Waiting to send bytes to a shared message queue. See Table28.5 through Table28.13. Current overall state of this backend. See. 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. See, At least one row per subscription, showing information about the subscription workers. Waiting for parallel bitmap scan to become initialized. Waiting to add a message to the shared catalog invalidation queue. 214 . Waiting for a read during reorder buffer management. 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. sync: This standby server is synchronous. replication_slot_io: Waiting for I/O on a replication slot. Therefore, while holding an exclusive lock, a process prevents other processes from acquiring a shared or exclusive lock. Waiting to read or update vacuum-related information for a B-tree index. 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. Thanks for letting us know we're doing a good job! 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. However, they are also used to ensure mutual exclusion for certain internal operations such as relation extension. 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. 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. postgres 26 Heap_Insert 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. Resets statistics for a single table or index in the current database or shared across all databases in the cluster to zero. 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. Connection string used by this WAL receiver, with security-sensitive fields obfuscated. This has no effect in a quorum-based synchronous replication. Waiting for other Parallel Hash participants to finish inserting tuples into new buckets. 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. 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. LWLock: The backend is waiting for a lightweight lock. Waiting in main loop of autovacuum launcher process. For example, to show the PIDs and current queries of all backends: Table28.20. Waiting for a buffered file to be truncated. Waiting to read or update replication slot state. Indexes can be used by simple index scans, bitmap index scans, and the optimizer. Serial number of the client certificate, or NULL if no client certificate was supplied or if SSL is not in use on this connection. The track_functions parameter controls exactly which functions are tracked. Waiting for truncate of mapping data during a logical rewrite. See, One row for each tracked function, showing statistics about executions of that function. Table28.6. Waiting to manage an extension's space allocation in shared memory. Increase the number of wal_buffers available to the database. The full object locks which last (usually) for the duration of a transaction and which you can see in pg_locks have info about them stored in shared memory. BufferCacheHitRatio metric dips. Priority of this standby server for being chosen as the synchronous standby in a priority-based synchronous replication. Waiting to write a protocol message to a shared message queue. Top-level transaction identifier of this backend, if any. Waiting to access a shared TID bitmap during a parallel bitmap index scan. Waiting to create, drop or use a replication origin. Some of the information in the dynamic statistics views shown in Table28.1 is security restricted. The parameter track_wal_io_timing enables monitoring of WAL write times. proc: Waiting to read or update the fast-path lock information. Waiting for other Parallel Hash participants to finish loading a hash table. Table28.19. See, One row for each table in the current database, showing statistics about I/O on that specific table. For details such as the functions' names, consult the definitions of the standard views. See, One row only, showing statistics about WAL activity. This lock is used to handle multiple sessions that all require access to the same Waiting for SLRU data to reach durable storage during a checkpoint or database shutdown. Possible values are: Wait event name if backend is currently waiting, otherwise NULL. quorum: This standby server is considered as a candidate for quorum standbys. Waiting for an elected Parallel Hash participant to decide on future batch growth. There is no order to the granting of LWLocks and in a high concurrency system this can cause contention. pg_stat_reset_single_table_counters ( oid ) void. Waiting in main loop of syslogger process. True if GSSAPI encryption is in use on this connection. Waiting for a write to a replication slot control file. The lag times reported in the pg_stat_replication view are measurements of the time taken for recent WAL to be written, flushed and replayed and for the sender to know about it. Resets statistics for a single function in the current database to zero. When recovery is performed at server start (e.g., after immediate shutdown, server crash, and point-in-time recovery), all statistics counters are reset. BK_1935: "IObuffer_locks,ControlLock()"IOControlLockControlLockIOSlruSharedData. 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. Waiting for logical rewrite mappings to reach durable storage during a checkpoint. Host name of the connected client, as reported by a reverse DNS lookup of, TCP port number that the client is using for communication with this backend, or. The wait_event and state columns are independent. idle: The backend is waiting for a new client command. Its purpose is for the same page to be read into the shared buffer. Waiting for startup process to send initial data for streaming replication. Waiting for recovery conflict resolution for a vacuum cleanup. See Table28.4. Waiting in main loop of WAL receiver process. Waiting for an immediate synchronization of a relation data file to durable storage. The pg_stat_replication_slots view will contain one row per logical replication slot, showing statistics about its usage. Waiting in main loop of WAL receiver process. The per-table and per-index functions take a table or index OID. Number of times in-progress transactions were streamed to the decoding output plugin while decoding changes from WAL for this slot. 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. pg_stat_get_backend_client_addr ( integer ) inet. Waiting in main loop of checkpointer process. 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. Waiting for background worker to shut down. The IO:DataFileRead wait event occurs while data is Waiting to read or update dynamic shared memory allocation information. Waiting to read or write a data page in memory. Waiting to read or update a process' fast-path lock information. See, One row per replication slot, showing statistics about the replication slot's usage. Amount of decoded transaction data spilled to disk while performing decoding of changes from WAL for this slot. It also tracks the total number of rows in each table, and information about . When using the cumulative statistics views and functions to monitor collected data, it is important to realize that the information does not update instantaneously. This counts top-level transactions only, and is not incremented for subtransactions. The columns wal_distance, block_distance and io_depth show current values, and the other columns show cumulative counters that can be reset with the pg_stat_reset_shared function. Waiting for a read during a file copy operation. The wait_event and state columns are independent. This event type indicates a process waiting for activity in its main processing loop. For details such as the functions' names, consult the definitions of the standard views. Waiting for a newly initialized WAL file to reach durable storage. Waits for a buffer pin ( BufferPin ). Waiting in a cost-based vacuum delay point. See, One row per database, showing database-wide statistics. Name of the user logged into this backend, Name of the application that is connected to this backend. Table28.17.pg_stat_recovery_prefetch View, Number of blocks prefetched because they were not in the buffer pool, Number of blocks not prefetched because they were already in the buffer pool, Number of blocks not prefetched because they would be zero-initialized, Number of blocks not prefetched because they didn't exist yet, Number of blocks not prefetched because a full page image was included in the WAL, Number of blocks not prefetched because they were already recently prefetched, How many bytes ahead the prefetcher is looking, How many blocks ahead the prefetcher is looking, How many prefetches have been initiated but are not yet known to have completed, Process ID of the subscription worker process, OID of the relation that the worker is synchronizing; null for the main apply worker, Last write-ahead log location received, the initial value of this field being 0. If this field is null, it indicates that the client is connected via a Unix socket on the server machine. If you've got a moment, please tell us how we can make the documentation better. Using pg_stat_reset() also resets counters that autovacuum uses to determine when to trigger a vacuum or an analyze. active: The backend is executing a query. Time elapsed between flushing recent WAL locally and receiving notification that this standby server has written, flushed and applied it. If a backend is in the active state, it may or may not be waiting on some event. Waiting to read or update background worker state. pg_stat_get_backend_wait_event ( integer ) text. Waiting for I/O on a transaction status SLRU buffer. Waiting to read or update the state of logical replication workers. The pg_stat_bgwriter view will always have a single row, containing global data for the cluster. Time when this process' current transaction was started, or null if no transaction is active. Waiting to read or update information about. 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. OID of this database, or 0 for objects belonging to a shared relation. PostgreSQL also supports reporting dynamic information about exactly what is going on in the system right now, such as the exact command currently being executed by other server processes, and which other connections exist in the system. PostgreSQL's cumulative statistics system supports collection and reporting of information about server activity. streaming: This WAL sender is streaming changes after its connected standby server has caught up with the primary. Alternatively, one can build custom views using the underlying cumulative statistics functions, as discussed in Section28.2.24. Waiting to associate a data block with a buffer in the buffer pool. async: This standby server is asynchronous. The pg_stat_user_tables and pg_stat_sys_tables views contain the same information, but filtered to only show user and system tables respectively. Waiting for WAL files required for a backup to be successfully archived. The pg_statio_user_tables and pg_statio_sys_tables views contain the same information, but filtered to only show user and system tables respectively. 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. Normally, WAL files are archived in order, oldest to newest, but that is not guaranteed, and does not hold under special circumstances like when promoting a standby or after crash recovery. The parameter track_functions enables tracking of usage of user-defined functions. For client backends, this is the time the client connected to the server. Presently, the collector can count accesses to tables and indexes in both disk-block and individual-row terms. buffer_mapping: Waiting to associate a data block with a buffer in the buffer pool. ), 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). Waiting for a write of mapping data during a logical rewrite. Extensions can register their specific waits ( Extension ). If enabled, calls to user-defined functions and the total time spent in each one are counted as well. Pointers to free buffers and to the next victim are protected by one buffer strategy lock spinlock. See. Thus, the server expects something to happen that is independent of its internal processes. Waiting for the control file to reach durable storage. Waiting to read data from the client while establishing a GSSAPI session. See, One row for each index in the current database, showing statistics about I/O on that specific index. Waiting to fill a dynamic shared memory backing file with zeroes. See, One row per database, showing database-wide statistics about query cancels due to conflict with recovery on standby servers. Waiting for confirmation from a remote server during synchronous replication. The pg_stat_all_indexes view will contain one row for each index in the current database, showing statistics about accesses to that specific index. Waiting for other Parallel Hash participants to finish repartitioning. gorthx on Twitter 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. This can be used to gauge the delay that. The server process is waiting for a timeout to expire. Waiting for I/O on a clog (transaction status) buffer. Waiting to setup, drop or use replication origin. This is consistent with the goal of measuring synchronous commit and transaction visibility delays for recent write transactions. This can be used to gauge the delay that synchronous_commit level remote_write incurred while committing if this server was configured as a synchronous standby.
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