Updated on 2023-10-23 GMT+08:00

PG_THREAD_WAIT_STATUS

PG_THREAD_WAIT_STATUS allows you to test the block waiting status about the backend thread and auxiliary thread of the current instance.

Table 1 PG_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. The value of this column is the same as that of debug_query_id.

tid

bigint

Current thread ID

sessionid

bigint

Current session ID

lwtid

integer

Lightweight thread ID

psessionid

bigint

Parent session ID

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 set to 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.

locktag

text

Information about the lock that the current thread is waiting for

lockmode

text

Lock mode that the current thread is waiting to obtain. The values include modes in the table-level lock, row-level lock, and page-level lock.

block_sessionid

bigint

ID of the session that blocks the current thread from obtaining the lock

global_sessionid

text

Global session ID

The waiting statuses in the wait_status column are as follows:

Table 2 Waiting status list

Value

Description

none

Waiting for no event

acquire lock

Waiting for locking until the locking succeeds or times out

acquire lwlock

Waiting for a lightweight lock

wait io

Waiting for I/O completion

wait cmd

Waiting for reading network communication packets to complete

wait pooler get conn

Waiting for the pooler to obtain the connection

wait pooler abort conn

Waiting for the pooler to terminate the connection

wait pooler clean conn

Waiting for the pooler to clear connections

pooler create conn: [nodename], total N

Waiting for the pooler to set up a connection. The connection is being established with the node specified by nodename, and there are N connections waiting to be set up.

get conn

Obtaining the connection to other nodes

set cmd: [nodename]

Waiting for running the SET, RESET, TRANSACTION BLOCK LEVEL PARA SET, or SESSION LEVEL PARA SET statement on the connection. The statement is being executed on the node specified by nodename.

cancel query

Canceling the SQL statement that is being executed through the connection

stop query

Stopping the query that is being executed through the connection

wait node: [nodename](plevel), total N, [phase]

Waiting for receiving data from a connected node. The thread is waiting for data from the plevel thread of the node specified by nodename. The data of N connections is waiting to be returned. If phase is included, the possible phases are as follows:
  • begin: The transaction is being started.
  • commit: The transaction is being committed.
  • rollback: The transaction is being rolled back.

wait transaction sync: xid

Waiting for synchronizing the transaction specified by xid

wait wal sync

Waiting for the completion of WAL of synchronization from the specified LSN to the standby instance

wait data sync

Waiting for the completion of data page synchronization to the standby instance

wait data sync queue

Waiting for putting the data pages that are in the row-store or the CU in the column-store into the synchronization queue

flush data: [nodename](plevel), [phase]

Waiting for sending data to the plevel thread of the node specified by nodename. If phase is included, the possible phase is wait quota, indicating that the current communication flow is waiting for the quota value.

stream get conn: [nodename], total N

Waiting for connecting to the consumer object of the node specified by nodename when the stream flow is initialized. There are N consumers waiting to be connected.

wait producer ready: [nodename](plevel), total N

Waiting for each producer to be ready when the stream flow is initialized. The thread is waiting for the procedure of the plevel thread on the nodename node to be ready. There are N producers waiting to be ready.

synchronize quit

Waiting for the threads in the stream thread group to quit when the stream plan ends

wait stream nodegroup destroy

Waiting for destroying the stream node group when the stream plan ends

wait active statement

Waiting for job execution under resource and load control

analyze: [relname], [phase]

The thread is doing ANALYZE to the relname table. If phase is included, the possible phase is autovacuum, indicating that the database automatically enables the AutoVacuum thread to execute ANALYZE.

vacuum: [relname], [phase]

The thread is doing VACUUM to the relname table. If phase is included, the possible phase is autovacuum, indicating that the database automatically enables the AutoVacuum thread to execute VACUUM.

vacuum full: [relname]

The thread is doing VACUUM FULL to the relname table.

create index

An index is being created.

HashJoin - [ build hash | write file ]

The HashJoin operator is being executed. In this phase, you need to pay attention to the execution time-consuming.
  • build hash: The HashJoin operator is creating a hash table.
  • write file: The HashJoin operator is writing data to disks.

HashAgg - [ build hash | write file ]

The HashAgg operator is being executed. In this phase, you need to pay attention to the execution time-consuming.
  • build hash: The HashAgg operator is creating a hash table.
  • write file: The HashAgg operator is writing data to disks.

HashSetop - [build hash | write file ]

The HashSetop operator is being executed. In this phase, you need to pay attention to the execution time-consuming.
  • build hash: The HashSetop operator is creating a hash table.
  • write file: The HashSetop operator is writing data to disks.

Sort | Sort - [fetch tuple | write file]

The Sort operator is used for sorting. fetch tuple indicates that the Sort operator is obtaining tuples, and write file indicates that the Sort operator is writing data to disks.

Material | Material - write file

The Material operator is being executed. write file indicates that the Material operator is writing data to disks.

NestLoop

The NestLoop operator is being executed.

wait memory

Waiting for obtaining the memory

wait sync consumer next step

Waiting for the consumer to execute the stream operator

wait sync producer next step

Waiting for the producer to execute the stream operator

standby read recovery conflict

The read-only mode of the standby node conflicts with the log replay mode.

standby get snapshot

The standby node obtains the snapshot in read-only mode.

wait reserve td

Waiting for the td application

vacuum gpi

Clearing the global partition index in the vacuum or autovacuum process.

If wait_status is acquire lwlock, acquire lock, or wait io, there is an event performing I/O operations or waiting for obtaining the corresponding lightweight lock or transaction lock.

The following table describes the corresponding wait events when wait_status is acquire lwlock. If wait_event is extension, the lightweight lock is dynamically allocated and is not monitored.

Table 3 List of wait events corresponding to lightweight locks

wait_event

Description

ShmemIndexLock

Used to protect the primary index table, a hash table, in shared memory.

OidGenLock

Used to prevent different threads from generating the same OID.

XidGenLock

Used to prevent two transactions from obtaining the same transaction ID.

ProcArrayLock

Used to prevent concurrent access to or concurrent modification on ProcArray shared arrays.

SInvalReadLock

Used to prevent concurrent execution with invalid message deletion.

SInvalWriteLock

Used to prevent concurrent execution with invalid message write and deletion.

WALInsertLock

Used to prevent concurrent execution with WAL insertion.

WALWriteLock

Used to prevent concurrent write from a WAL buffer to a disk.

ControlFileLock

Used to prevent concurrent read/write or concurrent write/write on the pg_control file.

CheckpointLock

Used to prevent multi-checkpoint concurrent execution.

CLogControlLock

Used to prevent concurrent access to or concurrent modification on the Clog control data structure.

SubtransControlLock

Used to prevent concurrent access to or concurrent modification on the subtransaction control data structure.

MultiXactGenLock

Used to allocate a unique MultiXact ID in serial mode.

MultiXactOffsetControlLock

Used to prevent concurrent read/write or concurrent write/write on pg_multixact/offset.

MultiXactMemberControlLock

Used to prevent concurrent read/write or concurrent write/write on pg_multixact/members.

RelCacheInitLock

Used to add a lock before any operations are performed on the init file when messages are invalid.

CheckpointerCommLock

Used to send file flush requests to a checkpointer. The request structure needs to be inserted to a request queue in serial mode.

TwoPhaseStateLock

Used to prevent concurrent access to or modification on two-phase information sharing arrays.

TablespaceCreateLock

Used to check whether a tablespace already exists.

BtreeVacuumLock

Used to prevent VACUUM from clearing pages that are being used by B-tree indexes.

AutovacuumLock

Used to access the autovacuum worker array in serial mode.

AutovacuumScheduleLock

Used to distribute tables requiring VACUUM in serial mode.

AutoanalyzeLock

Used to obtain and release resources related to a task that allows for autoanalyze execution.

SyncScanLock

Used to determine the start position of a relfilenode during heap scanning.

NodeTableLock

Used to protect a shared structure that stores database node information.

PoolerLock

Used to prevent two threads from simultaneously obtaining the same connection from a connection pool.

RelationMappingLock

Used to wait for the mapping file between system catalogs and storage locations to be updated.

AsyncCtlLock

Used to prevent concurrent access to or concurrent modification on the sharing notification status.

AsyncQueueLock

Used to prevent concurrent access to or concurrent modification on the sharing notification queue.

SerializableXactHashLock

Used to prevent concurrent read/write or concurrent write/write on a sharing structure for serializable transactions.

SerializableFinishedListLock

Used to prevent concurrent read/write or concurrent write/write on a shared linked list for completed serial transactions.

SerializablePredicateLockListLock

Used to protect a linked list of serializable transactions that have locks.

OldSerXidLock

Used to protect a structure that records serializable transactions that have conflicts.

FileStatLock

Used to protect a data structure that stores statistics file information.

SyncRepLock

Used to protect Xlog synchronization information during primary/standby replication.

DataSyncRepLock

Used to protect data page synchronization information during primary/standby replication.

CStoreColspaceCacheLock

Used to add a lock when CU space is allocated for a column-store table.

CStoreCUCacheSweepLock

Used to add a lock when CU caches used by a column-store table are cyclically washed out.

MetaCacheSweepLock

Used to add a lock when metadata is cyclically washed out.

ExtensionConnectorLibLock

Adds a lock when a specific dynamic library is loaded or uninstalled in ODBC connection initialization scenarios.

SearchServerLibLock

Used to add a lock on the file read operation when a specific dynamic library is initially loaded in GPU-accelerated scenarios.

LsnXlogChkFileLock

Used to serially update the Xlog flush points for primary and standby servers recorded in a specific structure.

ReplicationSlotAllocationLock

Used to add a lock when a primary server allocates stream replication slots during primary/standby replication.

ReplicationSlotControlLock

Used to prevent concurrent update of stream replication slot status during primary/standby replication.

ResourcePoolHashLock

Used to prevent concurrent access to or concurrent modification on a resource pool table, a hash table.

WorkloadStatHashLock

Used to prevent concurrent access to or concurrent modification on a hash table that contains SQL requests from the primary node of the database.

WorkloadIoStatHashLock

Used to prevent concurrent access to or concurrent modification on a hash table that contains I/O information of the current database node.

WorkloadCGroupHashLock

Used to prevent concurrent access to or concurrent modification on a hash table that contains Cgroup information.

OBSGetPathLock

Used to prevent concurrent read/write or concurrent write/write on an OBS path.

WorkloadUserInfoLock

Used to prevent concurrent access to or concurrent modification on a hash table that contains user information about load management. (The current feature is a lab feature. Contact Huawei technical support before using it.)

WorkloadRecordLock

Used to prevent concurrent access to or concurrent modification on a hash table that contains requests received by the primary node of the database during adaptive memory management.

WorkloadIOUtilLock

Used to protect a structure that records iostat and CPU load information.

WorkloadNodeGroupLock

Used to prevent concurrent access to or concurrent modification on a hash table that contains node group information in memory.

JobShmemLock

Used to protect global variables in the shared memory that is periodically read during a scheduled task.

OBSRuntimeLock

Used to obtain environment variables, for example, GASSHOME.

LLVMDumpIRLock

Used to export the assembly language for dynamically generating functions. The current feature is a lab feature. Contact Huawei technical support before using it.

LLVMParseIRLock

Used to compile and parse a finished IR function from the IR file at the start position of a query. The current feature is a lab feature. Contact Huawei technical support before using it.

CriticalCacheBuildLock

Used to load caches from a shared or local cache initialization file.

WaitCountHashLock

Used to protect a shared structure in user statement counting scenarios.

BufMappingLock

Used to protect operations on a shared-buffer mapping table.

LockMgrLock

Used to protect the information about a common lock structure.

PredicateLockMgrLock

Used to protect the information about a lock structure that has serializable transactions.

OperatorRealTLock

Used to prevent concurrent access to or concurrent modification on a global structure that contains real-time data at the operator level.

OperatorHistLock

Used to prevent concurrent access to or concurrent modification on a global structure that contains historical data at the operator level.

SessionRealTLock

Used to prevent concurrent access to or concurrent modification on a global structure that contains real-time data at the query level.

SessionHistLock

Used to prevent concurrent access to or concurrent modification on a global structure that contains historical data at the query level.

CacheSlotMappingLock

Used to protect global CU cache information.

BarrierLock

Used to ensure that only one thread is creating a barrier at a time.

dummyServerInfoCacheLock

Used to protect a global hash table where the information about database connections is cached.

RPNumberLock

Used by a database node on a computing GaussDB to count the number of threads for a task where plans are being executed.

CBMParseXlogLock

Used to protect the lock used when CBM parses Xlogs.

RelfilenodeReuseLock

Used to prevent the link to a reused column attribute file from being canceled by mistake.

RcvWriteLock

Used to prevent concurrent call of WalDataRcvWrite.

PercentileLock

Used to protect global percentile buffers.

CSNBufMappingLock

Used to protect CSN pages.

UniqueSQLMappingLock

Used to protect a unique SQL hash table.

DelayDDLLock

Used to prevent concurrent DDL operations.

CLOG Ctl

Used to prevent concurrent access to or concurrent modification on the Clog control data structure.

Async Ctl

Used to protect asynchronization buffers.

MultiXactOffset Ctl

Used to protect SLRU buffers of a MultiXact offset.

MultiXactMember Ctl

Used to protect SLRU buffer of a MultiXact member.

OldSerXid SLRU Ctl

Used to protect SLRU buffers of old transaction IDs.

ReplicationSlotLock

Used to protect a replication slot.

PGPROCLock

Used to protect the PGPROC structure.

MetaCacheLock

Used to protect meta caches.

DataCacheLock

Used to protect data caches.

InstrUserLock

Used to protect a user hash table.

BadBlockStatHashLock

Used to protect the hash table global_bad_block_stat

BufFreelistLock

Used to ensure the atomicity of free list operations in the shared buffer.

CUSlotListLock

Used to control concurrent operations on the slot of the column-store buffer.

AddinShmemInitLock

Used to protect the initialization of the shared memory object.

AlterPortLock

Used to protect the coordinator node from changing the registration port number.

FdwPartitionCaheLock

Management lock of the buffer of the HDFS partitioned table.

DfsConnectorCacheLock

Management lock of the DFSConnector buffer.

DfsSpaceCacheLock

Management lock of the HDFS tablespace management buffer.

FullBuildXlogCopyStartPtrLock

Used to protect Xlog copy operations in the full build.

DfsUserLoginLock

Used for HDFS user login and authentication.

LogicalReplicationSlotPersistentDataLock

Used to protect data in the replication slot during logical replication.

WorkloadSessionInfoLock

Used to protect the access to the session info memory hash table of the load management module. (The current feature is a lab feature. Contact Huawei technical support before using it.)

InstrWorkloadLock

Used to protect the access to the memory hash table that stores load management statistics. (The current feature is a lab feature. Contact Huawei technical support before using it.)

PgfdwLock

Used by the management instance to establish a connection to the foreign server.

InstanceTimeLock

Used to obtain time information of sessions in an instance.

XlogRemoveSegLock

Used to protect Xlog segment file recycling.

DnUsedSpaceHashLock

Used to update space usage information corresponding to a session.

CsnMinLock

Used to calculate CSNmin.

GPCCommitLock

Used to protect the addition of the global Plan Cache hash table. The current feature is a lab feature. Contact Huawei technical support before using it.

GPCClearLock

Used to protect the clearing of the global plan cache hash table. The current feature is a lab feature. Contact Huawei technical support before using it.

GPCTimelineLock

Used to protect the timeline check of the global plan cache hash table. The current feature is a lab feature. Contact Huawei technical support before using it.

TsTagsCacheLock

Used to manage the time series tag cache.

InstanceRealTLock

Used to protect the update of the hash table that stores shared instance statistics.

CLogBufMappingLock

Used to manage the cache of commit logs.

GPCMappingLock

Used to manage the global plan cache. The current feature is a lab feature. Contact Huawei technical support before using it.

GPCPrepareMappingLock

Used to manage the global plan cache. The current feature is a lab feature. Contact Huawei technical support before using it.

BufferIOLock

Used to protect I/O operations on pages in the shared buffer.

BufferContentLock

Used to protect the read and modification of the page content in the shared buffer.

CSNLOG Ctl

Used for CSN log management.

DoubleWriteLock

Used to manage doublewrite operations.

RowPageReplicationLock

Used to manage data page replication of row-store.

MatviewSeqnoLock

Used to manage the cache of materialized views.

GPRCMappingLock

Used to manage the access and modification operations of the global cache hash table of autonomous transactions.

extension

Other lightweight locks

StartBlockMappingLock

Used by globalstat to obtain information such as startblockarray from pgstat.

PldebugLock

Used to debug stored procedures and perform concurrent maintenance operations.

wait active statement

Waiting for job execution under resource and load control

wait memory

Waiting for obtaining the memory

IOStatLock

Used to concurrently maintain the hash table of resource management I/O statistics.

gtt_shared_ctl

Used to protect global temporary tables to share the concurrent read and write of hash tables.

The following table describes the corresponding wait events when wait_status is wait io.

Table 4 List of wait events corresponding to I/Os

wait_event

Description

BufFileRead

Reads data from a temporary file to a specified buffer.

BufFileWrite

Writes the content of a specified buffer to a temporary file.

ControlFileRead

Reads the pg_control file, mainly during database startup, checkpoint execution, and primary/standby verification.

ControlFileSync

Flushes the pg_control file to a disk, during database initialization.

ControlFileSyncUpdate

Flushes the pg_control file to a disk, mainly during database startup, checkpoint execution, and primary/standby verification.

ControlFileWrite

Writes the pg_control file, during database initialization.

ControlFileWriteUpdate

Updates the pg_control file, mainly during database startup, checkpoint execution, and primary/standby verification.

CopyFileRead

Reads a file during file copying.

CopyFileWrite

Writes a file during file copying.

DataFileExtend

Writes a file during file extension.

DataFileFlush

Flushes a table data file to a disk.

DataFileImmediateSync

Flushes a table data file to a disk immediately.

DataFilePrefetch

Reads a table data file asynchronously.

DataFileRead

Reads a table data file synchronously.

DataFileSync

Flushes table data file modifications to a disk.

DataFileTruncate

Truncates a table data file.

DataFileWrite

Writes a table data file.

LockFileAddToDataDirRead

Reads the postmaster.pid file.

LockFileAddToDataDirSync

Flushes the postmaster.pid file to a disk.

LockFileAddToDataDirWrite

Writes PID information into the postmaster.pid file.

LockFileCreateRead

Reads the LockFile file %s.lock.

LockFileCreateSync

Flushes the LockFile file %s.lock to a disk.

LockFileCreateWRITE

Writes PID information into the LockFile file %s.lock.

RelationMapRead

Reads the mapping file between system catalogs and storage locations.

RelationMapSync

Flushes the mapping file between system catalogs and storage locations to a disk.

RelationMapWrite

Writes the mapping file between system catalogs and storage locations.

ReplicationSlotRead

Reads a stream replication slot file during a restart.

ReplicationSlotRestoreSync

Flushes a stream replication slot file to a disk during a restart.

ReplicationSlotSync

Flushes a temporary stream replication slot file to a disk during checkpoint execution.

ReplicationSlotWrite

Writes a temporary stream replication slot file during checkpoint execution.

SLRUFlushSync

Flushes the pg_clog, pg_subtrans, and pg_multixact files to a disk, mainly during checkpoint execution and database shutdown.

SLRURead

Reads the pg_clog, pg_subtrans, and pg_multixact files.

SLRUSync

Writes dirty pages into the pg_clog, pg_subtrans, and pg_multixact files, and flushes the files to a disk, mainly during checkpoint execution and database shutdown.

SLRUWrite

Writes the pg_clog, pg_subtrans, and pg_multixact files.

TimelineHistoryRead

Reads the timeline history file during database startup.

TimelineHistorySync

Flushes the timeline history file to a disk during database startup.

TimelineHistoryWrite

Writes to the timeline history file during database startup.

TwophaseFileRead

Reads the pg_twophase file, mainly during two-phase transaction commit and restoration.

TwophaseFileSync

Flushes the pg_twophase file to a disk, mainly during two-phase transaction commit and restoration.

TwophaseFileWrite

Writes the pg_twophase file, mainly during two-phase transaction commit and restoration.

WALBootstrapSync

Flushes an initialized WAL file to a disk during database initialization.

WALBootstrapWrite

Writes an initialized WAL file during database initialization.

WALCopyRead

Read operation generated when an existing WAL file is read for replication after archiving and restoration.

WALCopySync

Flushes a replicated WAL file to a disk after archiving and restoration.

WALCopyWrite

Write operation generated when an existing WAL file is read for replication after archiving and restoration.

WALInitSync

Flushes a newly initialized WAL file to a disk during log reclaiming or writing.

WALInitWrite

Initializes a newly created WAL file to 0 during log reclaiming or writing.

WALRead

Reads data from Xlogs during redo operations on two-phase files.

WALSyncMethodAssign

Flushes all open WAL files to a disk.

WALWrite

Writes a WAL file.

WALBufferAccess

WAL buffer access (To ensure performance, only the number of access times is counted in the kernel code, and the access duration is not counted.)

WALBufferFull

Writes WAL files when the WAL buffer is full.

DoubleWriteFileRead

Doublewrites and reads a file.

DoubleWriteFileSync

Doublewrites a file and forcibly flushes files to disks.

DoubleWriteFileWrite

Doublewrites a file and writes a file.

PredoProcessPending

Waits for the playback of other records to complete during parallel log playback.

PredoApply

Waits for other threads to play back logs to the LSN of the current thread during parallel log playback.

DisableConnectFileRead

Reads the HA lock fragment logic file.

DisableConnectFileSync

Forcibly flushes the HA lock fragment logic file to disks.

DisableConnectFileWrite

Writes the HA lock fragment logic file.

The following table describes the corresponding wait events when wait_status is acquire lock.

Table 5 List of wait events corresponding to transaction locks

wait_event

Description

relation

Adds a lock to a table.

extend

Adds a lock to a table being scaled out.

partition

Adds a lock to a partitioned table.

partition_seq

Adds a lock to a partition of a partitioned table.

page

Adds a lock to a table page.

tuple

Adds a lock to a tuple on a page.

transactionid

Adds a lock to a transaction ID.

virtualxid

Adds a lock to a virtual transaction ID.

object

Adds a lock to an object.

cstore_freespace

Adds a lock to idle column-store space.

userlock

Adds a lock to a user.

advisory

Adds an advisory lock.