lwlock buffer_io postgres lwlock buffer_io postgres

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. Waiting for activity from child process when executing. Waiting to replace a page in WAL buffers. Therefore, while holding an exclusive lock, a process prevents other processes from acquiring a shared or exclusive lock. Waiting for a read during recheck of the data directory lock file. Alternatively, you can invoke pg_stat_clear_snapshot(), which will discard the current transaction's statistics snapshot (if any). IO: The server process is waiting for a IO to complete. Using pg_stat_reset() also resets counters that autovacuum uses to determine when to trigger a vacuum or an analyze. Waiting to update limit on notification message storage. It works like this: Waiting to find or allocate space in shared memory. Lag times work automatically for physical replication. Waiting to write zero bytes to a dynamic shared memory backing file. See, At least one row per subscription, showing information about the subscription workers. Another important point is that when a server process is asked to display any of the accumulated statistics, accessed values are cached until the end of its current transaction in the default configuration. The parameter track_counts controls whether cumulative statistics are collected about table and index accesses. 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. Waiting to read or update vacuum-related information for a B-tree index. A process acquires an LWLock in a shared mode to read from the buffer and an exclusive mode to write to the buffer. Waiting to read or update transaction status. Waiting for a write of a WAL page during bootstrapping. Time at which these statistics were last reset. Simple test for lock_waits log messages. This field will only be non-null for IP connections, and only when log_hostname is enabled. 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 Waiting for a read from a relation data file. Waiting for a replication origin to become inactive so it can be dropped. True if GSSAPI encryption is in use 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. The statistics collector transmits the collected information to other PostgreSQL processes through temporary files. potential: This standby server is now asynchronous, but can potentially become synchronous if one of current synchronous ones fails. Time elapsed between flushing recent WAL locally and receiving notification that this standby server has written and flushed it (but not yet applied it). Waiting for a read of a two phase state file. finish their input/output (I/O) operations when concurrently trying to access a page. 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. This is used by system processes waiting for activity in their main processing loop. The parameter track_activities enables monitoring of the current command being executed by any server process. Waiting in main loop of logical launcher process. This and other streaming counters for this slot can be used to tune logical_decoding_work_mem. PostgreSQL utilizes lightweight locks (LWLocks) to synchronize and control access to the buffer content. Waiting for a write to a replication slot control file. Waiting for stats dynamic shared memory allocator access, Waiting for stats shared memory hash table access, Waiting for shared memory stats data access. The server process is waiting for a timeout to expire. Waiting to get the start location of a scan on a table for synchronized scans. Waiting to read or update the state of prepared transactions. The server process is waiting for a lightweight lock. 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_stat_user_tables and pg_stat_sys_tables views contain the same information, but filtered to only show user and system tables respectively. 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. Alternatively, one can build custom views using the underlying statistics functions, as discussed in Section28.2.3. Waiting in main loop of archiver process. 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. Port number of the PostgreSQL instance this WAL receiver is connected to. The parameter track_io_timing enables monitoring of block read and write times. See, One row per subscription, showing statistics about errors. Number of in-progress transactions streamed to the decoding output plugin after the memory used by logical decoding to decode changes from WAL for this slot has exceeded logical_decoding_work_mem. Waiting to acquire a lock on a non-relation database object. Waiting for a relation data file to be extended. Synchronous state of this standby server. 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. Waiting for the termination of another backend. Waiting in main loop of logical replication launcher process. Waiting to allocate a new transaction ID. streaming: This WAL sender is streaming changes after its connected standby server has caught up with the primary. A database-wide ANALYZE is recommended after the statistics have been reset. Waiting to read or update old snapshot control information. Waiting during recovery when WAL data is not available from any source (. 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. However, these statistics do not give the entire story: due to the way in which PostgreSQL handles disk I/O, data that is not in the PostgreSQL buffer cache might still reside in the kernel's I/O cache, and might therefore still be fetched without requiring a physical read. 213 * Prior to PostgreSQL 9.4, we used an enum type called LWLockId to refer. The functions for per-function statistics take a function OID. Presently, the collector can count accesses to tables and indexes in both disk-block and individual-row terms. Waiting for a timeline history file received via streaming replication to reach durable storage. See, One row only, showing statistics about WAL activity. Waiting for a read from a replication slot control file. a page) has to be retrieved outside the shared buffer pool. Table28.12.pg_stat_database_conflicts View. Waiting in main loop of autovacuum launcher process. Waiting for recovery conflict resolution for a vacuum cleanup. Waiting to read or update sub-transaction information. The server process is waiting for some condition defined by an extension module. Waiting for a write to the relation map file. Returns the wait event type name if this backend is currently waiting, otherwise NULL. Waiting for a newly initialized WAL file to reach durable storage. The parameter track_functions enables tracking of usage of user-defined functions. 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. LWLock:buffer_mapping. Waiting for the relation map file to reach durable storage. Activity: The server process is idle. Serial number of the client certificate, or NULL if no client certificate was supplied or if SSL is not in use on this connection. Total number of WAL full page images generated, Number of times WAL data was written to disk because WAL buffers became full. This field is truncated if the DN field is longer than NAMEDATALEN (64 characters in a standard build). Waiting in main loop of autovacuum launcher process. Waiting to read or update the state of logical replication workers. It can be joined to pg_stat_activity or pg_stat_replication on the pid column to get more details about the connection. 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 to allocate or free a replication slot. Therefore, a bitmap scan increments the pg_stat_all_indexes.idx_tup_read count(s) for the index(es) it uses, and it increments the pg_stat_all_tables.idx_tup_fetch count for the table, but it does not affect pg_stat_all_indexes.idx_tup_fetch. pg_stat_get_activity ( integer ) setof record. Waiting to acquire an exclusive lock to truncate off any empty pages at the end of a table vacuumed. Waiting to access the multixact offset SLRU cache. 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. Note that only tables, indexes, and functions in the current database can be seen with these functions. Autovacuum worker or launcher waiting to update or read the current state of autovacuum workers. Waiting for a write during reorder buffer management. The pg_stat_database view will contain one row for each database in the cluster, showing database-wide statistics. Waiting to access the list of predicate locks held by serializable transactions. Waiting for a write while initializing a new WAL file. A process can wait for the data needed from a client ( Client) or another process ( IPC ). Waiting to read data from the client while establishing a GSSAPI session. 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. The pg_stat_wal_receiver view will contain only one row, showing statistics about the WAL receiver from that receiver's connected server. Waiting for other Parallel Hash participants to finish hashing the inner relation. 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. This view will only contain information on standby servers, since conflicts do not occur on primary servers. The overhead of a file is much more than wasting the remainder of a page. Waiting to update the relation map file used to store catalog to filenode mapping. Wait event name if backend is currently waiting, otherwise NULL. Waiting in main loop of background writer process. This has no effect in a quorum-based synchronous replication. Waiting to perform an operation on a list of locks held by serializable transactions. The pg_stat_wal view will always have a single row, containing data about WAL activity of the cluster. To use the Amazon Web Services Documentation, Javascript must be enabled. Process ID of the parallel group leader, if this process is a parallel query worker.