Text of this backend's most recent query. The following wait events are a subset of the list in Amazon Aurora PostgreSQL wait events. Waiting for a write to the relation map file. 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. IO: The server process is waiting for a IO to complete. The server process is waiting for exclusive access to a data buffer. Waiting to access the transaction status SLRU cache. Waiting in main loop of syslogger process. A transaction can also see its own statistics (not yet flushed out to the shared memory statistics) in the views pg_stat_xact_all_tables, pg_stat_xact_sys_tables, pg_stat_xact_user_tables, and pg_stat_xact_user_functions. Waiting to acquire a virtual transaction ID lock. Waiting to read or update replication slot state. See, One row for each table in the current database, showing statistics about accesses to that specific table. For details such as the functions' names, consult the definitions of the standard views. (See Chapter19 for details about setting configuration parameters.). Waiting to replace a page in WAL buffers. Topics Relevant engine versions Context Causes Actions Relevant engine versions Thanks for letting us know we're doing a good job! @ LWTRANCHE_REPLICATION_SLOT_IO. The server process is waiting for activity on a socket connected to a user application. This can be a host name, an IP address, or a directory path if the connection is via Unix socket. When the buffer manager receives a request, PostgreSQL uses the buffer_tag of the desired page. Waiting for a write during reorder buffer management. See, One row per database, showing database-wide statistics about query cancels due to conflict with recovery on standby servers. The track_functions parameter controls exactly which functions are tracked. 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. IP address of the client connected to this WAL sender. Port number of the PostgreSQL instance this WAL receiver is connected to. Table28.17.pg_statio_all_sequences View. Statistics Collection Configuration, One row per server process, showing information related to the current activity of that process, such as state and current query. There have been several occasions when a query is being executed dozens of times simultaneously by one or many users. OID of the user logged into this WAL sender process, Name of the user logged into this WAL sender process, Name of the application that is connected to this WAL sender. LWLock:buffer_mapping. This counter is incremented each time a transaction is spilled, and the same transaction may be spilled multiple times. Restrict the maximum number of connections to the database as a best practice. idle: The backend is waiting for a new client command. Waiting to access the list of finished serializable transactions. Returns the text of this backend's most recent query. Waiting to ensure that a table selected for autovacuum still needs vacuuming. Waiting in main loop of logical replication launcher process. idle: The backend is waiting for a new client command. 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. Also, the collector itself emits a new report at most once per PGSTAT_STAT_INTERVAL milliseconds (500 ms unless altered while building the server). Waiting to access the serializable transaction conflict SLRU cache. Waiting for data to reach durable storage while creating the data directory lock file. For details such as the functions' names, consult the definitions of the standard views. Use partitioned tables (which also have partitioned indexes). postgres7 Slru--1. This lock is used to handle multiple sessions that all require access to the same The access functions for per-database statistics take a database OID as an argument to identify which database to report on. checksum_last_failure timestamp with time zone. The overhead of a file is much more than wasting the remainder of a page. The parameter track_io_timing enables monitoring of block read and write times. It also tracks the total number of rows in each table, and information about vacuum and analyze actions for each table. Number of backends currently connected to this database. Returns the time when the backend's current transaction was started. Waiting to acquire a speculative insertion lock. 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 database, showing database-wide statistics. Waiting to add or examine predicate lock information. Waiting for a write to update the control file. postgres 51 LWLock--2_Serendipity_Shy-CSDN If this field is null, it indicates that this is an internal server process. ru> Date: 2015-11-19 14:04:28 Message-ID: 20151119170428.490de41d lp [Download RAW message or body] Thank you for the review. 105 #define BUFFER_MAPPING_LWLOCK_OFFSET NUM_INDIVIDUAL_LWLOCKS. 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. Indexes can be used by simple index scans, bitmap index scans, and the optimizer. Waiting for an asynchronous prefetch from a relation data file. Waiting for recovery conflict resolution for a vacuum cleanup. Waiting to read or update shared multixact state. Number of temporary files created by queries in this database. Waiting for group leader to clear transaction id at transaction end. See. It can be joined to pg_stat_activity or pg_stat_replication on the pid column to get more details about the connection. Waiting for changes to a relation data file to reach durable storage. Waiting in main loop of logical launcher process. Waiting for activity from child process when executing. Waiting for mapping data to reach durable storage during a logical rewrite. Waiting during base backup when throttling activity. For an asynchronous standby, the replay_lag column approximates the delay before recent transactions became visible to queries. Number of backends currently connected to this database, or NULL for shared objects. Waiting for a replication slot control file to reach durable storage while restoring it to memory. Waiting for logical rewrite mappings to reach durable storage. So the statistics will show static information as long as you continue the current transaction. A process acquires an LWLock in a shared mode to read from the buffer and . A database-wide ANALYZE is recommended after the statistics have been reset. Waiting for confirmation from a remote server during synchronous replication. If the argument is NULL, reset statistics for all subscriptions. Waiting for startup process to send initial data for streaming replication. Waiting to read or update dynamic shared memory state. However, current-query information collected by track_activities is always up-to-date. Waiting to acquire a lock on a page of a relation. Table28.12.pg_stat_database_conflicts View. Waiting for parallel query dynamic shared memory allocation. Pointers to free buffers and to the next victim are protected by one buffer strategy lock spinlock. The pg_stat_replication view will contain one row per WAL sender process, showing statistics about replication to that sender's connected standby server. Total number of WAL full page images generated, Number of times WAL data was written to disk because WAL buffers became full. Time when this process was started. Waiting for a write of a newly created timeline history file. 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. Returns the OID of the database this backend is connected to. PostgreSQL: Documentation: 10: 28.2. The Statistics Collector The combination of certificate serial number and certificate issuer uniquely identifies a certificate (unless the issuer erroneously reuses serial numbers). 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. idle in transaction (aborted): This state is similar to idle in transaction, except one of the statements in the transaction caused an error. Waiting to read or update dynamic shared memory allocation information. Waiting for a write of a two phase state file. 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. wait_event will identify the specific wait point. sync: This standby server is synchronous. postgresql - How to get rid of BufferMapping? - Database Administrators Waiting to find or allocate space in shared memory. To use the Amazon Web Services Documentation, Javascript must be enabled. See, One row per replication slot, showing statistics about the replication slot's usage. For more information, see LWLock:buffer_content (BufferContent). Here is an example of how wait events can be viewed: The pg_stat_replication view will contain one row per WAL sender process, showing statistics about replication to that sender's connected standby server. It is used per the rules above. Waiting for the relation map file to reach durable storage. Waiting to receive bytes from a shared message queue. Waiting in main loop of archiver process. Waiting for background worker to start up. The server process is waiting for a timeout to expire. Waiting to acquire a lock on a non-relation database object. Returns the time when the backend's most recent query was started. Waiting in main loop of WAL receiver process. Waiting to acquire a lock on page of a relation. pg_stat_get_backend_wait_event_type ( integer ) text. Waiting to read or update old snapshot control information. Waiting for parallel query dynamic shared memory allocation lock. Waiting for SSL while attempting connection. In particular, when the standby has caught up completely, pg_stat_replication shows the time taken to write, flush and replay the most recent reported WAL location rather than zero as some users might expect. sync: This standby server is synchronous. The pg_stat_recovery_prefetch view will contain only one row. When the server 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. See, At least one row per subscription, showing information about the subscription workers. This documentation is for an unsupported version of PostgreSQL. pg_stat_get_backend_pid ( integer ) integer, pg_stat_get_backend_start ( integer ) timestamp with time zone. Waiting for a read of a timeline history file. The next use of statistical information will (when in snapshot mode) cause a new snapshot to be built or (when in cache mode) accessed statistics to be cached. Note that this includes data that is streamed and/or spilled. Waiting for a write while adding a line to the data directory lock file. Resetting these counters can cause autovacuum to not perform necessary work, which can cause problems such as table bloat or out-dated table statistics. 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. 213 * Prior to PostgreSQL 9.4, we used an enum type called LWLockId to refer. wait_event will contain a name identifying the purpose of the lightweight lock. Waiting for a newly created timeline history file to reach durable storage. 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. Time when the currently active query was started, or if state is not active, when the last query was started. Waiting in WAL receiver to receive data from remote server. Total amount of time spent writing WAL buffers to disk via XLogWrite request, in milliseconds (if track_wal_io_timing is enabled, otherwise zero). Waiting for parallel workers to finish computing. This event type indicates a process waiting for activity in its main processing loop. The parameter track_io_timing enables monitoring of block read and write times. For more information, see LWLock:buffer_mapping. Extension: The server process is waiting for activity in an extension module. > However, someone with deeper knowledge of page pinning and buffer manager > internals could certainly devise a better solution. The type of event for which the backend is waiting, if any; otherwise NULL. The pg_statio_user_tables and pg_statio_sys_tables views contain the same information, but filtered to only show user and system tables respectively. 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. Waiting in background writer process, hibernating. Waiting to read or update information about. Returns the TCP port number that the client is using for communication. You can invoke pg_stat_clear_snapshot() to discard the current transaction's statistics snapshot or cached values (if any). Waiting in main loop of WAL writer process. Activity: The server process is idle. [prev in list] [next in list] [prev in thread] [next in thread] List: postgresql-general Subject: Re: [HACKERS] [PATCH] Refactoring of LWLock tranches From: Ildus Kurbangaliev <i.kurbangaliev postgrespro !