XIDs and Snapshots
|
Name |
Description |
|---|---|
|
xmin |
Earliest XID (txid) that is still active. All earlier transactions will either be committed and visible, or rolled back. |
|
xmax |
First as-yet-unassigned txid. All txids greater than or equal to this are not yet started as of the time of the snapshot, so they are invisible. |
|
xip_list |
Active txids at the time of the snapshot. The list includes only those active txids between xmin and xmax; there might be active txids higher than xmax. A txid that is greater than or equal to xmin and less than xmax and that is not in this list was already completed at the time of the snapshot, and is either visible or rolled back according to its commit status. The list does not include txids of subtransactions. |
The textual representation of txid_snapshot is xmin:xmax:xip_list.
For example, 10:20:10,14,15 means xmin=10, xmax=20, xip_list=10, 14, 15.
The following functions provide server transaction information in an exportable form. These functions are mainly used to determine which transactions were committed between two snapshots.
pgxc_is_committed(transaction_id)
Description: Specifies whether the given XID (gxid) of an ordinary table is committed or ignored. NULL indicates an unknown state (such as running, preparing, or freezing). In maintenance mode (when the GUC parameter xc_maintenance_mode is set to on), the statuses of all transactions with the specified bucket IDs and ordinary tables are traversed. If a status conflict occurs, for example, the status of the same transaction is committed in bucket 1 and rolled back in bucket 2, an error is reported. Exercise caution when enabling the mode. It is used by maintenance engineers for troubleshooting. Common users should not use the mode.
Return type: Boolean
pgxc_is_committed(transaction_id, bucketid)
Description: Commits or ignores the given transaction (gxid) if bucketid is specified. NULL indicates that the status is unknown (running, ready, or frozen). bucketid is the physical bucket ID of the hash bucket table. The value is –1 for an ordinary table. In maintenance mode (when the GUC parameter xc_maintenance_mode is set to on), if bucketid is set to –1, the statuses of all transactions with the specified bucket IDs and ordinary tables are traversed. If a status conflict occurs, for example, the status of the same transaction is committed in bucket 1 and rolled back in bucket 2, an error is reported. Exercise caution when enabling the mode. It is used by maintenance engineers for troubleshooting. Common users should not use the mode.
Return type: Boolean
txid_current()
Description: Obtains the current XID.
Return type: bigint
gs_txid_oldestxmin()
Description: Obtains the minimum XID (specified by oldesxmin).
Return type: bigint
txid_current_snapshot()
Description: Obtains the current snapshot.
Return type: txid_snapshot
txid_snapshot_xip(txid_snapshot)
Description: Obtains in-progress XIDs in a snapshot.
Return type: setof bigint
txid_snapshot_xmax(txid_snapshot)
Description: Obtains xmax of snapshots.
Return type: bigint
txid_snapshot_xmin(txid_snapshot)
Description: Obtains xmin of snapshots.
Return type: bigint
txid_visible_in_snapshot(bigint, txid_snapshot)
Description: Specifies whether the XID is visible in a snapshot (do not use subtransaction IDs).
Return type: Boolean
get_local_prepared_xact()
Description: Obtains the two-phase residual transaction information of the current node, including the XID, GID of the two-phase transaction, prepared time, owner OID, database OID, and node name of the current node.
Return type: xid, text, timestamptz, oid, text
get_remote_prepared_xacts()
Description: Obtains the two-phase residual transaction information of all remote nodes, including the XID, GID of the two-phase transaction, prepared time, owner name, database name, and node name.
Return type: xid, text, timestamptz, name, text
global_clean_prepared_xacts(text, text)
Description: Concurrently cleans two-phase residual transactions. Only the gs_clean tool can call this function for cleaning. In other situations, false is returned.
Return type: Boolean
pgxc_stat_get_wal_senders()
Description: Returns the sent logs of all primary DNs and the received logs of their corresponding standby DNs in the cluster. Only users with the system admin or monitor admin permission can use this function.
|
Column |
Description |
|---|---|
|
nodename |
Instance name. |
|
sender_pid |
PID of the thread for sending logs. |
|
local_role |
Instance role. |
|
peer_role |
Role of the instance on the receiver. |
|
peer_state |
Status of the instance on the receiver. |
|
state |
Synchronization status between instances. |
|
sender_sent_location |
Location where the sender sends logs. |
|
sender_write_location |
Location where the sender writes logs. |
|
sender_flush_location |
Location where the sender flushes logs to disks. |
|
sender_replay_location |
Log location of the current instance. If the DN is a primary DN, the location is the value of sender_flush_location. Otherwise, the location where the current instance log is replayed is used. |
|
receiver_received_location |
Location where the receiver receives logs. |
|
receiver_write_location |
Location where the receiver writes logs. |
|
receiver_flush_location |
Location where the receiver flushes logs to disks. |
|
receiver_replay_location |
Location where the receiver replays logs. |
pgxc_stat_get_wal_senders_status()
Description: Returns the receiving status of transaction logs on all nodes. Only users with the system admin or monitor admin permission can use this function.
Table 3 pgxc_stat_get_wal_senders_status output parameters describes the return values.
|
Column |
Description |
|---|---|
|
nodename |
Name of the primary node |
|
source_ip |
IP address of the primary node |
|
source_port |
Port of the primary node |
|
dest_ip |
IP address of the standby node |
|
dest_port |
Port of the standby node |
|
sender_pid |
PID of the sending thread |
|
local_role |
Type of the primary node |
|
peer_role |
Type of the standby node |
|
peer_state |
Status of the standby node |
|
state |
WAL sender status |
|
sender_sent_location |
Sending position of the primary node |
|
sender_write_location |
Writing position of the primary node |
|
sender_replay_location |
Redo position of the primary node |
|
receiver_received_location |
Receiving position of the standby node |
|
receiver_write_location |
Writing position of the standby node |
|
receiver_flush_location |
Flushing location of the standby node |
|
receiver_replay_location |
Redo location of the standby node |
gs_get_next_xid_csn()
Description: Returns the values of next_xid and next_csn on all nodes globally.
Table 4 gs_get_next_xid_csn return parameters describes the return values.
pg_control_system()
Description: Returns the status of the system control file.
Return type: SETOF record
pg_control_checkpoint()
Description: Returns the system checkpoint status
Return type: SETOF record
get_prepared_pending_xid()
Description: Returns nextxid when restoration is complete.
Parameter: nan
Return type: text
pg_clean_region_info()
Description: Clears the region map.
Parameter: nan
Return type: character varying
pg_get_replication_slot_name()
Description: Obtains the slot name.
Parameter: nan
Return type: text
pg_get_running_xacts()
Description: Obtains running xact.
Parameter: nan
Return type: handle integer, gxid xid, state tinyint, node text, xmin xid, vacuum Boolean, timeline bigint, prepare_xid xid, pid bigint, next_xid xid, dbid oid
pg_get_variable_info()
Description: Obtains the shared memory variable cache.
Parameter: nan
Return type: node_name text, nextOid oid, nextXid xid, oldestXid xid, xidVacLimit xid, oldestXidDB oid, lastExtendCSNLogpage xid, startExtendCSNLogpage xid, nextCommitSeqNo xid, latestCompletedXid xid, and startupMaxXid xid
pg_get_xidlimit()
Description: Obtains XID information from the shared memory.
Parameter: nan
Return type: nextXid xid, oldestXid xid, xidVacLimit xid, xidWarnLimit xid, xidStopLimit xid, xidWrapLimit xid, oldestXidDB oid
pg_relation_compression_ratio()
Description: Queries the compression rate of a table. By default, 1.0 is returned.
Parameter: text
Return type: real
pg_relation_with_compression()
Description: Specifies whether a table is compressed.
Parameter: text
Return type: Boolean
pg_stat_file_recursive()
Description: Lists all files in a path.
Parameter: location text
Return type: path text, filename text, size bigint, isdir Boolean
pg_stat_get_activity_for_temptable()
Description: Returns records of backend threads related to the temporary table.
Parameter: nan
Return type: datid oid, timelineid integer, tempid integer, and sessionid bigint
pg_stat_get_activity_ng()
Description: Returns records of backend threads related to nodegroup.
Parameter: pid bigint
Return type: datid oid, pid bigint, sessionid bigint, and node_group text
pg_stat_get_cgroup_info()
Description: Returns Cgroup information.
Parameter: nan
Return type: cgroup_name text, percent integer, usage_percent integer, shares bigint, usage bigint, cpuset text, relpath text, valid text, node_group text
pg_stat_get_realtime_info_internal()
Description: Returns real-time information. Currently, this API is unavailable. FailedToGetSessionInfo is returned.
Parameter: oid, oid, bigint, cstring, oid
Return type: text
pg_stat_get_wlm_session_iostat_info()
Description: Returns the session load I/O information.
Parameter: nan
Return type: threadid bigint, maxcurr_iops integer, mincurr_iops integer, maxpeak_iops integer, minpeak_iops integer, iops_limits integer, io_priority integer, and curr_io_limits integer
pg_test_err_contain_err()
Description: Tests the error type and return information.
Parameter: integer
Return type: void
pv_session_memory_detail_tp()
Description: Returns the memory usage of the session. For details, see pv_session_memory_detail.
Parameter: nan
Return type: sessid text, sesstype text, contextname text, level smallint, parent text, totalsize bigint, freesize bigint, usedsize bigint
gs_get_table_distribution()
Description: Returns the distribution of table data on each DN.
Parameter: table_name text, schema_name text
Return type: text
pv_builtin_functions()
Description: Displays information about all built-in system functions.
Parameter: nan
Return type: proname name, pronamespace oid, proowner oid, prolang oid, procost real, prorows real, provariadic oid, protransform regproc, proisagg Boolean, proiswindow Boolean, prosecdef Boolean, proleakproof Boolean, proisstrict Boolean, proretset Boolean, provolatile "char", pronargs smallint, pronargdefaults smallint, prorettype oid, proargtypes oidvector, proallargtypes integer[], proargmodes "char"[], proargnames text[], proargdefaults pg_node_tree, prosrc text, probin text, proconfig text[], proacl aclitem[], prodefaultargpos int2vector, fencedmode Boolean, proshippable Boolean, propackage Boolean, oid oid
pv_thread_memory_detail()
Description: Returns the memory information of each thread.
Parameter: nan
Return type: threadid text, tid bigint, thrdtype text, contextname text, level smallint, parent text, totalsize bigint, freesize bigint, usedsize bigint
pg_shared_memory_detail()
Description: Returns usage information about all generated shared memory contexts. For details about each column, see SHARED_MEMORY_DETAIL.
Parameter: nan
Return type: contextname text, level smallint, parent text, totalsize bigint, freesize bigint, usedsize bigint
pgxc_get_running_xacts()
Description: Returns information about running transactions on each node in the cluster. The field content is the same as that in PGXC_RUNNING_XACTS. Only users with the system admin or monitor admin permission can view the information.
Parameter: nan
Return type: setof record
pgxc_snapshot_status()
Description: Returns the status of key memory information in the GTM in GTM mode for fault locating. GTM-Free and GTM-Lite do not support this function.
Parameter: nan
Return type: xmin xid, xmax xid, xcnt int, oldestxmin xid, next_xid xid, timeline int, active_thread_num int, max_active_thread_num int, snapshot_num int, snapshot_totalsize bigint
Table 5 get_gtm_lite_status return parameters describes the return values.
|
Column |
Description |
|---|---|
|
xmin |
Minimum active XID in the GTM. |
|
xmax |
Largest XID committed in the GTM plus 1. Transactions whose IDs are greater than or equal to this value are active. |
|
xcnt |
Number of active transactions in the GTM. |
|
oldestxmin |
ID of the earliest accessed transaction in the GTM. |
|
next_xid |
ID of the next transaction allocated by the GTM. |
|
timeline |
Current time line in the GTM. |
|
active_thread_num |
Number of active worker threads in the GTM. |
|
max_active_thread_num |
Peak number of worker threads in the GTM within one minute. |
|
snapshot_num |
Number of snapshots delivered by the GTM within one minute. |
|
snapshot_totalsize |
Total size of snapshots delivered by the GTM within one minute. |
get_gtm_lite_status()
Description: Returns the backup XID and CSN in the GTM for fault locating. This system function is not supported in GTM-Free mode.
adm_hist_snapshot_func()
Description: Returns information about the snapshot execution time. To access this function, set the enable_wdr_snapshot parameter to on and obtain the permission to access the snapshot schema, snapshot table, and tables_snap_timestamp tables.
Parameter: nan
Return type: snap_id bigint, dbid oid, begin_interval_time timestamp(3), end_interval_time timestamp(3), flush_elapsed interval day(5) to second(1), begin_interval_time_tz timestamp(3) with time zone, end_interval_time_tz timestamp(3) with time zone
global_sql_patch_func()
Description: SQL patch information on each global node, which is used to return the result of the global_sql_patch view.
Table 7 global_sql_patch_func return parameters describes the return values.
|
Name |
Type |
Description |
|---|---|---|
|
node_name |
text |
Name of the node where the SQL patch is located. |
|
patch_name |
name |
Patch name. |
|
unique_sql_id |
bigint |
Global unique query ID. |
|
owner |
oid |
ID of the user who creates the patch. |
|
enable |
boolean |
Determines whether the patch takes effect. |
|
status |
"char" |
Patch status (reserved field). |
|
abort |
boolean |
Determines whether the value is AbortHint. |
|
hint_string |
text |
Hint text. |
|
description |
text |
Patch description. |
|
parent_unique_sql_id |
bigint |
Globally unique ID of the outer statement of the SQL statement for which the patch takes effect. The value of this parameter is 0 for statements outside a stored procedure. For statements inside the stored procedure, the value of this parameter is the globally unique ID of the statement that calls the stored procedure. |
gs_get_current_version()
Description: Returns the current compilation mode based on the current compilation macro. 'M' is returned.
Parameter: nan
Return type: char
gs_get_kernel_info()
Description: Global transaction information on each primary CN and DN.
Table 8 gs_get_kernel_info output parameters describes the return values.
|
Name |
Type |
Description |
|---|---|---|
|
node_name |
text |
Node name. |
|
module |
text |
Module name, including:
|
|
name |
text |
Name of the key data in the memory state, including:
|
|
value |
text |
Value of the key data in the memory state. |
Example:
gaussdb=#SELECT * FROM gs_get_kernel_info();
node_name | module | name | value
--------------+---------+-------------------------------+---------
coordinator1 | XACT | startup_max_xid | 16488
coordinator1 | XACT | recent_local_xmin | 16504
coordinator1 | XACT | recent_global_xmin | 16503
coordinator1 | STANDBY | standby_xmin | 0
coordinator1 | STANDBY | standby_redo_cleanup_xmin | 0
coordinator1 | STANDBY | standby_redo_cleanup_xmin_lsn | 0/0
coordinator1 | XACT | local_csn_min | 6014225
coordinator1 | XACT | replication_slot_xmin | 0
coordinator1 | XACT | replication_slot_catalog_xmin | 0
coordinator1 | UNDO | global_recycle_xid | 16501
coordinator1 | XACT | global_frozen_xid | 0
coordinator1 | XACT | recent_xmin | 16504
coordinator1 | XACT | next_csn | 6014226
coordinator1 | HOTPATH | hotpatch_additional_info |
coordinator1 | FULL_SQL| stmt_session_discard_records | 0
coordinator1 | FULL_SQL| stmt_shm_flush_discard_records| 0
coordinator1 | XACT | idle_in_trans_timeout_records | 0
datanode1 | XACT | startup_max_xid | 16488
datanode1 | XACT | recent_local_xmin | 15805
datanode1 | XACT | recent_global_xmin | 15805
datanode1 | STANDBY | standby_xmin | 0
datanode1 | STANDBY | standby_redo_cleanup_xmin | 0
datanode1 | STANDBY | standby_redo_cleanup_xmin_lsn | 0/0
datanode1 | XACT | local_csn_min | 6014225
datanode1 | XACT | replication_slot_xmin | 0
datanode1 | XACT | replication_slot_catalog_xmin | 0
datanode1 | UNDO | global_recycle_xid | 15805
datanode1 | XACT | global_frozen_xid | 0
datanode1 | XACT | recent_xmin | 15805
datanode1 | XACT | next_csn | 6014226
datanode1 | HOTPATH | hotpatch_additional_info |
datanode1 | FULL_SQL| stmt_session_discard_records | 0
datanode1 | FULL_SQL| stmt_shm_flush_discard_records| 0
datanode1 | XACT | idle_in_trans_timeout_records | 0
(34 row)
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