The following “parameters” are read-only, and are determined
when PostgreSQL™ is compiled or when it is
installed. As such, they have been excluded from the sample
postgresql.conf
file. These options report
various aspects of PostgreSQL™ behavior
that might be of interest to certain applications, particularly
administrative front-ends.
block_size
(integer)
Reports the size of a disk block. It is determined by the value
of BLCKSZ
when building the server. The default
value is 8192 bytes. The meaning of some configuration
variables (such as shared_buffers) is
influenced by block_size
. See Section 19.4 for information.
data_checksums
(boolean)
Reports whether data checksums are enabled for this cluster. See data checksums for more information.
data_directory_mode
(integer)
On Unix systems this parameter reports the permissions of the data
directory defined by (data_directory) at startup.
(On Microsoft Windows this parameter will always display
0700
). See
group access for more information.
debug_assertions
(boolean)
Reports whether PostgreSQL™ has been built
with assertions enabled. That is the case if the
macro USE_ASSERT_CHECKING is defined
when PostgreSQL™ is built (accomplished
e.g., by the configure option
--enable-cassert
). By
default PostgreSQL™ is built without
assertions.
integer_datetimes
(boolean)
Reports whether PostgreSQL™ was built with support for
64-bit-integer dates and times. As of PostgreSQL™ 10,
this is always on
.
lc_collate
(string)
Reports the locale in which sorting of textual data is done. See Section 23.1 for more information. This value is determined when a database is created.
lc_ctype
(string)
Reports the locale that determines character classifications.
See Section 23.1 for more information.
This value is determined when a database is created.
Ordinarily this will be the same as lc_collate
,
but for special applications it might be set differently.
max_function_args
(integer)
Reports the maximum number of function arguments. It is determined by
the value of FUNC_MAX_ARGS
when building the server. The
default value is 100 arguments.
max_identifier_length
(integer)
Reports the maximum identifier length. It is determined as one
less than the value of NAMEDATALEN
when building
the server. The default value of NAMEDATALEN
is
64; therefore the default
max_identifier_length
is 63 bytes, which
can be less than 63 characters when using multibyte encodings.
max_index_keys
(integer)
Reports the maximum number of index keys. It is determined by
the value of INDEX_MAX_KEYS
when building the server. The
default value is 32 keys.
segment_size
(integer)
Reports the number of blocks (pages) that can be stored within a file
segment. It is determined by the value of RELSEG_SIZE
when building the server. The maximum size of a segment file in bytes
is equal to segment_size
multiplied by
block_size
; by default this is 1GB.
server_encoding
(string)
Reports the database encoding (character set). It is determined when the database is created. Ordinarily, clients need only be concerned with the value of client_encoding.
server_version
(string)
Reports the version number of the server. It is determined by the
value of PG_VERSION
when building the server.
server_version_num
(integer)
Reports the version number of the server as an integer. It is determined
by the value of PG_VERSION_NUM
when building the server.
ssl_library
(string)
Reports the name of the SSL library that this
PostgreSQL™ server was built with (even if
SSL is not currently configured or in use on this instance), for
example OpenSSL
, or an empty string if none.
wal_block_size
(integer)
Reports the size of a WAL disk block. It is determined by the value
of XLOG_BLCKSZ
when building the server. The default value
is 8192 bytes.
wal_segment_size
(integer)
Reports the size of write ahead log segments. The default value is 16MB. See Section 29.4 for more information.