Resets statistics of the replication slot defined by the argument. The pg_statio_all_tables view will contain one row for each table in the current database (including TOAST tables), showing statistics about I/O on that specific table. Resets statistics for a single function in the current database to zero. This and other streaming counters for this slot can be used to tune logical_decoding_work_mem. BufferCacheHitRatio and LWLock:BufferIO wait Waiting for a WAL file to reach durable storage. This is the only column in this view that returns a value reflecting current state; all other columns return the accumulated values since the last reset. The server process is waiting for a heavyweight lock. Waiting to acquire a lock on a page of a relation. The latter will be less if any dead or not-yet-committed rows are fetched using the index, or if any heap fetches are avoided by means of an index-only scan. Presently, the collector can count accesses to tables and indexes in both disk-block and individual-row terms. Number of times this function has been called, Total time spent in this function and all other functions called by it, in milliseconds, Total time spent in this function itself, not including other functions called by it, in milliseconds. LWLock: The backend is waiting for a lightweight lock. Waiting to read or update shared notification state. See, One row per database, showing database-wide statistics about query cancels due to conflict with recovery on standby servers. Also, the collector itself emits a new report at most once per PGSTAT_STAT_INTERVAL milliseconds (500 ms unless altered while building the server). Waiting for a read of a logical mapping during reorder buffer management. The pg_stat_wal_receiver view will contain only one row, showing statistics about the WAL receiver from that receiver's connected server. This field will only be non-null for IP connections, and only when log_hostname is enabled. A transaction can also see its own statistics (not yet flushed out to the shared memory statistics) in the views pg_stat_xact_all_tables, pg_stat_xact_sys_tables, pg_stat_xact_user_tables, and pg_stat_xact_user_functions. Waiting for an asynchronous prefetch from a relation data file. Time when the currently active query was started, or if state is not active, when the last query was started. IPC: The server process is waiting for some activity from another process in the server. Possible types are autovacuum launcher, autovacuum worker, logical replication launcher, logical replication worker, parallel worker, background writer, client backend, checkpointer, archiver, startup, walreceiver, walsender and walwriter. Waiting for a write to a replication slot control file. For tranches registered by extensions, the name is specified by extension and this will be displayed as wait_event. buffer_mapping: Waiting to associate a data block with a buffer in the buffer pool. Waiting to read or update vacuum-related information for a B-tree index. Connection string used by this WAL receiver, with security-sensitive fields obfuscated. Additional Statistics Functions. Waiting to read or update a process' fast-path lock information. The pg_stat_wal view will always have a single row, containing data about WAL activity of the cluster. The pg_statio_user_indexes and pg_statio_sys_indexes views contain the same information, but filtered to only show user and system indexes respectively. Total amount of data written to temporary files by queries in this database. Waiting for I/O on a clog (transaction status) buffer. For client backends, this is the time the client connected to the server. Waiting for other Parallel Hash participants to finish loading a hash table. Number of times transactions were spilled to disk while decoding changes from WAL for this slot. Current WAL sender state. IP address of the client connected to this WAL sender. Waiting for I/O on an async (notify) buffer. operations, Large or bloated indexes that require the engine to read more pages than necessary into the shared buffer pool, Lack of indexes that forces the DB engine to read more pages from the tables than necessary, Checkpoints occurring too frequently or needing to flush too many modified pages, Sudden spikes for database connections trying to perform operations on the same page. disabled: This state is reported if track_activities is disabled in this backend. Waiting for a write while initializing a new WAL file. From the Actions drop-down menu, choose Create Read Replica. Waiting for SLRU data to reach durable storage following a page write. Returns a record of information about the backend with the specified process ID, or one record for each active backend in the system if NULL is specified. To reduce confusion for users expecting a different model of lag, the lag columns revert to NULL after a short time on a fully replayed idle system. In order to write the disk block into buffer memory, the buffer cache's hash table entry needs updating. Waiting for a read from a replication slot control file. Increase the number of wal_buffers available to the database. pg_stat_get_backend_activity_start ( integer ) timestamp with time zone. Waiting in main loop of logical replication apply process. Waiting to write a protocol message to a shared message queue. Waiting for a read of a serialized historical catalog snapshot. Waiting for a read during recheck of the data directory lock file. Provide feedback Other ways of looking at the statistics can be set up by writing queries that use the same underlying statistics access functions used by the standard views shown above. wait_event will identify the specific wait point. This facility is independent of the collector process. Alternatively, one can build custom views using the underlying cumulative statistics functions, as discussed in Section28.2.24. Waiting for I/O on commit timestamp buffer. Number of disk blocks read from this index. pg_stat_get_backend_activity ( integer ) text. Waiting for a read during a file copy operation. Waiting for a newly initialized WAL file to reach durable storage. Waiting for a timeline history file received via streaming replication to reach durable storage. Waiting to associate a data block with a buffer in the buffer pool. Waiting for base backup to read from a file. Waiting for logical rewrite mappings to reach durable storage. See, Only one row, showing statistics about blocks prefetched during recovery. The wait_event and state columns are independent. Possible values are: Last write-ahead log location sent on this connection, Last write-ahead log location written to disk by this standby server, Last write-ahead log location flushed to disk by this standby server, Last write-ahead log location replayed into the database on this standby server, Time elapsed between flushing recent WAL locally and receiving notification that this standby server has written it (but not yet flushed it or applied it). PostgreSQL 15.2, 14.7, 13.10, 12.14, and 11.19 Released, 28.2.1. Table28.34. When analyzing statistics interactively, or with expensive queries, the time delta between accesses to individual statistics can lead to significant skew in the cached statistics. This counter is incremented each time a transaction is spilled, and the same transaction may be spilled multiple times. Waiting for a write while adding a line to the data directory lock file. Each individual server process transmits new statistical counts to the collector just before going idle; so a query or transaction still in progress does not affect the displayed totals. See, One row for each index in the current database, showing statistics about accesses to that specific index. It is used per the rules above. The optimizer also accesses indexes to check for supplied constants whose values are outside the recorded range of the optimizer statistics because the optimizer statistics might be stale. pg_stat_get_activity ( integer ) setof record. please use Additional functions related to statistics collection are listed in Table28.19. Waiting for group leader to clear transaction id at transaction end. Waiting to access the sub-transaction SLRU cache. These times represent the commit delay that was (or would have been) introduced by each synchronous commit level, if the remote server was configured as a synchronous standby. In all other states, it shows the identifier of last query that was executed. Waiting to elect a Parallel Hash participant to allocate a hash table. Waiting for changes to a relation data file to reach durable storage. Waiting for a write when creating a new WAL segment by copying an existing one. idle in transaction (aborted): This state is similar to idle in transaction, except one of the statements in the transaction caused an error. Waiting for a write of a serialized historical catalog snapshot. Synchronous state of this standby server. These numbers do not act as stated above; instead they update continuously throughout the transaction. Waiting for a read of the relation map file. This has no effect in a quorum-based synchronous replication. ; Ensure that filesystem journaling is turned off for data files and WAL files. The pg_stat_recovery_prefetch view will contain only one row. Its purpose is for the same page to be read into the shared buffer. This and other spill counters can be used to gauge the I/O which occurred during logical decoding and allow tuning logical_decoding_work_mem. Waiting for data to reach durable storage while adding a line to the data directory lock file. A database-wide ANALYZE is recommended after the statistics have been reset. . However, these statistics do not give the entire story: due to the way in which PostgreSQL handles disk I/O, data that is not in the PostgreSQL buffer cache might still reside in the kernel's I/O cache, and might therefore still be fetched without requiring a physical read. Prevent sudden database connection spikes by using a connection pool. The pg_stat_all_tables view will contain one row for each table in the current database (including TOAST tables), showing statistics about accesses to that specific table. For client backends, this is the time the client connected to the server. If enabled, calls to user-defined functions and the total time spent in each one are counted as well. See Table28.4. The pg_stat_replication_slots view will contain one row per logical replication slot, showing statistics about its usage. Waiting to read or update background worker state. The optimizer also accesses indexes to check for supplied constants whose values are outside the recorded range of the optimizer statistics because the optimizer statistics might be stale. Waiting for logical rewrite mappings to reach durable storage during a checkpoint. PostgreSQL utilizes lightweight locks (LWLocks) to synchronize and control access to the buffer content. A database-wide ANALYZE is recommended after the statistics have been reset. Most such locks protect a particular data structure in shared memory. Waiting to add a message in shared invalidation queue. Waiting to read or write relation cache initialization file. If the current query is the first of its transaction, this column is equal to the query_start column. Logical decoding plugins may optionally emit tracking messages; if they do not, the tracking mechanism will simply display NULL lag. Waiting for an elected Parallel Hash participant to allocate the initial hash table. Waiting for a write of a WAL page during bootstrapping. pg_stat_get_backend_client_port ( integer ) integer. Only directly connected standbys are listed; no information is available about downstream standby servers. The function pg_stat_get_backend_idset provides a convenient way to generate one row for each active backend for invoking these functions. Waiting to retrieve messages from the shared catalog invalidation queue. If the standby server has entirely caught up with the sending server and there is no more WAL activity, the most recently measured lag times will continue to be displayed for a short time and then show NULL. to keep index reordering low and reduces its impact. Waiting for a write of a newly created timeline history file. The buffer_tag comprises three values: the RelFileNode and the fork number of the relation to which its page belongs, and the block number of its page. The pg_stat_database view will contain one row for each database in the cluster, showing database-wide statistics. The parameter track_functions enables tracking of usage of user-defined functions. Waiting to read while creating the data directory lock file. TCP port number that the client is using for communication with this backend, or -1 if a Unix socket is used. See, One row per connection (regular and replication), showing information about SSL used on this connection. Waiting to read or update transaction commit timestamps. Waiting for the page number needed to continue a parallel B-tree scan to become available. pg_stat_get_backend_client_addr ( integer ) inet. Waiting for another process to be attached to a shared message queue. Waiting in main loop of WAL receiver process. It can be joined to pg_stat_activity or pg_stat_replication on the pid column to get more details about the connection. The pg_stat_archiver view will always have a single row, containing data about the archiver process of the cluster. The pg_stat_database_conflicts view will contain one row per database, showing database-wide statistics about query cancels occurring due to conflicts with recovery on standby servers. All temporary files are counted, regardless of why the temporary file was created, and regardless of the, Number of deadlocks detected in this database, Time spent reading data file blocks by backends in this database, in milliseconds, Time spent writing data file blocks by backends in this database, in milliseconds, Number of queries in this database that have been canceled due to dropped tablespaces, Number of queries in this database that have been canceled due to lock timeouts, Number of queries in this database that have been canceled due to old snapshots, Number of queries in this database that have been canceled due to pinned buffers, Number of queries in this database that have been canceled due to deadlocks, Number of sequential scans initiated on this table, Number of live rows fetched by sequential scans, Number of index scans initiated on this table, Number of live rows fetched by index scans, Number of rows updated (includes HOT updated rows), Number of rows HOT updated (i.e., with no separate index update required), Estimated number of rows modified since this table was last analyzed, Last time at which this table was manually vacuumed (not counting, Last time at which this table was vacuumed by the autovacuum daemon, Last time at which this table was manually analyzed, Last time at which this table was analyzed by the autovacuum daemon, Number of times this table has been manually vacuumed (not counting, Number of times this table has been vacuumed by the autovacuum daemon, Number of times this table has been manually analyzed, Number of times this table has been analyzed by the autovacuum daemon, Number of index scans initiated on this index, Number of index entries returned by scans on this index, Number of live table rows fetched by simple index scans using this index, Number of disk blocks read from this table, Number of disk blocks read from all indexes on this table, Number of buffer hits in all indexes on this table, Number of disk blocks read from this table's TOAST table (if any), Number of buffer hits in this table's TOAST table (if any), Number of disk blocks read from this table's TOAST table indexes (if any), Number of buffer hits in this table's TOAST table indexes (if any), Number of disk blocks read from this index, Number of disk blocks read from this sequence, Number of times this function has been called, Total time spent in this function and all other functions called by it, in milliseconds, Total time spent in this function itself, not including other functions called by it, in milliseconds, Process ID of the server process handling the current session, Returns a record of information about the backend with the specified PID, or one record for each active backend in the system if, Returns the timestamp of the current statistics snapshot, Reset all statistics counters for the current database to zero (requires superuser privileges by default, but EXECUTE for this function can be granted to others.
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