We are concerned with finished queries in pg_stat_monitor, so state and
state_code columns were removed from the pg_stat_monitor_view as we only
list finished queries on it.
Removed state regression as it is not necessary anymore.
Also, this allowed us to remove the call to pgss_store on ExecutorStart,
which just updated query state to EXEC, thus saving some CPU.
This new GUC allows users to select which statements are tracked by
pg_stat_monitor:
- 'top': Default, track only top level queries.
- 'all': Track top along with sub/nested queries.
- 'none': Disable query monitoring.
To avoid redudancy, now users disable pg_stat_monitor by setting
pg_stat_monitor.track = 'none', similar to pg_stat_statements.
This new GUC is an enumeration, so the pg_stat_monitor_settings view was
adjusted to add a new column 'options' which lists the possible values
for the field.
The "value" and "default_value" columns in the pg_stat_monitor_settings
view was adjusted to be of type text, so we can better display the
enumeration values. Also the boolean types now have their values
displayed as either 'yes' or 'no' to easily distinguish them from the
integer types.
The pg_stat_monitor_errors view was created in order to help inspecting
internal errors that may occur in pg_stat_monitor module itself, it
contains the error message, its severity, the last time the error occurred
and the number of times that any given error ocurred.
Implementation details:
- A new lwlock was added to the pgssSharedState structure in order to
control access to the errors hash table.
- Increased RequestNamedLWLockTranche() no. of locks requested to 2.
- The function GetNamedLWLockTranche() returns an array of locks, we
use the first lock for controlling access to the usual buckets hash
table, and the second one to control access to the errors hash table.
- During module initialization (_PG_init) we increased the amount of
shared memory space requested to include space to the new errors hash
table: RequestAddinShmemSpace(... + pgsm_errors_size())
- The implementation in pgsm_errors.c simple uses a hash table to track
error messages, the message is also used as the key.
Diego Fronza
Ibrar Ahmed