28.2. 統計資訊收集器
版本:11
PostgreSQL 的統計資訊收集器是一個子系統,支援收集和回報有關伺服器活動的訊息。目前,收集器可以計算對磁盤區塊和單個資料列中資料表和索引的存取。它還追踪每個資料表中的總資料列數量,以及有關每個資料表的清理和分析操作的資訊。它還可以統計對使用者定義函數的呼叫以及每個函數所花費的總時間。
PostgreSQL 也支援回報有關系統當下正在發生什麼的動態訊息,例如目前正由其他伺服器程序所執行的明確指令,以及系統中正在進行的其他連線。此功能獨立於收集器程序。
28.2.1. 統計收集設定
由於統計信息的收集會增加查詢執行的成本,因此系統可以設定收集或不收集訊息。這由通常在 postgresql.conf 中的參數控制。(有關設定參數的詳細訊息,請參閱第 19 章。)
參數 track_activities 啓用監控任何伺服器程序正在執行的指令。
參數 track_counts 控制是否收集有關資料表和索引存取的統計資訊。
參數 track_functions 可以追踪使用者自訂函數的使用情況。
參數 track_io_timing 啓用監控磁碟區塊讀取和寫入時間。
通常這些參數會在 postgresql.conf 中設定,以便它們適用於所有伺服器程序,但也可以使用 SET 指令在各個連線中啓用或停用它們。(為了防止普通使用者將其活動隱藏於管理員之外,只允許超級使用者使用 SET 變更這些參數。)
統計資訊收集器透過臨時檔案將收集的資訊傳輸到其他 PostgreSQL 程序。這些檔案儲存在參數 stats_temp_directory 所指定的目錄中,預設為 pg_stat_tmp。為了獲得更好的效能,可以將 stats_temp_directory 指向記憶體的檔案系統,從而降低物理 I/O 需求。當伺服器完全地關閉時,統計資料的永久副本將儲存在 pg_stat 子目錄中,以便可以跨伺服器重新啟動並保留統計資訊。在伺服器啟動時進行回復(例如,在立即關閉,伺服器當機和實時回復之後),將重置所有統計計數器。
28.2.2. Viewing Statistics
Table 28.1 中列出了的幾個預先定義好的檢視表,可用於顯示系統的當下的狀態。Table 28.2 中還列出了其他幾個檢視表,可用於顯示統計訊息收集的結果。進一步可以使用基礎統計函數建構自訂的檢視表,如第 28.2.3 節中所述。
使用統計訊息監控收集的資料時,重要的是要瞭解到訊息並不會立即更新。每個伺服器程序在回到閒置狀態之前會向收集器發送新的統計計數;因此,仍在進行中的查詢或事務不會對顯示的數據產生影響。此外,收集器本身每 PGSTAT_STAT_INTERVAL 毫秒最多回報一次(500毫秒,除非在編譯伺服器時更改)。因此顯示的數據是落後於實際活動的。 但是,track_activities 所收集的目前查詢資訊是最新的。
另一個要點是,當要求伺服器程序顯示任何這些統計訊息時,它首先獲取收集器程序發出的最新報告,然後繼續將此快照結果用於所有統計檢視表和函數,直到其當下該事務結束。因此,只要您繼續該事務,統計數據就會顯示靜態結果。同樣地,當在事務中首次請求任何此類資訊時,收集關於所有連線的當下查詢資訊,將會在整個事務中顯示相同的資訊。這是一個正常的功能,而不是一個錯誤,因為它允許您對統計信息執行多個查詢並且關聯結果,而不必擔心數字在您交易當下發生變化。但是,如果要查看每個查詢的新結果,請確保在任何事務區塊之外執行查詢。或者,您可以呼叫 pg_stat_clear_snapshot(),它將丟棄當下事務的統計資訊快照(如果有的話)。下次使用統計資訊時將會去獲取新的快照。
事務還可以在檢視圖 pg_stat_xact_all_tables,pg_stat_xact_sys_tables,pg_stat_xact_user_tables 和pg_stat_xact_user_functions 中查看自己的統計訊息(尚未傳遞給收集器的)。 這些數字不符合上述原則;相反地,他們在整個交易過程中不斷更新。
Table 28.1. Dynamic Statistics Views
View Name | Description |
| 每個伺服器程序一個資料列,顯示與該程序的當時活動相關的訊息,例如狀態和當時查詢。有關詳細訊息,請參閱 pg_stat_activity。 |
| One row per WAL sender process, showing statistics about replication to that sender's connected standby server. See pg_stat_replication for details. |
| Only one row, showing statistics about the WAL receiver from that receiver's connected server. See pg_stat_wal_receiver for details. |
| At least one row per subscription, showing information about the subscription workers. See pg_stat_subscription for details. |
| One row per connection (regular and replication), showing information about SSL used on this connection. See pg_stat_ssl for details. |
| One row for each backend (including autovacuum worker processes) running |
Table 28.2. Collected Statistics Views
View Name | Description |
| One row only, showing statistics about the WAL archiver process's activity. See pg_stat_archiver for details. |
| One row only, showing statistics about the background writer process's activity. See pg_stat_bgwriter for details. |
| One row per database, showing database-wide statistics. See pg_stat_database for details. |
| One row per database, showing database-wide statistics about query cancels due to conflict with recovery on standby servers. See pg_stat_database_conflicts for details. |
| One row for each table in the current database, showing statistics about accesses to that specific table. See pg_stat_all_tables for details. |
| Same as |
| Same as |
| Similar to |
| Same as |
| Same as |
| One row for each index in the current database, showing statistics about accesses to that specific index. See pg_stat_all_indexes for details. |
| Same as |
| Same as |
| One row for each table in the current database, showing statistics about I/O on that specific table. See pg_statio_all_tables for details. |
| Same as |
| Same as |
| One row for each index in the current database, showing statistics about I/O on that specific index. See pg_statio_all_indexes for details. |
| Same as |
| Same as |
| One row for each sequence in the current database, showing statistics about I/O on that specific sequence. See pg_statio_all_sequences for details. |
| Same as |
| Same as |
| One row for each tracked function, showing statistics about executions of that function. See pg_stat_user_functions for details. |
| Similar to |
The per-index statistics are particularly useful to determine which indexes are being used and how effective they are.
The pg_statio_
views are primarily useful to determine the effectiveness of the buffer cache. 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. 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. Users interested in obtaining more detailed information on PostgreSQL I/O behavior are advised to use the PostgreSQL statistics collector in combination with operating system utilities that allow insight into the kernel's handling of I/O.
Table 28.3. pg_stat_activity
View
pg_stat_activity
ViewColumn | Type | Description |
|
| 此後端連線到的資料庫 OID |
|
| 此後端連線到的資料庫名稱 |
|
| 此後端的程序 ID |
|
| 登入此後端的使用者 OID |
|
| 登入到此後端的使用者名稱 |
|
| 連線到此後端的應用程序名稱 |
|
| 連線到此後端的客戶端的 IP 位址。如果此字串為空,則表示客戶端通過伺服器上的 Unix socket 連線,或者這是內部程序(如 autovacuum)。 |
|
| 已連接用戶端的主機名稱,由 client_addr 的反向 DNS 查詢回報。對於 IP 連線,只有在 log_hostname 啓用時,此字串才不是空字串。 |
|
| 用戶端用於與此後端通訊的 TCP 連接埠號碼,如果使用 Unix domain socket,則為 -1 |
|
| 此程序開始的時間。對於用戶端後端,這是用戶端連線到伺服器的時間。 |
|
| 此程序的當下交易事務已啟動的時間,如果沒有交易事務處於活動狀態,則為null。如果當下查詢是其交易事務的第一個,則此欄位等於 query_start 欄位。 |
|
| 最後一個查詢啟動時,當下活動查詢的啟動時間,或狀態是否處於活動狀態 |
|
| 狀態最後一次變更的時間 |
|
| The type of event for which the backend is waiting, if any; otherwise NULL. Possible values are: |
|
| Wait event name if backend is currently waiting, otherwise NULL. See Table 28.4 for details. |
|
| Current overall state of this backend. Possible values are: |
|
| Top-level transaction identifier of this backend, if any. |
|
| The current backend's |
|
| Text of this backend's most recent query. If |
|
| 當下後端的類型。可能的類型是 |
The pg_stat_activity
view will have one row per server process, showing information related to the current activity of that process.
Note
The wait_event
and state
columns are independent. If a backend is in the active
state, it may or may not be waiting
on some event. 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.
Table 28.4. wait_event
Description
Wait Event Type | Wait Event Name | Description |
|
| Waiting to find or allocate space in shared memory. |
| Waiting to allocate or assign an OID. | |
| Waiting to allocate or assign a transaction id. | |
| Waiting to get a snapshot or clearing a transaction id at transaction end. | |
| Waiting to retrieve or remove messages from shared invalidation queue. | |
| Waiting to add a message in shared invalidation queue. | |
| Waiting to replace a page in WAL buffers. | |
| Waiting for WAL buffers to be written to disk. | |
| Waiting to read or update the control file or creation of a new WAL file. | |
| Waiting to perform checkpoint. | |
| Waiting to read or update transaction status. | |
| Waiting to read or update sub-transaction information. | |
| Waiting to read or update shared multixact state. | |
| Waiting to read or update multixact offset mappings. | |
| Waiting to read or update multixact member mappings. | |
| Waiting to read or write relation cache initialization file. | |
| Waiting to manage fsync requests. | |
| Waiting to read or update the state of prepared transactions. | |
| Waiting to create or drop the tablespace. | |
| Waiting to read or update vacuum-related information for a B-tree index. | |
| Waiting to manage space allocation in shared memory. | |
| Autovacuum worker or launcher waiting to update or read the current state of autovacuum workers. | |
| Waiting to ensure that the table it has selected for a vacuum still needs vacuuming. | |
| Waiting to get the start location of a scan on a table for synchronized scans. | |
| Waiting to update the relation map file used to store catalog to filenode mapping. | |
| Waiting to read or update shared notification state. | |
| Waiting to read or update notification messages. | |
| Waiting to retrieve or store information about serializable transactions. | |
| Waiting to access the list of finished serializable transactions. | |
| Waiting to perform an operation on a list of locks held by serializable transactions. | |
| Waiting to read or record conflicting serializable transactions. | |
| Waiting to read or update information about synchronous replicas. | |
| Waiting to read or update background worker state. | |
| Waiting to read or update dynamic shared memory state. | |
| Waiting to update the | |
| Waiting to allocate or free a replication slot. | |
| Waiting to read or update replication slot state. | |
| Waiting to read or update transaction commit timestamps. | |
| Waiting to read or update the last value set for the transaction timestamp. | |
| Waiting to setup, drop or use replication origin. | |
| Waiting to read or truncate multixact information. | |
| Waiting to read or update old snapshot control information. | |
| Waiting to generate a random number. | |
| Waiting for action on logical replication worker to finish. | |
| Waiting to truncate the write-ahead log or waiting for write-ahead log truncation to finish. | |
| Waiting for I/O on a clog (transaction status) buffer. | |
| Waiting for I/O on commit timestamp buffer. | |
| Waiting for I/O a subtransaction buffer. | |
| Waiting for I/O on a multixact offset buffer. | |
| Waiting for I/O on a multixact_member buffer. | |
| Waiting for I/O on an async (notify) buffer. | |
| Waiting to I/O on an oldserxid buffer. | |
| Waiting to insert WAL into a memory buffer. | |
| Waiting to read or write a data page in memory. | |
| Waiting for I/O on a data page. | |
| Waiting to read or update the replication progress. | |
| Waiting for I/O on a replication slot. | |
| Waiting to read or update the fast-path lock information. | |
| Waiting to associate a data block with a buffer in the buffer pool. | |
| Waiting to add or examine locks for backends, or waiting to join or exit a locking group (used by parallel query). | |
| Waiting to add or examine predicate lock information. | |
| Waiting for parallel query dynamic shared memory allocation lock. | |
| Waiting for TBM shared iterator lock. | |
|
| Waiting to acquire a lock on a relation. |
| Waiting to extend a relation. | |
| Waiting to acquire a lock on page of a relation. | |
| Waiting to acquire a lock on a tuple. | |
| Waiting for a transaction to finish. | |
| Waiting to acquire a virtual xid lock. | |
| Waiting to acquire a speculative insertion lock. | |
| Waiting to acquire a lock on a non-relation database object. | |
| Waiting to acquire a user lock. | |
| Waiting to acquire an advisory user lock. | |
|
| Waiting to acquire a pin on a buffer. |
|
| Waiting in main loop of the archiver process. |
| Waiting in main loop of autovacuum launcher process. | |
| Waiting in background writer process, hibernating. | |
| Waiting in main loop of background writer process background worker. | |
| Waiting in main loop of checkpointer process. | |
| Waiting in main loop of logical launcher process. | |
| Waiting in main loop of logical apply process. | |
| Waiting in main loop of the statistics collector process. | |
| Waiting for WAL from any kind of source (local, archive or stream) at recovery. | |
| Waiting for WAL from a stream at recovery. | |
| Waiting in main loop of syslogger process. | |
| Waiting in main loop of WAL receiver process. | |
| Waiting in main loop of WAL sender process. | |
| Waiting in main loop of WAL writer process. | |
|
| Waiting to read data from the client. |
| Waiting to write data from the client. | |
| Waiting in WAL receiver to establish connection to remote server. | |
| Waiting in WAL receiver to receive data from remote server. | |
| Waiting for SSL while attempting connection. | |
| Waiting for startup process to send initial data for streaming replication. | |
| Waiting for WAL to be flushed in WAL sender process. | |
| Waiting for any activity when processing replies from WAL receiver in WAL sender process. | |
|
| Waiting in an extension. |
|
| Waiting for background worker to shut down. |
| Waiting for background worker to start up. | |
| Waiting for the page number needed to continue a parallel B-tree scan to become available. | |
| Waiting for activity from child process when executing | |
| Waiting for logical replication remote server to send data for initial table synchronization. | |
| Waiting for logical replication remote server to change state. | |
| Waiting for other process to be attached in shared message queue. | |
| Waiting to write a protocol message to a shared message queue. | |
| Waiting to receive bytes from a shared message queue. | |
| Waiting to send bytes to a shared message queue. | |
| Waiting for parallel workers to finish computing. | |
| Waiting for parallel bitmap scan to become initialized. | |
| Waiting for group leader to clear transaction id at transaction end. | |
| Waiting for a replication origin to become inactive to be dropped. | |
| Waiting for a replication slot to become inactive to be dropped. | |
| Waiting for a snapshot for a | |
| Waiting for confirmation from remote server during synchronous replication. | |
|
| Waiting during base backup when throttling activity. |
| Waiting in process that called | |
| Waiting to apply WAL at recovery because it is delayed. | |
|
| Waiting for a read from a buffered file. |
| Waiting for a write to a buffered file. | |
| Waiting for a read from the control file. | |
| Waiting for the control file to reach stable storage. | |
| Waiting for an update to the control file to reach stable storage. | |
| Waiting for a write to the control file. | |
| Waiting for a write to update the control file. | |
| Waiting for a read during a file copy operation. | |
| Waiting for a write during a file copy operation. | |
| Waiting for a relation data file to be extended. | |
| Waiting for a relation data file to reach stable storage. | |
| Waiting for an immediate synchronization of a relation data file to stable storage. | |
| Waiting for an asynchronous prefetch from a relation data file. | |
| Waiting for a read from a relation data file. | |
| Waiting for changes to a relation data file to reach stable storage. | |
| Waiting for a relation data file to be truncated. | |
| Waiting for a write to a relation data file. | |
| Waiting to write zero bytes to a dynamic shared memory backing file. | |
| Waiting for a read while adding a line to the data directory lock file. | |
| Waiting for data to reach stable storage while adding a line to the data directory lock file. | |
| Waiting for a write while adding a line to the data directory lock file. | |
| Waiting to read while creating the data directory lock file. | |
| Waiting for data to reach stable storage while creating the data directory lock file. | |
| Waiting for a write while creating the data directory lock file. | |
| Waiting for a read during recheck of the data directory lock file. | |
| Waiting for logical rewrite mappings to reach stable storage during a checkpoint. | |
| Waiting for mapping data to reach stable storage during a logical rewrite. | |
| Waiting for a write of mapping data during a logical rewrite. | |
| Waiting for logical rewrite mappings to reach stable storage. | |
| Waiting for a write of logical rewrite mappings. | |
| Waiting for a read of the relation map file. | |
| Waiting for the relation map file to reach stable storage. | |
| Waiting for a write to the relation map file. | |
| Waiting for a read during reorder buffer management. | |
| Waiting for a write during reorder buffer management. | |
| Waiting for a read of a logical mapping during reorder buffer management. | |
| Waiting for a read from a replication slot control file. | |
| Waiting for a replication slot control file to reach stable storage while restoring it to memory. | |
| Waiting for a replication slot control file to reach stable storage. | |
| Waiting for a write to a replication slot control file. | |
| Waiting for SLRU data to reach stable storage during a checkpoint or database shutdown. | |
| Waiting for a read of an SLRU page. | |
| Waiting for SLRU data to reach stable storage following a page write. | |
| Waiting for a write of an SLRU page. | |
| Waiting for a read of a serialized historical catalog snapshot. | |
| Waiting for a serialized historical catalog snapshot to reach stable storage. | |
| Waiting for a write of a serialized historical catalog snapshot. | |
| Waiting for a timeline history file received via streaming replication to reach stable storage. | |
| Waiting for a write of a timeline history file received via streaming replication. | |
| Waiting for a read of a timeline history file. | |
| Waiting for a newly created timeline history file to reach stable storage. | |
| Waiting for a write of a newly created timeline history file. | |
| Waiting for a read of a two phase state file. | |
| Waiting for a two phase state file to reach stable storage. | |
| Waiting for a write of a two phase state file. | |
| Waiting for WAL to reach stable storage during bootstrapping. | |
| Waiting for a write of a WAL page during bootstrapping. | |
| Waiting for a read when creating a new WAL segment by copying an existing one. | |
| Waiting a new WAL segment created by copying an existing one to reach stable storage. | |
| Waiting for a write when creating a new WAL segment by copying an existing one. | |
| Waiting for a newly initialized WAL file to reach stable storage. | |
| Waiting for a write while initializing a new WAL file. | |
| Waiting for a read from a WAL file. | |
| Waiting for a read from a timeline history file during walsender timeline command. | |
| Waiting for data to reach stable storage while assigning WAL sync method. | |
| Waiting for a write to a WAL file. |
Note
For tranches registered by extensions, the name is specified by extension and this will be displayed as wait_event
. It is quite possible that user has registered the tranche in one of the backends (by having allocation in dynamic shared memory) in which case other backends won't have that information, so we display extension
for such cases.
Here is an example of how wait events can be viewed
Table 28.5. pg_stat_replication
View
Column | Type | Description |
|
| Process ID of a WAL sender process |
|
| 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 |
|
| IP address of the client connected to this WAL sender. If this field is null, it indicates that the client is connected via a Unix socket on the server machine. |
|
| 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 WAL sender, or |
|
| Time when this process was started, i.e., when the client connected to this WAL sender |
|
| This standby's |
|
| Current WAL sender state. Possible values are: |
|
| Last write-ahead log location sent on this connection |
|
| Last write-ahead log location written to disk by this standby server |
|
| Last write-ahead log location flushed to disk by this standby server |
|
| Last write-ahead log location replayed into the database on this standby server |
|
| Time elapsed between flushing recent WAL locally and receiving notification that this standby server has written it (but not yet flushed it or applied it). This can be used to gauge the delay that |
|
| Time elapsed between flushing recent WAL locally and receiving notification that this standby server has written and flushed it (but not yet applied it). This can be used to gauge the delay that |
|
| Time elapsed between flushing recent WAL locally and receiving notification that this standby server has written, flushed and applied it. This can be used to gauge the delay that |
|
| Priority of this standby server for being chosen as the synchronous standby in a priority-based synchronous replication. This has no effect in a quorum-based synchronous replication. |
|
| Synchronous state of this standby server. Possible values are: |
The pg_stat_replication
view will contain one row per WAL sender process, showing statistics about replication to that sender's connected standby server. Only directly connected standbys are listed; no information is available about downstream standby servers.
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. 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. For an asynchronous standby, the replay_lag
column approximates the delay before recent transactions became visible to queries. 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.
Lag times work automatically for physical replication. Logical decoding plugins may optionally emit tracking messages; if they do not, the tracking mechanism will simply display NULL lag.
Note
The reported lag times are not predictions of how long it will take for the standby to catch up with the sending server assuming the current rate of replay. Such a system would show similar times while new WAL is being generated, but would differ when the sender becomes idle. 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. This is consistent with the goal of measuring synchronous commit and transaction visibility delays for recent write transactions. 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. Monitoring systems should choose whether to represent this as missing data, zero or continue to display the last known value.
Table 28.6. pg_stat_wal_receiver
View
Column | Type | Description |
|
| Process ID of the WAL receiver process |
|
| 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 |
|
| Last write-ahead log location already received and flushed to disk, the initial value of this field being the first log location used when WAL receiver is started |
|
| Timeline number of last write-ahead log location received and flushed to disk, the initial value of this field being the timeline number of the first log location used when WAL receiver is started |
|
| Send time of last message received from origin WAL sender |
|
| Receipt time of last message received from origin WAL sender |
|
| Last write-ahead log location reported to origin WAL sender |
|
| Time of last write-ahead log location reported to origin WAL sender |
|
| Replication slot name used by this WAL receiver |
|
| Connection string used by this WAL receiver, with security-sensitive fields obfuscated. |
The pg_stat_wal_receiver
view will contain only one row, showing statistics about the WAL receiver from that receiver's connected server.
Table 28.7. pg_stat_subscription
View
Column | Type | Description |
|
| OID of the subscription |
|
| Name of the subscription |
|
| Process ID of the subscription worker process |
|
| OID of the relation that the worker is synchronizing; null for the main apply worker |
|
| Last write-ahead log location received, the initial value of this field being 0 |
|
| Send time of last message received from origin WAL sender |
|
| Receipt time of last message received from origin WAL sender |
|
| Last write-ahead log location reported to origin WAL sender |
|
| Time of last write-ahead log location reported to origin WAL sender |
The pg_stat_subscription
view will contain one row per subscription for main worker (with null PID if the worker is not running), and additional rows for workers handling the initial data copy of the subscribed tables.
Table 28.8. pg_stat_ssl
View
Column | Type | Description |
|
| Process ID of a backend or WAL sender process |
|
| True if SSL is used on this connection |
|
| 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 |
|
| True if SSL compression is in use, false if not, or NULL if SSL is not in use on this connection |
|
| Distinguished Name (DN) field from the client certificate used, or NULL if no client certificate was supplied or if SSL is not in use on this connection. This field is truncated if the DN field is longer than |
The pg_stat_ssl
view will contain one row per backend or WAL sender process, showing statistics about SSL usage on this connection. It can be joined to pg_stat_activity
or pg_stat_replication
on the pid
column to get more details about the connection.
Table 28.9. pg_stat_archiver
View
Column | Type | Description |
|
| Number of WAL files that have been successfully archived |
|
| Name of the last WAL file successfully archived |
|
| Time of the last successful archive operation |
|
| Number of failed attempts for archiving WAL files |
|
| Name of the WAL file of the last failed archival operation |
|
| Time of the last failed archival operation |
|
| Time at which these statistics were last reset |
The pg_stat_archiver
view will always have a single row, containing data about the archiver process of the cluster.
Table 28.10. pg_stat_bgwriter
View
Column | Type | Description |
|
| Number of scheduled checkpoints that have been performed |
|
| Number of requested checkpoints that have been performed |
|
| Total amount of time that has been spent in the portion of checkpoint processing where files are written to disk, in milliseconds |
|
| Total amount of time that has been spent in the portion of checkpoint processing where files are synchronized to disk, in milliseconds |
|
| Number of buffers written during checkpoints |
|
| Number of buffers written by the background writer |
|
| Number of times the background writer stopped a cleaning scan because it had written too many buffers |
|
| Number of buffers written directly by a backend |
|
| Number of times a backend had to execute its own |
|
| Number of buffers allocated |
|
| Time at which these statistics were last reset |
The pg_stat_bgwriter
view will always have a single row, containing global data for the cluster.
Table 28.11. pg_stat_database
View
Column | Type | Description |
|
| OID of a database |
|
| Name of this database |
|
| Number of backends currently connected to this database. 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. |
|
| 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. (Conflicts occur only on standby servers; see pg_stat_database_conflicts for details.) |
|
| Number of temporary files created by queries in this database. 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. |
|
| Total amount of data written to temporary files by queries in this database. All temporary files are counted, regardless of why the temporary file was created, and regardless of the log_temp_files setting. |
|
| 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 |
|
| Time at which these statistics were last reset |
The pg_stat_database
view will contain one row for each database in the cluster, showing database-wide statistics.
Table 28.12. pg_stat_database_conflicts
View
Column | Type | Description |
|
| OID of a database |
|
| Name of this database |
|
| 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 |
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. This view will only contain information on standby servers, since conflicts do not occur on master servers.
Table 28.13. pg_stat_all_tables
View
Column | Type | Description |
|
| OID of a table |
|
| Name of the schema that this table is in |
|
| Name of this table |
|
| 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 inserted |
|
| Number of rows updated (includes HOT updated rows) |
|
| Number of rows deleted |
|
| Number of rows HOT updated (i.e., with no separate index update required) |
|
| Estimated number of live rows |
|
| Estimated number of dead rows |
|
| 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 |
|
|