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 may be of interest to certain applications, particularly administrative front-ends.
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 17.4 for information.
Reports whether PostgreSQL was built with support for 64-bit-integer dates and times. It is set by configuring with --enable-integer-datetimes when building PostgreSQL. The default value is off.
Reports the locale in which sorting of textual data is done. See Section 21.1 for more information. The value is determined when the database cluster is initialized.
Reports the locale that determines character classifications. See Section 21.1 for more information. The value is determined when the database cluster is initialized. Ordinarily this will be the same as lc_collate, but for special applications it might be set differently.
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.
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.
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.
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.
Reports the version number of the server. It is determined by the value of PG_VERSION when building the server.
Reports whether ordinary string literals ('...') treat backslashes literally, as specified in the SQL standard. The value is currently always off, indicating that backslashes are treated as escapes. It is planned that this will change to on in a future PostgreSQL release when string literal syntax changes to meet the standard. Applications may check this parameter to determine how string literals will be processed. The presence of this parameter can also be taken as an indication that the escape string syntax (E'...') is supported.