Relation (logical replication)

Logical replication Relation format. Identifies the message as a relation message.

Reading PG 18·Select a recorded version

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Layer: Logical replication payload; distinct from the frontend/backend message envelope
First field: Byte1('R')
manual path: /docs/18/protocol-logicalrep-message-formats.html
signature: Relation

Definition PG 18

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:

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).

Fields in documented order

Position	Format	Meaning
1	Byte1('R')	Identifies the message as a relation message.
2	Int32 (TransactionId)	Xid of the transaction (only present for streamed transactions). This field is available since protocol version 2.
3	Int32 (Oid)	OID of the relation.
4	String	Namespace (empty string for pg_catalog ).
5	String	Relation name.
6	Int8	Replica identity setting for the relation (same as relreplident in pg_class ).
7	Int16	Number of columns.
8	Int8	Flags for the column. Currently can be either 0 for no flags or 1 which marks the column as part of the key.
9	String	Name of the column.
10	Int32 (Oid)	OID of the column's data type.
11	Int32	Type modifier of the column ( atttypmod ).

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Complete source facts

fields

map[description:Identifies the message as a relation message. format:Byte1('R')], map[description:Xid of the transaction (only present for streamed transactions). This field is available since protocol version 2. format:Int32 (TransactionId)], map[description:OID of the relation. format:Int32 (Oid)], map[description:Namespace (empty string for pg_catalog ). format:String], map[description:Relation name. format:String], map[description:Replica identity setting for the relation (same as relreplident in pg_class ). format:Int8], map[description:Number of columns. format:Int16], map[description:Flags for the column. Currently can be either 0 for no flags or 1 which marks the column as part of the key. format:Int8], map[description:Name of the column. format:String], map[description:OID of the column's data type. format:Int32 (Oid)], map[description:Type modifier of the column ( atttypmod ). format:Int32]

Source references

Full definition and evidence JSON

Definition sources

center · PostgreSQL 18 · 555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f