PostgreSQL provides facilities to support dynamic tracing of the database server. This allows an external utility to be called at specific points in the code and thereby trace execution.
A number of probes or trace points are already inserted into the source code. These probes are intended to be used by database developers and administrators. By default the probes are not compiled into PostgreSQL; the user needs to explicitly tell the configure script to make the probes available.
Currently, the DTrace utility is supported, which, at the time of this writing, is available on Solaris, macOS, FreeBSD, NetBSD, and Oracle Linux. The SystemTap project for Linux provides a DTrace equivalent and can also be used. Supporting other dynamic tracing utilities is theoretically possible by changing the definitions for the macros in src/include/utils/probes.h.
By default, probes are not available, so you will need to explicitly tell the configure script to make the probes available in PostgreSQL. To include DTrace support specify --enable-dtrace to configure. See Section 16.4 for further information.
A number of standard probes are provided in the source code, as shown in Table 27.28; Table 27.29 shows the types used in the probes. More probes can certainly be added to enhance PostgreSQL's observability.
Name
Parameters
Description
transaction-start
(LocalTransactionId)
Probe that fires at the start of a new transaction. arg0 is the transaction ID.
transaction-commit
(LocalTransactionId)
Probe that fires when a transaction completes successfully. arg0 is the transaction ID.
transaction-abort
(LocalTransactionId)
Probe that fires when a transaction completes unsuccessfully. arg0 is the transaction ID.
query-start
(const char *)
Probe that fires when the processing of a query is started. arg0 is the query string.
query-done
(const char *)
Probe that fires when the processing of a query is complete. arg0 is the query string.
query-parse-start
(const char *)
Probe that fires when the parsing of a query is started. arg0 is the query string.
query-parse-done
(const char *)
Probe that fires when the parsing of a query is complete. arg0 is the query string.
query-rewrite-start
(const char *)
Probe that fires when the rewriting of a query is started. arg0 is the query string.
query-rewrite-done
(const char *)
Probe that fires when the rewriting of a query is complete. arg0 is the query string.
query-plan-start
()
Probe that fires when the planning of a query is started.
query-plan-done
()
Probe that fires when the planning of a query is complete.
query-execute-start
()
Probe that fires when the execution of a query is started.
query-execute-done
()
Probe that fires when the execution of a query is complete.
statement-status
(const char *)
Probe that fires anytime the server process updates its pg_stat_activity.status. arg0 is the new status string.
checkpoint-start
(int)
Probe that fires when a checkpoint is started. arg0 holds the bitwise flags used to distinguish different checkpoint types, such as shutdown, immediate or force.
checkpoint-done
(int, int, int, int, int)
Probe that fires when a checkpoint is complete. (The probes listed next fire in sequence during checkpoint processing.) arg0 is the number of buffers written. arg1 is the total number of buffers. arg2, arg3 and arg4 contain the number of WAL files added, removed and recycled respectively.
clog-checkpoint-start
(bool)
Probe that fires when the CLOG portion of a checkpoint is started. arg0 is true for normal checkpoint, false for shutdown checkpoint.
clog-checkpoint-done
(bool)
Probe that fires when the CLOG portion of a checkpoint is complete. arg0 has the same meaning as for clog-checkpoint-start.
subtrans-checkpoint-start
(bool)
Probe that fires when the SUBTRANS portion of a checkpoint is started. arg0 is true for normal checkpoint, false for shutdown checkpoint.
subtrans-checkpoint-done
(bool)
Probe that fires when the SUBTRANS portion of a checkpoint is complete. arg0 has the same meaning as for subtrans-checkpoint-start.
multixact-checkpoint-start
(bool)
Probe that fires when the MultiXact portion of a checkpoint is started. arg0 is true for normal checkpoint, false for shutdown checkpoint.
multixact-checkpoint-done
(bool)
Probe that fires when the MultiXact portion of a checkpoint is complete. arg0 has the same meaning as for multixact-checkpoint-start.
buffer-checkpoint-start
(int)
Probe that fires when the buffer-writing portion of a checkpoint is started. arg0 holds the bitwise flags used to distinguish different checkpoint types, such as shutdown, immediate or force.
buffer-sync-start
(int, int)
Probe that fires when we begin to write dirty buffers during checkpoint (after identifying which buffers must be written). arg0 is the total number of buffers. arg1 is the number that are currently dirty and need to be written.
buffer-sync-written
(int)
Probe that fires after each buffer is written during checkpoint. arg0 is the ID number of the buffer.
buffer-sync-done
(int, int, int)
Probe that fires when all dirty buffers have been written. arg0 is the total number of buffers. arg1 is the number of buffers actually written by the checkpoint process. arg2 is the number that were expected to be written (arg1 of buffer-sync-start); any difference reflects other processes flushing buffers during the checkpoint.
buffer-checkpoint-sync-start
()
Probe that fires after dirty buffers have been written to the kernel, and before starting to issue fsync requests.
buffer-checkpoint-done
()
Probe that fires when syncing of buffers to disk is complete.
twophase-checkpoint-start
()
Probe that fires when the two-phase portion of a checkpoint is started.
twophase-checkpoint-done
()
Probe that fires when the two-phase portion of a checkpoint is complete.
buffer-read-start
(ForkNumber, BlockNumber, Oid, Oid, Oid, int, bool)
Probe that fires when a buffer read is started. arg0 and arg1 contain the fork and block numbers of the page (but arg1 will be -1 if this is a relation extension request). arg2, arg3, and arg4 contain the tablespace, database, and relation OIDs identifying the relation. arg5 is the ID of the backend which created the temporary relation for a local buffer, or InvalidBackendId (-1) for a shared buffer. arg6 is true for a relation extension request, false for normal read.
buffer-read-done
(ForkNumber, BlockNumber, Oid, Oid, Oid, int, bool, bool)
Probe that fires when a buffer read is complete. arg0 and arg1 contain the fork and block numbers of the page (if this is a relation extension request, arg1 now contains the block number of the newly added block). arg2, arg3, and arg4 contain the tablespace, database, and relation OIDs identifying the relation. arg5 is the ID of the backend which created the temporary relation for a local buffer, or InvalidBackendId (-1) for a shared buffer. arg6 is true for a relation extension request, false for normal read. arg7 is true if the buffer was found in the pool, false if not.
buffer-flush-start
(ForkNumber, BlockNumber, Oid, Oid, Oid)
Probe that fires before issuing any write request for a shared buffer. arg0 and arg1 contain the fork and block numbers of the page. arg2, arg3, and arg4 contain the tablespace, database, and relation OIDs identifying the relation.
buffer-flush-done
(ForkNumber, BlockNumber, Oid, Oid, Oid)
Probe that fires when a write request is complete. (Note that this just reflects the time to pass the data to the kernel; it's typically not actually been written to disk yet.) The arguments are the same as for buffer-flush-start.
buffer-write-dirty-start
(ForkNumber, BlockNumber, Oid, Oid, Oid)
buffer-write-dirty-done
(ForkNumber, BlockNumber, Oid, Oid, Oid)
Probe that fires when a dirty-buffer write is complete. The arguments are the same as for buffer-write-dirty-start.
wal-buffer-write-dirty-start
()
wal-buffer-write-dirty-done
()
Probe that fires when a dirty WAL buffer write is complete.
wal-insert
(unsigned char, unsigned char)
Probe that fires when a WAL record is inserted. arg0 is the resource manager (rmid) for the record. arg1 contains the info flags.
wal-switch
()
Probe that fires when a WAL segment switch is requested.
smgr-md-read-start
(ForkNumber, BlockNumber, Oid, Oid, Oid, int)
Probe that fires when beginning to read a block from a relation. arg0 and arg1 contain the fork and block numbers of the page. arg2, arg3, and arg4 contain the tablespace, database, and relation OIDs identifying the relation. arg5 is the ID of the backend which created the temporary relation for a local buffer, or InvalidBackendId (-1) for a shared buffer.
smgr-md-read-done
(ForkNumber, BlockNumber, Oid, Oid, Oid, int, int, int)
Probe that fires when a block read is complete. arg0 and arg1 contain the fork and block numbers of the page. arg2, arg3, and arg4 contain the tablespace, database, and relation OIDs identifying the relation. arg5 is the ID of the backend which created the temporary relation for a local buffer, or InvalidBackendId (-1) for a shared buffer. arg6 is the number of bytes actually read, while arg7 is the number requested (if these are different it indicates trouble).
smgr-md-write-start
(ForkNumber, BlockNumber, Oid, Oid, Oid, int)
Probe that fires when beginning to write a block to a relation. arg0 and arg1 contain the fork and block numbers of the page. arg2, arg3, and arg4 contain the tablespace, database, and relation OIDs identifying the relation. arg5 is the ID of the backend which created the temporary relation for a local buffer, or InvalidBackendId (-1) for a shared buffer.
smgr-md-write-done
(ForkNumber, BlockNumber, Oid, Oid, Oid, int, int, int)
Probe that fires when a block write is complete. arg0 and arg1 contain the fork and block numbers of the page. arg2, arg3, and arg4 contain the tablespace, database, and relation OIDs identifying the relation. arg5 is the ID of the backend which created the temporary relation for a local buffer, or InvalidBackendId (-1) for a shared buffer. arg6 is the number of bytes actually written, while arg7 is the number requested (if these are different it indicates trouble).
sort-start
(int, bool, int, int, bool, int)
Probe that fires when a sort operation is started. arg0 indicates heap, index or datum sort. arg1 is true for unique-value enforcement. arg2 is the number of key columns. arg3 is the number of kilobytes of work memory allowed. arg4 is true if random access to the sort result is required. arg5 indicates serial when 0, parallel worker when 1, or parallel leader when 2.
sort-done
(bool, long)
Probe that fires when a sort is complete. arg0 is true for external sort, false for internal sort. arg1 is the number of disk blocks used for an external sort, or kilobytes of memory used for an internal sort.
lwlock-acquire
(char *, LWLockMode)
Probe that fires when an LWLock has been acquired. arg0 is the LWLock's tranche. arg1 is the requested lock mode, either exclusive or shared.
lwlock-release
(char *)
Probe that fires when an LWLock has been released (but note that any released waiters have not yet been awakened). arg0 is the LWLock's tranche.
lwlock-wait-start
(char *, LWLockMode)
Probe that fires when an LWLock was not immediately available and a server process has begun to wait for the lock to become available. arg0 is the LWLock's tranche. arg1 is the requested lock mode, either exclusive or shared.
lwlock-wait-done
(char *, LWLockMode)
Probe that fires when a server process has been released from its wait for an LWLock (it does not actually have the lock yet). arg0 is the LWLock's tranche. arg1 is the requested lock mode, either exclusive or shared.
lwlock-condacquire
(char *, LWLockMode)
Probe that fires when an LWLock was successfully acquired when the caller specified no waiting. arg0 is the LWLock's tranche. arg1 is the requested lock mode, either exclusive or shared.
lwlock-condacquire-fail
(char *, LWLockMode)
Probe that fires when an LWLock was not successfully acquired when the caller specified no waiting. arg0 is the LWLock's tranche. arg1 is the requested lock mode, either exclusive or shared.
lock-wait-start
(unsigned int, unsigned int, unsigned int, unsigned int, unsigned int, LOCKMODE)
Probe that fires when a request for a heavyweight lock (lmgr lock) has begun to wait because the lock is not available. arg0 through arg3 are the tag fields identifying the object being locked. arg4 indicates the type of object being locked. arg5 indicates the lock type being requested.
lock-wait-done
(unsigned int, unsigned int, unsigned int, unsigned int, unsigned int, LOCKMODE)
Probe that fires when a request for a heavyweight lock (lmgr lock) has finished waiting (i.e., has acquired the lock). The arguments are the same as for lock-wait-start.
deadlock-found
()
Probe that fires when a deadlock is found by the deadlock detector.
Type
Definition
LocalTransactionId
unsigned int
LWLockMode
int
LOCKMODE
int
BlockNumber
unsigned int
Oid
unsigned int
ForkNumber
int
bool
unsigned char
The example below shows a DTrace script for analyzing transaction counts in the system, as an alternative to snapshotting pg_stat_database before and after a performance test:
When executed, the example D script gives output such as:
SystemTap uses a different notation for trace scripts than DTrace does, even though the underlying trace points are compatible. One point worth noting is that at this writing, SystemTap scripts must reference probe names using double underscores in place of hyphens. This is expected to be fixed in future SystemTap releases.
You should remember that DTrace scripts need to be carefully written and debugged, otherwise the trace information collected might be meaningless. In most cases where problems are found it is the instrumentation that is at fault, not the underlying system. When discussing information found using dynamic tracing, be sure to enclose the script used to allow that too to be checked and discussed.
New probes can be defined within the code wherever the developer desires, though this will require a recompilation. Below are the steps for inserting new probes:
Decide on probe names and data to be made available through the probes
Add the probe definitions to src/backend/utils/probes.d
Include pg_trace.h if it is not already present in the module(s) containing the probe points, and insert TRACE_POSTGRESQL probe macros at the desired locations in the source code
Recompile and verify that the new probes are available
Example: Here is an example of how you would add a probe to trace all new transactions by transaction ID.
Decide that the probe will be named transaction-start and requires a parameter of type LocalTransactionId
Add the probe definition to src/backend/utils/probes.d:
Note the use of the double underline in the probe name. In a DTrace script using the probe, the double underline needs to be replaced with a hyphen, so transaction-start is the name to document for users.
At compile time, transaction__start is converted to a macro called TRACE_POSTGRESQL_TRANSACTION_START (notice the underscores are single here), which is available by including pg_trace.h. Add the macro call to the appropriate location in the source code. In this case, it looks like the following:
After recompiling and running the new binary, check that your newly added probe is available by executing the following DTrace command. You should see similar output:
There are a few things to be careful about when adding trace macros to the C code:
You should take care that the data types specified for a probe's parameters match the data types of the variables used in the macro. Otherwise, you will get compilation errors.
On most platforms, if PostgreSQL is built with --enable-dtrace, the arguments to a trace macro will be evaluated whenever control passes through the macro, even if no tracing is being done. This is usually not worth worrying about if you are just reporting the values of a few local variables. But beware of putting expensive function calls into the arguments. If you need to do that, consider protecting the macro with a check to see if the trace is actually enabled:
Each trace macro has a corresponding ENABLED macro.
Probe that fires when a server process begins to write a dirty buffer. (If this happens often, it implies that is too small or the background writer control parameters need adjustment.) arg0 and arg1 contain the fork and block numbers of the page. arg2, arg3, and arg4 contain the tablespace, database, and relation OIDs identifying the relation.
Probe that fires when a server process begins to write a dirty WAL buffer because no more WAL buffer space is available. (If this happens often, it implies that is too small.)
On most Unix platforms, PostgreSQL modifies its command title as reported by ps, so that individual server processes can readily be identified. A sample display is
(The appropriate invocation of ps varies across different platforms, as do the details of what is shown. This example is from a recent Linux system.) The first process listed here is the master server process. The command arguments shown for it are the same ones used when it was launched. The next five processes are background worker processes automatically launched by the master process. (The “stats collector” process will not be present if you have set the system not to start the statistics collector; likewise the “autovacuum launcher” process can be disabled.) Each of the remaining processes is a server process handling one client connection. Each such process sets its command line display in the form
The user, database, and (client) host items remain the same for the life of the client connection, but the activity indicator changes. The activity can be idle (i.e., waiting for a client command), idle in transaction (waiting for client inside a BEGIN block), or a command type name such as SELECT. Also, waiting is appended if the server process is presently waiting on a lock held by another session. In the above example we can infer that process 15606 is waiting for process 15610 to complete its transaction and thereby release some lock. (Process 15610 must be the blocker, because there is no other active session. In more complicated cases it would be necessary to look into the pg_locks system view to determine who is blocking whom.)
If cluster_name has been configured the cluster name will also be shown in ps output:
If you have turned off update_process_title then the activity indicator is not updated; the process title is set only once when a new process is launched. On some platforms this saves a measurable amount of per-command overhead; on others it's insignificant.
Solaris requires special handling. You must use /usr/ucb/ps, rather than /bin/ps. You also must use two w flags, not just one. In addition, your original invocation of the postgres command must have a shorter ps status display than that provided by each server process. If you fail to do all three things, the ps output for each server process will be the original postgres command line.
Another useful tool for monitoring database activity is the pg_locks system table. It allows the database administrator to view information about the outstanding locks in the lock manager. For example, this capability can be used to:
View all the locks currently outstanding, all the locks on relations in a particular database, all the locks on a particular relation, or all the locks held by a particular PostgreSQL session.
Determine the relation in the current database with the most ungranted locks (which might be a source of contention among database clients).
Determine the effect of lock contention on overall database performance, as well as the extent to which contention varies with overall database traffic.
Details of the pg_locks view appear in Section 51.74. For more information on locking and managing concurrency with PostgreSQL, refer to Chapter 13.
PostgreSQL has the ability to report the progress of certain commands during command execution. Currently, the only commands which support progress reporting are CREATE INDEX, VACUUM and CLUSTER. This may be expanded in the future.
Whenever CREATE INDEX or REINDEX is running, the pg_stat_progress_create_index view will contain one row for each backend that is currently creating indexes. The tables below describe the information that will be reported and provide information about how to interpret it.
pg_stat_progress_create_index ViewColumn
Type
Description
pid
integer
Process ID of backend.
datid
oid
OID of the database to which this backend is connected.
datname
name
Name of the database to which this backend is connected.
relid
oid
OID of the table on which the index is being created.
index_relid
oid
OID of the index being created or reindexed. During a non-concurrent CREATE INDEX, this is 0.
command
text
The command that is running: CREATE INDEX, CREATE INDEX CONCURRENTLY, REINDEX, or REINDEX CONCURRENTLY.
phase
text
lockers_total
bigint
Total number of lockers to wait for, when applicable.
lockers_done
bigint
Number of lockers already waited for.
current_locker_pid
bigint
Process ID of the locker currently being waited for.
blocks_total
bigint
Total number of blocks to be processed in the current phase.
blocks_done
bigint
Number of blocks already processed in the current phase.
tuples_total
bigint
Total number of tuples to be processed in the current phase.
tuples_done
bigint
Number of tuples already processed in the current phase.
partitions_total
bigint
When creating an index on a partitioned table, this column is set to the total number of partitions on which the index is to be created.
partitions_done
bigint
When creating an index on a partitioned table, this column is set to the number of partitions on which the index has been completed.
Phase
Description
initializing
CREATE INDEX or REINDEX is preparing to create the index. This phase is expected to be very brief.
waiting for writers before build
CREATE INDEX CONCURRENTLY or REINDEX CONCURRENTLY is waiting for transactions with write locks that can potentially see the table to finish. This phase is skipped when not in concurrent mode. Columns lockers_total, lockers_done and current_locker_pid contain the progress information for this phase.
building index
The index is being built by the access method-specific code. In this phase, access methods that support progress reporting fill in their own progress data, and the subphase is indicated in this column. Typically, blocks_total and blocks_done will contain progress data, as well as potentially tuples_total and tuples_done.
waiting for writers before validation
CREATE INDEX CONCURRENTLY or REINDEX CONCURRENTLY is waiting for transactions with write locks that can potentially write into the table to finish. This phase is skipped when not in concurrent mode. Columns lockers_total, lockers_done and current_locker_pid contain the progress information for this phase.
index validation: scanning index
CREATE INDEX CONCURRENTLY is scanning the index searching for tuples that need to be validated. This phase is skipped when not in concurrent mode. Columns blocks_total (set to the total size of the index) and blocks_done contain the progress information for this phase.
index validation: sorting tuples
CREATE INDEX CONCURRENTLY is sorting the output of the index scanning phase.
index validation: scanning table
CREATE INDEX CONCURRENTLY is scanning the table to validate the index tuples collected in the previous two phases. This phase is skipped when not in concurrent mode. Columns blocks_total (set to the total size of the table) and blocks_done contain the progress information for this phase.
waiting for old snapshots
CREATE INDEX CONCURRENTLY or REINDEX CONCURRENTLY is waiting for transactions that can potentially see the table to release their snapshots. This phase is skipped when not in concurrent mode. Columns lockers_total, lockers_done and current_locker_pid contain the progress information for this phase.
waiting for readers before marking dead
REINDEX CONCURRENTLY is waiting for transactions with read locks on the table to finish, before marking the old index dead. This phase is skipped when not in concurrent mode. Columns lockers_total, lockers_done and current_locker_pid contain the progress information for this phase.
waiting for readers before dropping
REINDEX CONCURRENTLY is waiting for transactions with read locks on the table to finish, before dropping the old index. This phase is skipped when not in concurrent mode. Columns lockers_total, lockers_done and current_locker_pid contain the progress information for this phase.
Whenever VACUUM is running, the pg_stat_progress_vacuum view will contain one row for each backend (including autovacuum worker processes) that is currently vacuuming. The tables below describe the information that will be reported and provide information about how to interpret it. Progress for VACUUM FULL commands is reported via pg_stat_progress_cluster because both VACUUM FULL and CLUSTER rewrite the table, while regular VACUUM only modifies it in place. See Section 27.4.3.
pg_stat_progress_vacuum ViewColumn
Type
Description
pid
integer
Process ID of backend.
datid
oid
OID of the database to which this backend is connected.
datname
name
Name of the database to which this backend is connected.
relid
oid
OID of the table being vacuumed.
phase
text
heap_blks_total
bigint
Total number of heap blocks in the table. This number is reported as of the beginning of the scan; blocks added later will not be (and need not be) visited by this VACUUM.
heap_blks_scanned
bigint
heap_blks_vacuumed
bigint
Number of heap blocks vacuumed. Unless the table has no indexes, this counter only advances when the phase is vacuuming heap. Blocks that contain no dead tuples are skipped, so the counter may sometimes skip forward in large increments.
index_vacuum_count
bigint
Number of completed index vacuum cycles.
max_dead_tuples
bigint
num_dead_tuples
bigint
Number of dead tuples collected since the last index vacuum cycle.
Phase
Description
initializing
VACUUM is preparing to begin scanning the heap. This phase is expected to be very brief.
scanning heap
VACUUM is currently scanning the heap. It will prune and defragment each page if required, and possibly perform freezing activity. The heap_blks_scanned column can be used to monitor the progress of the scan.
vacuuming indexes
vacuuming heap
VACUUM is currently vacuuming the heap. Vacuuming the heap is distinct from scanning the heap, and occurs after each instance of vacuuming indexes. If heap_blks_scanned is less than heap_blks_total, the system will return to scanning the heap after this phase is completed; otherwise, it will begin cleaning up indexes after this phase is completed.
cleaning up indexes
VACUUM is currently cleaning up indexes. This occurs after the heap has been completely scanned and all vacuuming of the indexes and the heap has been completed.
truncating heap
VACUUM is currently truncating the heap so as to return empty pages at the end of the relation to the operating system. This occurs after cleaning up indexes.
performing final cleanup
VACUUM is performing final cleanup. During this phase, VACUUM will vacuum the free space map, update statistics in pg_class, and report statistics to the statistics collector. When this phase is completed, VACUUM will end.
Whenever CLUSTER or VACUUM FULL is running, the pg_stat_progress_cluster view will contain a row for each backend that is currently running either command. The tables below describe the information that will be reported and provide information about how to interpret it.
pg_stat_progress_cluster ViewColumn
Type
Description
pid
integer
Process ID of backend.
datid
oid
OID of the database to which this backend is connected.
datname
name
Name of the database to which this backend is connected.
relid
oid
OID of the table being clustered.
command
text
The command that is running. Either CLUSTER or VACUUM FULL.
phase
text
cluster_index_relid
oid
If the table is being scanned using an index, this is the OID of the index being used; otherwise, it is zero.
heap_tuples_scanned
bigint
Number of heap tuples scanned. This counter only advances when the phase is seq scanning heap, index scanning heap or writing new heap.
heap_tuples_written
bigint
Number of heap tuples written. This counter only advances when the phase is seq scanning heap, index scanning heap or writing new heap.
heap_blks_total
bigint
Total number of heap blocks in the table. This number is reported as of the beginning of seq scanning heap.
heap_blks_scanned
bigint
Number of heap blocks scanned. This counter only advances when the phase is seq scanning heap.
index_rebuild_count
bigint
Number of indexes rebuilt. This counter only advances when the phase is rebuilding index.
Phase
Description
initializing
The command is preparing to begin scanning the heap. This phase is expected to be very brief.
seq scanning heap
The command is currently scanning the table using a sequential scan.
index scanning heap
CLUSTER is currently scanning the table using an index scan.
sorting tuples
CLUSTER is currently sorting tuples.
writing new heap
CLUSTER is currently writing the new heap.
swapping relation files
The command is currently swapping newly-built files into place.
rebuilding index
The command is currently rebuilding an index.
performing final cleanup
The command is performing final cleanup. When this phase is completed, CLUSTER or VACUUM FULL will end.
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資訊。目前，收集器可以以磁區和單個資料列的方式計算對資料表和索引的存取。它也追踪著每個資料表中的總資料筆數，以及有關每個資料表的清理和分析操作的資訊。它還可以計算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 也支援回報有關目前系統中確切正在發生情況的動態資訊，例如目前由其他伺服器程序執行的確切指令以及系統中存在哪些其他連線。此功能獨立於收集器程序。
由於收集統計資訊會增加查詢執行的成本，因此可以將系統配置為收集或不收集資訊。這由通常由 postgresql.conf 中的配置參數所控制。 （有關設定配置參數的詳細資訊，請參閱。）
The parameter enables monitoring of the current command being executed by any server process.
The parameter controls whether statistics are collected about table and index accesses.
The parameter enables tracking of usage of user-defined functions.
The parameter enables monitoring of block read and write times.
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 command. (To prevent ordinary users from hiding their activity from the administrator, only superusers are allowed to change these parameters with SET.)
The statistics collector transmits the collected information to other PostgreSQL processes through temporary files. These files are stored in the directory named by the parameter, pg_stat_tmp by default. For better performance, stats_temp_directory can be pointed at a RAM-based file system, decreasing physical I/O requirements. 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. When recovery is performed at server start (e.g. after immediate shutdown, server crash, and point-in-time recovery), all statistics counters are reset.
Several predefined views, listed in , are available to show the current state of the system. There are also several other views, listed in , available to show the results of statistics collection. Alternatively, one can build custom views using the underlying statistics functions, as discussed in .
When using the statistics to monitor collected data, it is important to realize that the information does not update instantaneously. Each individual server process transmits new statistical counts to the collector just before going idle; so a query or transaction still in progress does not affect the displayed totals. Also, the collector itself emits a new report at most once per PGSTAT_STAT_INTERVAL milliseconds (500 ms unless altered while building the server). So the displayed information lags behind actual activity. However, current-query information collected by track_activities is always up-to-date.
Another important point is that when a server process is asked to display any of these statistics, it first fetches the most recent report emitted by the collector process and then continues to use this snapshot for all statistical views and functions until the end of its current transaction. So the statistics will show static information as long as you continue the current transaction. 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. This is a feature, not a bug, because it allows you to perform several queries on the statistics and correlate the results without worrying that the numbers are changing underneath you. But if you want to see new results with each query, be sure to do the queries outside any transaction block. Alternatively, you can invoke pg_stat_clear_snapshot(), which will discard the current transaction's statistics snapshot (if any). The next use of statistical information will cause a new snapshot to be fetched.
A transaction can also see its own statistics (as yet untransmitted to the collector) in the views pg_stat_xact_all_tables, pg_stat_xact_sys_tables, pg_stat_xact_user_tables, and pg_stat_xact_user_functions. These numbers do not act as stated above; instead they update continuously throughout the transaction.
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.
pg_stat_activity ViewThe pg_stat_activity view will have one row per server process, showing information related to the current activity of that process.
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.
wait_event DescriptionFor 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 27.5. pg_stat_replication View
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.
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.
pg_stat_wal_receiver ViewThe pg_stat_wal_receiver view will contain only one row, showing statistics about the WAL receiver from that receiver's connected server.
pg_stat_subscription ViewThe 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.
pg_stat_ssl ViewThe 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.
pg_stat_gssapi ViewThe pg_stat_gssapi view will contain one row per backend, showing information about GSSAPI 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.
pg_stat_archiver ViewThe pg_stat_archiver view will always have a single row, containing data about the archiver process of the cluster.
pg_stat_bgwriter ViewThe pg_stat_bgwriter view will always have a single row, containing global data for the cluster.
pg_stat_database ViewThe pg_stat_database view will contain one row for each database in the cluster, plus one for the shared objects, showing database-wide statistics.
pg_stat_database_conflicts ViewThe 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.
pg_stat_all_tables ViewThe 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. The pg_stat_user_tables and pg_stat_sys_tables views contain the same information, but filtered to only show user and system tables respectively.
pg_stat_all_indexes ViewThe pg_stat_all_indexes view will contain one row for each index in the current database, showing statistics about accesses to that specific index. 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.
Indexes can be used by simple index scans, “bitmap” index scans, and the optimizer. In a bitmap scan the output of several indexes can be combined via AND or OR rules, so it is difficult to associate individual heap row fetches with specific indexes when a bitmap scan is used. 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 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.
The idx_tup_read and idx_tup_fetch counts can be different even without any use of bitmap scans, because idx_tup_read counts index entries retrieved from the index while idx_tup_fetch counts live rows fetched from the table. 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.
pg_statio_all_tables ViewThe 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. 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.
pg_statio_all_indexes ViewThe pg_statio_all_indexes view will contain one row for each index in the current database, showing statistics about I/O on that specific index. 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.
pg_statio_all_sequences ViewThe 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.
pg_stat_user_functions ViewOther ways of looking at the statistics can be set up by writing queries that use the same underlying statistics access functions used by the standard views shown above. For details such as the functions' names, consult the definitions of the standard views. (For example, in psql you could issue \d+ pg_stat_activity.) The access functions for per-database statistics take a database OID as an argument to identify which database to report on. The per-table and per-index functions take a table or index OID. The functions for per-function statistics take a function OID. Note that only tables, indexes, and functions in the current database can be seen with these functions.
Current processing phase of index creation. See .
Current processing phase of vacuum. See .
Number of heap blocks scanned. Because the is used to optimize scans, some blocks will be skipped without inspection; skipped blocks are included in this total, so that this number will eventually become equal to heap_blks_total when the vacuum is complete. This counter only advances when the phase is scanning heap.
Number of dead tuples that we can store before needing to perform an index vacuum cycle, based on .
VACUUM is currently vacuuming the indexes. If a table has any indexes, this will happen at least once per vacuum, after the heap has been completely scanned. It may happen multiple times per vacuum if is insufficient to store the number of dead tuples found.
Current processing phase. See .
Some of the information in the dynamic statistics views shown in is security restricted. Ordinary users can only see all the information about their own sessions (sessions belonging to a role that they are a member of). In rows about other sessions, many columns will be null. Note, however, that the existence of a session and its general properties such as its sessions user and database are visible to all users. Superusers and members of the built-in role pg_read_all_stats (see also ) can see all the information about all sessions.
The pg_stat_user_functions view will contain one row for each tracked function, showing statistics about executions of that function. The parameter controls exactly which functions are tracked.
Additional functions related to statistics collection are listed in .
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. Sometimes it may be more convenient to obtain just a subset of this information. In such cases, an older set of per-backend statistics access functions can be used; these are shown in . These access functions use a backend ID number, which ranges from one to the number of currently active backends. The function pg_stat_get_backend_idset provides a convenient way to generate one row for each active backend for invoking these functions. For example, to show the PIDs and current queries of all backends:
View Name
Description
pg_stat_activity
One row per server process, showing information related to the current activity of that process, such as state and current query. See pg_stat_activity for details.
pg_stat_replication
One row per WAL sender process, showing statistics about replication to that sender's connected standby server. See pg_stat_replication for details.
pg_stat_wal_receiver
Only one row, showing statistics about the WAL receiver from that receiver's connected server. See pg_stat_wal_receiver for details.
pg_stat_subscription
At least one row per subscription, showing information about the subscription workers. See pg_stat_subscription for details.
pg_stat_ssl
One row per connection (regular and replication), showing information about SSL used on this connection. See pg_stat_ssl for details.
pg_stat_gssapi
One row per connection (regular and replication), showing information about GSSAPI authentication and encryption used on this connection. See pg_stat_gssapi for details.
pg_stat_progress_create_index
One row for each backend running CREATE INDEX or REINDEX, showing current progress. See Section 27.4.1.
pg_stat_progress_vacuum
One row for each backend (including autovacuum worker processes) running VACUUM, showing current progress. See Section 27.4.2.
pg_stat_progress_cluster
One row for each backend running CLUSTER or VACUUM FULL, showing current progress. See Section 27.4.3.
View Name
Description
pg_stat_archiver
One row only, showing statistics about the WAL archiver process's activity. See pg_stat_archiver for details.
pg_stat_bgwriter
One row only, showing statistics about the background writer process's activity. See pg_stat_bgwriter for details.
pg_stat_database
One row per database, showing database-wide statistics. See pg_stat_database for details.
pg_stat_database_conflicts
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.
pg_stat_all_tables
One row for each table in the current database, showing statistics about accesses to that specific table. See pg_stat_all_tables for details.
pg_stat_sys_tables
Same as pg_stat_all_tables, except that only system tables are shown.
pg_stat_user_tables
Same as pg_stat_all_tables, except that only user tables are shown.
pg_stat_xact_all_tables
Similar to pg_stat_all_tables, but counts actions taken so far within the current transaction (which are not yet included in pg_stat_all_tables and related views). The columns for numbers of live and dead rows and vacuum and analyze actions are not present in this view.
pg_stat_xact_sys_tables
Same as pg_stat_xact_all_tables, except that only system tables are shown.
pg_stat_xact_user_tables
Same as pg_stat_xact_all_tables, except that only user tables are shown.
pg_stat_all_indexes
One row for each index in the current database, showing statistics about accesses to that specific index. See pg_stat_all_indexes for details.
pg_stat_sys_indexes
Same as pg_stat_all_indexes, except that only indexes on system tables are shown.
pg_stat_user_indexes
Same as pg_stat_all_indexes, except that only indexes on user tables are shown.
pg_statio_all_tables
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.
pg_statio_sys_tables
Same as pg_statio_all_tables, except that only system tables are shown.
pg_statio_user_tables
Same as pg_statio_all_tables, except that only user tables are shown.
pg_statio_all_indexes
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.
pg_statio_sys_indexes
Same as pg_statio_all_indexes, except that only indexes on system tables are shown.
pg_statio_user_indexes
Same as pg_statio_all_indexes, except that only indexes on user tables are shown.
pg_statio_all_sequences
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.
pg_statio_sys_sequences
Same as pg_statio_all_sequences, except that only system sequences are shown. (Presently, no system sequences are defined, so this view is always empty.)
pg_statio_user_sequences
Same as pg_statio_all_sequences, except that only user sequences are shown.
pg_stat_user_functions
One row for each tracked function, showing statistics about executions of that function. See pg_stat_user_functions for details.
pg_stat_xact_user_functions
Similar to pg_stat_user_functions, but counts only calls during the current transaction (which are not yet included in pg_stat_user_functions).
Column
Type
Description
datid
oid
OID of the database this backend is connected to
datname
name
Name of the database this backend is connected to
pid
integer
Process ID of this backend
usesysid
oid
OID of the user logged into this backend
usename
name
Name of the user logged into this backend
application_name
text
Name of the application that is connected to this backend
client_addr
inet
IP address of the client connected to this backend. 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.
client_hostname
text
Host name of the connected client, as reported by a reverse DNS lookup of client_addr. This field will only be non-null for IP connections, and only when log_hostname is enabled.
client_port
integer
TCP port number that the client is using for communication with this backend, or -1 if a Unix socket is used
backend_start
timestamp with time zone
Time when this process was started. For client backends, this is the time the client connected to the server.
xact_start
timestamp with time zone
Time when this process' current transaction was started, or null if no transaction is active. If the current query is the first of its transaction, this column is equal to the query_start column.
query_start
timestamp with time zone
Time when the currently active query was started, or if state is not active, when the last query was started
state_change
timestamp with time zone
Time when the state was last changed
wait_event_type
text
The type of event for which the backend is waiting, if any; otherwise NULL. Possible values are:
LWLock: The backend is waiting for a lightweight lock. Each such lock protects a particular data structure in shared memory. wait_event will contain a name identifying the purpose of the lightweight lock. (Some locks have specific names; others are part of a group of locks each with a similar purpose.)
Lock: The backend is waiting for a heavyweight lock. Heavyweight locks, also known as lock manager locks or simply locks, primarily protect SQL-visible objects such as tables. However, they are also used to ensure mutual exclusion for certain internal operations such as relation extension. wait_event will identify the type of lock awaited.
BufferPin: The server process is waiting to access to a data buffer during a period when no other process can be examining that buffer. Buffer pin waits can be protracted if another process holds an open cursor which last read data from the buffer in question.
Activity: The server process is idle. This is used by system processes waiting for activity in their main processing loop. wait_event will identify the specific wait point.
Extension: The server process is waiting for activity in an extension module. This category is useful for modules to track custom waiting points.
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. wait_event will identify the specific wait point.
IPC: The server process is waiting for some activity from another process in the server. wait_event will identify the specific wait point.
Timeout: The server process is waiting for a timeout to expire. wait_event will identify the specific wait point.
IO: The server process is waiting for a IO to complete. wait_event will identify the specific wait point.
wait_event
text
Wait event name if backend is currently waiting, otherwise NULL. See Table 27.4for details.
state
text
Current overall state of this backend. Possible values are:
active: The backend is executing a query.
idle: The backend is waiting for a new client command.
idle in transaction: The backend is in a transaction, but is not currently executing a query.
idle in transaction (aborted): This state is similar to idle in transaction, except one of the statements in the transaction caused an error.
fastpath function call: The backend is executing a fast-path function.
disabled: This state is reported if track_activities is disabled in this backend.
backend_xid
xid
Top-level transaction identifier of this backend, if any.
backend_xmin
xid
The current backend's xmin horizon.
query
text
Text of this backend's most recent query. If state is active this field shows the currently executing query. In all other states, it shows the last query that was executed. By default the query text is truncated at 1024 characters; this value can be changed via the parameter track_activity_query_size.
backend_type
text
Type of current backend. Possible types are autovacuum launcher, autovacuum worker, logical replication launcher, logical replication worker, parallel worker, background writer, client backend, checkpointer, startup, walreceiver, walsender and walwriter. In addition, background workers registered by extensions may have additional types.
Wait Event Type
Wait Event Name
Description
LWLock
ShmemIndexLock
Waiting to find or allocate space in shared memory.
OidGenLock
Waiting to allocate or assign an OID.
XidGenLock
Waiting to allocate or assign a transaction id.
ProcArrayLock
Waiting to get a snapshot or clearing a transaction id at transaction end.
SInvalReadLock
Waiting to retrieve or remove messages from shared invalidation queue.
SInvalWriteLock
Waiting to add a message in shared invalidation queue.
WALBufMappingLock
Waiting to replace a page in WAL buffers.
WALWriteLock
Waiting for WAL buffers to be written to disk.
ControlFileLock
Waiting to read or update the control file or creation of a new WAL file.
CheckpointLock
Waiting to perform checkpoint.
CLogControlLock
Waiting to read or update transaction status.
SubtransControlLock
Waiting to read or update sub-transaction information.
MultiXactGenLock
Waiting to read or update shared multixact state.
MultiXactOffsetControlLock
Waiting to read or update multixact offset mappings.
MultiXactMemberControlLock
Waiting to read or update multixact member mappings.
RelCacheInitLock
Waiting to read or write relation cache initialization file.
CheckpointerCommLock
Waiting to manage fsync requests.
TwoPhaseStateLock
Waiting to read or update the state of prepared transactions.
TablespaceCreateLock
Waiting to create or drop the tablespace.
BtreeVacuumLock
Waiting to read or update vacuum-related information for a B-tree index.
AddinShmemInitLock
Waiting to manage space allocation in shared memory.
AutovacuumLock
Autovacuum worker or launcher waiting to update or read the current state of autovacuum workers.
AutovacuumScheduleLock
Waiting to ensure that the table it has selected for a vacuum still needs vacuuming.
SyncScanLock
Waiting to get the start location of a scan on a table for synchronized scans.
RelationMappingLock
Waiting to update the relation map file used to store catalog to filenode mapping.
AsyncCtlLock
Waiting to read or update shared notification state.
AsyncQueueLock
Waiting to read or update notification messages.
SerializableXactHashLock
Waiting to retrieve or store information about serializable transactions.
SerializableFinishedListLock
Waiting to access the list of finished serializable transactions.
SerializablePredicateLockListLock
Waiting to perform an operation on a list of locks held by serializable transactions.
OldSerXidLock
Waiting to read or record conflicting serializable transactions.
SyncRepLock
Waiting to read or update information about synchronous replicas.
BackgroundWorkerLock
Waiting to read or update background worker state.
DynamicSharedMemoryControlLock
Waiting to read or update dynamic shared memory state.
AutoFileLock
Waiting to update the postgresql.auto.conf file.
ReplicationSlotAllocationLock
Waiting to allocate or free a replication slot.
ReplicationSlotControlLock
Waiting to read or update replication slot state.
CommitTsControlLock
Waiting to read or update transaction commit timestamps.
CommitTsLock
Waiting to read or update the last value set for the transaction timestamp.
ReplicationOriginLock
Waiting to setup, drop or use replication origin.
MultiXactTruncationLock
Waiting to read or truncate multixact information.
OldSnapshotTimeMapLock
Waiting to read or update old snapshot control information.
LogicalRepWorkerLock
Waiting for action on logical replication worker to finish.
CLogTruncationLock
Waiting to execute txid_status or update the oldest transaction id available to it.
clog
Waiting for I/O on a clog (transaction status) buffer.
commit_timestamp
Waiting for I/O on commit timestamp buffer.
subtrans
Waiting for I/O a subtransaction buffer.
multixact_offset
Waiting for I/O on a multixact offset buffer.
multixact_member
Waiting for I/O on a multixact_member buffer.
async
Waiting for I/O on an async (notify) buffer.
oldserxid
Waiting for I/O on an oldserxid buffer.
wal_insert
Waiting to insert WAL into a memory buffer.
buffer_content
Waiting to read or write a data page in memory.
buffer_io
Waiting for I/O on a data page.
replication_origin
Waiting to read or update the replication progress.
replication_slot_io
Waiting for I/O on a replication slot.
proc
Waiting to read or update the fast-path lock information.
buffer_mapping
Waiting to associate a data block with a buffer in the buffer pool.
lock_manager
Waiting to add or examine locks for backends, or waiting to join or exit a locking group (used by parallel query).
predicate_lock_manager
Waiting to add or examine predicate lock information.
serializable_xact
Waiting to perform an operation on a serializable transaction in a parallel query.
parallel_query_dsa
Waiting for parallel query dynamic shared memory allocation lock.
tbm
Waiting for TBM shared iterator lock.
parallel_append
Waiting to choose the next subplan during Parallel Append plan execution.
parallel_hash_join
Waiting to allocate or exchange a chunk of memory or update counters during Parallel Hash plan execution.
Lock
relation
Waiting to acquire a lock on a relation.
extend
Waiting to extend a relation.
page
Waiting to acquire a lock on page of a relation.
tuple
Waiting to acquire a lock on a tuple.
transactionid
Waiting for a transaction to finish.
virtualxid
Waiting to acquire a virtual xid lock.
speculative token
Waiting to acquire a speculative insertion lock.
object
Waiting to acquire a lock on a non-relation database object.
userlock
Waiting to acquire a user lock.
advisory
Waiting to acquire an advisory user lock.
BufferPin
BufferPin
Waiting to acquire a pin on a buffer.
Activity
ArchiverMain
Waiting in main loop of the archiver process.
AutoVacuumMain
Waiting in main loop of autovacuum launcher process.
BgWriterHibernate
Waiting in background writer process, hibernating.
BgWriterMain
Waiting in main loop of background writer process background worker.
CheckpointerMain
Waiting in main loop of checkpointer process.
LogicalApplyMain
Waiting in main loop of logical apply process.
LogicalLauncherMain
Waiting in main loop of logical launcher process.
PgStatMain
Waiting in main loop of the statistics collector process.
RecoveryWalAll
Waiting for WAL from a stream at recovery.
RecoveryWalStream
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.
SysLoggerMain
Waiting in main loop of syslogger process.
WalReceiverMain
Waiting in main loop of WAL receiver process.
WalSenderMain
Waiting in main loop of WAL sender process.
WalWriterMain
Waiting in main loop of WAL writer process.
Client
ClientRead
Waiting to read data from the client.
ClientWrite
Waiting to write data to the client.
GSSOpenServer
Waiting to read data from the client while establishing the GSSAPI session.
LibPQWalReceiverConnect
Waiting in WAL receiver to establish connection to remote server.
LibPQWalReceiverReceive
Waiting in WAL receiver to receive data from remote server.
SSLOpenServer
Waiting for SSL while attempting connection.
WalReceiverWaitStart
Waiting for startup process to send initial data for streaming replication.
WalSenderWaitForWAL
Waiting for WAL to be flushed in WAL sender process.
WalSenderWriteData
Waiting for any activity when processing replies from WAL receiver in WAL sender process.
Extension
Extension
Waiting in an extension.
IPC
BgWorkerShutdown
Waiting for background worker to shut down.
BgWorkerStartup
Waiting for background worker to start up.
BtreePage
Waiting for the page number needed to continue a parallel B-tree scan to become available.
CheckpointDone
Waiting for a checkpoint to complete.
CheckpointStart
Waiting for a checkpoint to start.
ClogGroupUpdate
Waiting for group leader to update transaction status at transaction end.
ExecuteGather
Waiting for activity from child process when executing Gather node.
Hash/Batch/Allocating
Waiting for an elected Parallel Hash participant to allocate a hash table.
Hash/Batch/Electing
Electing a Parallel Hash participant to allocate a hash table.
Hash/Batch/Loading
Waiting for other Parallel Hash participants to finish loading a hash table.
Hash/Build/Allocating
Waiting for an elected Parallel Hash participant to allocate the initial hash table.
Hash/Build/Electing
Electing a Parallel Hash participant to allocate the initial hash table.
Hash/Build/HashingInner
Waiting for other Parallel Hash participants to finish hashing the inner relation.
Hash/Build/HashingOuter
Waiting for other Parallel Hash participants to finish partitioning the outer relation.
Hash/GrowBatches/Allocating
Waiting for an elected Parallel Hash participant to allocate more batches.
Hash/GrowBatches/Deciding
Electing a Parallel Hash participant to decide on future batch growth.
Hash/GrowBatches/Electing
Electing a Parallel Hash participant to allocate more batches.
Hash/GrowBatches/Finishing
Waiting for an elected Parallel Hash participant to decide on future batch growth.
Hash/GrowBatches/Repartitioning
Waiting for other Parallel Hash participants to finishing repartitioning.
Hash/GrowBuckets/Allocating
Waiting for an elected Parallel Hash participant to finish allocating more buckets.
Hash/GrowBuckets/Electing
Electing a Parallel Hash participant to allocate more buckets.
Hash/GrowBuckets/Reinserting
Waiting for other Parallel Hash participants to finish inserting tuples into new buckets.
LogicalSyncData
Waiting for logical replication remote server to send data for initial table synchronization.
LogicalSyncStateChange
Waiting for logical replication remote server to change state.
MessageQueueInternal
Waiting for other process to be attached in shared message queue.
MessageQueuePutMessage
Waiting to write a protocol message to a shared message queue.
MessageQueueReceive
Waiting to receive bytes from a shared message queue.
MessageQueueSend
Waiting to send bytes to a shared message queue.
ParallelBitmapScan
Waiting for parallel bitmap scan to become initialized.
ParallelCreateIndexScan
Waiting for parallel CREATE INDEX workers to finish heap scan.
ParallelFinish
Waiting for parallel workers to finish computing.
ProcArrayGroupUpdate
Waiting for group leader to clear transaction id at transaction end.
Promote
Waiting for standby promotion.
ReplicationOriginDrop
Waiting for a replication origin to become inactive to be dropped.
ReplicationSlotDrop
Waiting for a replication slot to become inactive to be dropped.
SafeSnapshot
Waiting for a snapshot for a READ ONLY DEFERRABLE transaction.
SyncRep
Waiting for confirmation from remote server during synchronous replication.
Timeout
BaseBackupThrottle
Waiting during base backup when throttling activity.
PgSleep
Waiting in process that called pg_sleep.
RecoveryApplyDelay
Waiting to apply WAL at recovery because it is delayed.
IO
BufFileRead
Waiting for a read from a buffered file.
BufFileWrite
Waiting for a write to a buffered file.
ControlFileRead
Waiting for a read from the control file.
ControlFileSync
Waiting for the control file to reach stable storage.
ControlFileSyncUpdate
Waiting for an update to the control file to reach stable storage.
ControlFileWrite
Waiting for a write to the control file.
ControlFileWriteUpdate
Waiting for a write to update the control file.
CopyFileRead
Waiting for a read during a file copy operation.
CopyFileWrite
Waiting for a write during a file copy operation.
DataFileExtend
Waiting for a relation data file to be extended.
DataFileFlush
Waiting for a relation data file to reach stable storage.
DataFileImmediateSync
Waiting for an immediate synchronization of a relation data file to stable storage.
DataFilePrefetch
Waiting for an asynchronous prefetch from a relation data file.
DataFileRead
Waiting for a read from a relation data file.
DataFileSync
Waiting for changes to a relation data file to reach stable storage.
DataFileTruncate
Waiting for a relation data file to be truncated.
DataFileWrite
Waiting for a write to a relation data file.
DSMFillZeroWrite
Waiting to write zero bytes to a dynamic shared memory backing file.
LockFileAddToDataDirRead
Waiting for a read while adding a line to the data directory lock file.
LockFileAddToDataDirSync
Waiting for data to reach stable storage while adding a line to the data directory lock file.
LockFileAddToDataDirWrite
Waiting for a write while adding a line to the data directory lock file.
LockFileCreateRead
Waiting to read while creating the data directory lock file.
LockFileCreateSync
Waiting for data to reach stable storage while creating the data directory lock file.
LockFileCreateWrite
Waiting for a write while creating the data directory lock file.
LockFileReCheckDataDirRead
Waiting for a read during recheck of the data directory lock file.
LogicalRewriteCheckpointSync
Waiting for logical rewrite mappings to reach stable storage during a checkpoint.
LogicalRewriteMappingSync
Waiting for mapping data to reach stable storage during a logical rewrite.
LogicalRewriteMappingWrite
Waiting for a write of mapping data during a logical rewrite.
LogicalRewriteSync
Waiting for logical rewrite mappings to reach stable storage.
LogicalRewriteTruncate
Waiting for truncate of mapping data during a logical rewrite.
LogicalRewriteWrite
Waiting for a write of logical rewrite mappings.
RelationMapRead
Waiting for a read of the relation map file.
RelationMapSync
Waiting for the relation map file to reach stable storage.
RelationMapWrite
Waiting for a write to the relation map file.
ReorderBufferRead
Waiting for a read during reorder buffer management.
ReorderBufferWrite
Waiting for a write during reorder buffer management.
ReorderLogicalMappingRead
Waiting for a read of a logical mapping during reorder buffer management.
ReplicationSlotRead
Waiting for a read from a replication slot control file.
ReplicationSlotRestoreSync
Waiting for a replication slot control file to reach stable storage while restoring it to memory.
ReplicationSlotSync
Waiting for a replication slot control file to reach stable storage.
ReplicationSlotWrite
Waiting for a write to a replication slot control file.
SLRUFlushSync
Waiting for SLRU data to reach stable storage during a checkpoint or database shutdown.
SLRURead
Waiting for a read of an SLRU page.
SLRUSync
Waiting for SLRU data to reach stable storage following a page write.
SLRUWrite
Waiting for a write of an SLRU page.
SnapbuildRead
Waiting for a read of a serialized historical catalog snapshot.
SnapbuildSync
Waiting for a serialized historical catalog snapshot to reach stable storage.
SnapbuildWrite
Waiting for a write of a serialized historical catalog snapshot.
TimelineHistoryFileSync
Waiting for a timeline history file received via streaming replication to reach stable storage.
TimelineHistoryFileWrite
Waiting for a write of a timeline history file received via streaming replication.
TimelineHistoryRead
Waiting for a read of a timeline history file.
TimelineHistorySync
Waiting for a newly created timeline history file to reach stable storage.
TimelineHistoryWrite
Waiting for a write of a newly created timeline history file.
TwophaseFileRead
Waiting for a read of a two phase state file.
TwophaseFileSync
Waiting for a two phase state file to reach stable storage.
TwophaseFileWrite
Waiting for a write of a two phase state file.
WALBootstrapSync
Waiting for WAL to reach stable storage during bootstrapping.
WALBootstrapWrite
Waiting for a write of a WAL page during bootstrapping.
WALCopyRead
Waiting for a read when creating a new WAL segment by copying an existing one.
WALCopySync
Waiting a new WAL segment created by copying an existing one to reach stable storage.
WALCopyWrite
Waiting for a write when creating a new WAL segment by copying an existing one.
WALInitSync
Waiting for a newly initialized WAL file to reach stable storage.
WALInitWrite
Waiting for a write while initializing a new WAL file.
WALRead
Waiting for a read from a WAL file.
WALSenderTimelineHistoryRead
Waiting for a read from a timeline history file during walsender timeline command.
WALSync
Waiting for a WAL file to reach stable storage.
WALSyncMethodAssign
Waiting for data to reach stable storage while assigning WAL sync method.
WALWrite
Waiting for a write to a WAL file.
Column
Type
Description
pid
integer
Process ID of a WAL sender process
usesysid
oid
OID of the user logged into this WAL sender process
usename
name
Name of the user logged into this WAL sender process
application_name
text
Name of the application that is connected to this WAL sender
client_addr
inet
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.
client_hostname
text
Host name of the connected client, as reported by a reverse DNS lookup of client_addr. This field will only be non-null for IP connections, and only when log_hostname is enabled.
client_port
integer
TCP port number that the client is using for communication with this WAL sender, or -1 if a Unix socket is used
backend_start
timestamp with time zone
Time when this process was started, i.e., when the client connected to this WAL sender
backend_xmin
xid
This standby's xmin horizon reported by hot_standby_feedback.
state
text
Current WAL sender state. Possible values are:
startup: This WAL sender is starting up.
catchup: This WAL sender's connected standby is catching up with the primary.
streaming: This WAL sender is streaming changes after its connected standby server has caught up with the primary.
backup: This WAL sender is sending a backup.
stopping: This WAL sender is stopping.
sent_lsn
pg_lsn
Last write-ahead log location sent on this connection
write_lsn
pg_lsn
Last write-ahead log location written to disk by this standby server
flush_lsn
pg_lsn
Last write-ahead log location flushed to disk by this standby server
replay_lsn
pg_lsn
Last write-ahead log location replayed into the database on this standby server
write_lag
interval
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 synchronous_commit level remote_write incurred while committing if this server was configured as a synchronous standby.
flush_lag
interval
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 synchronous_commit level on incurred while committing if this server was configured as a synchronous standby.
replay_lag
interval
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 synchronous_commit level remote_apply incurred while committing if this server was configured as a synchronous standby.
sync_priority
integer
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.
sync_state
text
Synchronous state of this standby server. Possible values are:
async: This standby server is asynchronous.
potential: This standby server is now asynchronous, but can potentially become synchronous if one of current synchronous ones fails.
sync: This standby server is synchronous.
quorum: This standby server is considered as a candidate for quorum standbys.
reply_time
timestamp with time zone
Send time of last reply message received from standby server
Column
Type
Description
pid
integer
Process ID of the WAL receiver process
status
text
Activity status of the WAL receiver process
receive_start_lsn
pg_lsn
First write-ahead log location used when WAL receiver is started
receive_start_tli
integer
First timeline number used when WAL receiver is started
received_lsn
pg_lsn
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
received_tli
integer
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
last_msg_send_time
timestamp with time zone
Send time of last message received from origin WAL sender
last_msg_receipt_time
timestamp with time zone
Receipt time of last message received from origin WAL sender
latest_end_lsn
pg_lsn
Last write-ahead log location reported to origin WAL sender
latest_end_time
timestamp with time zone
Time of last write-ahead log location reported to origin WAL sender
slot_name
text
Replication slot name used by this WAL receiver
sender_host
text
Host of the PostgreSQL instance this WAL receiver is connected to. This can be a host name, an IP address, or a directory path if the connection is via Unix socket. (The path case can be distinguished because it will always be an absolute path, beginning with /.)
sender_port
integer
Port number of the PostgreSQL instance this WAL receiver is connected to.
conninfo
text
Connection string used by this WAL receiver, with security-sensitive fields obfuscated.
Column
Type
Description
subid
oid
OID of the subscription
subname
text
Name of the subscription
pid
integer
Process ID of the subscription worker process
relid
Oid
OID of the relation that the worker is synchronizing; null for the main apply worker
received_lsn
pg_lsn
Last write-ahead log location received, the initial value of this field being 0
last_msg_send_time
timestamp with time zone
Send time of last message received from origin WAL sender
last_msg_receipt_time
timestamp with time zone
Receipt time of last message received from origin WAL sender
latest_end_lsn
pg_lsn
Last write-ahead log location reported to origin WAL sender
latest_end_time
timestamp with time zone
Time of last write-ahead log location reported to origin WAL sender
Column
Type
Description
pid
integer
Process ID of a backend or WAL sender process
ssl
boolean
True if SSL is used on this connection
version
text
Version of SSL in use, or NULL if SSL is not in use on this connection
cipher
text
Name of SSL cipher in use, or NULL if SSL is not in use on this connection
bits
integer
Number of bits in the encryption algorithm used, or NULL if SSL is not used on this connection
compression
boolean
True if SSL compression is in use, false if not, or NULL if SSL is not in use on this connection
client_dn
text
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 NAMEDATALEN (64 characters in a standard build).
client_serial
numeric
Serial number of the client certificate, or NULL if no client certificate was supplied or if SSL is not in use on this connection. The combination of certificate serial number and certificate issuer uniquely identifies a certificate (unless the issuer erroneously reuses serial numbers).
issuer_dn
text
DN of the issuer of the client certificate, or NULL if no client certificate was supplied or if SSL is not in use on this connection. This field is truncated like client_dn.
Column
Type
Description
pid
integer
Process ID of a backend
gss_authenticated
boolean
True if GSSAPI authentication was used for this connection
principal
text
Principal used to authenticate this connection, or NULL if GSSAPI was not used to authenticate this connection. This field is truncated if the principal is longer than NAMEDATALEN (64 characters in a standard build).
encrypted
boolean
True if GSSAPI encryption is in use on this connection
Column
Type
Description
archived_count
bigint
Number of WAL files that have been successfully archived
last_archived_wal
text
Name of the last WAL file successfully archived
last_archived_time
timestamp with time zone
Time of the last successful archive operation
failed_count
bigint
Number of failed attempts for archiving WAL files
last_failed_wal
text
Name of the WAL file of the last failed archival operation
last_failed_time
timestamp with time zone
Time of the last failed archival operation
stats_reset
timestamp with time zone
Time at which these statistics were last reset
Column
Type
Description
checkpoints_timed
bigint
Number of scheduled checkpoints that have been performed
checkpoints_req
bigint
Number of requested checkpoints that have been performed
checkpoint_write_time
double precision
Total amount of time that has been spent in the portion of checkpoint processing where files are written to disk, in milliseconds
checkpoint_sync_time
double precision
Total amount of time that has been spent in the portion of checkpoint processing where files are synchronized to disk, in milliseconds
buffers_checkpoint
bigint
Number of buffers written during checkpoints
buffers_clean
bigint
Number of buffers written by the background writer
maxwritten_clean
bigint
Number of times the background writer stopped a cleaning scan because it had written too many buffers
buffers_backend
bigint
Number of buffers written directly by a backend
buffers_backend_fsync
bigint
Number of times a backend had to execute its own fsync call (normally the background writer handles those even when the backend does its own write)
buffers_alloc
bigint
Number of buffers allocated
stats_reset
timestamp with time zone
Time at which these statistics were last reset
Column
Type
Description
datid
oid
OID of this database, or 0 for objects belonging to a shared relation
datname
name
Name of this database, or NULL for the shared objects.
numbackends
integer
Number of backends currently connected to this database, or NULL for the shared objects. 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.
xact_commit
bigint
Number of transactions in this database that have been committed
xact_rollback
bigint
Number of transactions in this database that have been rolled back
blks_read
bigint
Number of disk blocks read in this database
blks_hit
bigint
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)
tup_returned
bigint
Number of rows returned by queries in this database
tup_fetched
bigint
Number of rows fetched by queries in this database
tup_inserted
bigint
Number of rows inserted by queries in this database
tup_updated
bigint
Number of rows updated by queries in this database
tup_deleted
bigint
Number of rows deleted by queries in this database
conflicts
bigint
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.)
temp_files
bigint
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.
temp_bytes
bigint
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.
deadlocks
bigint
Number of deadlocks detected in this database
checksum_failures
bigint
Number of data page checksum failures detected in this database (or on a shared object), or NULL if data checksums are not enabled.
checksum_last_failure
timestamp with time zone
Time at which the last data page checksum failure was detected in this database (or on a shared object), or NULL if data checksums are not enabled.
blk_read_time
double precision
Time spent reading data file blocks by backends in this database, in milliseconds
blk_write_time
double precision
Time spent writing data file blocks by backends in this database, in milliseconds
stats_reset
timestamp with time zone
Time at which these statistics were last reset
Column
Type
Description
datid
oid
OID of a database
datname
name
Name of this database
confl_tablespace
bigint
Number of queries in this database that have been canceled due to dropped tablespaces
confl_lock
bigint
Number of queries in this database that have been canceled due to lock timeouts
confl_snapshot
bigint
Number of queries in this database that have been canceled due to old snapshots
confl_bufferpin
bigint
Number of queries in this database that have been canceled due to pinned buffers
confl_deadlock
bigint
Number of queries in this database that have been canceled due to deadlocks
Column
Type
Description
relid
oid
OID of a table
schemaname
name
Name of the schema that this table is in
relname
name
Name of this table
seq_scan
bigint
Number of sequential scans initiated on this table
seq_tup_read
bigint
Number of live rows fetched by sequential scans
idx_scan
bigint
Number of index scans initiated on this table
idx_tup_fetch
bigint
Number of live rows fetched by index scans
n_tup_ins
bigint
Number of rows inserted
n_tup_upd
bigint
Number of rows updated (includes HOT updated rows)
n_tup_del
bigint
Number of rows deleted
n_tup_hot_upd
bigint
Number of rows HOT updated (i.e., with no separate index update required)
n_live_tup
bigint
Estimated number of live rows
n_dead_tup
bigint
Estimated number of dead rows
n_mod_since_analyze
bigint
Estimated number of rows modified since this table was last analyzed
last_vacuum
timestamp with time zone
Last time at which this table was manually vacuumed (not counting VACUUM FULL)
last_autovacuum
timestamp with time zone
Last time at which this table was vacuumed by the autovacuum daemon
last_analyze
timestamp with time zone
Last time at which this table was manually analyzed
last_autoanalyze
timestamp with time zone
Last time at which this table was analyzed by the autovacuum daemon
vacuum_count
bigint
Number of times this table has been manually vacuumed (not counting VACUUM FULL)
autovacuum_count
bigint
Number of times this table has been vacuumed by the autovacuum daemon
analyze_count
bigint
Number of times this table has been manually analyzed
autoanalyze_count
bigint
Number of times this table has been analyzed by the autovacuum daemon
Column
Type
Description
relid
oid
OID of the table for this index
indexrelid
oid
OID of this index
schemaname
name
Name of the schema this index is in
relname
name
Name of the table for this index
indexrelname
name
Name of this index
idx_scan
bigint
Number of index scans initiated on this index
idx_tup_read
bigint
Number of index entries returned by scans on this index
idx_tup_fetch
bigint
Number of live table rows fetched by simple index scans using this index
Column
Type
Description
relid
oid
OID of a table
schemaname
name
Name of the schema that this table is in
relname
name
Name of this table
heap_blks_read
bigint
Number of disk blocks read from this table
heap_blks_hit
bigint
Number of buffer hits in this table
idx_blks_read
bigint
Number of disk blocks read from all indexes on this table
idx_blks_hit
bigint
Number of buffer hits in all indexes on this table
toast_blks_read
bigint
Number of disk blocks read from this table's TOAST table (if any)
toast_blks_hit
bigint
Number of buffer hits in this table's TOAST table (if any)
tidx_blks_read
bigint
Number of disk blocks read from this table's TOAST table indexes (if any)
tidx_blks_hit
bigint
Number of buffer hits in this table's TOAST table indexes (if any)
Column
Type
Description
relid
oid
OID of the table for this index
indexrelid
oid
OID of this index
schemaname
name
Name of the schema this index is in
relname
name
Name of the table for this index
indexrelname
name
Name of this index
idx_blks_read
bigint
Number of disk blocks read from this index
idx_blks_hit
bigint
Number of buffer hits in this index
Column
Type
Description
relid
oid
OID of a sequence
schemaname
name
Name of the schema this sequence is in
relname
name
Name of this sequence
blks_read
bigint
Number of disk blocks read from this sequence
blks_hit
bigint
Number of buffer hits in this sequence
Column
Type
Description
funcid
oid
OID of a function
schemaname
name
Name of the schema this function is in
funcname
name
Name of this function
calls
bigint
Number of times this function has been called
total_time
double precision
Total time spent in this function and all other functions called by it, in milliseconds
self_time
double precision
Total time spent in this function itself, not including other functions called by it, in milliseconds
Function
Return Type
Description
pg_backend_pid()
integer
Process ID of the server process handling the current session
pg_stat_get_activity(integer)
setof record
Returns a record of information about the backend with the specified PID, or one record for each active backend in the system if NULL is specified. The fields returned are a subset of those in the pg_stat_activity view.
pg_stat_get_snapshot_timestamp()
timestamp with time zone
Returns the timestamp of the current statistics snapshot
pg_stat_clear_snapshot()
void
Discard the current statistics snapshot
pg_stat_reset()
void
將目前資料庫的所有統計數據計數器重置為零（預設情況下需要超級使用者權限，但是也可以將此函數的 EXECUTE 權限授予其他人。）
pg_stat_reset_shared(text)
void
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). Calling pg_stat_reset_shared('bgwriter') will zero all the counters shown in the pg_stat_bgwriter view. Calling pg_stat_reset_shared('archiver') will zero all the counters shown in the pg_stat_archiver view.
pg_stat_reset_single_table_counters(oid)
void
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)
pg_stat_reset_single_function_counters(oid)
void
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)
Function
Return Type
Description
pg_stat_get_backend_idset()
setof integer
Set of currently active backend ID numbers (from 1 to the number of active backends)
pg_stat_get_backend_activity(integer)
text
Text of this backend's most recent query
pg_stat_get_backend_activity_start(integer)
timestamp with time zone
Time when the most recent query was started
pg_stat_get_backend_client_addr(integer)
inet
IP address of the client connected to this backend
pg_stat_get_backend_client_port(integer)
integer
TCP port number that the client is using for communication
pg_stat_get_backend_dbid(integer)
oid
OID of the database this backend is connected to
pg_stat_get_backend_pid(integer)
integer
Process ID of this backend
pg_stat_get_backend_start(integer)
timestamp with time zone
Time when this process was started
pg_stat_get_backend_userid(integer)
oid
OID of the user logged into this backend
pg_stat_get_backend_wait_event_type(integer)
text
Wait event type name if backend is currently waiting, otherwise NULL. See Table 27.4 for details.
pg_stat_get_backend_wait_event(integer)
text
Wait event name if backend is currently waiting, otherwise NULL. See Table 27.4 for details.
pg_stat_get_backend_xact_start(integer)
timestamp with time zone
Time when the current transaction was started