See, One row for each index in the current database, showing statistics about I/O on that specific index. This is controlled by configuration parameters that are normally set in postgresql.conf. Waiting in main loop of background writer process background worker. Number of disk blocks read from this index. Waiting to ensure that the table it has selected for a vacuum still needs vacuuming. See, One row per subscription, showing statistics about errors. If a backend is in the active state, it may or may not be waiting on some event. We're sorry we let you down. pg_stat_get_backend_activity_start ( integer ) timestamp with time zone. Waiting for logical rewrite mappings to reach durable storage. Waiting to apply WAL during recovery because of a delay setting. If you see anything in the documentation that is not correct, does not match ), Reset some cluster-wide statistics counters to zero, depending on the argument (requires superuser privileges by default, but EXECUTE for this function can be granted to others). When a server, including a physical replica, shuts down cleanly, a permanent copy of the statistics data is stored in the pg_stat subdirectory, so that statistics can be retained across server restarts. LWLock:BufferIO - Amazon Aurora Waiting for a newly initialized WAL file to reach durable storage. Number of decoded transactions sent to the decoding output plugin for this slot. Waiting for a timeline history file received via streaming replication to reach durable storage. Waiting to write a protocol message to a shared message queue. 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. postgres 26 Heap_Insert Activity: The server process is idle. See, At least one row per subscription, showing information about the subscription workers. If this field is null, it indicates either that the client is connected via a Unix socket on the server machine or that this is an internal process such as autovacuum. postgres/README at master postgres/postgres GitHub All temporary files are counted, regardless of why the temporary file was created, and regardless of the log_temp_files setting. Waiting to access the list of predicate locks held by the current serializable transaction during a parallel query. Sometimes it may be more convenient to obtain just a subset of this information. Top-level transaction identifier of this backend, if any. Client: The server process is waiting for some activity on a socket from user applications, and that the server expects something to happen that is independent from its internal processes. Waiting for I/O on a transaction status SLRU buffer. quorum: This standby server is considered as a candidate for quorum standbys. The buffer_mapping LWLock wait event will be . Some of the information in the dynamic statistics views shown in Table28.1 is security restricted. postgresql - How to get rid of BufferMapping? - Database Administrators Also, the collector itself emits a new report at most once per PGSTAT_STAT_INTERVAL milliseconds (500 ms unless altered while building the server). But processes can also await other events: Waits for input/output ( IO) occur when a process needs to read or write data. Possible values are: Wait event name if backend is currently waiting, otherwise NULL. Java,java,file,io,buffer,Java,File,Io,Buffer,Java10242^n If the argument is NULL, all counters shown in the pg_stat_slru view for all SLRU caches are reset. 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). Therefore, while holding an exclusive lock, a process prevents other processes from acquiring a shared or exclusive lock. Waiting to read or write relation cache initialization file. This should not be used for data integrity checks. The statistics collector transmits the collected information to other PostgreSQL processes through temporary files. For more information on lightweight locks, see Locking Overview. This is a feature, not a bug, because it allows you to perform several queries on the statistics and correlate the results without worrying that the numbers are changing underneath you. wait_event will identify the specific wait point. The reported lag times are not predictions of how long it will take for the standby to catch up with the sending server assuming the current rate of replay. Additional Statistics Functions. LWLock:BufferIO. The LWLock:BufferIO event occurs when Aurora PostgreSQL or RDS for PostgreSQL is waiting for other processes to True if GSSAPI encryption is in use on this connection. Possible values are: Top-level transaction identifier of this backend, if any. When the buffer manager receives a request, PostgreSQL uses the buffer_tag of the desired page. IPC: The server process is waiting for some activity from another process in the server. Waiting for a write during reorder buffer management. pg_stat_get_backend_wait_event ( integer ) text. Waiting to add a message to the shared catalog invalidation queue. Alone the requirement of separate fsyncs and everything is pretty bothersome. Waiting for an update to the control file to reach durable storage. Waiting when WAL data is not available from any kind of sources (local, archive or stream) before trying again to retrieve WAL data, at recovery. The parameter track_wal_io_timing enables monitoring of WAL write times. In particular, when the standby has caught up completely, pg_stat_replication shows the time taken to write, flush and replay the most recent reported WAL location rather than zero as some users might expect. By default the query text is truncated at 1024 bytes; this value can be changed via the parameter track_activity_query_size. Waiting in main loop of autovacuum launcher process. Waiting in background writer process, hibernating. Time at which the last data page checksum failure was detected in this database (or on a shared object), or NULL if data checksums are not enabled. Waiting to read or update multixact offset mappings. Javascript is disabled or is unavailable in your browser. 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. Waiting to access the shared per-process data structures (typically, to get a snapshot or report a session's transaction ID). Resets all statistics counters for the current database to zero. pg_stat_get_backend_wait_event_type ( integer ) text. See, One row per connection (regular and replication), showing information about SSL used on this connection. Time when this process was started. So the displayed information lags behind actual activity. The parameter track_io_timing enables monitoring of block read and write times. There are also several other views, listed in Table28.2, available to show the accumulated statistics. These access functions use a backend ID number, which ranges from one to the number of currently active backends. Waiting to read or update old snapshot control information. In order to write the disk block into buffer memory, the buffer cache's hash table entry needs updating. idle in transaction: The backend is in a transaction, but is not currently executing a query. Waiting for a read while adding a line to the data directory lock file. Sometimes it may be more convenient to obtain just a subset of this information. For details such as the functions' names, consult the definitions of the standard views. Waiting to read or update dynamic shared memory allocation information. 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. The pg_stat_bgwriter view will always have a single row, containing global data for the cluster. If the argument is NULL, reset statistics for all subscriptions. Waiting for a relation data file to be truncated. Note that this includes the transactions that are streamed and/or spilled. Waiting for a write to the relation map file. Normally these parameters are set in postgresql.conf so that they apply to all server processes, but it is possible to turn them on or off in individual sessions using the SET command. Waiting for a replication slot control file to reach durable storage. Waiting to read or update the last value set for the transaction timestamp. Waiting to read or write a data page in memory. See, One row for each backend (including autovacuum worker processes) running, One row only, showing statistics about the WAL archiver process's activity. Process ID of a backend or WAL sender process, Version of SSL in use, or NULL if SSL is not in use on this connection, Name of SSL cipher in use, or NULL if SSL is not in use on this connection, Number of bits in the encryption algorithm used, or NULL if SSL is not used on this connection. Waiting for logical rewrite mappings to reach durable storage. @ LWTRANCHE_REPLICATION_SLOT_IO. Waiting for a read of a timeline history file. Waiting for mapping data to reach durable storage during a logical rewrite. A process can wait for the data needed from a client ( Client) or another process ( IPC ). Resets statistics of the replication slot defined by the argument. Waiting for a serialized historical catalog snapshot to reach durable storage. Time elapsed between flushing recent WAL locally and receiving notification that this standby server has written, flushed and applied it. PostgreSQL is one of the most popular open-source databases in the world and has successful implementations across several mission-critical environments across various domains, using real-time high-end OLTP applications performing millions and billions of transactions per day. Another important point is that when a server process is asked to display any of these statistics, it first fetches the most recent report emitted by the collector process and then continues to use this snapshot for all statistical views and functions until the end of its current transaction. See, One row per replication slot, showing statistics about the replication slot's usage. Additional functions related to the cumulative statistics system are listed in Table28.34. The IO:DataFileRead wait event occurs while data is Each individual server process flushes out accumulated statistics to shared memory just before going idle, but not more frequently than once per PGSTAT_MIN_INTERVAL milliseconds (1 second unless altered while building the server); so a query or transaction still in progress does not affect the displayed totals and the displayed information lags behind actual activity. Similarly, information about the current queries of all sessions is collected when any such information is first requested within a transaction, and the same information will be displayed throughout the transaction. Returns the time when this process was started. Presently, the collector can count accesses to tables and indexes in both disk-block and individual-row terms. 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. Waiting for confirmation from a remote server during synchronous replication. 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. This lock is used to handle multiple sessions that all require access to the same Waiting for truncate of mapping data during a logical rewrite. TCP port number that the client is using for communication with this WAL sender, or -1 if a Unix socket is used, Time when this process was started, i.e., when the client connected to this WAL sender. replication_origin: Waiting to read or update the replication progress. It is quite possible that user has registered the tranche in one of the backends (by having allocation in dynamic shared memory) in which case other backends won't have that information, so we display extension for such cases. Waiting to read while creating the data directory lock file. postgres 51 LWLock--2_Serendipity_Shy-CSDN Waiting to access the list of finished serializable transactions. OID of this database, or 0 for objects belonging to a shared relation. Detailed Description . 202302_Serendipity_Shy_CSDN Returns the time when the backend's most recent query was started. Waiting for a read when creating a new WAL segment by copying an existing one. Since collection of statistics adds some overhead to query execution, the system can be configured to collect or not collect information. Serial number of the client certificate, or NULL if no client certificate was supplied or if SSL is not in use on this connection. I am not the DBA, but receive reports occasionally when an application is causing load on the system. Waiting for an elected Parallel Hash participant to allocate more batches. See, One row per SLRU, showing statistics of operations. If this field is null, it indicates that the client is connected via a Unix socket on the server machine. If enabled, calls to user-defined functions and the total time spent in each one are counted as well. Waiting to read or update sub-transaction information. See, One row per connection (regular and replication), showing information about SSL used on this connection. Time spent reading data file blocks by backends in this database, in milliseconds (if track_io_timing is enabled, otherwise zero), Time spent writing data file blocks by backends in this database, in milliseconds (if track_io_timing is enabled, otherwise zero), Time spent by database sessions in this database, in milliseconds (note that statistics are only updated when the state of a session changes, so if sessions have been idle for a long time, this idle time won't be included), Time spent executing SQL statements in this database, in milliseconds (this corresponds to the states active and fastpath function call in pg_stat_activity), idle_in_transaction_time double precision, Time spent idling while in a transaction in this database, in milliseconds (this corresponds to the states idle in transaction and idle in transaction (aborted) in pg_stat_activity), Total number of sessions established to this database, Number of database sessions to this database that were terminated because connection to the client was lost, Number of database sessions to this database that were terminated by fatal errors, Number of database sessions to this database that were terminated by operator intervention. Waiting to read or update dynamic shared memory state. Alternatively, you can invoke pg_stat_clear_snapshot(), which will discard the current transaction's statistics snapshot (if any). Waiting to read or update a process' fast-path lock information. For tranches registered by extensions, the name is specified by extension and this will be displayed as wait_event. The counter gets incremented for both top-level transactions and subtransactions. Normally these parameters are set in postgresql.conf so that they apply to all server processes, but it is possible to turn them on or off in individual sessions using the SET command. Table28.15.pg_stat_replication_slots View, A unique, cluster-wide identifier for the replication slot. Waiting to update the relation map file used to store catalog to filenode mapping. Waiting for a write to a replication slot control file. If the state is active and wait_event is non-null, it means that a query is being executed, but is being blocked somewhere in the system. When using the cumulative statistics views and functions to monitor collected data, it is important to realize that the information does not update instantaneously. It also tracks the total number of rows in each table, and information about . Superusers and roles with privileges of built-in role pg_read_all_stats (see also Section22.5) can see all the information about all sessions. Returns the set of currently active backend ID numbers (from 1 to the number of active backends). pg_stat_get_backend_client_port ( integer ) integer. 213 * Prior to PostgreSQL 9.4, we used an enum type called LWLockId to refer. Waiting in main loop of background writer process. The function pg_stat_get_backend_idset provides a convenient way to generate one row for each active backend for invoking these functions. Waiting for a read from a replication slot control file. Waiting for parallel bitmap scan to become initialized.
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