PostgreSQL Instance Statistics Views Overview - PolarDB

Describes the views and functions in PolarDB for PostgreSQL that you can query to obtain instance-level statistics, helping you troubleshoot performance issues.

Basic instance information

pg_stat_database

The pg_stat_database view displays statistics for each database in the cluster.

Parameter	Type	Description
`datid`	oid	The object identifier (OID) of the database.
`datname`	name	The database name.
`numbackends`	integer	The number of backends currently connected to the database. This is the only column that reflects the current state; all other columns return cumulative values since the last statistics reset.
`xact_commit`	bigint	The total number of transactions committed in the database.
`xact_rollback`	bigint	The total number of transactions rolled back in the database.
`blks_read`	bigint	The total number of disk blocks physically read in the database.
`blks_hit`	bigint	The number of disk block reads served from the buffer cache. This count reflects only hits in the PolarDB for PostgreSQL buffer; hits in the OS file system cache are not included.
`tup_returned`	bigint	The number of rows returned by queries in the database.
`tup_fetched`	bigint	The number of rows fetched by queries in the database.
`tup_inserted`	bigint	The number of rows inserted by queries in the database.
`tup_updated`	bigint	The number of rows updated by queries in the database.
`tup_deleted`	bigint	The number of rows deleted by queries in the database.
`conflicts`	bigint	The number of queries canceled due to read-only node replay conflicts.
`temp_files`	bigint	The number of temporary files created by queries in the database. All temporary files are counted, regardless of why they were created or the `log_temp_files` setting.
`temp_bytes`	bigint	The total amount of data written to temporary files by queries in the database. All temporary files are counted, regardless of why they were created or the `log_temp_files` setting.
`deadlocks`	bigint	The number of deadlocks detected in the database.
`blk_read_time`	double precision	The time spent by backends reading data files in the database, in milliseconds.
`blk_write_time`	double precision	The time spent by backends writing data files in the database, in milliseconds.
`stats_reset`	timestamp with time zone	The last time the statistics were reset.

pg_stat_bgwriter

The pg_stat_bgwriter view contains a single row with cluster-wide statistics about the background writer process.

Parameter	Type	Description
`checkpoints_timed`	bigint	The number of scheduled checkpoints performed.
`checkpoints_req`	bigint	The number of requested checkpoints performed.
`checkpoint_write_time`	double precision	The time spent writing files to disk during checkpoints, in milliseconds.
`checkpoint_sync_time`	double precision	The time spent synchronizing files to disk during checkpoints, in milliseconds.
`buffers_checkpoint`	bigint	The number of buffers written during checkpoints.
`buffers_clean`	bigint	The number of buffers written by the background writer process.
`maxwritten_clean`	bigint	The number of times the background writer stopped a cleaning scan because too many buffers were written at once.
`buffers_backend`	bigint	The number of buffers written directly by backends.
`buffers_backend_fsync`	bigint	The number of times a backend executed an fsync call instead of the background writer. The background writer normally handles write operations, but backends may also perform writes.
`buffers_alloc`	bigint	The number of buffers allocated.
`stats_reset`	timestamp with time zone	The last time the statistics were reset.

Activity status

polar_stat_activity

The polar_stat_activity view displays the status of each backend process, providing cumulative totals per process.

Parameter	Type	Description
`datid`	oid	The OID of the database.
`datname`	name	The database name.
`pid`	integer	The process ID.
`usesysid`	oid	The OID of the user.
`usename`	name	The user name.
`application_name`	text	The name of the application connected to the database.
`client_addr`	inet	The IP address of the connected client.
`client_hostname`	text	The host name of the connected client.
`client_port`	integer	The TCP port used for communication between the client and the database.
`backend_start`	timestamp	The time when the process started.
`xact_start`	timestamp	The time when the current transaction started.
`query_start`	timestamp	The time when the current SQL statement started executing.
`state_change`	timestamp	The time when the process state last changed.
`wait_event_type`	text	The category of event the backend is waiting for. Returns NULL if the backend is not waiting. Valid values: `LWLock`, `Lock`, `BufferPin`, `Activity`, `Extension`, `Client`, `IPC`, `Timeout`, `IO`. See the wait events table below for details.
`wait_event`	text	The name of the wait event. Returns NULL if the backend is not waiting.
`state`	text	The current state of the process.
`backend_xid`	xid	The transaction identifier (XID) of the backend.
`backend_xmin`	xid	The xmin value of the backend.
`query`	text	The SQL statement being executed.
`backend_type`	text	The type of the backend process.
`queryid`	bigint	The unique ID of the SQL statement.
`wait_object`	text	The wait object. Populated when the backend is waiting for an event.
`wait_type`	text	The type of the wait object. Populated when the backend is waiting for an event.
`wait_time_ms`	double	The wait time elapsed, in milliseconds. Populated when the backend is waiting for an event.
`cpu_user`	bigint	The user CPU usage of the backend.
`cpu_sys`	bigint	The system CPU usage of the backend.
`rss`	bigint	The memory usage of the backend, in bytes.
`pfs_read_ps`	bigint	The cumulative number of read operations on the Polar File System (PFS).
`pfs_write_ps`	bigint	The cumulative number of write operations on PFS.
`pfs_read_throughput`	bigint	The cumulative read throughput of PFS, in bytes.
`pfs_write_throughput`	bigint	The cumulative write throughput of PFS, in bytes.
`pfs_read_latency_ms`	double	The read latency for PFS operations, in milliseconds.
`pfs_write_latency_ms`	double	The write latency for PFS operations, in milliseconds.
`local_read_ps`	bigint	The cumulative number of read operations on the local file system.
`local_write_ps`	bigint	The cumulative number of write operations on the local file system.
`local_read_throughput`	bigint	The cumulative read throughput of the local file system, in bytes.
`local_write_throughput`	bigint	The cumulative write throughput of the local file system, in bytes.
`local_read_latency_ms`	double	The read latency for local file system operations, in milliseconds.
`local_write_latency_ms`	double	The write latency for local file system operations, in milliseconds.

Wait events

The following table describes the wait events returned in the wait_event_type and wait_event columns.

Wait event type	Wait event name	Description
`LWLock`	ShmemIndexLock	Waiting to find or allocate space in shared memory.
	OidGenLock	Waiting to allocate or assign an OID.
	XidGenLock	Waiting to allocate or assign a transaction ID (XID).
	ProcArrayLock	Waiting to obtain a snapshot or clear an XID at the end of a transaction.
	SInvalReadLock	Waiting to retrieve or remove a message from the shared invalidation message queue.
	SInvalWriteLock	Waiting to add a message to the shared invalidation message queue.
	WALBufMappingLock	Waiting to replace a page in the write-ahead logging (WAL) buffer.
	WALWriteLock	Waiting for a WAL buffer to be written to disk.
	ControlFileLock	Waiting to read or update the control file, or to create a WAL file.
	CheckpointLock	Waiting to perform a checkpoint.
	CLogControlLock	Waiting to read or update transaction status.
	SubtransControlLock	Waiting to read or update subtransaction information.
	MultiXactGenLock	Waiting to read or update the shared multixact state.
	MultiXactOffsetControlLock	Waiting to read or update multixact offset mappings.
	MultiXactMemberControlLock	Waiting to read or update multixact member mappings.
	RelCacheInitLock	Waiting to read or write the relation cache initialization file.
	CheckpointerCommLock	Waiting to manage fsync() calls.
	TwoPhaseStateLock	Waiting to read or update the status of a prepared transaction.
	TablespaceCreateLock	Waiting to create or drop a tablespace.
	BtreeVacuumLock	Waiting to read or update vacuum-related information for a B-tree index.
	AddinShmemInitLock	Waiting to manage space allocation in shared memory.
	AutovacuumLock	Waiting to update or read the status of an autovacuum worker.
	AutovacuumScheduleLock	Waiting to confirm that the table selected for vacuuming still needs to be vacuumed.
	SyncScanLock	Waiting to get the starting scan location for synchronized scans on a table.
	RelationMappingLock	Waiting to update the relation mapping file used for catalog-to-filenode mappings.
	AsyncCtlLock	Waiting to read or update the shared notification state.
	AsyncQueueLock	Waiting to read or update notification messages.
	SerializableXactHashLock	Waiting to retrieve or store information about serializable transactions.
	SerializableFinishedListLock	Waiting to access the list of finished serializable transactions.
	SerializablePredicateLockListLock	Waiting to perform operations on locks held by serializable transactions.
	OldSerXidLock	Waiting to read or record conflicting serializable transactions.
	SyncRepLock	Waiting to read or update information about synchronous replicas.
	BackgroundWorkerLock	Waiting to read or update the background worker state.
	DynamicSharedMemoryControlLock	Waiting to read or update the dynamic shared memory state.
	AutoFileLock	Waiting to update the `postgresql.auto.conf` file.
	ReplicationSlotAllocationLock	Waiting to allocate or drop a replication slot.
	ReplicationSlotControlLock	Waiting to read or update the state of a replication slot.
	CommitTsControlLock	Waiting to read or update transaction commit timestamps.
	CommitTsLock	Waiting to read or update the last transaction timestamp value.
	ReplicationOriginLock	Waiting to set up, drop, or use a replication origin.
	MultiXactTruncationLock	Waiting to read or truncate multixact information.
	OldSnapshotTimeMapLock	Waiting to read or update control information about old snapshots.
	BackendRandomLock	Waiting to generate a random number.
	LogicalRepWorkerLock	Waiting for an action on a logical replication worker to complete.
	CLogTruncationLock	Waiting to truncate a WAL file, or waiting for an in-progress WAL truncation to complete.
	clog	Waiting for I/O on a commit log (CLOG) buffer. A CLOG records the commit status of transactions.
	commit_timestamp	Waiting for I/O on a commit timestamp buffer.
	subtrans	Waiting for I/O on a subtransaction buffer.
	multixact_offset	Waiting for I/O on a multixact offset buffer.
	multixact_member	Waiting for I/O on a multixact member buffer.
	async	Waiting for I/O on an async buffer.
	oldserxid	Waiting for I/O on an oldserxid buffer.
	wal_insert	Waiting to insert a WAL record into a memory buffer.
	buffer_content	Waiting to read or write a data page in memory.
	buffer_io	Waiting for I/O on a data page.
	replication_origin	Waiting to read or update replication progress.
	replication_slot_io	Waiting for I/O on a replication slot.
	proc	Waiting to read or update fast-path lock information.
	buffer_mapping	Waiting to associate a data block with a buffer in the buffer pool.
	lock_manager	Waiting to join or exit a locking group, or to add or check locks used by backends. Occurs during parallel queries.
	predicate_lock_manager	Waiting to add or check predicate lock information.
	parallel_query_dsa	Waiting for the dynamic shared memory allocation lock for parallel execution.
	tbm	Waiting for the shared iterator lock on a TIDBitmap.
	parallel_append	Waiting to select the next subplan while executing a Parallel Append plan.
	parallel_hash_join	Waiting to allocate or exchange memory chunks, or to update counters while executing a Parallel Hash plan.
`Lock`	relation	Waiting to acquire a lock on a relation.
	extend	Waiting to extend a relation.
	page	Waiting to acquire a lock on a relation page.
	tuple	Waiting to acquire a lock on a tuple.
	transactionid	Waiting for a transaction to complete.
	virtualxid	Waiting to acquire a virtual XID lock.
	speculative token	Waiting to acquire a speculative insertion lock.
	object	Waiting to acquire a lock on a non-relational database object.
	userlock	Waiting to acquire a user lock.
	advisory	Waiting to acquire an advisory lock.
`BufferPin`	BufferPin	Waiting to pin a buffer.
`Activity`	ArchiverMain	Waiting in the main loop of the archiver process.
	AutoVacuumMain	Waiting in the main loop of the autovacuum launcher process.
	BgWriterHibernate	Waiting in the background writer process while the instance is in hibernation.
	BgWriterMain	Waiting in the main loop of the background writer process.
	CheckpointerMain	Waiting in the main loop of the checkpointer process.
	LogicalApplyMain	Waiting in the main loop of the logical replication apply process.
	LogicalLauncherMain	Waiting in the main loop of the logical replication launcher process.
	PgStatMain	Waiting in the main loop of the statistics collector process.
	RecoveryWalAll	Waiting for WAL data from any source (local file, archive, or stream) during instance recovery.
	RecoveryWalStream	Waiting for WAL data from a stream during instance recovery.
	SysLoggerMain	Waiting in the main loop of the syslog process.
	WalReceiverMain	Waiting in the main loop of the WAL receiver process.
	WalSenderMain	Waiting in the main loop of the WAL sender process.
	WalWriterMain	Waiting in the main loop of the WAL writer process.
`Client`	ClientRead	Waiting to read data from the client.
	ClientWrite	Waiting to write data to the client.
	LibPQWalReceiverConnect	Waiting in the WAL receiver process to connect to a remote server.
	LibPQWalReceiverReceive	Waiting in the WAL receiver process to receive data from a remote server.
	SSLOpenServer	Waiting for SSL handshake during connection establishment.
	WalReceiverWaitStart	Waiting for the startup process to send initial data for streaming replication.
	WalSenderWaitForWAL	Waiting for WAL data to be flushed in the WAL sender process.
	WalSenderWriteData	Waiting while processing replies from the WAL receiver in the WAL sender process.
`Extension`	Extension	Waiting in an extension module.
`IPC`	BgWorkerShutdown	Waiting for a background worker to shut down.
	BgWorkerStartup	Waiting for a background worker to start up.
	BtreePage	Waiting for a page number needed to continue a parallel B-tree scan.
	ClogGroupUpdate	Waiting for the group leader to update transaction status when a transaction ends.
	ExecuteGather	Waiting for activity from a child process while executing a Gather node.
	Hash/Batch/Allocating	Waiting for the elected Parallel Hash participant to allocate hash tables.
	Hash/Batch/Electing	Waiting for a Parallel Hash participant to be elected to allocate hash tables.
	Hash/Batch/Loading	Waiting for other Parallel Hash participants to finish loading hash tables.
	Hash/Build/Allocating	Waiting for the elected Parallel Hash participant to allocate the initial hash table.
	Hash/Build/Electing	Waiting for a Parallel Hash participant to be elected to allocate the initial hash table.
	Hash/Build/HashingInner	Waiting for other Parallel Hash participants to finish hashing inner relations.
	Hash/Build/HashingOuter	Waiting for other Parallel Hash participants to finish hashing outer relations.
	Hash/GrowBatches/Allocating	Waiting for the elected Parallel Hash participant to allocate additional hash table batches.
	Hash/GrowBatches/Deciding	Waiting for a Parallel Hash participant to be elected to decide the batch count increase.
	Hash/GrowBatches/Electing	Waiting for a Parallel Hash participant to be elected to allocate additional batches.
	Hash/GrowBatches/Finishing	Waiting for the elected Parallel Hash participant to decide the batch count increase.
	Hash/GrowBatches/Repartitioning	Waiting for other Parallel Hash participants to finish repartitioning.
	Hash/GrowBuckets/Allocating	Waiting for the elected Parallel Hash participant to finish allocating additional buckets.
	Hash/GrowBuckets/Electing	Waiting for a Parallel Hash participant to be elected to allocate additional buckets.
	Hash/GrowBuckets/Reinserting	Waiting for other Parallel Hash participants to insert tuples into new buckets.
	LogicalSyncData	Waiting for the remote logical replication server to send data for initial table synchronization.
	LogicalSyncStateChange	Waiting for the remote logical replication server to change state.
	MessageQueueInternal	Waiting for other processes to attach to a shared message queue.
	MessageQueuePutMessage	Waiting to write a protocol message to a shared message queue.
	MessageQueueReceive	Waiting to receive bytes from a shared message queue.
	MessageQueueSend	Waiting to send bytes to a shared message queue.
	ParallelBitmapScan	Waiting for a parallel bitmap scan to be initialized.
	ParallelCreateIndexScan	Waiting for parallel CREATE INDEX workers to finish heap scans.
	ParallelFinish	Waiting for parallel workers to finish computing.
	ProcArrayGroupUpdate	Waiting for the group leader to clear the XID after a transaction completes.
	ReplicationOriginDrop	Waiting for a replication origin to become inactive so it can be deleted.
	ReplicationSlotDrop	Waiting for a replication slot to become inactive so it can be deleted.
	SafeSnapshot	Waiting for a snapshot usable in a READ ONLY DEFERRABLE transaction.
	SyncRep	Waiting for confirmation from the remote server during synchronous replication.
`Timeout`	BaseBackupThrottle	Waiting during the base backup phase while throttling is active.
	PgSleep	Waiting in a process that called the `pg_sleep` function.
	RecoveryApplyDelay	Waiting to apply WAL during recovery because WAL application is delayed.
`IO`	BufFileRead	Waiting to read data from a buffered file.
	BufFileWrite	Waiting to write data to a buffered file.
	ControlFileRead	Waiting to read data from the control file.
	ControlFileSync	Waiting for the control file to reach stable storage.
	ControlFileSyncUpdate	Waiting for a control file update to reach stable storage.
	ControlFileWrite	Waiting to write data to the control file.
	ControlFileWriteUpdate	Waiting to write an update to the control file.
	CopyFileRead	Waiting to read data while copying a file.
	CopyFileWrite	Waiting to write data while copying a file.
	DataFileExtend	Waiting for a relation data file to be extended.
	DataFileFlush	Waiting for a relation data file to reach stable storage.
	DataFileImmediateSync	Waiting for a relation data file to be immediately synced to stable storage.
	DataFilePrefetch	Waiting for an asynchronous prefetch from a relation data file.
	DataFileRead	Waiting to read data from a relation data file.
	DataFileSync	Waiting for changes to a relation data file to reach stable storage.
	DataFileTruncate	Waiting for a relation data file to be truncated.
	DataFileWrite	Waiting to write data to a relation data file.
	DSMFillZeroWrite	Waiting to write zeros to a dynamic shared memory backing file.
	LockFileAddToDataDirRead	Waiting to read data while adding a row to the data directory lock file.
	LockFileAddToDataDirSync	Waiting for a row to reach stable storage while adding it to the data directory lock file.
	LockFileAddToDataDirWrite	Waiting to write data while adding a row to the data directory lock file.
	LockFileCreateRead	Waiting to read data while creating the data directory lock file.
	LockFileCreateSync	Waiting for data to reach stable storage while creating the data directory lock file.
	LockFileCreateWrite	Waiting to write data while creating the data directory lock file.
	LockFileReCheckDataDirRead	Waiting to read data while rechecking the data directory lock file.
	LogicalRewriteCheckpointSync	Waiting for logical rewrite mappings to reach stable storage during a checkpoint.
	LogicalRewriteMappingSync	Waiting for mapping data to reach stable storage during a logical rewrite.
	LogicalRewriteMappingWrite	Waiting to write mapping data during a logical rewrite.
	LogicalRewriteSync	Waiting for logical rewrite mappings to reach stable storage.
	LogicalRewriteWrite	Waiting to write data to logical rewrite mappings.
	RelationMapRead	Waiting to read data from the relation mapping file.
	RelationMapSync	Waiting for the relation mapping file to reach stable storage.
	RelationMapWrite	Waiting to write data to the relation mapping file.
	ReorderBufferRead	Waiting to read data during reorder buffer management.
	ReorderBufferWrite	Waiting to write data during reorder buffer management.
	ReorderLogicalMappingRead	Waiting to read a logical mapping during reorder buffer management.
	ReplicationSlotRead	Waiting to read data from a replication slot control file.
	ReplicationSlotRestoreSync	Waiting for a replication slot control file to reach stable storage while it is being restored into memory.
	ReplicationSlotSync	Waiting for a replication slot control file to reach stable storage.
	ReplicationSlotWrite	Waiting to write data to a replication slot control file.
	SLRUFlushSync	Waiting for Segmented Least Recently Used (SLRU) data to reach stable storage during a checkpoint or database shutdown.
	SLRURead	Waiting to read data from an SLRU page.
	SLRUSync	Waiting for SLRU data to reach stable storage after a page write.
	SLRUWrite	Waiting to write data to an SLRU page.
	SnapbuildRead	Waiting to read data from a serialized historical catalog snapshot.
	SnapbuildSync	Waiting for a serialized historical catalog snapshot to reach stable storage.
	SnapbuildWrite	Waiting to write data to a serialized historical catalog snapshot.
	TimelineHistoryFileSync	Waiting for a timeline history file received via streaming replication to reach stable storage.
	TimelineHistoryFileWrite	Waiting to write a timeline history file received via streaming replication.
	TimelineHistoryRead	Waiting to read data from a timeline history file.
	TimelineHistorySync	Waiting for a newly created timeline history file to reach stable storage.
	TimelineHistoryWrite	Waiting to write data to a newly created timeline history file.
	TwophaseFileRead	Waiting to read data from a two-phase state file.
	TwophaseFileSync	Waiting for a two-phase state file to reach stable storage.
	TwophaseFileWrite	Waiting to write data to a two-phase state file.
	WALBootstrapSync	Waiting for WAL data to reach stable storage during bootstrapping.
	WALBootstrapWrite	Waiting to write data to a WAL page during bootstrapping.
	WALCopyRead	Waiting to read data while creating a WAL segment by copying an existing segment.
	WALCopySync	Waiting for a WAL segment created by copying an existing segment to reach stable storage.
	WALCopyWrite	Waiting to write data while creating a WAL segment by copying an existing segment.
	WALInitSync	Waiting for a newly initialized WAL file to reach stable storage.
	WALInitWrite	Waiting to write data while initializing a new WAL file.
	WALRead	Waiting to read data from a WAL file.
	WALSenderTimelineHistoryRead	Waiting to read a timeline history file while running the walsender timeline command.
	WALSyncMethodAssign	Waiting for data to reach stable storage while assigning the WAL sync method.
	WALWrite	Waiting to write data to a WAL file.

polar_stat_activity_rt

The polar_stat_activity_rt view provides real-time status data for all backend processes. Unlike polar_stat_activity, this view does not provide cumulative totals.

Parameter	Type	Description
`pid`	integer	The process ID.
`backend_type`	text	The type of the backend process.
`cpu_user`	bigint	The user CPU usage of the backend.
`cpu_sys`	bigint	The system CPU usage of the backend.
`rss`	bigint	The memory usage of the backend, in bytes.
`local_read_ps`	bigint	The cumulative number of read operations on the local file system.
`local_write_ps`	bigint	The cumulative number of write operations on the local file system.
`local_read_throughput`	bigint	The cumulative read throughput of the local file system, in bytes.
`local_write_throughput`	bigint	The cumulative write throughput of the local file system, in bytes.
`local_read_latency_ms`	double	The read latency for local file system operations, in milliseconds.
`local_write_latency_ms`	double	The write latency for local file system operations, in milliseconds.

polar_delta

polar_delta is a function that queries the incremental (delta) values of a view between successive calls.

Important

polar_delta is provided by the polar_monitor plugin, which is built into PolarDB for PostgreSQL. To activate the plugin, run CREATE EXTENSION polar_monitor.

To use polar_delta:

Create a view with a dimension column and one or more value columns.
- Dimension column names must start with d.
- Value column names must start with v.

Query the view using one of the following statements:

SELECT * FROM polar_delta(NULL::view_name);
\watch 1 SELECT * FROM polar_delta(NULL::view_name);

Resources

Shared memory

Global data structures such as the buffer pool and latches are allocated in shared memory at startup. The following views provide shared memory monitoring information.

polar_stat_shmem

The polar_stat_shmem view provides detailed monitoring information for each type of shared memory.

Parameter	Type	Description
`shmname`	text	The name of the shared memory segment.
`shmsize`	bigint	The size of the shared memory segment, in bytes.
`shmtype`	text	The type of the shared memory segment.

polar_stat_shmem_total_size

The polar_stat_shmem_total_size view provides aggregated monitoring information about shared memory, grouped by type.

Parameter	Type	Description
`shmsize`	bigint	The total size of the shared memory type, in bytes.
`shmtype`	text	The type of the shared memory.

Session private memory

PolarDB dynamically allocates and releases private memory during execution. Session-level memory metrics are available in the polar_stat_activity view. For context-level memory details, use the following function and view.

polar_get_mcxt()

The polar_get_mcxt() function returns memory context information for a given backend process.

Parameter	Type	Description
`pid`	integer	The ID of the session process.
`name`	text	The name of the memory context.
`level`	int	The level of the memory context.
`nblocks`	bigint	The number of allocated blocks.
`freechunks`	bigint	The number of free chunks.
`totalspace`	bigint	The total memory allocated, in bytes.
`freespace`	bigint	The free memory available, in bytes.

polar_backends_mcxt

The polar_backends_mcxt view provides memory context information grouped by backend type.

Parameter	Type	Description
`pid`	integer	The process ID.
`name`	text	The name of the memory context.
`nblocks`	bigint	The number of allocated blocks.
`freechunks`	bigint	The number of free chunks.
`totalspace`	bigint	The total memory allocated, in bytes.
`freespace`	bigint	The free memory available, in bytes.

I/O

Session-level I/O metrics are available in the polar_stat_activity view. The following views provide file-level I/O statistics and latency distribution.

polar_stat_io_info

The polar_stat_io_info view provides I/O monitoring information grouped by file type.

Parameter	Type	Description
`filetype`	text	The type of the file.
`fileloc`	text	The file system where the file resides. Valid values: local file system, Polar File System (PFS).
`open_count`	numeric	The number of times the file has been opened.
`open_latency_us`	double	The total latency for opening the file, in microseconds.
`close_count`	numeric	The number of times the file has been closed.
`read_count`	numeric	The number of times the file has been read.
`write_count`	numeric	The number of times the file has been written.
`read_throughput`	numeric	The cumulative read throughput of the file system, in bytes.
`write_throughput`	numeric	The cumulative write throughput of the file system, in bytes.
`read_latency_us`	double	The total latency for reading the file, in microseconds.
`write_latency_us`	double	The total latency for writing to the file, in microseconds.
`seek_count`	numeric	The number of times `seek()` was called.
`seek_latency_us`	double	The total latency for `seek()` calls, in microseconds.
`creat_count`	numeric	The number of times a file was created.
`creat_latency_us`	double	The total latency for file creation, in microseconds.
`fsync_count`	numeric	The number of times `fsync()` was called.
`fsync_latency_us`	double	The total latency for `fsync()` calls, in microseconds.
`falloc_count`	numeric	The number of times `fallocate()` was called.
`falloc_latency_us`	double	The total latency for `fallocate()` calls, in microseconds.

polar_stat_io_latency

The polar_stat_io_latency view provides I/O latency distribution grouped by operation type.

Parameter	Type	Description
`iokind`	text	The I/O operation type. Valid values: `fsync`, `creat`, `seek`, `open`, `read`, `write`, `falloc`.
`num_lessthan200us`	numeric	The number of operations with latency less than 200 microseconds.
`num_lessthan400us`	numeric	The number of operations with latency between 200 and 400 microseconds.
`num_lessthan600us`	numeric	The number of operations with latency between 400 and 600 microseconds.
`num_lessthan800us`	numeric	The number of operations with latency between 600 and 800 microseconds.
`num_lessthan1ms`	numeric	The number of operations with latency between 800 microseconds and 1 millisecond.
`num_lessthan10ms`	numeric	The number of operations with latency between 1 and 10 milliseconds.
`num_lessthan100ms`	numeric	The number of operations with latency between 10 and 100 milliseconds.
`num_morethan100ms`	numeric	The number of operations with latency greater than 100 milliseconds.

Network

The following function and view provide network monitoring information.

polar_proc_stat_network()

The polar_proc_stat_network() function returns per-process network statistics.

Parameter	Type	Description
`pid`	bigint	The process ID.
`send_bytes`	bigint	The total number of bytes sent.
`send_count`	bigint	The cumulative number of send operations.
`recv_bytes`	bigint	The total number of bytes received.
`recv_count`	bigint	The cumulative number of receive operations.
`sendq`	bigint	The send queue length on the socket.
`recvq`	bigint	The receive queue length on the socket.
`cwnd`	bigint	The congestion window size of the socket.
`rtt`	bigint	The round-trip time (RTT) of TCP packets, in microseconds.
`retrans`	bigint	The cumulative number of TCP retransmissions.
`tcpinfo_update_time`	bigint	The Unix timestamp (in seconds) of the last update to TCP socket metrics. The `sendq`, `recvq`, `cwnd`, `rtt`, and `retrans` values are updated once per second; this field shows when they were last refreshed.

Lock

The following views provide lock monitoring information.

polar_stat_lwlock

The polar_stat_lwlock view provides lightweight lock (LWLock) statistics.

Parameter	Type	Description
`tranche`	smallint	The lock ID.
`name`	text	The lock name.
`sh_acquire_count`	bigint	The number of times a shared lock was acquired.
`ex_acquire_count`	bigint	The number of times an exclusive lock was acquired.
`block_count`	bigint	The number of lock blocks that occurred.
`lock_nums`	bigint	The number of lightweight locks.
`wait_time`	bigint	The total lock wait time.

pg_locks

The pg_locks view provides information about heavyweight locks held or awaited by server processes.

Parameter	Type	Description
`locktype`	text	The type of the lockable object. Valid values: `relation`, `extend`, `page`, `tuple`, `transactionid`, `virtualxid`, `object`, `userlock`, `advisory`.
`database`	oid	The OID of the database in which the locked object resides. Returns `0` for shared objects and `NULL` for XID locks.
`relation`	oid	The OID of the relation being locked. Returns `NULL` if the object is not a relation or is only part of a relation.
`page`	integer	The page number within the relation. Returns `NULL` if the object is not a tuple or relation page.
`tuple`	smallint	The tuple number within the page. Returns `NULL` if the object is not a tuple.
`virtualxid`	text	The virtual transaction ID being locked. Returns `NULL` if the object is not a virtual XID.
`transactionid`	xid	The transaction ID being locked. Returns `NULL` if the object is not an XID.
`classid`	oid	The OID of the system catalog containing the locked object. Returns `NULL` if the object is not a general database object.
`objid`	oid	The ID of the locked object within the system catalog. Returns `NULL` if the object is not a general database object.
`objsubid`	smallint	The ID of the locked column. The values in `classid` and `objid` refer to the table itself. Returns `0` for other general database objects, and `NULL` if the object is not a general database object.
`virtualtransaction`	text	The virtual transaction ID of the transaction holding or awaiting the lock.
`pid`	integer	The PID of the server process holding or awaiting the lock. Returns `NULL` if the lock is held by a prepared transaction.
`mode`	text	The name of the lock mode held or requested by this process.
`granted`	boolean	`true` if the lock is held; `false` if the lock is being waited for.
`fastpath`	boolean	`true` if the lock was acquired via the fast path; `false` if it was acquired from the main lock table.

polar_stat_lock

The polar_stat_lock view provides lock statistics aggregated by lock type.

Parameter	Type	Description
`id`	integer	The primary key.
`lock_type`	text	The type of the lock.
`invalid`	numeric	Indicates that the lock is invalid.
`accesssharelock`	numeric	The number of ACCESS SHARE locks.
`rowsharelock`	numeric	The number of ROW SHARE locks.
`rowexclusivelock`	numeric	The number of ROW EXCLUSIVE locks.
`shareupdateexclusivelock`	numeric	The number of SHARE UPDATE EXCLUSIVE locks.
`sharelock`	numeric	The number of SHARE locks.
`sharerowexclusivelock`	numeric	The number of SHARE ROW EXCLUSIVE locks.
`exclusivelock`	numeric	The number of EXCLUSIVE locks.
`accessexclusivelock`	numeric	The number of ACCESS EXCLUSIVE locks.
`block_count`	numeric	The number of lock blocks caused by lock contention.
`fastpath_count`	numeric	The number of fast-path locks acquired locally.
`wait_time`	numeric	The total lock wait time.

SLRU

The polar_stat_slru() view provides monitoring information about Segmented Least Recently Used (SLRU) cache data.

Parameter	Type	Description
`slru_type`	text	The SLRU type (primary key).
`slots_number`	integer	The total number of page slots.
`valid_pages`	integer	The number of pages in use.
`empty_pages`	integer	The number of empty pages.
`reading_pages`	integer	The number of pages currently being read.
`writing_pages`	integer	The number of pages currently being written.
`wait_readings`	integer	The number of wait events for read operations.
`wait_writings`	integer	The number of wait events for write operations.
`read_count`	bigint	The total number of read operations.
`read_only_count`	bigint	The number of read-only operations.
`read_upgrade_count`	bigint	The number of read operations in upgrade mode.
`victim_count`	bigint	The number of cache evictions.
`victim_write_count`	bigint	The number of cache evictions that required writing evicted data to disk.
`write_count`	bigint	The total number of write operations.
`zero_count`	bigint	The number of times cache data was cleared.
`flush_count`	bigint	The total number of flush operations.
`truncate_count`	bigint	The total number of truncate operations.
`storage_read_count`	bigint	The number of times data was read from disk.
`storage_write_count`	bigint	The number of times data was written to disk.

cgroup

The following views provide system resource and cgroup monitoring information.

polar_stat_cgroup

The polar_stat_cgroup view provides statistics about system resources and control groups (cgroups).

Parameter	Type	Description
`subtype`	text	The cgroup type. Valid values: `IO`, `Memory`, `CPU`.
`infotype`	text	The cgroup metric being reported.
`count`	bigint	The resource usage count.

polar_cgroup_quota

The polar_cgroup_quota view provides cgroup quota information.

Parameter	Type	Description
`subtype`	text	The cgroup type. Valid values: `IO`, `Memory`, `CPU`.
`infotype`	text	The cgroup metric being reported.
`count`	bigint	The cgroup quota value.