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. The server process is waiting for some interaction with another server process. active: The backend is executing a query. (Conflicts occur only on standby servers; see pg_stat_database_conflicts for details.). The access functions for per-database statistics take a database OID as an argument to identify which database to report on. Waiting for a newly created timeline history file to reach durable storage. Waiting for truncate of mapping data during a logical rewrite. Waiting in main loop of startup process for WAL to arrive, during streaming recovery. The pg_stat_database view will contain one row for each database in the cluster, plus one for shared objects, showing database-wide statistics. Logical decoding plugins may optionally emit tracking messages; if they do not, the tracking mechanism will simply display NULL lag. Waiting for the page number needed to continue a parallel B-tree scan to become available. The IO:DataFileRead wait event occurs while data is Waiting to read or write a data page in memory. 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. Number of WAL files that have been successfully archived, Name of the WAL file most recently successfully archived, last_archived_time timestamp with time zone, Time of the most recent successful archive operation, Number of failed attempts for archiving WAL files, Name of the WAL file of the most recent failed archival operation, last_failed_time timestamp with time zone, Time of the most recent failed archival operation. please use 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. The pg_stat_bgwriter view will always have a single row, containing global data for the cluster. Waiting to ensure that a table selected for autovacuum still needs vacuuming. wait_event will identify the type of lock awaited. Possible values are: active: The backend is executing a query. to keep index reordering low and reduces its impact. The pg_stat_replication_slots view will contain one row per logical replication slot, showing statistics about its usage. Returns the text of this backend's most recent query. The type of event for which the backend is waiting, if any; otherwise NULL. PostgreSQL 's statistics collector is a subsystem that supports collection and reporting of information about server activity. (Conflicts occur only on standby servers; see, Number of temporary files created by queries in this database. Waiting for a buffered file to be truncated. This documentation is for an unsupported version of PostgreSQL. Waiting in WAL receiver to receive data from remote server. Waiting to elect a Parallel Hash participant to allocate more buckets. Waiting to read or update replication slot state. postgres 26 Heap_Insert Resets statistics for a single function in the current database to zero. Synchronous state of this standby server. There are also several other views, listed in Table28.2, available to show the results of statistics collection. Avoid PostgreSQL LWLock:buffer_content locks in Amazon Aurora: Tips and best practices. Therefore it is not safe to assume that all files older than last_archived_wal have also been successfully archived. Waiting for a replication slot control file to reach durable storage. Returns the time when this process was started. Waiting for WAL to reach durable storage during bootstrapping. 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 to elect a Parallel Hash participant to allocate more batches. See, One row per WAL sender process, showing statistics about replication to that sender's connected standby server. 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. The pg_stat_user_functions view will contain one row for each tracked function, showing statistics about executions of that function. Waiting for a newly created timeline history file to reach durable storage. I am not the DBA, but receive reports occasionally when an application is causing load on the system. Several predefined views, listed in Table28.1, are available to show the current state of the system. The pg_stat_wal_receiver view will contain only one row, showing statistics about the WAL receiver from that receiver's connected server. The WALWriteLock wait occurs while PostgreSQL flushes WAL records to disk or during a WAL segment switch.. How to reduce this wait . fastpath function call: The backend is executing a fast-path function. 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. 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. 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. PostgreSQL's cumulative statistics system supports collection and reporting of information about server activity. Wait Events of Type BufferPin, Table28.8. Waiting to read or write relation cache initialization file. Waiting for a write when creating a new WAL segment by copying an existing one. The pg_stat_subscription_stats view will contain one row per subscription. For details such as the functions' names, consult the definitions of the standard views. However, current-query information collected by track_activities is always up-to-date. Its purpose is for the same page to be read into the shared buffer. Waiting for the version file to be written while creating a database. It works like this: Current overall state of this backend. Waiting for other Parallel Hash participants to finish repartitioning. Waiting to add a message in shared invalidation queue. Waiting in main loop of checkpointer process. Number of transactions spilled to disk once the memory used by logical decoding to decode changes from WAL has exceeded logical_decoding_work_mem. Waiting in main loop of background writer process background worker. Waiting to read or update dynamic shared memory allocation information. Number of times WAL buffers were written out to disk via XLogWrite request. The parameter track_io_timing enables monitoring of block read and write times. Possible values are: Activity status of the WAL receiver process, First write-ahead log location used when WAL receiver is started, First timeline number used when WAL receiver is started, Last write-ahead log location already received and flushed to disk, the initial value of this field being the first log location used when WAL receiver is started, Timeline number of last write-ahead log location received and flushed to disk, the initial value of this field being the timeline number of the first log location used when WAL receiver is started, Send time of last message received from origin WAL sender, Receipt time of last message received from origin WAL sender, Last write-ahead log location reported to origin WAL sender, Time of last write-ahead log location reported to origin WAL sender, Replication slot name used by this WAL receiver. Presently, the collector can count accesses to tables and indexes in both disk-block and individual-row terms. Waiting to read or update notification messages. LWLock- buffer_mapping. 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. Table28.31.pg_statio_all_sequences View, Number of disk blocks read from this sequence. LWLock:buffer_mapping. 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 for SLRU data to reach durable storage following a page write. See, One row per connection (regular and replication), showing information about GSSAPI authentication and encryption used on this connection. When using the statistics to monitor collected data, it is important to realize that the information does not update instantaneously. Waiting for a write to the relation map file. See, One row for each sequence in the current database, showing statistics about I/O on that specific sequence. Note that this includes the transactions that are streamed and/or spilled. Waiting for I/O on a multixact offset buffer. See Table28.5 through Table28.13. Waiting for changes to a relation data file to reach durable storage. Waiting for the relation map file to reach durable storage. Waiting for a read from a timeline history file during a walsender timeline command. The access functions for per-database statistics take a database OID as an argument to identify which database to report on. Waiting for a read from the control file. It can also count calls to user-defined functions and the total time spent in each one. Waiting for data to reach durable storage while creating the data directory lock file. Waiting for a serialized historical catalog snapshot to reach durable storage. The argument can be bgwriter to reset all the counters shown in the pg_stat_bgwriter view, archiver to reset all the counters shown in the pg_stat_archiver view, wal to reset all the counters shown in the pg_stat_wal view or recovery_prefetch to reset all the counters shown in the pg_stat_recovery_prefetch view. Waiting for mapping data to reach durable storage during a logical rewrite. Waiting for an immediate synchronization of a relation data file to durable storage. In some cases, the name assigned by an extension will not be available in all server processes; so an LWLock wait event might be reported as just extension rather than the extension-assigned name. this form 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. Indexes can be used by simple index scans, bitmap index scans, and the optimizer. Alternatively, one can build custom views using the underlying statistics functions, as discussed in Section28.2.3. Waiting to associate a data block with a buffer in the buffer pool. Waiting to read or update transaction commit timestamps. wait_event will identify the specific wait point. Waiting to read or update shared notification state. Waiting between writes while performing a checkpoint. 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. Waiting for SSL while attempting connection. The parameter track_activities enables monitoring of the current command being executed by any server process. Waiting to read while creating the data directory lock file. Sometimes it may be more convenient to obtain just a subset of this information. Waiting for a write to a relation data file. See, One row per connection (regular and replication), showing information about SSL used on this connection. Waiting for a write to a relation data file. Type of current backend. Waiting for a newly initialized WAL file to reach durable storage. number of buffers needed by the current workload, The size of the shared buffer pool not being well balanced with the number of pages being evicted by other 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. 105 #define BUFFER_MAPPING_LWLOCK_OFFSET NUM_INDIVIDUAL_LWLOCKS. Wait event name if backend is currently waiting, otherwise NULL. You The pg_stat_user_functions view will contain one row for each tracked function, showing statistics about executions of that function. 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. 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 I/O on a sub-transaction SLRU buffer. The wait_event and state columns are independent. Waiting to read or record conflicting serializable transactions. Send time of last reply message received from standby server. Waiting in WAL receiver to establish connection to remote server. 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. Waiting to allocate a new transaction ID. If a backend is in the active state, it may or may not be waiting on some event. Waiting for a two phase state file to reach durable storage. See, One row for each tracked function, showing statistics about executions of that function. Number of transactions in this database that have been committed, Number of transactions in this database that have been rolled back, Number of disk blocks read in this database, Number of times disk blocks were found already in the buffer cache, so that a read was not necessary (this only includes hits in the PostgreSQL buffer cache, not the operating system's file system cache), Number of rows returned by queries in this database, Number of rows fetched by queries in this database, Number of rows inserted by queries in this database, Number of rows updated by queries in this database, Number of rows deleted by queries in this database, Number of queries canceled due to conflicts with recovery in this database. The parameter track_functions enables tracking of usage of user-defined functions. These access functions use a backend ID number, which ranges from one to the number of currently active backends. Ordinary users can only see all the information about their own sessions (sessions belonging to a role that they are a member of). ru> Date: 2015-11-19 14:04:28 Message-ID: 20151119170428.490de41d lp [Download RAW message or body] Thank you for the review. If this field is null, it indicates that the client is connected via a Unix socket on the server machine. 214 . The server process is waiting for activity on a socket connected to a user application. pg_blocking_pids function. IP address of the client connected to this WAL sender. 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.