The functions for per-function statistics take a function OID. 39919 LWLock buffer_mapping 5119 Client ClientRead 3116 IO DataFileRead . Waits for a buffer pin ( BufferPin ). See, One row per WAL sender process, showing statistics about replication to that sender's connected standby server. Waiting for a write while creating the data directory lock file. wait_event will identify the specific wait point. buffer_mapping | DBmarlin Docs and Knowledge Base See, One row for each sequence in the current database, showing statistics about I/O on that specific sequence. Waiting in main loop of logical launcher process. Such a system would show similar times while new WAL is being generated, but would differ when the sender becomes idle. If this field is null, it indicates that the client is connected via a Unix socket on the server machine. Waiting for a read of a logical mapping during reorder buffer management. Waiting to read or update information about synchronous replicas. Users interested in obtaining more detailed information on PostgreSQL I/O behavior are advised to use the PostgreSQL statistics views in combination with operating system utilities that allow insight into the kernel's handling of I/O. Indexes can be used by simple index scans, bitmap index scans, and the optimizer. See. Time at which these statistics were last reset. pg_stat_reset_replication_slot ( text ) void. fastpath function call: The backend is executing a fast-path function. Waiting for a read of a serialized historical catalog snapshot. The idx_tup_read and idx_tup_fetch counts can be different even without any use of bitmap scans, because idx_tup_read counts index entries retrieved from the index while idx_tup_fetch counts live rows fetched from the table. query performance - PostgreSQL LWLock: lock_manager issue - Database Waiting to elect a Parallel Hash participant to allocate the initial hash table. 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. Waiting for a write to update the control file. See, One row per database, showing database-wide statistics. Waiting for SSL while attempting connection. IP address of the client connected to this WAL sender. Waiting for I/O on a clog (transaction status) buffer. Waiting while sending synchronization requests to the checkpointer, because the request queue is full. This has no effect in a quorum-based synchronous replication. Waiting to acquire a speculative insertion lock. This effect can mean that you have a small shared buffers setting. Waiting to access the sub-transaction SLRU cache. Copyright 1996-2023 The PostgreSQL Global Development Group, PostgreSQL 15.2, 14.7, 13.10, 12.14, and 11.19 Released, 28.2.1. Waiting for an update to the control file to reach durable storage. The next use of statistical information will (when in snapshot mode) cause a new snapshot to be built or (when in cache mode) accessed statistics to be cached. Waiting to acquire a lock on page of a relation. Waiting to get a snapshot or clearing a transaction id at transaction end. Waiting for a read of a serialized historical catalog snapshot. Waiting in WAL receiver to establish connection to remote server. The following wait events are a subset of the list in Amazon Aurora PostgreSQL wait events. Waiting for a write while adding a line to the data directory lock file. Also, the collector itself emits a new report at most once per PGSTAT_STAT_INTERVAL milliseconds (500 ms unless altered while building the server). LWLock in PostgreSQL - Programmer Sought Waiting for other Parallel Hash participants to finish hashing the inner relation. See, One row for each table in the current database, showing statistics about accesses to that specific table. Waiting to elect a Parallel Hash participant to decide on future batch growth. Waiting to access the multixact offset SLRU cache. Waiting to acquire a lock on a non-relation database object. PostgreSQL accesses certain on-disk information via SLRU (simple least-recently-used) caches. From pg_stat_activity i noticed that the wait_event_type and wait_event of these queries is as follows: This can be used to gauge the delay that synchronous_commit level on incurred while committing if this server was configured as a synchronous standby. pg_stat_get_backend_userid ( integer ) oid. For more information, see LWLock:buffer_mapping. These access functions use a backend ID number, which ranges from one to the number of currently active backends. (See Chapter20 for details about setting configuration parameters.). Resets statistics to zero for a single SLRU cache, or for all SLRUs in the cluster. This function is restricted to superusers by default, but other users can be granted EXECUTE to run the function. 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. For better performance, stats_temp_directory can be pointed at a RAM-based file system, decreasing physical I/O requirements. 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. 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. WALWriteLock | DBmarlin Docs and Knowledge Base The LWLock:BufferIO event occurs when Aurora PostgreSQL or RDS for PostgreSQL is waiting for other processes to finish their input/output (I/O) operations when concurrently trying to access a page. Waiting in background writer process, hibernating. The pg_stat_subscription_stats view will contain one row per subscription. Waiting for a serialized historical catalog snapshot to reach durable storage. Users interested in obtaining more detailed information on PostgreSQL I/O behavior are advised to use the PostgreSQL statistics collector in combination with operating system utilities that allow insight into the kernel's handling of I/O. Extensions can register their specific waits ( Extension ). 214 . The pg_stat_wal view will always have a single row, containing data about WAL activity of the cluster. Waiting to read or update transaction status. See, Only one row, showing statistics about the WAL receiver from that receiver's connected server. Choose the appropriate target Region. 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. If the current query is the first of its transaction, this column is equal to the query_start column. 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. See. Waiting for a write while initializing a new WAL file. Waiting to access the commit timestamp SLRU cache. Waiting for a replication slot control file to reach durable storage. Resetting these counters can cause autovacuum to not perform necessary work, which can cause problems such as table bloat or out-dated table statistics. The argument can be one of CommitTs, MultiXactMember, MultiXactOffset, Notify, Serial, Subtrans, or Xact to reset the counters for only that entry. The fields returned are a subset of those in the pg_stat_activity view. Connection string used by this WAL receiver, with security-sensitive fields obfuscated. 106 . When the number of actual disk reads is much smaller than the number of buffer hits, then the cache is satisfying most read requests without invoking a kernel call. Number of deadlocks detected in this database. Thanks for letting us know this page needs work. Waiting for another process to be attached to a shared message queue. 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. Waiting for a read of the relation map file. Waiting for other Parallel Hash participants to finish loading a hash table. The pg_stat_user_indexes and pg_stat_sys_indexes views contain the same information, but filtered to only show user and system indexes respectively. Common causes for the LWLock:BufferIO event to appear in top waits include the following: Multiple backends or connections trying to access the same page that's The per-table and per-index functions take a table or index OID. Table28.19.pg_stat_subscription_stats View, Number of times an error occurred while applying changes, Number of times an error occurred during the initial table synchronization. Waiting in main loop of syslogger process. 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. Waiting to add or examine predicate lock information. My application is using Postgres as DBMS, the version of Postgres that i'm using is 10.3 with the extension Postgis installed. Waiting for the page number needed to continue a parallel B-tree scan to become available. pg_stat_get_activity ( integer ) setof record. might need to increase it or scale up your DB instance class. If state is active this field shows the currently executing query. Type of current backend. All temporary files are counted, regardless of why the temporary file was created (e.g., sorting or hashing), and regardless of the, Total amount of data written to temporary files by queries in this database. Waiting in main loop of logical replication apply process. Waiting for a write of a WAL page during bootstrapping. Waiting for a write of a WAL page during bootstrapping. See, Only one row, showing statistics about blocks prefetched during recovery. Only directly connected standbys are listed; no information is available about downstream standby servers. Please refer to your browser's Help pages for instructions. True if GSSAPI authentication was used for this connection. We're sorry we let you down. Waiting to access a shared TID bitmap during a parallel bitmap index scan. Waiting for parallel query dynamic shared memory allocation. Waiting to add a message to the shared catalog invalidation queue. A backend process is waiting to associate a data block with a buffer in the shared buffer pool.