potential: This standby server is now asynchronous, but can potentially become synchronous if one of current synchronous ones fails. Monitoring systems should choose whether to represent this as missing data, zero or continue to display the last known value. See, One row only, showing statistics about the WAL archiver process's activity. pg_stat_get_snapshot_timestamp () timestamp with time zone, Returns the timestamp of the current statistics snapshot, or NULL if no statistics snapshot has been taken. This field is truncated if the DN field is longer than NAMEDATALEN (64 characters in a standard build). Possible values are: Wait event name if backend is currently waiting, otherwise NULL. Waiting to access the list of predicate locks held by serializable transactions. For more information, see LWLock:buffer_mapping. The following wait events are a subset of the list in Amazon Aurora PostgreSQL wait events. See Section30.5 for more information about the internal WAL function XLogWrite. Waiting for a write of mapping data during a logical rewrite. Waiting for a read during a file copy operation. Therefore it is not safe to assume that all files older than last_archived_wal have also been successfully archived. 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. Waiting for I/O on a clog (transaction status) buffer. If the argument is NULL, resets statistics for all the replication slots. Waiting for data to reach durable storage while adding a line to the data directory lock file. Lag times work automatically for physical replication. Waiting to get the start location of a scan on a table for synchronized scans. A transaction can also see its own statistics (as yet untransmitted to the collector) in the views pg_stat_xact_all_tables, pg_stat_xact_sys_tables, pg_stat_xact_user_tables, and pg_stat_xact_user_functions. Principal used to authenticate this connection, or NULL if GSSAPI was not used to authenticate this connection. Waiting to read or update replication slot state. * The BM_IO_IN_PROGRESS flag acts as a kind of lock, used to wait for I/O on a: buffer to complete (and in releases before 14, it was accompanied by a: per-buffer LWLock). 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. Waiting for the relation map file to reach durable storage. Its This facility is independent of the cumulative statistics system. Waiting to ensure that a table selected for autovacuum still needs vacuuming. Waiting in main loop of syslogger process. Time when this process' current transaction was started, or null if no transaction is active. Aurora PostgreSQL wait events PDF RSS The following table lists the wait events for Aurora PostgreSQL that most commonly indicate performance problems, and summarizes the most common causes and corrective actions. I am not the DBA, but receive reports occasionally when an application is causing load on the system. Waiting to read or update replication slot state. Attempts to free it PostgreSQL Entangled in Locks - PGCon Waiting for a read of a two phase state file. For better performance, stats_temp_directory can be pointed at a RAM-based file system, decreasing physical I/O requirements. Returns the OID of the user logged into this backend. This field will only be non-null for IP connections, and only when log_hostname is enabled. Number of blocks zeroed during initializations, Number of times disk blocks were found already in the SLRU, so that a read was not necessary (this only includes hits in the SLRU, not the operating system's file system cache), Number of disk blocks written for this SLRU, Number of blocks checked for existence for this SLRU, Number of flushes of dirty data for this SLRU. 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. Monitoring systems should choose whether to represent this as missing data, zero or continue to display the last known value. Name of the user logged into this backend, Name of the application that is connected to this backend. Waiting to create or drop the tablespace. Waiting to manage an extension's space allocation in shared memory. Waiting for a write of a serialized historical catalog snapshot. 202302_Serendipity_Shy_CSDN TCP port number that the client is using for communication with this backend, or -1 if a Unix socket is used. See, One row for each tracked function, showing statistics about executions of that function. However, they are also used to ensure mutual exclusion for certain internal operations such as relation extension. might need to increase it or scale up your DB instance class. This is controlled by configuration parameters that are normally set in postgresql.conf. IO: The server process is waiting for a IO to complete. Copyright 1996-2023 The PostgreSQL Global Development Group, PostgreSQL 15.2, 14.7, 13.10, 12.14, and 11.19 Released, 28.2.1. backup: This WAL sender is sending a backup. Waiting for a relation data file to be truncated. Waiting to read or write a data page in memory. Waiting for SLRU data to reach durable storage following a page write. See, At least one row per subscription, showing information about the subscription workers. active: The backend is executing a query. Number of temporary files created by queries in this database. The WALWriteLock wait occurs while PostgreSQL flushes WAL records to disk or during a WAL segment switch.. How to reduce this wait . Number of backends currently connected to this database. 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. 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. pg_stat_get_backend_userid ( integer ) oid. Calling, Reset statistics for a single table or index in the current database to zero (requires superuser privileges by default, but EXECUTE for this function can be granted to others), Reset statistics for a single function in the current database to zero (requires superuser privileges by default, but EXECUTE for this function can be granted to others), Set of currently active backend ID numbers (from 1 to the number of active backends), Time when the most recent query was started, IP address of the client connected to this backend, TCP port number that the client is using for communication, Wait event type name if backend is currently waiting, otherwise NULL. Waiting in WAL receiver to establish connection to remote server. Current WAL sender state. idle in transaction (aborted): This state is similar to idle in transaction, except one of the statements in the transaction caused an error. > However, someone with deeper knowledge of page pinning and buffer manager > internals could certainly devise a better solution. This wait event information is relevant for all Aurora PostgreSQL 13 versions. Waiting for a logical replication remote server to send data for initial table synchronization. Waiting during recovery when WAL data is not available from any source (. Here is an example of how wait events can be viewed. Waiting to access the shared per-process data structures (typically, to get a snapshot or report a session's transaction ID). Waiting for group leader to clear transaction id at transaction end. (The path case can be distinguished because it will always be an absolute path, beginning with /.). It is used per the rules above. Using pg_stat_reset() also resets counters that autovacuum uses to determine when to trigger a vacuum or an analyze. PostgreSQL 15.2, 14.7, 13.10, 12.14, and 11.19 Released, 28.2.1. Waiting for other Parallel Hash participants to finish inserting tuples into new buckets. Waiting in main loop of background writer process. 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. Waiting to read while creating the data directory lock file. See, One row for each index in the current database, showing statistics about accesses to that specific index. See, One row for each sequence in the current database, showing statistics about I/O on that specific sequence. Note that only tables, indexes, and functions in the current database can be seen with these functions. If the argument is other (or indeed, any unrecognized name), then the counters for all other SLRU caches, such as extension-defined caches, are reset. The LWLock:BufferIO wait event precedes the IO:DataFileRead wait event. DN of the issuer of the client certificate, or NULL if no client certificate was supplied or if SSL is not in use on this connection. Waiting to access a parallel query's information about type modifiers that identify anonymous record types. a page) has to be retrieved outside the shared buffer pool. 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. The new locking scheme avoids grabbing system-wide exclusive locks in common code paths. Waiting for parallel workers to finish computing. replication_origin: Waiting to read or update the replication progress. Returns the text of this backend's most recent query. See, One row for each table in the current database, showing statistics about accesses to that specific table. 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. Waiting to read or update background worker state. The LWLock:BufferIO event occurs when RDS for PostgreSQL or Aurora PostgreSQL is waiting for other processes to finish their I/O operations. NULL if this process is a parallel group leader or does not participate in parallel query. Possible values are: async: This standby server is asynchronous. This includes the sync time when wal_sync_method is either open_datasync or open_sync. Waiting for base backup to read from a file. See, One row for each table in the current database, showing statistics about accesses to that specific table. Text of this backend's most recent query. A backend process is waiting to associate a data block with a buffer in the shared buffer pool. disabled: This state is reported if track_activities is disabled in this backend. Number of backends currently connected to this database, or NULL for shared objects. Waiting to access the multixact member SLRU cache. 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.

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