PGXC_THREAD_WAIT_STATUS

PGXC_THREAD_WAIT_STATUS displays all the call layer hierarchy relationship between threads of the SQL statements on all the nodes in a cluster, and the waiting status of the block for each thread, so that you can easily locate the causes of process response failures and similar phenomena.

The definitions of PGXC_THREAD_WAIT_STATUS view and PG_THREAD_WAIT_STATUS view are the same, because the essence of the PGXC_THREAD_WAIT_STATUS view is the query summary result of the PG_THREAD_WAIT_STATUS view on each node in the cluster.

**Table 1** PGXC_THREAD_WAIT_STATUS columns
Name	Type	Description
node_name	text	Current node name
db_name	text	Database name
thread_name	text	Thread name
query_id	bigint	Query ID. It is equivalent to debug_query_id.
tid	bigint	Thread ID of the current thread
lwtid	integer	Lightweight thread ID of the current thread
ptid	integer	Parent thread of the streaming thread
tlevel	integer	Level of the streaming thread
smpid	integer	Concurrent thread ID
wait_status	text	Waiting status of the current thread. For details about the waiting status, see Table 2.
wait_event	text	If wait_status is acquire lock, acquire lwlock, or wait io, this column describes the lock, lightweight lock, and I/O information, respectively. If wait_status is not any of the three values, this column is empty.

Example:

Assume you run a statement on coordinator1, and no response is returned after a long period of time. In this case, establish another connection to coordinator1 to check the thread status on it.

 select * from pg_thread_wait_status where query_id > 0;
  node_name   | db_name  | thread_name  | query_id |       tid       | lwtid | ptid  | tlevel | smpid |     wait_status   |   wait_event   
--------------+----------+--------------+----------+-----------------+-------+-------+--------+-------+----------------------
 coordinator1 | gaussdb | gsql         | 20971544 | 140274089064208 | 22579 |       |      0 |     0 | wait node: datanode4 |
(1 rows)

Furthermore, you can view the statement working status on each node in the entire cluster. In the following example, no DNs have threads blocked, and there is a huge amount of data to be read, causing slow execution.

select * from pgxc_thread_wait_status where query_id=20971544;
  node_name   | db_name  | thread_name  | query_id |       tid       | lwtid | ptid  | tlevel | smpid |     wait_status   |  wait_event   
--------------+----------+--------------+----------+-----------------+-------+-------+--------+-------+----------------------
 datanode1    | gaussdb | coordinator1 | 20971544 | 139902867994384 | 22735 |       |      0 |     0 | wait node: datanode3 |
 datanode1    | gaussdb | coordinator1 | 20971544 | 139902838634256 | 22970 | 22735 |      5 |     0 | synchronize quit     |
 datanode1    | gaussdb | coordinator1 | 20971544 | 139902607947536 | 22972 | 22735 |      5 |     1 | synchronize quit     |
 datanode2    | gaussdb | coordinator1 | 20971544 | 140632156796688 | 22736 |       |      0 |     0 | wait node: datanode3 |
 datanode2    | gaussdb | coordinator1 | 20971544 | 140632030967568 | 22974 | 22736 |      5 |     0 | synchronize quit     |
 datanode2    | gaussdb | coordinator1 | 20971544 | 140632081299216 | 22975 | 22736 |      5 |     1 | synchronize quit     |
 datanode3    | gaussdb | coordinator1 | 20971544 | 140323627988752 | 22737 |       |      0 |     0 | wait node: datanode3 |
 datanode3    | gaussdb | coordinator1 | 20971544 | 140323523131152 | 22976 | 22737 |      5 |     0 | net flush data       |
 datanode3    | gaussdb | coordinator1 | 20971544 | 140323548296976 | 22978 | 22737 |      5 |     1 | net flush data
 datanode4    | gaussdb | coordinator1 | 20971544 | 140103024375568 | 22738 |       |      0 |     0 | wait node: datanode3
 datanode4    | gaussdb | coordinator1 | 20971544 | 140102919517968 | 22979 | 22738 |      5 |     0 | synchronize quit     |
 datanode4    | gaussdb | coordinator1 | 20971544 | 140102969849616 | 22980 | 22738 |      5 |     1 | synchronize quit     |
 coordinator1 | gaussdb | gsql         | 20971544 | 140274089064208 | 22579 |       |      0 |     0 | wait node: datanode4  |
(13 rows)