Amount of transaction data decoded for sending transactions to the decoding output plugin while decoding changes from WAL for this slot. Waiting for a serialized historical catalog snapshot to reach durable storage. Only directly connected standbys are listed; no information is available about downstream standby servers. Therefore it is not safe to assume that all files older than last_archived_wal have also been successfully archived. See, One row per database, showing database-wide statistics. See, At least one row per subscription, showing information about the subscription workers. Resetting these counters can cause autovacuum to not perform necessary work, which can cause problems such as table bloat or out-dated table statistics. please use 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. See. The server process is waiting for some condition defined by an extension module. Table28.19. See, One row only, showing statistics about the background writer process's activity. But if you want to see new results with each query, be sure to do the queries outside any transaction block. 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. The counter gets incremented for both top-level transactions and subtransactions.
Re: Improve WALRead() to suck data directly from WAL buffers when Waiting to synchronize workers during Parallel Hash Join plan execution. pg_stat_get_backend_pid ( integer ) integer, pg_stat_get_backend_start ( integer ) timestamp with time zone. See, One row for each index in the current database, showing statistics about accesses to that specific index.
5mins of Postgres E25: Postgres lock monitoring, LWLocks and the log Waiting to read or update information about serializable transactions. The per-table and per-index functions take a table or index OID. Waiting for a read of a serialized historical catalog snapshot. Total amount of data written to temporary files by queries in this database. See, One row per connection (regular and replication), showing information about GSSAPI authentication and encryption used on this connection. The parameter track_counts controls whether cumulative statistics are collected about table and index accesses. The parameter track_activities enables monitoring of the current command being executed by any server process. This is used by system processes waiting for activity in their main processing loop. Waiting for SSL while attempting connection. pg_stat_get_backend_userid ( integer ) oid. IP address of the client connected to this WAL sender. When using the cumulative statistics views and functions to monitor collected data, it is important to realize that the information does not update instantaneously. Indexes can be used by simple index scans, bitmap index scans, and the optimizer. TCP port number that the client is using for communication with this backend, or -1 if a Unix socket is used. PostgreSQL utilizes lightweight locks (LWLocks) to synchronize and control access to the buffer content. disabled: This state is reported if track_activities is disabled in this backend. Waiting for a two phase state file to reach durable storage. PostgreSQL 's statistics collector is a subsystem that supports collection and reporting of information about server activity. Waiting for other process to be attached in shared message queue. Waiting for an elected Parallel Hash participant to finish allocating more buckets. Possible values are: Wait event name if backend is currently waiting, otherwise NULL. Waiting to acquire a lock on a page of a relation. Waiting to access the shared per-process data structures (typically, to get a snapshot or report a session's transaction ID). idle: The backend is waiting for a new client command. 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. Waiting to read or update vacuum-related information for a B-tree index. The pg_stat_archiver view will always have a single row, containing data about the archiver process of the cluster. Waiting for WAL to reach durable storage during bootstrapping. 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. 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. The latter will be less if any dead or not-yet-committed rows are fetched using the index, or if any heap fetches are avoided by means of an index-only scan. Waiting to retrieve or remove messages from shared invalidation queue.
'Re: [HACKERS] [PATCH] Refactoring of LWLock tranches' - MARC Waiting for SSL while attempting connection. 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. It can also count calls to user-defined functions and the total time spent in each one.
LWLock- buffer_mapping : r/PostgreSQL - reddit.com Waiting to read or update multixact offset mappings. This view will only contain information on standby servers, since conflicts do not occur on primary servers. Waiting for a read during recheck of the data directory lock file.
Locks in PostgreSQL: 4. Locks in memory - Habr In addition, background workers registered by extensions may have additional types. Waiting to add or examine predicate lock information. 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). Waiting to access a parallel query's information about composite types. In all other states, it shows the identifier of last query that was executed. Waiting in main loop of WAL receiver process. The wait_event and state columns are independent. Waiting for a read of a logical mapping during reorder buffer management. idle in transaction: The backend is in a transaction, but is not currently executing a query. 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. If this field is null, it indicates that the client is connected via a Unix socket on the server machine. 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.
Waiting for a replication origin to become inactive to be dropped. Number of decoded transactions sent to the decoding output plugin for this slot. Waiting for a read during recheck of the data directory lock file. Time when this process' current transaction was started, or null if no transaction is active. See Table28.4 for details. Last write-ahead log location already received and written to disk, but not flushed. Waiting for a write during reorder buffer management. 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. LWTRANCHE_BUFFER_CONTENT @ LWTRANCHE_BUFFER_CONTENT. Number of transactions spilled to disk once the memory used by logical decoding to decode changes from WAL has exceeded logical_decoding_work_mem. This is the only column in this view that returns a value reflecting current state; all other columns return the accumulated values since the last reset. See, One row per database, showing database-wide statistics about query cancels due to conflict with recovery on standby servers. Returns the set of currently active backend ID numbers (from 1 to the number of active backends). Waiting to read or record conflicting serializable transactions. This block has to be read from outside the shared buffer pool, defined by the Waiting for WAL to be flushed in WAL sender process. 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. Each buffer header also contains an LWLock, the "buffer content lock", that *does* represent the right to access the data: in the buffer. Total amount of time spent syncing WAL files to disk via issue_xlog_fsync request, in milliseconds (if track_wal_io_timing is enabled, fsync is on, and wal_sync_method is either fdatasync, fsync or fsync_writethrough, otherwise zero). 105 #define BUFFER_MAPPING_LWLOCK_OFFSET NUM_INDIVIDUAL_LWLOCKS. 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. 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.
PostgreSQL: Documentation: 11: 28.2. The Statistics Collector Extensions can register their specific waits ( Extension ). All temporary files are counted, regardless of why the temporary file was created, and regardless of the log_temp_files setting. Waiting for startup process to send initial data for streaming replication. Waiting for I/O on a clog (transaction status) buffer. See, One row for each table in the current database, showing statistics about accesses to that specific table. Waiting for WAL to reach durable storage during bootstrapping. See, At least one row per subscription, showing information about the subscription workers. See, One row per connection (regular and replication), showing information about SSL used on this connection. Each shared buffer has an I/O lock that is associated with the LWLock:BufferIO wait event, each time a block (or This is consistent with the goal of measuring synchronous commit and transaction visibility delays for recent write transactions. PostgreSQL Entangled in Locks: Attempts to free it - Amit Kapila - Dilip Kumar PGCon 2017 . Waiting for parallel query dynamic shared memory allocation. Waiting to write a protocol message to a shared message queue. 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. See, One row only, showing statistics about the background writer process's activity. , LWTRANCHE_MXACTMEMBER_BUFFERS, LWTRANCHE_ASYNC_BUFFERS, LWTRANCHE_OLDSERXID_BUFFERS, LWTRANCHE_WAL_INSERT, LWTRANCHE_BUFFER_CONTENT, LWTRANCHE_BUFFER_IO_IN_PROGRESS, LWTRANCHE . Table28.31.pg_statio_all_sequences View, Number of disk blocks read from this sequence. 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 manage an extension's space allocation in shared memory. 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. Waiting to insert WAL into a memory buffer. Waiting to get a snapshot or clearing a transaction id at transaction end.
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. Waiting in WAL receiver to receive data from remote server. pg_stat_get_activity ( integer ) setof record. Waiting for I/O on a multixact member SLRU buffer. 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. Identifier of this backend's most recent query. Waiting for a write of mapping data during a logical rewrite. Then identify which query (For example, in psql you could issue \d+ pg_stat_activity.) From the Actions drop-down menu, choose Create Read Replica. Waiting for background worker to start up. 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.