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 specified. 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
must be a comma-separated
list of schema names. Any name that is not an existing schema, or is
a schema for which the user does not have USAGE
permission, is silently ignored.
If one of the list items is the special name
$user
, then the schema having the name returned by
SESSION_USER
is substituted, if there is such a schema
and the user has USAGE
permission for it.
(If not, $user
is ignored.)
The system catalog schema, pg_catalog
, is always
searched, whether it is mentioned in the path or not. If it is
mentioned in the path then it will be searched in the specified
order. If pg_catalog
is not in the path then it will
be searched before searching any of the path items.
Likewise, the current session's temporary-table schema,
pg_temp_
, is always searched if it
exists. It can be explicitly listed in the path by using the
alias nnn
pg_temp
. If it is not listed in the path then
it is searched first (even before pg_catalog
). However,
the temporary schema is only searched for relation (table, view,
sequence, etc) and data type names. It is never searched for
function or operator names.
When objects are created without specifying a particular target
schema, they will be placed in the first valid schema named in
search_path
. An error is reported if the search
path is empty.
The default value for this parameter is
"$user", public
.
This setting 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
(see Section 9.25).
This is not quite the same as
examining the value of search_path
, since
current_schemas
shows how the items
appearing in search_path
were resolved.
For more information on schema handling, see Section 5.8.
row_security
(boolean
)
This variable controls whether to raise an error in lieu of applying a
row security policy. When set to on
, policies apply
normally. When set to off
, queries fail which would
otherwise apply at least one policy. The default is on
.
Change to off
where limited row visibility could cause
incorrect results; for example, pg_dump makes that
change by default. This variable has no effect on roles which bypass
every row security policy, to wit, superusers and roles with
the BYPASSRLS
attribute.
For more information on row security policies, see CREATE POLICY.
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. If a nondefault tablespace
is specified, the user must have CREATE
privilege
for it, or creation attempts will fail.
This variable is not used for temporary tables; for them, temp_tablespaces is consulted instead.
This variable is also not used when creating databases. By default, a new database inherits its tablespace setting from the template database it is copied from.
For more information on tablespaces, see Section 22.6.
temp_tablespaces
(string
)
This variable specifies tablespaces in which to create temporary
objects (temp tables and indexes on temp tables) when a
CREATE
command does not explicitly specify a tablespace.
Temporary files for purposes such as sorting large data sets
are also created in these tablespaces.
The value is a list of names of tablespaces. When there is more than one name in the list, PostgreSQL chooses a random member of the list each time a temporary object is to be created; except that within a transaction, successively created temporary objects are placed in successive tablespaces from the list. If the selected element of the list is an empty string, PostgreSQL will automatically use the default tablespace of the current database instead.
When temp_tablespaces
is set interactively, specifying a
nonexistent tablespace is an error, as is specifying a tablespace for
which the user does not have CREATE
privilege. However,
when using a previously set value, nonexistent tablespaces are
ignored, as are tablespaces for which the user lacks
CREATE
privilege. In particular, this rule applies when
using a value set in postgresql.conf
.
The default value is an empty string, which results in all temporary objects being created in the default tablespace of the current database.
See also default_tablespace.
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 avoids side
effects of the validation process and avoids false positives due
to problems such as forward references. Set this parameter
to off
before loading functions on behalf of other
users; pg_dump does so automatically.
default_transaction_isolation
(enum
)
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 13 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.
default_transaction_deferrable
(boolean
)
When running at the serializable
isolation level,
a deferrable read-only SQL transaction may be delayed before
it is allowed to proceed. However, once it begins executing
it does not incur any of the overhead required to ensure
serializability; so serialization code will have no reason to
force it to abort because of concurrent updates, making this
option suitable for long-running read-only transactions.
This parameter controls the default deferrable status of each
new transaction. It currently has no effect on read-write
transactions or those operating at isolation levels lower
than serializable
. The default is off
.
Consult SET TRANSACTION for more information.
session_replication_role
(enum
)
Controls firing of replication-related triggers and rules for the
current session. Setting this variable requires
superuser privilege and results in discarding any previously cached
query plans. Possible values are origin
(the default),
replica
and local
.
See ALTER TABLE for
more information.
statement_timeout
(integer
)
Abort any statement that takes more than 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 this off.
Setting statement_timeout
in
postgresql.conf
is not recommended because it would
affect all sessions.
lock_timeout
(integer
)
Abort any statement that waits longer than the specified number of
milliseconds while attempting to acquire a lock on a table, index,
row, or other database object. The time limit applies separately to
each lock acquisition attempt. The limit applies both to explicit
locking requests (such as LOCK TABLE
, or SELECT
FOR UPDATE
without NOWAIT
) and to implicitly-acquired
locks. If log_min_error_statement
is set to
ERROR
or lower, the statement that timed out will be
logged. A value of zero (the default) turns this off.
Unlike statement_timeout
, this timeout can only occur
while waiting for locks. Note that if statement_timeout
is nonzero, it is rather pointless to set lock_timeout
to
the same or larger value, since the statement timeout would always
trigger first.
Setting lock_timeout
in
postgresql.conf
is not recommended because it would
affect all sessions.
idle_in_transaction_session_timeout
(integer
)
Terminate any session with an open transaction that has been idle for longer than the specified duration in milliseconds. This allows any locks held by that session to be released and the connection slot to be reused; it also allows tuples visible only to this transaction to be vacuumed. See Section 24.1 for more details about this.
The default value of 0 disables this feature.
vacuum_freeze_table_age
(integer
)
VACUUM
performs an aggressive scan if the table's
pg_class
.relfrozenxid
field has reached
the age specified by this setting. An aggressive scan differs from
a regular VACUUM
in that it visits every page that might
contain unfrozen XIDs or MXIDs, not just those that might contain dead
tuples. The default is 150 million transactions. Although users can
set this value anywhere from zero to two billions, VACUUM
will silently limit the effective value to 95% of
autovacuum_freeze_max_age, so that a
periodical manual VACUUM
has a chance to run before an
anti-wraparound autovacuum is launched for the table. For more
information see
Section 24.1.5.
vacuum_freeze_min_age
(integer
)
Specifies the cutoff age (in transactions) that VACUUM
should use to decide whether to freeze row versions
while scanning a table.
The default is 50 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 24.1.5.
vacuum_multixact_freeze_table_age
(integer
)
VACUUM
performs an aggressive scan if the table's
pg_class
.relminmxid
field has reached
the age specified by this setting. An aggressive scan differs from
a regular VACUUM
in that it visits every page that might
contain unfrozen XIDs or MXIDs, not just those that might contain dead
tuples. The default is 150 million multixacts.
Although users can set this value anywhere from zero to two billions,
VACUUM
will silently limit the effective value to 95% of
autovacuum_multixact_freeze_max_age, so that a
periodical manual VACUUM
has a chance to run before an
anti-wraparound is launched for the table.
For more information see Section 24.1.5.1.
vacuum_multixact_freeze_min_age
(integer
)
Specifies the cutoff age (in multixacts) that VACUUM
should use to decide whether to replace multixact IDs with a newer
transaction ID or multixact ID while scanning a table. The default
is 5 million multixacts.
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_multixact_freeze_max_age,
so that there is not an unreasonably short time between forced
autovacuums.
For more information see Section 24.1.5.1.
bytea_output
(enum
)
Sets the output format for values of type bytea
.
Valid values are hex
(the default)
and escape
(the traditional PostgreSQL
format). See Section 8.4 for more
information. The bytea
type always
accepts both formats on input, regardless of this setting.
xmlbinary
(enum
)
Sets how binary values are to be encoded in XML. This applies
for example when bytea
values are converted to
XML by the functions xmlelement
or
xmlforest
. Possible values are
base64
and hex
, which
are both defined in the XML Schema standard. The default is
base64
. For further information about
XML-related functions, see Section 9.14.
The actual choice here is mostly a matter of taste, constrained only by possible restrictions in client applications. Both methods support all possible values, although the hex encoding will be somewhat larger than the base64 encoding.
xmloption
(enum
)
Sets whether DOCUMENT
or
CONTENT
is implicit when converting between
XML and character string values. See Section 8.13 for a description of this. Valid
values are DOCUMENT
and
CONTENT
. The default is
CONTENT
.
According to the SQL standard, the command to set this option is
SET XML OPTION { DOCUMENT | CONTENT };
This syntax is also available in PostgreSQL.
gin_pending_list_limit
(integer
)
Sets the maximum size of the GIN pending list which is used
when fastupdate
is enabled. If the list grows
larger than this maximum size, it is cleaned up by moving
the entries in it to the main GIN data structure in bulk.
The default is four megabytes (4MB
). This setting
can be overridden for individual GIN indexes by changing
index storage parameters.
See Section 64.4.1 and Section 64.5
for more information.
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 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.
IntervalStyle
(enum
)
Sets the display format for interval values.
The value sql_standard
will produce
output matching SQL standard interval literals.
The value postgres
(which is the default) will produce
output matching PostgreSQL releases prior to 8.4
when the DateStyle
parameter was set to ISO
.
The value postgres_verbose
will produce output
matching PostgreSQL releases prior to 8.4
when the DateStyle
parameter was set to non-ISO
output.
The value iso_8601
will produce output matching the time
interval “format with designators” defined in section
4.4.3.2 of ISO 8601.
The IntervalStyle
parameter also affects the
interpretation of ambiguous interval input. See
Section 8.5.4 for more information.
TimeZone
(string
)
Sets the time zone for displaying and interpreting time stamps.
The built-in default is GMT
, but that is typically
overridden in postgresql.conf
; initdb
will install a setting there corresponding to its system environment.
See Section 8.5.3 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 Section B.3 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 3, 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.
See also Section 8.1.3.
client_encoding
(string
)
Sets the client-side encoding (character set). The default is to use the database encoding. The character sets supported by the PostgreSQL server are described in Section 23.3.1.
lc_messages
(string
)
Sets the language in which messages are displayed. Acceptable values are system-dependent; see Section 23.1 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, and an improper value might obscure the readability of the server logs.
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 23.1 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 23.1 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 dates and times, for example
with the to_char
family of
functions. Acceptable values are system-dependent; see Section 23.1 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.
default_text_search_config
(string
)
Selects the text search configuration that is used by those variants
of the text search functions that do not have an explicit argument
specifying the configuration.
See Chapter 12 for further information.
The built-in default is pg_catalog.simple
, but
initdb will initialize the
configuration file with a setting that corresponds to the
chosen lc_ctype
locale, if a configuration
matching that locale can be identified.
Several settings are available for preloading shared libraries into the
server, in order to load additional functionality or achieve performance
benefits. For example, a setting of
'$libdir/mylib'
would cause
mylib.so
(or on some platforms,
mylib.sl
) to be preloaded from the installation's standard
library directory. The differences between the settings are when they
take effect and what privileges are required to change them.
PostgreSQL procedural language libraries can
be preloaded in this way, typically by using the
syntax '$libdir/plXXX'
where
XXX
is pgsql
, perl
,
tcl
, or python
.
Only shared libraries specifically intended to be used with PostgreSQL
can be loaded this way. 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. You
might be able to use operating-system facilities such
as LD_PRELOAD
for that.
In general, refer to the documentation of a specific module for the recommended way to load that module.
local_preload_libraries
(string
)
This variable specifies one or more shared libraries that are to be preloaded at connection start. It contains a comma-separated list of library names, where each name is interpreted as for the LOAD command. Whitespace between entries is ignored; surround a library name with double quotes if you need to include whitespace or commas in the name. The parameter value only takes effect at the start of the connection. Subsequent changes have no effect. If a specified library is not found, the connection attempt will fail.
This option can be set by any user. Because of that, 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
.
The intent of this feature is to allow unprivileged users to load
debugging or performance-measurement libraries into specific sessions
without requiring an explicit LOAD
command. To that end,
it would be typical to set this parameter using
the PGOPTIONS
environment variable on the client or by
using
ALTER ROLE SET
.
However, unless a module is specifically designed to be used in this way by non-superusers, this is usually not the right setting to use. Look at session_preload_libraries instead.
session_preload_libraries
(string
)
This variable specifies one or more shared libraries that are to be preloaded at connection start. It contains a comma-separated list of library names, where each name is interpreted as for the LOAD command. Whitespace between entries is ignored; surround a library name with double quotes if you need to include whitespace or commas in the name. The parameter value only takes effect at the start of the connection. Subsequent changes have no effect. If a specified library is not found, the connection attempt will fail. Only superusers can change this setting.
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, auto_explain could be enabled for all
sessions under a given user name by setting this parameter
with ALTER ROLE SET
. Also, this parameter can be changed
without restarting the server (but changes only take effect when a new
session is started), so it is easier to add new modules this way, even
if they should apply to all sessions.
Unlike shared_preload_libraries, there is no large performance advantage to loading a library at session start rather than when it is first used. There is some advantage, however, when connection pooling is used.
shared_preload_libraries
(string
)
This variable specifies one or more shared libraries to be preloaded at server start. It contains a comma-separated list of library names, where each name is interpreted as for the LOAD command. Whitespace between entries is ignored; surround a library name with double quotes if you need to include whitespace or commas in the name. This parameter can only be set at server start. If a specified library is not found, the server will fail to start.
Some libraries need to perform certain operations that can only take place at postmaster start, such as allocating shared memory, reserving light-weight locks, or starting background workers. Those libraries must be loaded at server start through this parameter. See the documentation of each library for details.
Other libraries can also be preloaded. By preloading a shared library, the library startup time is avoided when the library is first used. However, the time to start each new server process might increase slightly, even if that process never uses the library. So this parameter is recommended only for libraries that will be used in most sessions. Also, changing this parameter requires a server restart, so this is not the right setting to use for short-term debugging tasks, say. Use session_preload_libraries for that instead.
On Windows hosts, preloading a library at server start will not reduce
the time required to start each new server process; each server process
will re-load all preload libraries. However, shared_preload_libraries
is still useful on Windows hosts for libraries that need to
perform operations at postmaster start time.
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
must 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 scans. For more information see Section 64.5.