Internal system functions

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Internal system functions#

The following are internal system functions. Many are used when creating various views. We recommend that you do not use the functions directly but instead use the views that they serve.

General internal functions#

bdr.bdr_get_commit_decisions#

Convenience routine to inspect shared memory state.

Synopsis#

bdr.bdr_get_commit_decisions(dbid OID,
            origin_node_id OID,
            origin_xid xid,
            local_xid xid,
            decision "char",
            decision_ts timestamptz,
            is_camo boolean)

bdr.bdr_track_commit_decision#

Save the transaction commit status in the shared memory hash table. This function is used by the upgrade scripts to transfer commit decisions saved in bdr.commit_decisions catalog to the shared memory hash table. The transaction commit status will also be logged to the WAL and hence can be reloaded from WAL.

Synopsis#

bdr.bdr_track_commit_decision(OID, xid, xid, "char", timestamptz, boolean);

bdr.consensus_kv_fetch#

Fetch value from the consistent KV Store in JSON format.

Synopsis#

bdr.consensus_kv_fetch(IN key text) RETURNS jsonb

Parameters#

Parameter

Description

key

An arbitrary key to fetch.

Notes#

This function is an internal function, mainly used by HARP.

Warning

Don't use this function in user applications.

bdr.consensus_kv_store#

Stores value in the consistent KV Store.

Returns the timestamp of the value expiration time. This function depends on ttl . If ttl is NULL , then this function returns infinity . If the value was deleted, it returns -infinity .

Synopsis#

bdr.consensus_kv_store(key text, value jsonb,
        prev_value jsonb DEFAULT NULL, ttl int DEFAULT NULL)

Parameters#

Parameter

Description

key

An arbitrary unique key to insert, update, or delete.

value

JSON value to store. If NULL, any existing record is deleted.

prev_value

If set, the write operation is done only if the current value is equal to prev_value.

ttl

Time-to-live of the new value, in milliseconds.

Notes#

This is an internal function, mainly used by HARP.

Warning

Don't use this function in user applications.

bdr.decode_message_payload#

PGD message payload function that decodes the payloads of consensus messages to a more human-readable output. Used primarily by the bdr.global_consensus_journal_details debug view.

bdr.decode_message_response_payload#

PGD message payload function that decodes the payloads of responses to consensus messages to a more human-readable output. Used primarily by the bdr.global_consensus_journal_details debug view.

bdr.difference_fix_origin_create#

Creates a replication origin with a given name passed as an argument but adding a bdr_ prefix. Returns the internal id of the origin. This function has the same functionality as pg_replication_origin_create() except this function requires bdr_superuser rather than postgres superuser permissions.

bdr.difference_fix_session_reset#

Marks the current session as not replaying from any origin, essentially resetting the effect of bdr.difference_fix_session_setup() . It returns void. This function has the same functionality as pg_replication_origin_session_reset() except this function requires bdr_superuser rather than postgres superuser permissions.

Synopsis#

bdr.difference_fix_session_reset()

bdr.difference_fix_session_setup#

Marks the current session as replaying from the current origin. The function uses the pre-created bdr_local_only_origin local replication origin implicitly for the session. It allows replay progress to be reported and returns void. This function has the same functionality as pg_replication_origin_session_setup() except that this function requires bdr_superuser rather than postgres superuser permissions. The earlier form of the function, bdr.difference_fix_session_setup(text) , was deprecated and will be removed in a future release.

Synopsis#

bdr.difference_fix_session_setup()

bdr.difference_fix_xact_set_avoid_conflict#

Marks the current transaction as replaying a transaction that committed at LSN ‘0/0’ and timestamp ‘2000-01-01’. This function has the same functionality as pg_replication_origin_xact_setup('0/0', '2000-01-01') except this function requires bdr_superuser rather than postgres superuser permissions.

Synopsis#

bdr.difference_fix_xact_set_avoid_conflict()

bdr.drop_node#

Drops a node’s metadata.

After a node has been PARTED its metadata remains present in the cluster’s nodes. For example, the node will remain in the bdr.node_sumary results, marked as PARTED , until the node is dropped.

Calling bdr.drop_node('some node', force := true) can be necessary and appropriate when a node becomes stuck while parting. Note that it skips past syncing any data out of the node being dropped, if there is any data on that node that still needs to be synced out. If a node stuck parting has already been reimaged or deleted, there is no harm in calling bdr.drop_node on it. Note that this must be called for this stuck node on all nodes in the cluster so they all have a consistent view that the node has been dropped.

This function removes the metadata for a given node from the local database. The node can be either:

  • The local node, in which case it removes all the node metadata, including information about remote nodes.

  • A remote node, in which case it removes only metadata for that specific node.

Use of this internal function is limited to:

  • When you’re instructed to by EDB Technical Support.

  • Where you’re specifically instructed to in the documentation.

Use bdr.part_node to remove a node from a PGD group. That function sets the node to PARTED state and enables reuse of the node name.

bdr.drop_node(node_name text, cascade boolean DEFAULT false, force boolean DEFAULT false)

Parameters#

Parameter

Description

node_name

Name of an existing node.

cascade

Deprecated, will be removed in a future release.

force

Circumvents all sanity checks and forces the removal of all metadata for the given PGD node despite a possible danger of causing inconsistencies. Only Technical Support uses a forced node drop in case of emergencies related to parting.

Notes#

Before you run this function, part the node using bdr.part_node() .

This function removes metadata for a given node from the local database. The node can be the local node, in which case all the node metadata is removed, including information about remote nodes. Or it can be the remote node, in which case only metadata for that specific node is removed.

Note

PGD can have a maximum of 1024 node records (both ACTIVE and PARTED) at one time because each node has a unique sequence number assigned to it, for use by snowflakeid and timeshard sequences. PARTED nodes aren't automatically cleaned up. If this becomes a problem, you can use this function to remove those records.

bdr.get_global_locks#

Shows information about global locks held on the local node.

Used to implement the bdr.global_locks view to provide a more detailed overview of the locks.

bdr.get_node_conflict_resolvers#

Displays a text string of all the conflict resolvers on the local node.

bdr.get_slot_flush_timestamp#

Retrieves the timestamp of the last flush position confirmation for a given replication slot.

Used internally to implement the bdr.node_slots view.

bdr.internal_alter_sequence_set_kind#

A function previously used internally for replication of the various function calls. No longer used by the current version of PGD. Exists only for backward compatibility during rolling upgrades.

bdr.internal_replication_set_add_table#

A function previously used internally for replication of the various function calls. No longer used by the current version of PGD. Exists only for backward compatibility during rolling upgrades.

bdr.internal_replication_set_remove_table#

A function previously used internally for replication of the various function calls. No longer used by the current version of PGD. Exists only for backward compatibility during rolling upgrades.

bdr.internal_submit_join_request#

Submits a consensus request for joining a new node.

Needed by the PGD group reconfiguration internal mechanisms.

bdr.isolation_test_session_is_blocked#

A helper function, extending (and actually invoking) the original pg_isolation_test_session_is_blocked with an added check for blocks on global locks.

Used for isolation/concurrency tests.

bdr.local_node_info#

Displays information for the local node needed by the PGD group reconfiguration internal mechanisms.

The view bdr.local_node_summary provides similar information useful for user consumption.

bdr.msgb_connect#

Connects to the connection pooler of another node. Used by the consensus protocol.

bdr.msgb_deliver_message#

Sends messages to another node’s connection pooler. Used by the consensus protocol.

bdr.node_catchup_state_name#

Converts catchup state code in name.

Synopsis#

bdr.node_catchup_state_name(catchup_state oid);

Parameters#

Parameter

Description

catchup_state

Oid code of the catchup state.

bdr.node_kind_name#

Returns human-friendly name of the node kind (data|standby|witness|subscriber-only).

bdr.peer_state_name#

Transforms the node state (node_state ) into a textual representation. Used mainly to implement the bdr.node_summary view.

bdr.pg_xact_origin#

Returns the origin id of a given transaction.

Synopsis#

bdr.pg_xact_origin(xmin xid)

Parameters#

Parameter

Description

xid

Transaction id whose origin is returned.

bdr.reconcile_2pc_status_name#

Converts a numerical reconciliation status code into its corresponding textual representation. This function is primarily used to populate the bdr.reconcile_2pc_requests_summary view.

Synopsis#

bdr.reconcile_2pc_status_name(reconcile_status oid) RETURNS text

Parameters#

Parameter

Description

reconcile_status

The OID code representing the specific reconciliation status to be converted.

bdr.request_replay_progress_update#

Requests the immediate writing of a ‘replay progress update’ Raft message. Used mainly for test purposes but can also be used to test if the consensus mechanism is working.

bdr.reset_relation_stats#

Returns a Boolean result after resetting the relation stats, as viewed by bdr.stat_relation .

bdr.reset_subscription_stats#

Returns a Boolean result after resetting the statistics created by subscriptions, as viewed by bdr.stat_subscription .

bdr.resynchronize_table_from_node#

Resynchronizes the relation from a remote node.

Synopsis#

bdr.resynchronize_table_from_node(node_name name, relation regclass)

Parameters#

Parameter

Description

node_name

The node from which to copy or resync the relation data.

relation

The relation to copy from the remote node.

Notes#

This function acquires a global DML lock on the relation, truncates the relation locally, and copies data into it from the remote node.

The relation must exist on both nodes with the same name and definition.

The following are supported:

  • Resynchronizing partitioned tables with identical partition definitions

  • Resynchronizing partitioned table to nonpartitioned table and vice versa

  • Resynchronizing referenced tables by temporarily dropping and re-creating foreign key constraints

After running the function on a referenced table, if the referenced column data no longer matches the referencing column values, the function throws an error. After resynchronizing the referencing table data, rerun the function.

Furthermore, it supports resynchronization of tables with generated columns by computing the generated column values locally after copying the data from remote node.

Currently, row_filters are ignored by this function.

The bdr.resynchronize_table_from_node function can be executed only by the owner of the table, provided the owner has bdr_superuser privileges.

bdr.seq_currval#

Part of the internal implementation of global sequence manipulation.

Invoked automatically when currval() is called on a galloc or snowflakeid sequence.

bdr.seq_lastval#

Part of the internal implementation of global sequence manipulation.

Invoked automatically when lastval() is called on a galloc or snowflakeid sequence.

bdr.seq_nextval#

Part of the internal implementation of global sequence increments.

Invoked automatically when nextval() is called on a galloc or snowflakeid sequence

bdr.show_subscription_status#

Retrieves information about the subscription status. Used mainly to implement the bdr.subscription_summary view.

bdr.show_workers#

Information related to the bdr workers.

Synopsis#

bdr.show_workers(
    worker_pid int,
    worker_role int,
    worker_role_name text,
    worker_subid oid)

bdr.show_writers#

Function used in the bdr.writers view.

bdr.sync_status_name#

Converts sync state code into a textual representation. Used mainly to implement the bdr.sync_node_requests_summary

view.

Synopsis#

bdr.sync_status_name(sync_state oid)

Parameters#

Parameter

Description

sync_state

Oid code of the sync state.

Task manager functions#

bdr.taskmgr_set_leader#

Requests the given node to be the task manager leader node. The leader node is responsible for creating new tasks. (Currently only autopartition makes use of this facility.) A witness node, a logical standby, or a subscriber-only node can’t become a leader. Such requests will fail with an error.

Synopsis#

bdr.taskmgr_set_leader(node name, wait_for_completion boolean DEFAULT true);

bdr.taskmgr_get_last_completed_workitem#

Return the id of the last workitem successfully completed on all nodes in the cluster.

Synopsis#

bdr.taskmgr_get_last_completed_workitem();

bdr.taskmgr_work_queue_check_status#

Lets you see the status of the background workers that are doing their job to generate and finish the tasks.

The status can be seen through these views:

  • bdr.taskmgr_work_queue_local_status

  • bdr.taskmgr_work_queue_global_status

Synopsis#

bdr.taskmgr_work_queue_check_status(workid bigint
                           local boolean DEFAULT false);

Parameters#

Parameter

Description

workid

The key of the task.

local

Check the local status only.

Notes#

Taskmgr workers are always running in the background, even before the bdr.autopartition function is called for the first time. If an invalid workid is used, the function returns unknown . In-progress is the typical status.

bdr.get_min_required_replication_slots#

Returns the minimum value needed for max_replication_slots so a node join can complete without exhausting available slots. The estimate reserves headroom for the temporary catch-up subscription that briefly coexists with the steady-state subscriptions during a join. On Postgres versions earlier than 18, where max_active_replication_origins is aliased to max_replication_slots , the returned value also covers the origin requirement. PGD-CLI uses this function internally, but you can also run it directly when sizing a cluster.

bdr.get_min_required_active_replication_origins#

Returns the minimum value needed for max_active_replication_origins , the configuration parameter introduced in Postgres 18. On earlier Postgres versions, where max_active_replication_origins is aliased to max_replication_slots , this value is informational only. PGD-CLI uses this function internally, but you can also run it directly when sizing a cluster.

bdr.get_min_required_worker_processes#

Internal function intended for use by PGD-CLI.

bdr.stat_last_reset_time#

Internal function used to retrieve the most recent reset timestamp for a specific statistics category. For standard monitoring, each statistic that supports bdr.stat_reset includes a stats_reset column in the bdr.stat_commit_scope view, which provides this information in a more accessible format for user consumption.

bdr.stat_get_activity#

Internal function underlying view bdr.stat_activity . Do not use directly. Use the bdr.stat_activity view instead.

bdr.stat_get_commit_scope#

Internal function to fetch commit scope statistics. For standard monitoring and troubleshooting, use the bdr.stat_commit_scope view, which provides the same information in a more accessible format.

bdr.stat_get_commit_scope_proc_wait#

Internal function used to retrieve the wait state statistics for processes associated with specific commit scopes. For standard monitoring and troubleshooting, use the bdr.stat_commit_scope view, which provides a more accessible representation of this data.

bdr.stat_get_reconcile_commit_scope#

Internal function used to retrieve reconciliation statistics for commit scopes. For standard monitoring and troubleshooting, use the bdr.stat_reconcile_commit_scope view, which provides a more accessible and user-friendly representation of this data.

bdr.worker_role_id_name#

Internal helper function used when generating view bdr.worker_tasks . Do not use directly. Use the bdr.worker_tasks view instead.

bdr.lag_history#

Internal function used when generating view bdr.node_replication_rates . Do not use directly. Use the bdr.node_replication_rates view instead.

bdr.get_raft_instance_by_nodegroup#

Internal function used when generating view bdr.group_raft_details . Do not use directly. Use the bdr.group_raft_details view instead.

bdr.monitor_camo_on_all_nodes#

Internal function used when generating view bdr.group_camo_details . Do not use directly. Use the bdr.group_camo_details view instead.

bdr.monitor_raft_details_on_all_nodes#

Internal function used when generating view bdr.group_raft_details . Do not use directly. Use the bdr.group_raft_details view instead.

bdr.monitor_replslots_details_on_all_nodes#

Internal function used when generating view bdr.group_replslots_details . Do not use directly. Use the bdr.group_replslots_details view instead.

bdr.monitor_subscription_details_on_all_nodes#

Internal function used when generating view bdr.group_subscription_summary . Do not use directly. Use the bdr.group_subscription_summary view instead.

bdr.monitor_version_details_on_all_nodes#

Internal function used when generating view bdr.group_versions_details . Do not use directly. Use the bdr.group_versions_details view instead.

bdr.node_group_member_info#

Internal function used when generating view bdr.group_raft_details . Do not use directly. Use the bdr.group_raft_details view instead.

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