*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/postmaster/autovacuum.c,v 1.36 2007/03/23 21:23:13 alvherre Exp $
+ * $PostgreSQL: pgsql/src/backend/postmaster/autovacuum.c,v 1.37 2007/03/23 21:45:17 alvherre Exp $
*
*-------------------------------------------------------------------------
*/
NON_EXEC_STATIC void AutoVacWorkerMain(int argc, char *argv[]);
NON_EXEC_STATIC void AutoVacLauncherMain(int argc, char *argv[]);
+static void do_start_worker(void);
static void do_autovacuum(PgStat_StatDBEntry *dbentry);
static List *autovac_get_database_list(void);
static void test_rel_for_autovac(Oid relid, PgStat_StatTabEntry *tabentry,
AutoVacLauncherMain(int argc, char *argv[])
{
sigjmp_buf local_sigjmp_buf;
- List *dblist;
- bool for_xid_wrap;
- autovac_dbase *db;
MemoryContext avlauncher_cxt;
/* we are a postmaster subprocess now */
for (;;)
{
- TransactionId xidForceLimit;
- ListCell *cell;
int worker_pid;
/*
}
}
- /* Get a list of databases */
- dblist = autovac_get_database_list();
+ do_start_worker();
- /*
- * Determine the oldest datfrozenxid/relfrozenxid that we will allow
- * to pass without forcing a vacuum. (This limit can be tightened for
- * particular tables, but not loosened.)
- */
- recentXid = ReadNewTransactionId();
- xidForceLimit = recentXid - autovacuum_freeze_max_age;
- /* ensure it's a "normal" XID, else TransactionIdPrecedes misbehaves */
- if (xidForceLimit < FirstNormalTransactionId)
- xidForceLimit -= FirstNormalTransactionId;
-
- /*
- * Choose a database to connect to. We pick the database that was least
- * recently auto-vacuumed, or one that needs vacuuming to prevent Xid
- * wraparound-related data loss. If any db at risk of wraparound is
- * found, we pick the one with oldest datfrozenxid, independently of
- * autovacuum times.
- *
- * Note that a database with no stats entry is not considered, except for
- * Xid wraparound purposes. The theory is that if no one has ever
- * connected to it since the stats were last initialized, it doesn't need
- * vacuuming.
- *
- * XXX This could be improved if we had more info about whether it needs
- * vacuuming before connecting to it. Perhaps look through the pgstats
- * data for the database's tables? One idea is to keep track of the
- * number of new and dead tuples per database in pgstats. However it
- * isn't clear how to construct a metric that measures that and not cause
- * starvation for less busy databases.
- */
- db = NULL;
- for_xid_wrap = false;
- foreach(cell, dblist)
- {
- autovac_dbase *tmp = lfirst(cell);
-
- /* Find pgstat entry if any */
- tmp->entry = pgstat_fetch_stat_dbentry(tmp->oid);
-
- /* Check to see if this one is at risk of wraparound */
- if (TransactionIdPrecedes(tmp->frozenxid, xidForceLimit))
- {
- if (db == NULL ||
- TransactionIdPrecedes(tmp->frozenxid, db->frozenxid))
- db = tmp;
- for_xid_wrap = true;
- continue;
- }
- else if (for_xid_wrap)
- continue; /* ignore not-at-risk DBs */
-
- /*
- * Otherwise, skip a database with no pgstat entry; it means it
- * hasn't seen any activity.
- */
- if (!tmp->entry)
- continue;
-
- /*
- * Remember the db with oldest autovac time. (If we are here,
- * both tmp->entry and db->entry must be non-null.)
- */
- if (db == NULL ||
- tmp->entry->last_autovac_time < db->entry->last_autovac_time)
- db = tmp;
- }
-
- /* Found a database -- process it */
- if (db != NULL)
- {
- LWLockAcquire(AutovacuumLock, LW_EXCLUSIVE);
- AutoVacuumShmem->process_db = db->oid;
- LWLockRelease(AutovacuumLock);
-
- SendPostmasterSignal(PMSIGNAL_START_AUTOVAC_WORKER);
- }
-
sleep:
/*
* in emergency mode, exit immediately so that the postmaster can
proc_exit(0); /* done */
}
+/*
+ * do_start_worker
+ *
+ * Bare-bones procedure for starting an autovacuum worker from the launcher.
+ * It determines what database to work on, sets up shared memory stuff and
+ * signals postmaster to start the worker.
+ */
+static void
+do_start_worker(void)
+{
+ List *dblist;
+ bool for_xid_wrap;
+ autovac_dbase *db;
+ ListCell *cell;
+ TransactionId xidForceLimit;
+
+ /* Get a list of databases */
+ dblist = autovac_get_database_list();
+
+ /*
+ * Determine the oldest datfrozenxid/relfrozenxid that we will allow
+ * to pass without forcing a vacuum. (This limit can be tightened for
+ * particular tables, but not loosened.)
+ */
+ recentXid = ReadNewTransactionId();
+ xidForceLimit = recentXid - autovacuum_freeze_max_age;
+ /* ensure it's a "normal" XID, else TransactionIdPrecedes misbehaves */
+ if (xidForceLimit < FirstNormalTransactionId)
+ xidForceLimit -= FirstNormalTransactionId;
+
+ /*
+ * Choose a database to connect to. We pick the database that was least
+ * recently auto-vacuumed, or one that needs vacuuming to prevent Xid
+ * wraparound-related data loss. If any db at risk of wraparound is
+ * found, we pick the one with oldest datfrozenxid, independently of
+ * autovacuum times.
+ *
+ * Note that a database with no stats entry is not considered, except for
+ * Xid wraparound purposes. The theory is that if no one has ever
+ * connected to it since the stats were last initialized, it doesn't need
+ * vacuuming.
+ *
+ * XXX This could be improved if we had more info about whether it needs
+ * vacuuming before connecting to it. Perhaps look through the pgstats
+ * data for the database's tables? One idea is to keep track of the
+ * number of new and dead tuples per database in pgstats. However it
+ * isn't clear how to construct a metric that measures that and not cause
+ * starvation for less busy databases.
+ */
+ db = NULL;
+ for_xid_wrap = false;
+ foreach(cell, dblist)
+ {
+ autovac_dbase *tmp = lfirst(cell);
+
+ /* Find pgstat entry if any */
+ tmp->entry = pgstat_fetch_stat_dbentry(tmp->oid);
+
+ /* Check to see if this one is at risk of wraparound */
+ if (TransactionIdPrecedes(tmp->frozenxid, xidForceLimit))
+ {
+ if (db == NULL ||
+ TransactionIdPrecedes(tmp->frozenxid, db->frozenxid))
+ db = tmp;
+ for_xid_wrap = true;
+ continue;
+ }
+ else if (for_xid_wrap)
+ continue; /* ignore not-at-risk DBs */
+
+ /*
+ * Otherwise, skip a database with no pgstat entry; it means it
+ * hasn't seen any activity.
+ */
+ if (!tmp->entry)
+ continue;
+
+ /*
+ * Remember the db with oldest autovac time. (If we are here,
+ * both tmp->entry and db->entry must be non-null.)
+ */
+ if (db == NULL ||
+ tmp->entry->last_autovac_time < db->entry->last_autovac_time)
+ db = tmp;
+ }
+
+ /* Found a database -- process it */
+ if (db != NULL)
+ {
+ LWLockAcquire(AutovacuumLock, LW_EXCLUSIVE);
+ AutoVacuumShmem->process_db = db->oid;
+ LWLockRelease(AutovacuumLock);
+
+ SendPostmasterSignal(PMSIGNAL_START_AUTOVAC_WORKER);
+ }
+}
+
/* SIGHUP: set flag to re-read config file at next convenient time */
static void
avl_sighup_handler(SIGNAL_ARGS)
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