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diff --git a/doc/src/sgml/protocol.sgml b/doc/src/sgml/protocol.sgml new file mode 100644 index 00000000000..af5acc1e0f7 --- /dev/null +++ b/doc/src/sgml/protocol.sgml @@ -0,0 +1,1509 @@ +<Chapter> +<DocInfo> +<Author> +<FirstName>Phil</FirstName> +<Surname>Thompson</Surname> +</Author> +<Date>1998-02-02</Date> +</DocInfo> +<Title>Frontend/Backend Protocol</Title> + +<Para> +<Note> +<Para> +Written by <ULink url="mailto:phil@river-bank.demon.co.uk">Phil Thompson</ULink> +</Para> +</Note> + +<Para> +<ProductName>Postgres</ProductName> uses a message-based protocol for communication between frontends +and backends. The protocol is implemented over <Acronym>TCP/IP</Acronym> and also on Unix sockets. +<ProductName>Postgres</ProductName> v6.3 introduced version numbers into the protocol. +This was done in such +a way as to still allow connections from earlier versions of frontends, but +this document does not cover the protocol used by those earlier versions. + +<Para> +This document describes the initial version-numbered protocol, designated v1.0. +Higher level features built on this protocol (for example, how <FileName>libpq</FileName> passes +certain environment variables after the connection is established) +are covered elsewhere. + +<Sect1> +<Title>Overview</Title> + +<Para> +The three major components are the frontend (running on the client) and the +postmaster and backend (running on the server). The postmaster and backend +have different roles but may be implemented by the same executable. + +<Para> +A frontend sends a startup packet to the postmaster. This includes the names +of the user and the database the user wants to connect to. The postmaster then +uses this, and the information in the pg_hba.conf(5) file to determine what +further authentication information it requires the frontend to send (if any) +and responds to the frontend accordingly. + +<Para> +The frontend then sends any required authentication information. Once the +postmaster validates this it responds to the frontend that it is authenticated +and hands over to a backend. + +<Para> +Subsequent communications are query and result packets exchanged between the +frontend and the backend. The postmaster takes no further part in the +communication. + +<Para> +When the frontend wishes to disconnect it sends an appropriate packet and +closes the connection without waiting for a response for the backend. + +<Para> +Packets are sent as a data stream. The first byte determines what should be +expected in the rest of the packet. The exception is packets send from a +frontend to the postmaster, which comprise a packet length then the packet +itself. The difference is historical. + +<Sect1> +<Title>Protocol</Title> + +<Para> +This section describes the message flow. There are four different types of +flows depending on the state of the connection: + authentication, query, function call, and termination. + +<Sect2> +<Title>Authentication</Title> + +<Para> +The frontend sends a StartupPacket. The postmaster uses this and the contents +of the pg_hba.conf(5) file to determine what authentication method the frontend +must use. The postmaster then responds with one of the following messages: + +<Para> +<VariableList> +<VarListEntry> +<Term> + ErrorResponse +</Term> +<ListItem> +<Para> + The postmaster then immediately closes the connection. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + AuthenticationOk +</Term> +<ListItem> +<Para> + The postmaster then hands over to the backend. The postmaster + takes no further part in the communication. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + AuthenticationKerberosV4 +</Term> +<ListItem> +<Para> + The frontend must then take part in a Kerberos V4 + authentication dialog (not described here) with the postmaster. + If this is successful, the postmaster responds with an + AuthenticationOk, otherwise it responds with an ErrorResponse. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + AuthenticationKerberosV5 +</Term> +<ListItem> +<Para> + The frontend must then take part in a Kerberos V5 + authentication dialog (not described here) with the postmaster. + If this is successful, the postmaster responds with an + AuthenticationOk, otherwise it responds with an ErrorResponse. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + AuthenticationUnencryptedPassword +</Term> +<ListItem> +<Para> + The frontend must then send an UnencryptedPasswordPacket. + If this is the correct password, the postmaster responds with + an AuthenticationOk, otherwise it responds with an + ErrorResponse. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + AuthenticationEncryptedPassword +</Term> +<ListItem> +<Para> + The frontend must then send an EncryptedPasswordPacket. + If this is the correct password, the postmaster responds with + an AuthenticationOk, otherwise it responds with an + ErrorResponse. +</Para> +</ListItem> +</VarListEntry> +</VariableList> +</Para> + +<Para> +If the frontend does not support the authentication method requested by the +postmaster, then it should immediately close the connection. + +<Sect2> +<Title>Query</Title> + +<Para> +The frontend sends a Query message to the backend. The response sent by the +backend depends on the contents of the query. The possible responses are as +follows. + +<Para> +<VariableList> +<VarListEntry> +<Term> + CompletedResponse +</Term> +<ListItem> +<Para> + The query completed normally. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + CopyInResponse +</Term> +<ListItem> +<Para> + The backend is ready to copy data from the frontend to a + relation. The frontend should then send a CopyDataRows + message. The backend will then respond with a + CompletedResponse message with a tag of "COPY". +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + CopyOutResponse +</Term> +<ListItem> +<Para> + The backend is ready to copy data from a relation to the + frontend. It then sends a CopyDataRows message, and then a + CompletedResponse message with a tag of "COPY". +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + CursorResponse +</Term> +<ListItem> +<Para> + The query was either an insert(l), delete(l), update(l), + fetch(l) or a select(l) command. + If the transaction has been + aborted then the backend sends a CompletedResponse message with + a tag of "*ABORT STATE*". Otherwise the following responses + are sent. +</Para> +<Para> + For an insert(l) command, the backend then sends a + CompletedResponse message with a tag of "INSERT <Replaceable>oid</Replaceable> <Replaceable>rows</Replaceable>" + where <Replaceable>rows</Replaceable> is the number of rows inserted, and <Replaceable>oid</Replaceable> is the + object ID of the inserted row if <Replaceable>rows</Replaceable> is 1, otherwise <Replaceable>oid</Replaceable> + is 0. +</Para> +<Para> + For a delete(l) command, the backend then sends a + CompletedResponse message with a tag of "DELETE <Replaceable>rows</Replaceable>" where + <Replaceable>rows</Replaceable> is the number of rows deleted. +</Para> +<Para> + For an update(l) command, the backend then sends a + CompletedResponse message with a tag of "UPDATE <Replaceable>rows</Replaceable>" where + <Replaceable>rows</Replaceable> is the number of rows deleted. +</Para> +<Para> + For a fetch(l) or select(l) command, the backend sends a + RowDescription message. This is then followed by an AsciiRow + or BinaryRow message (depending on if a binary cursor was + specified) for each row being returned to the frontend. + Finally, the backend sends a CompletedResponse message with a + tag of "SELECT". +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + EmptyQueryResponse +</Term> +<ListItem> +<Para> + The query was empty. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + ErrorResponse +</Term> +<ListItem> +<Para> + An error has occurred. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + NoticeResponse +</Term> +<ListItem> +<Para> + A warning message has been issued in relation to the query. + Notices are in addition to other responses, ie. the backend + will send another response message immediately afterwards. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + NotificationResponse +</Term> +<ListItem> +<Para> + A notify(l) command has been executed for a relation for + which a previous listen(l) command was executed. Notifications + are in addition to other responses, ie. the backend will send + another response message immediately afterwards. +</Para> +</ListItem> +</VarListEntry> +</VariableList> +</Para> + +<Para> +A frontend must be prepared to accept ErrorResponse and NoticeResponse +messages whenever it is expecting any other type of message. + +<Sect2> +<Title>Function Call</Title> + +<Para> +The frontend sends a FunctionCall message to the backend. The response sent by +the backend depends on the result of the function call. The possible responses +are as follows. + +<Para> +<VariableList> +<VarListEntry> +<Term> + ErrorResponse +</Term> +<ListItem> +<Para> + An error has occurred. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + FunctionResultResponse +</Term> +<ListItem> +<Para> + The function call was executed and returned a result. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + FunctionVoidResponse +</Term> +<ListItem> +<Para> + The function call was executed and returned no result. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + NoticeResponse +</Term> +<ListItem> +<Para> + A warning message has been issued in relation to the function + call. Notices are in addition to other responses, ie. the + backend will send another response message immediately + afterwards. +</Para> +</ListItem> +</VarListEntry> +</VariableList> +</Para> + +<Para> +A frontend must be prepared to accept ErrorResponse and NoticeResponse +messages whenever it is expecting any other type of message. + +<Sect2> +<Title>Termination</Title> + +<Para> +The frontend sends a Terminate message and immediately closes the connection. +On receipt of the message, the backend immediately closes the connection and +terminates. + + +<Sect1> +<Title>Message Data Types</Title> + +<Para> +This section describes the base data types used in messages. + +<Para> +<VariableList> +<VarListEntry> +<Term> + Int<Replaceable>n</Replaceable>(<Replaceable>i</Replaceable>) +</Term> +<ListItem> +<Para> + An <Replaceable>n</Replaceable> bit integer in network byte order. + If <Replaceable>i</Replaceable> is specified it + is the literal value. Eg. Int16, Int32(42). +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + LimString<Replaceable>n</Replaceable>(<Replaceable>s</Replaceable>) +</Term> +<ListItem> +<Para> + A character array of exactly <Replaceable>n</Replaceable> bytes interpreted as a '\0' + terminated string. The '\0' is omitted if there is + insufficient room. If <Replaceable>s</Replaceable> is specified it is the literal value. + Eg. LimString32, LimString64("user"). +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + String(<Replaceable>s</Replaceable>) +</Term> +<ListItem> +<Para> + A conventional C '\0' terminated string with no length + limitation. A frontend should always read the full string + even though it may have to discard characters if it's buffers + aren't big enough. +<Note> +<Para> +Is 8193 bytes the largest allowed size? +</Para> +</Note> + If <Replaceable>s</Replaceable> is specified it is the literal value. + Eg. String, String("user"). +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + Byte<Replaceable>n</Replaceable>(<Replaceable>c</Replaceable>) +</Term> +<ListItem> +<Para> + Exactly <Replaceable>n</Replaceable> bytes. If <Replaceable>c</Replaceable> is specified it is the literal + value. Eg. Byte, Byte1('\n'). +</Para> +</ListItem> +</VarListEntry> +</VariableList> +</Para> + +<Sect1> +<Title>Message Formats</Title> + +<Para> +This section describes the detailed format of each message. Each can be sent +by either a frontend (F), a postmaster/backend (B), or both (F & B). + +<Para> + +<VariableList> +<VarListEntry> +<Term> +AsciiRow (B) +</Term> +<ListItem> +<Para> +<VariableList> +<VarListEntry> +<Term> + Byte1('D') +</Term> +<ListItem> +<Para> + Identifies the message, in the context in which it is sent (see + CopyInResponse), as an <Acronym>ASCII</Acronym> row. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + Byte<Replaceable>n</Replaceable> +</Term> +<ListItem> +<Para> + + A bit map with one bit for each field in the row. The 1st + field corresponds to bit 7 of the 1st byte, the 2nd field + corresponds to bit 6 of the 1st byte, the 8th field corresponds + to bit 0 of the 1st byte, the 9th field corresponds to bit 8 of + the 2nd byte, and so on. The bit is set if the value of the + corresponding field is not NULL. +</Para> +<Para> + Then, for each field, there is the following: +<VariableList> +<VarListEntry> +<Term> + Int32 +</Term> +<ListItem> +<Para> + Specifies the size of the value of the field, including + this size. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + Byte<Replaceable>n</Replaceable> +</Term> +<ListItem> +<Para> + Specifies the value of the field itself in <Acronym>ASCII</Acronym> + characters. <Replaceable>n</Replaceable> is the above size minus 4. +</Para> +</ListItem> +</VarListEntry> +</VariableList> + +</Para> +</ListItem> +</VarListEntry> +</VariableList> + +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> +AuthenticationOk (B) +</Term> +<ListItem> +<Para> + +<VariableList> +<VarListEntry> +<Term> + Byte1('R') +</Term> +<ListItem> +<Para> + Identifies the message as an authentication request. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + Int32(0) +</Term> +<ListItem> +<Para> + Specifies that the authentication was successful. +</Para> +</ListItem> +</VarListEntry> +</VariableList> + +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> +AuthenticationKerberosV4 (B) +</Term> +<ListItem> +<Para> + +<VariableList> +<VarListEntry> +<Term> + Byte1('R') +</Term> +<ListItem> +<Para> + Identifies the message as an authentication request. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + Int32(1) +</Term> +<ListItem> +<Para> + Specifies that Kerberos V4 authentication is required. +</Para> +</ListItem> +</VarListEntry> +</VariableList> + + +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> +AuthenticationKerberosV5 (B) +</Term> +<ListItem> +<Para> + +<VariableList> +<VarListEntry> +<Term> + Byte1('R') +</Term> +<ListItem> +<Para> + Identifies the message as an authentication request. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + Int32(2) +</Term> +<ListItem> +<Para> + Specifies that Kerberos V5 authentication is required. +</Para> +</ListItem> +</VarListEntry> +</VariableList> + + +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> +AuthenticationUnencryptedPassword (B) +</Term> +<ListItem> +<Para> + +<VariableList> +<VarListEntry> +<Term> + Byte1('R') +</Term> +<ListItem> +<Para> + Identifies the message as an authentication request. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + Int32(3) +</Term> +<ListItem> +<Para> + Specifies that an unencrypted password is required. +</Para> +</ListItem> +</VarListEntry> +</VariableList> + + +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> +AuthenticationEncryptedPassword (B) +</Term> +<ListItem> +<Para> + +<VariableList> +<VarListEntry> +<Term> + Byte1('R') +</Term> +<ListItem> +<Para> + Identifies the message as an authentication request. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + Int32(4) +</Term> +<ListItem> +<Para> + Specifies that an encrypted password is required. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + Byte2 +</Term> +<ListItem> +<Para> + The salt to use when encrypting the password. +</Para> +</ListItem> +</VarListEntry> +</VariableList> + +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> +BinaryRow (B) +</Term> +<ListItem> +<Para> + +<VariableList> +<VarListEntry> +<Term> + Byte1('B') +</Term> +<ListItem> +<Para> + Identifies the message, in the context in which it is sent (see + CopyOutResponse), as a binary row. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + Byte<Replaceable>n</Replaceable> +</Term> +<ListItem> +<Para> + A bit map with one bit for each field in the row. The 1st + field corresponds to bit 7 of the 1st byte, the 2nd field + corresponds to bit 6 of the 1st byte, the 8th field corresponds + to bit 0 of the 1st byte, the 9th field corresponds to bit 8 of + the 2nd byte, and so on. The bit is set if the value of the + corresponding field is not NULL. +</Para> +<Para> + Then, for each field, there is the following: +<VariableList> +<VarListEntry> +<Term> + Int32 +</Term> +<ListItem> +<Para> + Specifies the size of the value of the field, excluding + this size. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + Byte<Replaceable>n</Replaceable> +</Term> +<ListItem> +<Para> + Specifies the value of the field itself in binary + format. <Replaceable>n</Replaceable> is the above size. +</Para> +</ListItem> +</VarListEntry> +</VariableList> + +</Para> +</ListItem> +</VarListEntry> +</VariableList> + +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> +CompletedResponse (B) +</Term> +<ListItem> +<Para> + +<VariableList> +<VarListEntry> +<Term> + Byte1('C') +</Term> +<ListItem> +<Para> + Identifies the message as a completed response. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + String +</Term> +<ListItem> +<Para> + The command tag. This is usually (but not always) a single + word that identifies which SQL command was completed. +</Para> +</ListItem> +</VarListEntry> +</VariableList> + + +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> +CopyDataRows (B & F) +</Term> +<ListItem> +<Para> + This is a stream of rows where each row is terminated by a Char1('\n'). + This is then followed by the sequence Char1('\\'), Char1('.'), + Char1('\n'). +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> +CopyInResponse (B) +</Term> +<ListItem> +<Para> + +<VariableList> +<VarListEntry> +<Term> + Byte1('D') +</Term> +<ListItem> +<Para> + Identifies the message, in the context in which it is sent (see + AsciiRow), as a copy in started response. +</Para> +</ListItem> +</VarListEntry> +</VariableList> + + +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> +CopyOutResponse (B) +</Term> +<ListItem> +<Para> + +<VariableList> +<VarListEntry> +<Term> + Byte1('B') +</Term> +<ListItem> +<Para> + Identifies the message, in the context in which it is sent (see + BinaryRow), as a copy out started response. +</Para> +</ListItem> +</VarListEntry> +</VariableList> + + +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> +CursorResponse (B) +</Term> +<ListItem> +<Para> + +<VariableList> +<VarListEntry> +<Term> + Byte1('P') +</Term> +<ListItem> +<Para> + Identifies the message as a cursor response. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + String +</Term> +<ListItem> +<Para> + The name of the cursor. This will be "blank" if the cursor is + implicit. +</Para> +</ListItem> +</VarListEntry> +</VariableList> + + +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> +EmptyQueryResponse (B) +</Term> +<ListItem> +<Para> + +<VariableList> +<VarListEntry> +<Term> + Byte1('I') +</Term> +<ListItem> +<Para> + Identifies the message as an empty query response. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + String("") +</Term> +<ListItem> +<Para> + Unused. +</Para> +</ListItem> +</VarListEntry> +</VariableList> + + +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> +EncryptedPasswordPacket (F) +</Term> +<ListItem> +<Para> + +<VariableList> +<VarListEntry> +<Term> + Int32 +</Term> +<ListItem> +<Para> + The size of the packet in bytes. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + String +</Term> +<ListItem> +<Para> + The encrypted (using crypt()) password. +</Para> +</ListItem> +</VarListEntry> +</VariableList> + + +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> +ErrorResponse (B) +</Term> +<ListItem> +<Para> + +<VariableList> +<VarListEntry> +<Term> + Byte1('E') +</Term> +<ListItem> +<Para> + Identifies the message as an error. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + String +</Term> +<ListItem> +<Para> + The error message itself. +</Para> +</ListItem> +</VarListEntry> +</VariableList> + + +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> +FunctionCall (F) +</Term> +<ListItem> +<Para> + +<VariableList> +<VarListEntry> +<Term> + Byte1('F') +</Term> +<ListItem> +<Para> + Identifies the message as a function call. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + String("") +</Term> +<ListItem> +<Para> + Unused. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + Int32 +</Term> +<ListItem> +<Para> + Specifies the object ID of the function to call. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + Int32 +</Term> +<ListItem> +<Para> + Specifies the number of arguments being supplied to the + function. +</Para> +<Para> + Then, for each argument, there is the following: +<VariableList> +<VarListEntry> +<Term> + Int32 +</Term> +<ListItem> +<Para> + Specifies the size of the value of the argument, + excluding this size. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + Byte<Replaceable>n</Replaceable> +</Term> +<ListItem> +<Para> + Specifies the value of the field itself in binary + format. <Replaceable>n</Replaceable> is the above size. +</Para> +</ListItem> +</VarListEntry> +</VariableList> + +</Para> +</ListItem> +</VarListEntry> +</VariableList> + +<Para> + +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> +FunctionResultResponse (B) +</Term> +<ListItem> +<Para> + +<VariableList> +<VarListEntry> +<Term> + Byte1('V') +</Term> +<ListItem> +<Para> + Identifies the message as a function call result. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + Byte1('G') +</Term> +<ListItem> +<Para> + Specifies that an actual result was returned. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + Int32 +</Term> +<ListItem> +<Para> + Specifies the size of the value of the result, excluding this + size. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + Byte<Replaceable>n</Replaceable> +</Term> +<ListItem> +<Para> + Specifies the value of the result itself in binary format. + <Replaceable>n</Replaceable> is the above size. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + Byte1('0') +</Term> +<ListItem> +<Para> + Unused. (Strictly speaking, FunctionResultResponse and + FunctionVoidResponse are the same thing but with some optional + parts to the message.) +</Para> +</ListItem> +</VarListEntry> +</VariableList> + + +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> +FunctionVoidResponse (B) +</Term> +<ListItem> +<Para> + +<VariableList> +<VarListEntry> +<Term> + Byte1('V') +</Term> +<ListItem> +<Para> + Identifies the message as a function call result. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + Byte1('0') +</Term> +<ListItem> +<Para> + Specifies that no actual result was returned. +</Para> +</ListItem> +</VarListEntry> +</VariableList> + + +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> +NoticeResponse (B) +</Term> +<ListItem> +<Para> + +<VariableList> +<VarListEntry> +<Term> + Byte1('N') +</Term> +<ListItem> +<Para> + Identifies the message as a notice. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + String +</Term> +<ListItem> +<Para> + The notice message itself. +</Para> +</ListItem> +</VarListEntry> +</VariableList> + + +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> +NotificationResponse (B) +</Term> +<ListItem> +<Para> + +<VariableList> +<VarListEntry> +<Term> + Byte1('A') +</Term> +<ListItem> +<Para> + Identifies the message as a notification response. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + Int32 +</Term> +<ListItem> +<Para> + The process ID of the backend process. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + String +</Term> +<ListItem> +<Para> + The name of the relation that the notify has been raised on. +</Para> +</ListItem> +</VarListEntry> +</VariableList> + + +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> +Query (F) +</Term> +<ListItem> +<Para> + +<VariableList> +<VarListEntry> +<Term> + Byte1('Q') +</Term> +<ListItem> +<Para> + Identifies the message as query. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + String +</Term> +<ListItem> +<Para> + The query itself. +</Para> +</ListItem> +</VarListEntry> +</VariableList> + + +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> +RowDescription (B) +</Term> +<ListItem> +<Para> + +<VariableList> +<VarListEntry> +<Term> + Byte1('T') +</Term> +<ListItem> +<Para> + Identifies the message as a row description. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + Int16 +</Term> +<ListItem> +<Para> + Specifies the number of fields in a row (and may be zero). +</Para> +<Para> + Then, for each field, there is the following: +<VariableList> +<VarListEntry> +<Term> + String +</Term> +<ListItem> +<Para> + Specifies the field name. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + Int32 +</Term> +<ListItem> +<Para> + Specifies the object ID of the field type. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + Int16 +</Term> +<ListItem> +<Para> + Specifies the type size. +</Para> +</ListItem> +</VarListEntry> +</VariableList> + +</Para> +</ListItem> +</VarListEntry> +</VariableList> + + +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> +StartupPacket (F) +</Term> +<ListItem> +<Para> + +<VariableList> +<VarListEntry> +<Term> + Int32(296) +</Term> +<ListItem> +<Para> + The size of the packet in bytes. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + Int32 +</Term> +<ListItem> +<Para> + The protocol version number. The most significant 16 bits are + the major version number. The least 16 significant bits are + the minor version number. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + LimString64 +</Term> +<ListItem> +<Para> + The database name, defaults to the user name if omitted. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + LimString32 +</Term> +<ListItem> +<Para> + The user name. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + LimString64 +</Term> +<ListItem> +<Para> + Any additional command line arguments to be passed to the + backend by the postmaster. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + LimString64 +</Term> +<ListItem> +<Para> + Unused. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + LimString64 +</Term> +<ListItem> +<Para> + The optional tty the backend should use for debugging messages. +</Para> +</ListItem> +</VarListEntry> +</VariableList> + + +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> +Terminate (F) +</Term> +<ListItem> +<Para> + +<VariableList> +<VarListEntry> +<Term> + Byte1('X') +</Term> +<ListItem> +<Para> + Identifies the message as a termination. +</Para> +</ListItem> +</VarListEntry> +</VariableList> + + +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> +UnencryptedPasswordPacket (F) +</Term> +<ListItem> +<Para> + +<VariableList> +<VarListEntry> +<Term> + Int32 +</Term> +<ListItem> +<Para> + The size of the packet in bytes. +</Para> +</ListItem> +</VarListEntry> +<VarListEntry> +<Term> + String +</Term> +<ListItem> +<Para> + The unencrypted password. +</Para> +</ListItem> +</VarListEntry> +</VariableList> + +</Para> +</ListItem> +</VarListEntry> +</VariableList> +</Para> + +</Chapter> |