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
+ information. In such cases, another set of per-backend statistics
access functions can be used; these are shown in
linkend="monitoring-stats-backend-funcs-table"/>.
- These access functions use a backend ID number, which ranges from one
- to the number of currently active backends.
+ These access functions use the session's backend ID number, which is a
+ small positive integer that is distinct from the backend ID of any
+ concurrent session, although a session's ID can be recycled as soon as
+ it exits. The backend ID is used, among other things, to identify the
+ session's temporary schema if it has one.
The function pg_stat_get_backend_idset provides a
- convenient way to generate one row for each active backend for
+ convenient way to list all the active backends' ID numbers for
invoking these functions. For example, to show the
PIDs and
current queries of all backends:
-SELECT pg_stat_get_backend_pid(s.backendid) AS pid,
- pg_stat_get_backend_activity(s.backendid) AS query
- FROM (SELECT pg_stat_get_backend_idset() AS backendid) AS s;
+SELECT pg_stat_get_backend_pid(backendid) AS pid,
+ pg_stat_get_backend_activity(backendid) AS query
+FROM pg_stat_get_backend_idset() AS backendid;
setof integer
- Returns the set of currently active backend ID numbers (from 1 to the
- number of active backends).
+ Returns the set of currently active backend ID numbers.
/* Only valid entries get included into the local array */
if (localentry->backendStatus.st_procpid > 0)
{
+ /*
+ * The BackendStatusArray index is exactly the BackendId of the
+ * source backend. Note that this means localBackendStatusTable
+ * is in order by backend_id. pgstat_fetch_stat_beentry() depends
+ * on that.
+ */
+ localentry->backend_id = i;
BackendIdGetTransactionIds(i,
&localentry->backend_xid,
&localentry->backend_xmin);
return MyBEEntry->st_query_id;
}
+/* ----------
+ * cmp_lbestatus
+ *
+ * Comparison function for bsearch() on an array of LocalPgBackendStatus.
+ * The backend_id field is used to compare the arguments.
+ * ----------
+ */
+static int
+cmp_lbestatus(const void *a, const void *b)
+{
+ const LocalPgBackendStatus *lbestatus1 = (const LocalPgBackendStatus *) a;
+ const LocalPgBackendStatus *lbestatus2 = (const LocalPgBackendStatus *) b;
+
+ return lbestatus1->backend_id - lbestatus2->backend_id;
+}
/* ----------
* pgstat_fetch_stat_beentry() -
*
* Support function for the SQL-callable pgstat* functions. Returns
- * our local copy of the current-activity entry for one backend.
+ * our local copy of the current-activity entry for one backend,
+ * or NULL if the given beid doesn't identify any known session.
+ *
+ * The beid argument is the BackendId of the desired session
+ * (note that this is unlike pgstat_fetch_stat_local_beentry()).
*
* NB: caller is responsible for a check if the user is permitted to see
* this info (especially the querystring).
* ----------
*/
PgBackendStatus *
-pgstat_fetch_stat_beentry(int beid)
+pgstat_fetch_stat_beentry(BackendId beid)
{
+ LocalPgBackendStatus key;
+ LocalPgBackendStatus *ret;
+
pgstat_read_current_status();
- if (beid < 1 || beid > localNumBackends)
- return NULL;
+ /*
+ * Since the localBackendStatusTable is in order by backend_id, we can use
+ * bsearch() to search it efficiently.
+ */
+ key.backend_id = beid;
+ ret = (LocalPgBackendStatus *) bsearch(&key, localBackendStatusTable,
+ localNumBackends,
+ sizeof(LocalPgBackendStatus),
+ cmp_lbestatus);
+ if (ret)
+ return &ret->backendStatus;
- return &localBackendStatusTable[beid - 1].backendStatus;
+ return NULL;
}
* Like pgstat_fetch_stat_beentry() but with locally computed additions (like
* xid and xmin values of the backend)
*
+ * The beid argument is a 1-based index in the localBackendStatusTable
+ * (note that this is unlike pgstat_fetch_stat_beentry()).
+ * Returns NULL if the argument is out of range (no current caller does that).
+ *
* NB: caller is responsible for a check if the user is permitted to see
* this info (especially the querystring).
* ----------
* pgstat_fetch_stat_numbackends() -
*
* Support function for the SQL-callable pgstat* functions. Returns
- * the maximum current backend id.
+ * the number of sessions known in the localBackendStatusTable, i.e.
+ * the maximum 1-based index to pass to pgstat_fetch_stat_local_beentry().
* ----------
*/
int
{
FuncCallContext *funcctx;
int *fctx;
- int32 result;
/* stuff done only on the first call of the function */
if (SRF_IS_FIRSTCALL())
funcctx = SRF_FIRSTCALL_INIT();
fctx = MemoryContextAlloc(funcctx->multi_call_memory_ctx,
- 2 * sizeof(int));
+ sizeof(int));
funcctx->user_fctx = fctx;
fctx[0] = 0;
- fctx[1] = pgstat_fetch_stat_numbackends();
}
/* stuff done on every call of the function */
fctx = funcctx->user_fctx;
fctx[0] += 1;
- result = fctx[0];
- if (result <= fctx[1])
+ /*
+ * We recheck pgstat_fetch_stat_numbackends() each time through, just in
+ * case the local status data has been refreshed since we started. It's
+ * plenty cheap enough if not. If a refresh does happen, we'll likely
+ * miss or duplicate some backend IDs, but we're content not to crash.
+ * (Refreshing midway through such a query would be problematic usage
+ * anyway, since the backend IDs we've already returned might no longer
+ * refer to extant sessions.)
+ */
+ if (fctx[0] <= pgstat_fetch_stat_numbackends())
{
/* do when there is more left to send */
- SRF_RETURN_NEXT(funcctx, Int32GetDatum(result));
+ LocalPgBackendStatus *local_beentry = pgstat_fetch_stat_local_beentry(fctx[0]);
+
+ SRF_RETURN_NEXT(funcctx, Int32GetDatum(local_beentry->backend_id));
}
else
{
int i;
local_beentry = pgstat_fetch_stat_local_beentry(curr_backend);
-
- if (!local_beentry)
- continue;
-
beentry = &local_beentry->backendStatus;
/*
* Report values for only those backends which are running the given
* command.
*/
- if (!beentry || beentry->st_progress_command != cmdtype)
+ if (beentry->st_progress_command != cmdtype)
continue;
/* Value available to all callers */
/* Get the next one in the list */
local_beentry = pgstat_fetch_stat_local_beentry(curr_backend);
- if (!local_beentry)
- {
- int i;
-
- /* Ignore missing entries if looking for specific PID */
- if (pid != -1)
- continue;
-
- for (i = 0; i < lengthof(nulls); i++)
- nulls[i] = true;
-
- nulls[5] = false;
- values[5] = CStringGetTextDatum("");
-
- tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
- continue;
- }
-
beentry = &local_beentry->backendStatus;
/* If looking for specific PID, ignore all the others */
result = 0;
for (beid = 1; beid <= tot_backends; beid++)
{
- PgBackendStatus *beentry = pgstat_fetch_stat_beentry(beid);
+ LocalPgBackendStatus *local_beentry = pgstat_fetch_stat_local_beentry(beid);
- if (beentry && beentry->st_databaseid == dbid)
+ if (local_beentry->backendStatus.st_databaseid == dbid)
result++;
}
#include "datatype/timestamp.h"
#include "libpq/pqcomm.h"
#include "miscadmin.h" /* for BackendType */
+#include "storage/backendid.h"
#include "utils/backend_progress.h"
*/
PgBackendStatus backendStatus;
+ /*
+ * The backend ID. For auxiliary processes, this will be set to a value
+ * greater than MaxBackends (since auxiliary processes do not have proper
+ * backend IDs).
+ */
+ BackendId backend_id;
+
/*
* The xid of the current transaction if available, InvalidTransactionId
* if not.
* ----------
*/
extern int pgstat_fetch_stat_numbackends(void);
-extern PgBackendStatus *pgstat_fetch_stat_beentry(int beid);
+extern PgBackendStatus *pgstat_fetch_stat_beentry(BackendId beid);
extern LocalPgBackendStatus *pgstat_fetch_stat_local_beentry(int beid);
extern char *pgstat_clip_activity(const char *raw_activity);
-- Test pg_stat_bgwriter checkpointer-related stats, together with pg_stat_wal
SELECT checkpoints_req AS rqst_ckpts_before FROM pg_stat_bgwriter \gset
--- Test pg_stat_wal
+-- Test pg_stat_wal (and make a temp table so our temp schema exists)
SELECT wal_bytes AS wal_bytes_before FROM pg_stat_wal \gset
-CREATE TABLE test_stats_temp AS SELECT 17;
+CREATE TEMP TABLE test_stats_temp AS SELECT 17;
DROP TABLE test_stats_temp;
-- Checkpoint twice: The checkpointer reports stats after reporting completion
-- of the checkpoint. But after a second checkpoint we'll see at least the
t
(1 row)
+-- Test pg_stat_get_backend_idset() and some allied functions.
+-- In particular, verify that their notion of backend ID matches
+-- our temp schema index.
+SELECT (current_schemas(true))[1] = ('pg_temp_' || beid::text) AS match
+FROM pg_stat_get_backend_idset() beid
+WHERE pg_stat_get_backend_pid(beid) = pg_backend_pid();
+ match
+-------
+ t
+(1 row)
+
-----
-- Test that resetting stats works for reset timestamp
-----
-- Test pg_stat_bgwriter checkpointer-related stats, together with pg_stat_wal
SELECT checkpoints_req AS rqst_ckpts_before FROM pg_stat_bgwriter \gset
--- Test pg_stat_wal
+-- Test pg_stat_wal (and make a temp table so our temp schema exists)
SELECT wal_bytes AS wal_bytes_before FROM pg_stat_wal \gset
-CREATE TABLE test_stats_temp AS SELECT 17;
+CREATE TEMP TABLE test_stats_temp AS SELECT 17;
DROP TABLE test_stats_temp;
-- Checkpoint twice: The checkpointer reports stats after reporting completion
SELECT checkpoints_req > :rqst_ckpts_before FROM pg_stat_bgwriter;
SELECT wal_bytes > :wal_bytes_before FROM pg_stat_wal;
+-- Test pg_stat_get_backend_idset() and some allied functions.
+-- In particular, verify that their notion of backend ID matches
+-- our temp schema index.
+SELECT (current_schemas(true))[1] = ('pg_temp_' || beid::text) AS match
+FROM pg_stat_get_backend_idset() beid
+WHERE pg_stat_get_backend_pid(beid) = pg_backend_pid();
-----
-- Test that resetting stats works for reset timestamp
projects / postgresql.git / commitdiff