pg_stat_get_backend_client_port ( integer ) integer. 213 * Prior to PostgreSQL 9.4, we used an enum type called LWLockId to refer. Waiting for a write of a serialized historical catalog snapshot. Waiting to read or update background worker state. In contrast, when starting from an unclean shutdown (e.g., after an immediate shutdown, a server crash, starting from a base backup, and point-in-time recovery), all statistics counters are reset. buffer_mapping | DBmarlin Docs and Knowledge Base 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). Resets statistics for a single function in the current database to zero. Waiting to manage space allocation in shared memory. Waiting for a logical replication remote server to change state. Wait event name if backend is currently waiting, otherwise NULL. The pg_stat_wal_receiver view will contain only one row, showing statistics about the WAL receiver from that receiver's connected server. LWLock: The backend is waiting for a lightweight lock. wait_event will contain a name identifying the purpose of the lightweight lock. Waiting for other Parallel Hash participants to finish loading a hash table. Waiting to read or update shared multixact state. If this field is null, it indicates either that the client is connected via a Unix socket on the server machine or that this is an internal process such as autovacuum. The pg_statio_all_sequences view will contain one row for each sequence in the current database, showing statistics about I/O on that specific sequence. The statistics collector transmits the collected information to other PostgreSQL processes through temporary files. The function pg_stat_get_backend_idset provides a convenient way to generate one row for each active backend for invoking these functions. replication_slot_io: Waiting for I/O on a replication slot. Waiting to access the sub-transaction SLRU cache. The pg_stat_wal view will always have a single row, containing data about WAL activity of the cluster. Waiting to perform an operation on a list of locks held by serializable transactions. These files are stored in the directory named by the stats_temp_directory parameter, pg_stat_tmp by default. See, One row for each table in the current database, showing statistics about I/O on that specific table. 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. 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 wait_event and state columns are independent. Waiting to retrieve messages from the shared catalog invalidation queue. 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 logical replication apply process. Waiting to read or write relation cache initialization file. Time elapsed between flushing recent WAL locally and receiving notification that this standby server has written and flushed it (but not yet applied it). LWLock:BufferIO. 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. pg_stat_get_activity ( integer ) setof record. Waiting for a buffered file to be truncated. Amount of transaction data decoded for sending transactions to the decoding output plugin while decoding changes from WAL for this slot. wait_event will identify the specific wait point. This includes the sync time when wal_sync_method is either open_datasync or open_sync. idle in transaction: The backend is in a transaction, but is not currently executing a query. Conversely, if it's known that statistics are only accessed once, caching accessed statistics is unnecessary and can be avoided by setting stats_fetch_consistency to none. The pg_statio_ views are primarily useful to determine the effectiveness of the buffer cache. wait_event will identify the specific wait point. Waiting for a relation data file to reach durable storage. Time when this process was started. Locks in PostgreSQL: 4. Locks in memory : Postgres Professional idle in transaction (aborted): This state is similar to idle in transaction, except one of the statements in the transaction caused an error. active: The backend is executing a query. 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. You can split your Returns a record of information about the backend with the specified process ID, or one record for each active backend in the system if NULL is specified. True if GSSAPI encryption is in use on this connection. ), Reset some cluster-wide statistics counters to zero, depending on the argument (requires superuser privileges by default, but EXECUTE for this function can be granted to others). The optimizer also accesses indexes to check for supplied constants whose values are outside the recorded range of the optimizer statistics because the optimizer statistics might be stale. Waiting for a write of a timeline history file received via streaming replication. Waiting to elect a Parallel Hash participant to allocate a hash table. Waiting for a write to a replication slot control file. The fields returned are a subset of those in the pg_stat_activity view. , LWTRANCHE_MXACTMEMBER_BUFFERS, LWTRANCHE_ASYNC_BUFFERS, LWTRANCHE_OLDSERXID_BUFFERS, LWTRANCHE_WAL_INSERT, LWTRANCHE_BUFFER_CONTENT, LWTRANCHE_BUFFER_IO_IN_PROGRESS, LWTRANCHE . If this field is null, it indicates either that the client is connected via a Unix socket on the server machine or that this is an internal process such as autovacuum. a page) has to be retrieved outside the shared buffer pool. This can be used to gauge the delay that synchronous_commit level remote_apply incurred while committing if this server was configured as a synchronous standby. checksum_last_failure timestamp with time zone. potential: This standby server is now asynchronous, but can potentially become synchronous if one of current synchronous ones fails. Amazon Aurora PostgreSQL wait events - Amazon Aurora Time when this process' current transaction was started, or null if no transaction is active. When the buffer manager receives a request, PostgreSQL uses the buffer_tag of the desired page. Waiting to read or update multixact offset mappings. Re: [HACKERS] Sequence Access Method WIP So the statistics will show static information as long as you continue the current transaction. But processes can also await other events: Waits for input/output ( IO) occur when a process needs to read or write data. Possible values are: async: This standby server is asynchronous. Waiting to update limit on notification message storage. Waiting for WAL buffers to be written to disk. 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 for logical rewrite mappings to reach durable storage. workload into more reader nodes. The pg_stat_database view will contain one row for each database in the cluster, plus one for shared objects, showing database-wide statistics. pg_stat_get_backend_wait_event ( integer ) text. See, One row for each index in the current database, showing statistics about I/O on that specific index. Waiting for a newly created timeline history file to reach durable storage. Wait Events of Type Extension. See, One row for each table in the current database, showing statistics about I/O on that specific table. The parameter track_counts controls whether cumulative statistics are collected about table and index accesses. Returns the text of this backend's most recent query. You These numbers do not act as stated above; instead they update continuously throughout the transaction. Waiting for another process to be attached to a shared message queue. This lock is used to handle multiple sessions that all require access to the same When a buffer is read from disk (or written to disk), an IO in progress lock is also acquired, which indicates to other processes that the page is being read (or written) they can queue up if they need to do something with this page. Waiting in a cost-based vacuum delay point. By default the query text is truncated at 1024 bytes; this value can be changed via the parameter track_activity_query_size. LWLock:BufferIO - Amazon Relational Database Service AWSDocumentationAmazon RDS and Aurora DocumentationUser Guide Relevant engine versionsContextCausesActions LWLock:BufferIO The buffer_tag comprises three values: the RelFileNode and the fork number of the relation to which its page belongs, and the block number of its page. When using the cumulative statistics views and functions to monitor collected data, it is important to realize that the information does not update instantaneously. Waiting for a newly created timeline history file to reach durable storage. Waiting to access the list of finished serializable transactions. The type of event for which the backend is waiting, if any; otherwise NULL. Number of temporary files created by queries in this database. It also tracks the total number of rows in each table, and information about vacuum and analyze actions for each table. Waiting for an asynchronous prefetch from a relation data file. See, Only one row, showing statistics about the WAL receiver from that receiver's connected server. This effect can mean that you have a small shared buffers setting. Waiting for other Parallel Hash participants to finish inserting tuples into new buckets. From pg_stat_activity i noticed that the wait_event_type and wait_event of these queries is as follows: Thanks for letting us know we're doing a good job! Waiting for recovery conflict resolution for a vacuum cleanup. See, Time when the current transaction was started. See, One row per connection (regular and replication), showing information about GSSAPI authentication and encryption used on this connection. Host name of the connected client, as reported by a reverse DNS lookup of, TCP port number that the client is using for communication with this backend, or. See, One row only, showing statistics about WAL activity. Waiting to update limits on transaction id and multixact consumption. Waiting for group leader to clear transaction id at transaction end. Then identify which query async: This standby server is asynchronous. Before PostgreSQL 8.1, all operations of the shared buffer manager itself were protected by a single system-wide lock, the BufMgrLock, which unsurprisingly proved to be a source of contention. Some of the information in the dynamic statistics views shown in Table28.1 is security restricted. Waiting for a write to a relation data file. 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 for a read from a relation data file. 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_recovery_prefetch view will contain only one row. Waiting for I/O on an async (notify) buffer. The wait_event and state columns are independent. See, One row per WAL sender process, showing statistics about replication to that sender's connected standby server. Presently, the collector can count accesses to tables and indexes in both disk-block and individual-row terms. See, One row per connection (regular and replication), showing information about SSL used on this connection. Waiting in main loop of startup process for WAL to arrive, during streaming recovery. disabled: This state is reported if track_activities is disabled in this backend. The LWLock:BufferIO event occurs when Aurora PostgreSQL or RDS for PostgreSQL is waiting for other processes to But if you want to see new results with each query, be sure to do the queries outside any transaction block. 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. Streaming only works with top-level transactions (subtransactions can't be streamed independently), so the counter is not incremented for subtransactions. Current WAL sender state. Waiting for stats dynamic shared memory allocator access, Waiting for stats shared memory hash table access, Waiting for shared memory stats data access. When analyzing statistics interactively, or with expensive queries, the time delta between accesses to individual statistics can lead to significant skew in the cached statistics. Alternatively, one can build custom views using the underlying statistics functions, as discussed in Section28.2.3. The server process is waiting for a timeout to expire. See, One row only, showing statistics about the WAL archiver process's activity. Waiting to access a shared tuple store during parallel query. Waiting for an elected Parallel Hash participant to allocate a hash table. Resetting these counters can cause autovacuum to not perform necessary work, which can cause problems such as table bloat or out-dated table statistics. 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 The pg_stat_replication_slots view will contain one row per logical replication slot, showing statistics about its usage. See Table28.4 for details. 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. Waiting for a read from a timeline history file during walsender timeline command. Waiting between writes while performing a checkpoint. Lock: The backend is waiting for a heavyweight lock. Waiting to elect a Parallel Hash participant to allocate more buckets. Waiting in main loop of checkpointer process. Waiting for parallel workers to finish computing. See, One row only, showing statistics about the background writer process's activity. Waiting for a replication slot to become inactive so it can be dropped. Waiting to read or update transaction commit timestamps. This has no effect in a quorum-based synchronous replication. 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. The pg_stat_subscription_stats view will contain one row per subscription. Waiting for WAL buffers to be written to disk. 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 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. All temporary files are counted, regardless of why the temporary file was created, and regardless of the log_temp_files setting. Waiting for a read while adding a line to the data directory lock file. Waiting to choose the next subplan during Parallel Append plan execution. Waiting for a write of logical rewrite mappings. If you see anything in the documentation that is not correct, does not match 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. 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. See, One row per connection (regular and replication), showing information about SSL used on this connection. The full object locks which last (usually) for the duration of a transaction and which you can see in pg_locks have info about them stored in shared memory. A process acquires an LWLock in a shared mode to read from the buffer and an exclusive mode to write to the buffer. All temporary files are counted, regardless of why the temporary file was created (e.g., sorting or hashing), and regardless of the log_temp_files setting. Waiting to acquire a speculative insertion lock. The parameter track_io_timing enables monitoring of block read and write times. Every PostgreSQL process collects statistics locally, then updates the shared data at appropriate intervals. Waiting to read or update information about synchronous replicas. Javascript is disabled or is unavailable in your browser. See, One row for each index in the current database, showing statistics about accesses to that specific index. OID of this database, or 0 for objects belonging to a shared relation. Returns the process ID of the server process attached to the current session. Waiting for WAL files required for a backup to be successfully archived. Waiting in background writer process, hibernating. Waiting for a write of a WAL page during bootstrapping. Waiting for a replication slot control file to reach durable storage. If the argument is NULL, reset statistics for all subscriptions. Number of times WAL buffers were written out to disk via XLogWrite request. The LWLock:BufferIO event occurs when RDS for PostgreSQL or Aurora PostgreSQL is waiting for other processes to finish their I/O operations. The track_functions parameter controls exactly which functions are tracked. Waiting to acquire an advisory user lock. Waiting to elect a Parallel Hash participant to allocate more batches. Waiting when WAL data is not available from any kind of sources (local, archive or stream) before trying again to retrieve WAL data, at recovery. The access functions for per-database statistics take a database OID as an argument to identify which database to report on. Note that this includes data that is streamed and/or spilled. Waiting to allocate or assign a transaction id. Number of times WAL files were synced to disk via issue_xlog_fsync request (if fsync is on and wal_sync_method is either fdatasync, fsync or fsync_writethrough, otherwise zero). Waiting for a write of a two phase state file. Waiting for an immediate synchronization of a relation data file to durable storage. As soon as the page is read inside the shared buffer pool, the LWLock:BufferIO lock is released. The pg_stat_bgwriter view will always have a single row, containing global data for the cluster. True if GSSAPI authentication was used for this connection. gorthx on Twitter * 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). Waiting for a replication slot to become inactive to be dropped. Re: Improve WALRead() to suck data directly from WAL buffers when possible Total number of WAL full page images generated, Number of times WAL data was written to disk because WAL buffers became full. LWLock:BufferIO - Amazon Aurora Waiting in main loop of WAL receiver process.