Logical Replication Functions

pg_create_logical_replication_slot('slot_name', 'plugin_name')
Description: Creates a logical replication slot.
Parameter description:
- slot_name
  Indicates the name of the streaming replication slot.
  Value range: a string, supporting only letters, digits, and the following special characters: _?-.
- plugin_name
  Indicates the name of the plugin.
  Value range: a string, supporting mppdb_decoding
Return type: name, text
Note: The first return value is the slot name, and the second is the start LSN position for decoding in the logical replication slot. Users who invoke this function must have the SYSADMIN permission, the REPLICATION permission, or inherit the gs_role_replication permission of the built-in role. Currently, this function can be invoked only on the host.
pg_create_physical_replication_slot('slot_name', 'isDummyStandby')
Description: Creates a physical replication slot.
Parameter description:
- slot_name
  Indicates the name of the streaming replication slot.
  Value range: a string, supporting only letters, digits, and the following special characters: _?-.
- isDummyStandby
  Specifies whether the replication slot is created by connecting the secondary server to the primary server.
  Type: bool
Return type: name, text
Note: A user with the SYSADMIN or REPLICATION permission or a user who inherits the gs_role_replication permission of the built-in role can invoke this function.
pg_drop_replication_slot('slot_name')
Description: Deletes a streaming replication slot.
Parameter description:
- slot_name
  Indicates the name of the streaming replication slot.
  Value range: a string, supporting only letters, digits, and the following special characters: _?-.
Return type: void
Note: A user with the SYSADMIN or REPLICATION permission or a user who inherits the gs_role_replication permission of the built-in role can invoke this function. Currently, this function can be invoked only on the host.
pg_logical_slot_peek_changes('slot_name', 'LSN', upto_nchanges, 'options_name', 'options_value')
Description: Performs decoding but does not go to the next streaming replication slot. (The decoding result will be returned again on future calls.)
Parameter description:
- slot_name
  Indicates the name of the streaming replication slot.
  Value range: a string, supporting only letters, digits, and the following special characters: _?-.
- LSN
  Indicates a target LSN. Decoding is performed only when an LSN is less than or equal to this value.
  Value range: a string, in the format of xlogid/xrecoff, for example, 1/2AAFC60 (If this parameter is set to NULL, the target LSN indicating the end position of decoding is not specified.)
- upto_nchanges
  Indicates the number of decoded records (including the begin and commit timestamps). Assume that there are three transactions, which involve 3, 5, and 7 records, respectively. If upto_nchanges is set to 4, 8 records of the first two transactions will be decoded. Specifically, decoding is stopped when the number of decoded records exceeds the value of upto_nchanges after decoding in the first two transactions is finished.
  Value range: a non-negative integer
  NOTE: If any of the LSN and upto_nchanges values are reached, decoding ends.
- options: Specifies optional parameters, consisting of options_name and options_value.
  - include-xids
    Indicates whether the decoded data column contains XID information.
    Valid value: 0 and 1. The default value is 1.
    - 0: The decoded data column does not contain XID information.
    - 1: The decoded data column contains XID information.
  - skip-empty-xacts
    Indicates whether to ignore empty transaction information during decoding.
    Valid value: 0 and 1. The default value is 0.
    - 0: The empty transaction information is not ignored during decoding.
    - 1: The empty transaction information is ignored during decoding.
  - include-timestamp
    Indicates whether decoded information contains the commit timestamp.
    Valid value: 0 and 1. The default value is 0.
    - 0: The decoded information does not contain the commit timestamp.
    - 1: The decoded information contains the commit timestamp.
  - only-local
    Specifies whether to decode only local logs.
    Value range: 0 and 1. The default value is 1.
    - 0: Non-local logs and local logs are decoded.
    - 1: Only local logs are decoded.
  - force-binary
    Specifies whether to output the decoding result in binary format.
    Value range: 0
    - 0: The decoding result is output in text format.
Return type: text, xid, text
Note: The function returns the decoding result. Each decoding result contains three columns, corresponding to the above return types and indicating the LSN position, XID, and decoded content, respectively.
Users who invoke this function must have the SYSADMIN permission, the REPLICATION permission, or inherit the gs_role_replication permission of the built-in role.
pg_logical_slot_get_changes('slot_name', 'LSN', upto_nchanges, 'options_name', 'options_value')
Description: Performs decoding and goes to the next streaming replication slot.
Parameter: This function has the same parameters as pg_logical_slot_peek_changes. For details, see pg_logical_slot_peek_ch….
Note: A user with the SYSADMIN or REPLICATION permission or a user who inherits the gs_role_replication permission of the built-in role can invoke this function. Currently, this function can be invoked only on the host.
pg_logical_slot_peek_binary_changes('slot_name', 'LSN', upto_nchanges, 'options_name', 'options_value')
Description: Performs decoding in binary mode and does not go to the next streaming replication slot. (The decoded data can be obtained again during the next decoding.)
Parameter description:
- slot_name
  Indicates the name of the streaming replication slot.
  Value range: a string, supporting only letters, digits, and the following special characters: _?-.
- LSN
  Indicates a target LSN. Decoding is performed only when an LSN is less than or equal to this value.
  Value range: a string, in the format of xlogid/xrecoff, for example, 1/2AAFC60 (If this parameter is set to NULL, the target LSN indicating the end position of decoding is not specified.)
- upto_nchanges
  Indicates the number of decoded records (including the begin and commit timestamps). Assume that there are three transactions, which involve 3, 5, and 7 records, respectively. If upto_nchanges is set to 4, 8 records of the first two transactions will be decoded. Specifically, decoding is stopped when the number of decoded records exceeds the value of upto_nchanges after decoding in the first two transactions is finished.
  Value range: a non-negative integer
  NOTE: If any of the LSN and upto_nchanges values are reached, decoding ends.
- options: Specifies optional parameters, consisting of options_name and options_value.
  - include-xids
    Indicates whether the decoded data column contains XID information.
    Valid value: 0 and 1. The default value is 1.
    - 0: The decoded data column does not contain XID information.
    - 1: The decoded data column contains XID information.
  - skip-empty-xacts
    Indicates whether to ignore empty transaction information during decoding.
    Valid value: 0 and 1. The default value is 0.
    - 0: The empty transaction information is not ignored during decoding.
    - 1: The empty transaction information is ignored during decoding.
  - include-timestamp
    Indicates whether decoded information contains the commit timestamp.
    Valid value: 0 and 1. The default value is 0.
    - 0: The decoded information does not contain the commit timestamp.
    - 1: The decoded information contains the commit timestamp.
  - only-local
    Specifies whether to decode only local logs.
    Value range: 0 and 1. The default value is 1.
    - 0: Non-local logs and local logs are decoded.
    - 1: Only local logs are decoded.
  - force-binary
    Specifies whether to output the decoding result in binary format.
    Value range: 0 or 1. The default value is 0. The result is output in binary format.
Return type: text, xid, bytea
Note: The function returns the decoding result. Each decoding result contains three columns, corresponding to the above return types and indicating the LSN position, XID, and decoded content in binary format, respectively. Users who invoke this function must have the SYSADMIN permission, the REPLICATION permission, or inherit the gs_role_replication permission of the built-in role.
pg_logical_slot_get_binary_changes('slot_name', 'LSN', upto_nchanges, 'options_name', 'options_value')
Description: Performs decoding in binary mode and does not go to the next streaming replication slot.
Parameter: This function has the same parameters as pg_logical_slot_peek_binary_changes. For details, see •pg_logical_slot_peek_bi…
Note: A user with the SYSADMIN or REPLICATION permission or a user who inherits the gs_role_replication permission of the built-in role can invoke this function.
pg_replication_slot_advance ('slot_name', 'LSN')
Description: Directly goes to the streaming replication slot for a specified LSN, without outputting any decoding result.
Parameter description:
- slot_name
  Indicates the name of the streaming replication slot.
  Value range: a string, supporting only letters, digits, and the following special characters: _?-.
- LSN
  Indicates a target LSN. Next decoding will be performed only in transactions whose commission position is greater than this value. If an input LSN is smaller than the position recorded in the current streaming replication slot, the function directly returns. If the input LSN is greater than the LSN of the current physical log, the latter LSN will be directly used for decoding.
  Value range: a string, in the format of xlogid/xrecoff
Return type: name, text
Note: A return result contains the slot name and LSN that is actually used for decoding. Users who invoke this function must have the SYSADMIN permission, the REPLICATION permission, or inherit the gs_role_replication permission of the built-in role. Currently, this function can be invoked only on the host.

pg_get_replication_slots

Description: Obtains the replication slot list.

Return type: text, text, text, oid, boolean, xid, xid, text, boolean

Example:

openGauss=# select * from pg_get_replication_slots();
 slot_name |     plugin     | slot_type | datoid | active | xmin | catalog_xmin | restart_lsn | dummy_standby
-----------+----------------+-----------+--------+--------+------+--------------+-------------+---------------
 wkl001    | mppdb_decoding | logical   |  15914 | f      |      |      2079556 | 4/1B81D920  | f
 dn_6002   |                | physical  |      0 | t      |      |              | 8/7CB63BD8  | f
 dn_6004   |                | physical  |      0 | t      |      |              | 8/7CB63BD8  | f
 dn_6003   |                | physical  |      0 | t      |      |              | 8/7CB63BD8  | f
 gfslot001 | mppdb_decoding | logical   |  15914 | f      |      |      2412553 | 4/A54B2428  | f
(5 rows)