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@@ -31,7 +31,7 @@ When `pg_wait_sampling` is enabled, it collects two kinds of statistics.
a client who periodically reads this history and dumps it somewhere, user
can have continuous history of wait events.
* Waits profile. It's implemented as in-memory hash table where samples
are accumulated per each wait event and can be divided by process,
are accumulated per each wait event and can be divided by process, wait event,
query and other dimensions. This hash table can be reset by user request.
Assuming there is a client who periodically dumps profile and resets it,
user can have statistics of wait events over time.
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@@ -99,20 +99,6 @@ Usage
`pg_wait_sampling_current` view – information about current wait events for
all processes including background workers.
| Column name | Column type | Description |
| ----------- | ----------- | ----------------------- |
| pid | int4 | Id of process |
| event_type | text | Name of wait event type |
| event | text | Name of wait event |
| queryid | int8 | Id of query |
`pg_wait_sampling_get_current(pid int4)` returns the same table for single given
process.
`pg_wait_sampling_current_extended` view – information about current wait events for
all processes including background workers. Structure of this view can be changed
between verions.
| Column name | Column type | Description |
| ------------------- | ----------- | --------------------------- |
| pid | int4 | Id of process |
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@@ -129,28 +115,15 @@ between verions.
| client_hostname | text | Client hostname |
| appname | text | Application name |
`pg_wait_sampling_get_current_extended (pid int4)` returns the same table for single given
`pg_wait_sampling_get_current (pid int4)` returns the same table for single given
process.
`pg_wait_sampling_history` view – history of wait events obtained by sampling into
in-memory ring buffer.
| Column name | Column type | Description |
| ----------- | ----------- | ----------------------- |
| pid | int4 | Id of process |
| ts | timestamptz | Sample timestamp |
| event_type | text | Name of wait event type |
| event | text | Name of wait event |
| queryid | int8 | Id of query |
`pg_wait_sampling_history_extended` view – history of wait events obtained by
sampling into in-memory ring buffer. Structure of this view can be changed
between verions
| Column name | Column type | Description |
| ------------------- | ----------- | --------------------------- |
| pid | int4 | Id of process |
| ts | timestamptz | Sample timestamp |
| event_type | text | Name of wait event type |
| event | text | Name of wait event |
| queryid | int8 | Id of query |
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@@ -163,22 +136,13 @@ between verions
| client_addr | text | Client address |
| client_hostname | text | Client hostname |
| appname | text | Application name |
| ts | timestamptz | Sample timestamp |
`pg_wait_sampling_reset_history()` function resets the history.
`pg_wait_sampling_profile` view – profile of wait events obtained by sampling into
in-memory hash table.
| Column name | Column type | Description |
| ----------- | ----------- | ----------------------- |
| pid | int4 | Id of process |
| event_type | text | Name of wait event type |
| event | text | Name of wait event |
| queryid | int8 | Id of query |
| count | int8 | Count of samples |
`pg_wait_sampling_profile_extended` view – history of wait events obtained by
sampling into in-memory ring buffer. Structure of this view can be changed
between verions
| Column name | Column type | Description |
| ------------------- | ----------- | --------------------------- |
| pid | int4 | Id of process |
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@@ -201,16 +165,16 @@ between verions
The work of wait event statistics collector worker is controlled by following
GUCs.
| Parameter name | Data type | Description | Default value |
|-------------------------------------| --------- |---------------------------------------------|--------------: |
| pg_wait_sampling.history_size | int4 | Size of history in-memory ring buffer | 5000 |
| pg_wait_sampling.history_period | int4 | Period for history sampling in milliseconds | 10 |
| pg_wait_sampling.profile_period | int4 | Period for profile sampling in milliseconds | 10 |
| pg_wait_sampling.profile_pid | bool | Whether profile should be per pid | true |
| pg_wait_sampling.profile_queries | enum | Whether profile should be per query | top |
| pg_wait_sampling.sample_cpu | bool | Whether on CPU backends should be sampled | true |
| pg_wait_sampling.history_dimensions | text | Additional columns in extended history view | 'none ' |
| pg_wait_sampling.profile_dimensions | text | Additional columns in extended profile view | 'none ' |
| Parameter name | Data type | Description | Default value |
|-------------------------------------| --------- |---------------------------------------------|---------------------------------------------- |
| pg_wait_sampling.history_size | int4 | Size of history in-memory ring buffer | 5000 |
| pg_wait_sampling.history_period | int4 | Period for history sampling in milliseconds | 10 |
| pg_wait_sampling.profile_period | int4 | Period for profile sampling in milliseconds | 10 |
| pg_wait_sampling.profile_pid | bool | Whether profile should be per pid | true |
| pg_wait_sampling.profile_queries | enum | Whether profile should be per query | top |
| pg_wait_sampling.sample_cpu | bool | Whether on CPU backends should be sampled | true |
| pg_wait_sampling.history_dimensions | text | Additional columns in extended history view | 'pid, wait_event_type, wait_event, query_id ' |
| pg_wait_sampling.profile_dimensions | text | Additional columns in extended profile view | 'pid, wait_event_type, wait_event, query_id ' |
If `pg_wait_sampling.profile_pid` is set to false, sampling profile wouldn't be
collected in per-process manner. In this case the value of pid could would
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@@ -226,10 +190,11 @@ will be NULL.
`pg_wait_sampling.history_dimenstions` and `pg_wait_sampling.profile_dimensions`
determine what additional columns will be sampled in `history/profile_extended`
views. Possible values are `none`, `all`, `role_id`, `database_id`,
`parallel_leader_pid`, `backend_type`, `backend_state`, `backend_start_time`,
`client_addr`, `client_hostname`, `appname` and any combination of column names.
`none` and `all` cannot be used together with any other values and must be used alone.
views. Possible values are `all`, `pid`, `wait_event_type`, `wait_event`,
`query_id`, `role_id`, `database_id`, `parallel_leader_pid`, `backend_type`,
`backend_state`, `backend_start_time`, `client_addr`, `client_hostname`,
`appname` and any combination of column names.
`all` cannot be used together with any other values and must be used alone.
> [!WARNING]
> Turning on any of the following columns: `backend_type`, `backend_state`,
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@@ -238,9 +203,13 @@ views. Possible values are `none`, `all`, `role_id`, `database_id`,
> BackendStatusTable. This is especially noticeable with PostgreSQL 13-16
Values of these GUC variables can be changed only in config file or with ALTER SYSTEM.
Then you need to reload server's configuration (such as with pg_reload_conf function)
Then you need to reload server's configuration (such as with ` pg_reload_conf` function)
for changes to take effect.
> [!WARNING]
> When using `pg_reload_conf` you also need to invoke `pg_wait_sampling_reset_history()`
> and `pg_wait_sampling_reset_profile()` for correct application of new dimensions
See
[PostgreSQL documentation](http://www.postgresql.org/docs/devel/static/monitoring-stats.html#WAIT-EVENT-TABLE)
for list of possible wait events.
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