See, One row for each sequence in the current database, showing statistics about I/O on that specific sequence. Resets statistics for a single function in the current database to zero. Waiting for another process to be attached to a shared message queue. Waiting for a two phase state file to reach durable storage. Returns the TCP port number that the client is using for communication. In all other states, it shows the identifier of last query that was executed. The combination of certificate serial number and certificate issuer uniquely identifies a certificate (unless the issuer erroneously reuses serial numbers). Increase the number of wal_buffers available to the database. IP address of the client connected to this WAL sender. pg_stat_get_activity, the underlying function of the pg_stat_activity view, returns a set of records containing all the available information about each backend process. Waiting to access the multixact offset SLRU cache. See, One row per database, showing database-wide statistics. proc: Waiting to read or update the fast-path lock information. See, One row per connection (regular and replication), showing information about SSL used on this connection. Waiting for a read during a file copy operation. Note that only tables, indexes, and functions in the current database can be seen with these functions. Verify whether you have unused indexes, then remove them. Waiting for I/O on an async (notify) buffer. your experience with the particular feature or requires further clarification, Waiting to update limits on transaction id and multixact consumption. Waiting to find or allocate space in shared memory. This counter is incremented each time a transaction is streamed, and the same transaction may be streamed multiple times. If you see anything in the documentation that is not correct, does not match The pg_stat_bgwriter view will always have a single row, containing global data for the cluster. Waiting to allocate a new transaction ID. Lag times work automatically for physical replication. Provide feedback Wait Events of Type BufferPin, Table28.8. Each shared buffer has an I/O lock that is associated with the LWLock:BufferIO wait event, each time a block (or Waiting to replace a page in WAL buffers. Waiting for a write to the relation map file. Waits for lightweight locks ( LWLock ). pg_stat_get_activity, the underlying function of the pg_stat_activity view, returns a set of records containing all the available information about each backend process. The pg_stat_activity view will have one row per server process, showing information related to the current activity of that process. From pg_stat_activity i noticed that the wait_event_type and wait_event of these queries is as follows: See, Only one row, showing statistics about the WAL receiver from that receiver's connected server. 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. To minimize skew, stats_fetch_consistency can be set to snapshot, at the price of increased memory usage for caching not-needed statistics data. Waiting to read or update the state of logical replication workers. See, One row for each index in the current database, showing statistics about accesses to that specific index. The LWLock:BufferIO event occurs when Aurora PostgreSQL or RDS for PostgreSQL is waiting for other processes to The fields returned are a subset of those in the pg_stat_activity view. My application is using Postgres as DBMS, the version of Postgres that i'm using is 10.3 with the extension Postgis installed. Please refer to your browser's Help pages for instructions. Waiting for WAL from a stream at recovery. Lock: The backend is waiting for a heavyweight lock. Topics Relevant engine versions Context Causes Actions Relevant engine versions The pg_stat_user_functions view will contain one row for each tracked function, showing statistics about executions of that function. Per-Backend Statistics Functions, pg_stat_get_backend_idset () setof integer. 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 in main loop of WAL sender process. idle in transaction: The backend is in a transaction, but is not currently executing a query. Client: The server process is waiting for some activity on a socket from user applications, and that the server expects something to happen that is independent from its internal processes. * 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). PostgreSQL 's statistics collector is a subsystem that supports collection and reporting of information about server activity. Waiting for startup process to send initial data for streaming replication. I've made . Then identify which query Indexes can be used by simple index scans, bitmap index scans, and the optimizer. Waiting in main loop of WAL writer process. Waiting to send bytes to a shared message queue. Number of data page checksum failures detected in this database (or on a shared object), or NULL if data checksums are not enabled. sync: This standby server is synchronous. 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. Top-level transaction identifier of this backend, if any. Waiting to read or update dynamic shared memory state. 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 for a write while adding a line to the data directory lock file. wait_event will identify the type of lock awaited. Resetting these counters can cause autovacuum to not perform necessary work, which can cause problems such as table bloat or out-dated table statistics. ru> Date: 2015-11-19 14:04:28 Message-ID: 20151119170428.490de41d lp [Download RAW message or body] Thank you for the review. Such a system would show similar times while new WAL is being generated, but would differ when the sender becomes idle. Per-Backend Statistics Functions, Copyright 1996-2023 The PostgreSQL Global Development Group. 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. See, One row for each sequence in the current database, showing statistics about I/O on that specific sequence. Waiting to access the list of finished serializable transactions. For an asynchronous standby, the replay_lag column approximates the delay before recent transactions became visible to queries. Waiting for WAL files required for a backup to be successfully archived. Waiting to create, drop or use a replication origin. Waiting for a write while creating the data directory lock file. Waiting for parallel bitmap scan to become initialized. Waiting to select the starting location of a synchronized table scan. Waiting to receive bytes from a shared message queue. Waiting for a write during a file copy operation. The parameter track_io_timing enables monitoring of block read and write times. 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. 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. See Table28.5 through Table28.13. 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. Waiting for a read of a timeline history file. Waiting to read while creating the data directory lock file. When the buffer manager receives a request, PostgreSQL uses the buffer_tag of the desired page. Waiting for a relation data file to be extended. Waiting for a read of a serialized historical catalog snapshot. See Table28.4. Waiting for a newly initialized WAL file to reach durable storage. 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. Waiting to access a parallel query's information about composite types. If the argument is NULL, all counters shown in the pg_stat_slru view for all SLRU caches are reset. Waiting to read or update the replication progress. Waiting for background worker to start up. Connection string used by this WAL receiver, with security-sensitive fields obfuscated. This is controlled by configuration parameters that are normally set in postgresql.conf. To reduce confusion for users expecting a different model of lag, the lag columns revert to NULL after a short time on a fully replayed idle system. I'd like to know more about what these locks could imply if anything. Waiting for a newly created timeline history file to reach durable storage. Waiting for a replication slot control file to reach durable storage while restoring it to memory. Amount of transaction data decoded for sending transactions to the decoding output plugin while decoding changes from WAL for this slot. Waiting to read or update replication slot state. 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. True if GSSAPI encryption is in use on this connection. Waiting for activity from a child process while executing a. Waiting for truncate of mapping data during a logical rewrite. 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. 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. disabled: This state is reported if track_activities is disabled in this backend. See, At least one row per subscription, showing information about the subscription workers. For more information on lightweight locks, see Locking Overview. Number of decoded transactions sent to the decoding output plugin for this slot. Waiting to acquire an exclusive lock to truncate off any empty pages at the end of a table vacuumed. quorum: This standby server is considered as a candidate for quorum standbys. Waiting during base backup when throttling activity. The per-table and per-index functions take a table or index OID. Waiting for a relation data file to be truncated. See, One row for each backend (including autovacuum worker processes) running, One row only, showing statistics about the WAL archiver process's activity. There have been several occasions when a query is being executed dozens of times simultaneously by one or many users. Waiting for I/O on a sub-transaction SLRU buffer. Waiting for I/O on a multixact offset buffer. The pg_stat_subscription_stats view will contain one row per subscription. pg_stat_get_backend_userid ( integer ) oid. Buffer pin waits can be protracted if another process holds an open cursor which last read data from the buffer in question. See, One row for each table in the current database, showing statistics about accesses to that specific table. This can be used to gauge the delay that. Waiting to read or write a data page in memory. 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. Returns the process ID of the server process attached to the current session. Waiting for a read from a timeline history file during a walsender timeline command. Waiting to choose the next subplan during Parallel Append plan execution. These numbers do not act as stated above; instead they update continuously throughout the transaction. Waiting for data to reach durable storage while assigning a new WAL sync method. Waiting for the termination of another backend. For example, to show the PIDs and current queries of all backends: Table28.20. backup: This WAL sender is sending a backup. Waiting to ensure that the table it has selected for a vacuum still needs vacuuming. OID of the database this backend is connected to, Name of the database this backend is connected to. Waiting in main loop of logical apply process. idle in transaction (aborted): This state is similar to idle in transaction, except one of the statements in the transaction caused an error. 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).