is checked to guarantee compatibility. For this reason, non-PostgreSQL libraries cannot be loaded in this way.