StartupMessage

StartupMessage is a frontend protocol message. Length of message contents in bytes, including self.

Reading PG 18·Select a recorded version

Direction: Frontend → backend
First wire field: Int32
Field entries: 8
Documented flow contexts: Canceling Requests in Progress; SSL Session Encryption; GSSAPI Session Encryption
direction: F
manual path: /docs/18/protocol-message-formats.html
signature: StartupMessage (F)

Definition PG 18

Int32: Length of message contents in bytes, including self.
Int32(196610): The protocol version number. The most significant 16 bits are the major version number (3 for the protocol described here). The least significant 16 bits are the minor version number (2 for the protocol described here).

The protocol version number is followed by one or more pairs of parameter name and value strings. A zero byte is required as a terminator after the last name/value pair. Parameters can appear in any order. user is required, others are optional. Each parameter is specified as:

String

The parameter name. Currently recognized names are:

user: The database user name to connect as. Required; there is no default.
database: The database to connect to. Defaults to the user name.
options: Command-line arguments for the backend. (This is deprecated in favor of setting individual run-time parameters.) Spaces within this string are considered to separate arguments, unless escaped with a backslash (\); write \\ to represent a literal backslash.
replication: Used to connect in streaming replication mode, where a small set of replication commands can be issued instead of SQL statements. Value can be true, false, or database, and the default is false. See Section 54.4 for details.

In addition to the above, other parameters may be listed. Parameter names beginning with _pq_. are reserved for use as protocol extensions, while others are treated as run-time parameters to be set at backend start time. Such settings will be applied during backend start (after parsing the command-line arguments if any) and will act as session defaults.

String

The parameter value.

Wire fields in documented order

Position	Format	Meaning
1	Int32	Length of message contents in bytes, including self.
2	Int32(196610)	The protocol version number. The most significant 16 bits are the major version number (3 for the protocol described here). The least significant 16 bits are the minor version number (2 for the protocol described here).
3	String	The parameter name. Currently recognized names are: user The database user name to connect as. Required; there is no default. database The database to connect to. Defaults to the user name. options Command-line arguments for the backend. (This is deprecated in favor of setting individual run-time parameters.) Spaces within this string are considered to separate arguments, unless escaped with a backslash ( \ ); write \\ to represent a literal backslash. replication Used to connect in streaming replication mode, where a small set of replication commands can be issued instead of SQL statements. Value can be true , false , or database , and the default is false . See Section 54.4 for details. In addition to the above, other parameters may be listed. Parameter names beginning with _pq_. are reserved for use as protocol extensions, while others are treated as run-time parameters to be set at backend start time. Such settings will be applied during backend start (after parsing the command-line arguments if any) and will act as session defaults.
4	user	The database user name to connect as. Required; there is no default.
5	database	The database to connect to. Defaults to the user name.
6	options	Command-line arguments for the backend. (This is deprecated in favor of setting individual run-time parameters.) Spaces within this string are considered to separate arguments, unless escaped with a backslash ( \ ); write \\ to represent a literal backslash.
7	replication	Used to connect in streaming replication mode, where a small set of replication commands can be issued instead of SQL statements. Value can be true , false , or database , and the default is false . See Section 54.4 for details.
8	String	The parameter value.

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Complete source facts

fields

map[description:Length of message contents in bytes, including self. format:Int32], map[description:The protocol version number. The most significant 16 bits are the major version number (3 for the protocol described here). The least significant 16 bits are the minor version number (2 for the protocol described here). format:Int32(196610)], map[description:The parameter name. Currently recognized names are: user The database user name to connect as. Required; there is no default. database The database to connect to. Defaults to the user name. options Command-line arguments for the backend. (This is deprecated in favor of setting individual run-time parameters.) Spaces within this string are considered to separate arguments, unless escaped with a backslash ( \ ); write \\ to represent a literal backslash. replication Used to connect in streaming replication mode, where a small set of replication commands can be issued instead of SQL statements. Value can be true , false , or database , and the default is false . See Section 54.4 for details. In addition to the above, other parameters may be listed. Parameter names beginning with _pq_. are reserved for use as protocol extensions, while others are treated as run-time parameters to be set at backend start time. Such settings will be applied during backend start (after parsing the command-line arguments if any) and will act as session defaults. format:String], map[description:The database user name to connect as. Required; there is no default. format:user], map[description:The database to connect to. Defaults to the user name. format:database], map[description:Command-line arguments for the backend. (This is deprecated in favor of setting individual run-time parameters.) Spaces within this string are considered to separate arguments, unless escaped with a backslash ( \ ); write \\ to represent a literal backslash. format:options], map[description:Used to connect in streaming replication mode, where a small set of replication commands can be issued instead of SQL statements. Value can be true , false , or database , and the default is false . See Section 54.4 for details. format:replication], map[description:The parameter value. format:String]

Source references

Full definition and evidence JSON

Definition sources

center · PostgreSQL 18 · 555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f

Text language: en · 555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f