55.9. Logical Replication Message Formats

55.9. Logical Replication Message Formats
Prev	Up	Chapter 55. Frontend/Backend Protocol	Home	Next

+ This section describes the detailed format of each logical replication + message. These messages are either returned by the replication slot SQL + interface or are sent by a walsender. In the case of a walsender, they are + encapsulated inside replication protocol WAL messages as described in + Section 55.4, and generally obey the same message + flow as physical replication. +

Begin

Byte1('B'): + Identifies the message as a begin message. +
Int64 (XLogRecPtr): + The final LSN of the transaction. +
Int64 (TimestampTz): + Commit timestamp of the transaction. The value is in number + of microseconds since PostgreSQL epoch (2000-01-01). +
Int32 (TransactionId): + Xid of the transaction. +

Message

Byte1('M'): + Identifies the message as a logical decoding message. +
Int32 (TransactionId): + Xid of the transaction (only present for streamed transactions). + This field is available since protocol version 2. +
Int8: + Flags; Either 0 for no flags or 1 if the logical decoding + message is transactional. +
Int64 (XLogRecPtr): + The LSN of the logical decoding message. +
String: + The prefix of the logical decoding message. +
Int32: + Length of the content. +
Byten: + The content of the logical decoding message. +

Commit

Byte1('C'): + Identifies the message as a commit message. +
Int8(0): + Flags; currently unused. +
Int64 (XLogRecPtr): + The LSN of the commit. +
Int64 (XLogRecPtr): + The end LSN of the transaction. +
Int64 (TimestampTz): + Commit timestamp of the transaction. The value is in number + of microseconds since PostgreSQL epoch (2000-01-01). +

Origin

Byte1('O'): + Identifies the message as an origin message. +
Int64 (XLogRecPtr): + The LSN of the commit on the origin server. +
String: + Name of the origin. +

+ Note that there can be multiple Origin messages inside a single transaction. +

Relation

Byte1('R'): + Identifies the message as a relation message. +
Int32 (TransactionId): + Xid of the transaction (only present for streamed transactions). + This field is available since protocol version 2. +
Int32 (Oid): + OID of the relation. +
String: + Namespace (empty string for pg_catalog). +
String: + Relation name. +
Int8: + Replica identity setting for the relation (same as + relreplident in pg_class). +
Int16: + Number of columns. +

+ Next, the following message part appears for each column included in + the publication (except generated columns): +

Int8: + Flags for the column. Currently can be either 0 for no flags + or 1 which marks the column as part of the key. +
String: + Name of the column. +
Int32 (Oid): + OID of the column's data type. +
Int32: + Type modifier of the column (atttypmod). +

Type

Byte1('Y'): + Identifies the message as a type message. +
Int32 (TransactionId): + Xid of the transaction (only present for streamed transactions). + This field is available since protocol version 2. +
Int32 (Oid): + OID of the data type. +
String: + Namespace (empty string for pg_catalog). +
String: + Name of the data type. +

Insert

Byte1('I'): + Identifies the message as an insert message. +
Int32 (TransactionId): + Xid of the transaction (only present for streamed transactions). + This field is available since protocol version 2. +
Int32 (Oid): + OID of the relation corresponding to the ID in the relation + message. +
Byte1('N'): + Identifies the following TupleData message as a new tuple. +
TupleData: + TupleData message part representing the contents of new tuple. +

Update

Byte1('U'): + Identifies the message as an update message. +
Int32 (TransactionId): + Xid of the transaction (only present for streamed transactions). + This field is available since protocol version 2. +
Int32 (Oid): + OID of the relation corresponding to the ID in the relation + message. +
Byte1('K'): + Identifies the following TupleData submessage as a key. + This field is optional and is only present if + the update changed data in any of the column(s) that are + part of the REPLICA IDENTITY index. +
Byte1('O'): + Identifies the following TupleData submessage as an old tuple. + This field is optional and is only present if table in which + the update happened has REPLICA IDENTITY set to FULL. +
TupleData: + TupleData message part representing the contents of the old tuple + or primary key. Only present if the previous 'O' or 'K' part + is present. +
Byte1('N'): + Identifies the following TupleData message as a new tuple. +
TupleData: + TupleData message part representing the contents of a new tuple. +

+ The Update message may contain either a 'K' message part or an 'O' message part + or neither of them, but never both of them. +

Delete

Byte1('D'): + Identifies the message as a delete message. +
Int32 (TransactionId): + Xid of the transaction (only present for streamed transactions). + This field is available since protocol version 2. +
Int32 (Oid): + OID of the relation corresponding to the ID in the relation + message. +
Byte1('K'): + Identifies the following TupleData submessage as a key. + This field is present if the table in which the delete has + happened uses an index as REPLICA IDENTITY. +
Byte1('O'): + Identifies the following TupleData message as an old tuple. + This field is present if the table in which the delete + happened has REPLICA IDENTITY set to FULL. +
TupleData: + TupleData message part representing the contents of the old tuple + or primary key, depending on the previous field. +

+ The Delete message may contain either a 'K' message part or an 'O' message part, + but never both of them. +

Truncate

Byte1('T'): + Identifies the message as a truncate message. +
Int32 (TransactionId): + Xid of the transaction (only present for streamed transactions). + This field is available since protocol version 2. +
Int32: + Number of relations +
Int8: + Option bits for TRUNCATE: + 1 for CASCADE, 2 for RESTART IDENTITY +
Int32 (Oid): + OID of the relation corresponding to the ID in the relation + message. This field is repeated for each relation. +

+ The following messages (Stream Start, Stream Stop, Stream Commit, and + Stream Abort) are available since protocol version 2. +

Stream Start

Byte1('S'): + Identifies the message as a stream start message. +
Int32 (TransactionId): + Xid of the transaction. +
Int8: + A value of 1 indicates this is the first stream segment for + this XID, 0 for any other stream segment. +

Stream Stop

Byte1('E'): + Identifies the message as a stream stop message. +

Stream Commit

Byte1('c'): + Identifies the message as a stream commit message. +
Int32 (TransactionId): + Xid of the transaction. +
Int8(0): + Flags; currently unused. +
Int64 (XLogRecPtr): + The LSN of the commit. +
Int64 (XLogRecPtr): + The end LSN of the transaction. +
Int64 (TimestampTz): + Commit timestamp of the transaction. The value is in number + of microseconds since PostgreSQL epoch (2000-01-01). +

Stream Abort

Byte1('A'): + Identifies the message as a stream abort message. +
Int32 (TransactionId): + Xid of the transaction. +
Int32 (TransactionId): + Xid of the subtransaction (will be same as xid of the transaction for top-level + transactions). +

+ The following messages (Begin Prepare, Prepare, Commit Prepared, Rollback Prepared, Stream Prepare) + are available since protocol version 3. +

Begin Prepare

Byte1('b'): + Identifies the message as the beginning of a prepared transaction message. +
Int64 (XLogRecPtr): + The LSN of the prepare. +
Int64 (XLogRecPtr): + The end LSN of the prepared transaction. +
Int64 (TimestampTz): + Prepare timestamp of the transaction. The value is in number + of microseconds since PostgreSQL epoch (2000-01-01). +
Int32 (TransactionId): + Xid of the transaction. +
String: + The user defined GID of the prepared transaction. +

Prepare

Byte1('P'): + Identifies the message as a prepared transaction message. +
Int8(0): + Flags; currently unused. +
Int64 (XLogRecPtr): + The LSN of the prepare. +
Int64 (XLogRecPtr): + The end LSN of the prepared transaction. +
Int64 (TimestampTz): + Prepare timestamp of the transaction. The value is in number + of microseconds since PostgreSQL epoch (2000-01-01). +
Int32 (TransactionId): + Xid of the transaction. +
String: + The user defined GID of the prepared transaction. +

Commit Prepared

Byte1('K'): + Identifies the message as the commit of a prepared transaction message. +
Int8(0): + Flags; currently unused. +
Int64 (XLogRecPtr): + The LSN of the commit of the prepared transaction. +
Int64 (XLogRecPtr): + The end LSN of the commit of the prepared transaction. +
Int64 (TimestampTz): + Commit timestamp of the transaction. The value is in number + of microseconds since PostgreSQL epoch (2000-01-01). +
Int32 (TransactionId): + Xid of the transaction. +
String: + The user defined GID of the prepared transaction. +

Rollback Prepared

Byte1('r'): + Identifies the message as the rollback of a prepared transaction message. +
Int8(0): + Flags; currently unused. +
Int64 (XLogRecPtr): + The end LSN of the prepared transaction. +
Int64 (XLogRecPtr): + The end LSN of the rollback of the prepared transaction. +
Int64 (TimestampTz): + Prepare timestamp of the transaction. The value is in number + of microseconds since PostgreSQL epoch (2000-01-01). +
Int64 (TimestampTz): + Rollback timestamp of the transaction. The value is in number + of microseconds since PostgreSQL epoch (2000-01-01). +
Int32 (TransactionId): + Xid of the transaction. +
String: + The user defined GID of the prepared transaction. +

Stream Prepare

Byte1('p'): + Identifies the message as a stream prepared transaction message. +
Int8(0): + Flags; currently unused. +
Int64 (XLogRecPtr): + The LSN of the prepare. +
Int64 (XLogRecPtr): + The end LSN of the prepared transaction. +
Int64 (TimestampTz): + Prepare timestamp of the transaction. The value is in number + of microseconds since PostgreSQL epoch (2000-01-01). +
Int32 (TransactionId): + Xid of the transaction. +
String: + The user defined GID of the prepared transaction. +

+ The following message parts are shared by the above messages. +

TupleData

Int16: + Number of columns. +

+ Next, one of the following submessages appears for each column (except generated columns): + +

Byte1('n'): + Identifies the data as NULL value. +

+ Or +

Byte1('u'): + Identifies unchanged TOASTed value (the actual value is not + sent). +

+ Or +

Byte1('t'): + Identifies the data as text formatted value. +

+ Or +

Byte1('b'): + Identifies the data as binary formatted value. +
Int32: + Length of the column value. +
Byten: + The value of the column, either in binary or in text format. + (As specified in the preceding format byte). + n is the above length. +

Prev	Up	Next
55.8. Error and Notice Message Fields	Home	55.10. Summary of Changes since Protocol 2.0