Don't balance vacuum cost delay when per-table settings are in effect

When there are cost-delay-related storage options set for a table,
trying to make that table participate in the autovacuum cost-limit
balancing algorithm produces undesirable results: instead of using the
configured values, the global values are always used,
as illustrated by Mark Kirkwood in
http://www.postgresql.org/message-id/52FACF15.8020507@catalyst.net.nz

Since the mechanism is already complicated, just disable it for those
cases rather than trying to make it cope.  There are undesirable
side-effects from this too, namely that the total I/O impact on the
system will be higher whenever such tables are vacuumed.  However, this
is seen as less harmful than slowing down vacuum, because that would
cause bloat to accumulate.  Anyway, in the new system it is possible to
tweak options to get the precise behavior one wants, whereas with the
previous system one was simply hosed.

This has been broken forever, so backpatch to all supported branches.
This might affect systems where cost_limit and cost_delay have been set
for individual tables.

diff --git a/doc/src/sgml/maintenance.sgml b/doc/src/sgml/maintenance.sgml
index d692308cf494f61266bbf95d69db8c2fd33f3b76..8764e0091ac55681f71e965062c3a1b1b42e3e56 100644 (file)
--- a/doc/src/sgml/maintenance.sgml
+++ b/doc/src/sgml/maintenance.sgml
@@ -792,10 +792,13 @@ analyze threshold = analyze base threshold + analyze scale factor * number of tu
    </para>
 
    <para>
-    When multiple workers are running, the cost limit is
+    When multiple workers are running, the cost delay parameters are
     <quote>balanced</quote> among all the running workers, so that the
-    total impact on the system is the same, regardless of the number
-    of workers actually running.
+    total I/O impact on the system is the same regardless of the number
+    of workers actually running.  However, any workers processing tables whose
+    <literal>autovacuum_vacuum_cost_delay</> or
+    <literal>autovacuum_vacuum_cost_limit</> have been set are not considered
+    in the balancing algorithm.
    </para>
   </sect2>
  </sect1>

diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c
index c240d2444c8bfd41fb59b4cce6694e2f3434ec66..1d6e3f35f94a67fec37b38c7991c2b40a4132dfa 100644 (file)
--- a/src/backend/postmaster/autovacuum.c
+++ b/src/backend/postmaster/autovacuum.c
@@ -193,6 +193,7 @@ typedef struct autovac_table
        int                     at_multixact_freeze_table_age;
        int                     at_vacuum_cost_delay;
        int                     at_vacuum_cost_limit;
+       bool            at_dobalance;
        bool            at_wraparound;
        char       *at_relname;
        char       *at_nspname;
@@ -223,6 +224,7 @@ typedef struct WorkerInfoData
        Oid                     wi_tableoid;
        PGPROC     *wi_proc;
        TimestampTz wi_launchtime;
+       bool            wi_dobalance;
        int                     wi_cost_delay;
        int                     wi_cost_limit;
        int                     wi_cost_limit_base;
@@ -1716,6 +1718,7 @@ FreeWorkerInfo(int code, Datum arg)
                MyWorkerInfo->wi_tableoid = InvalidOid;
                MyWorkerInfo->wi_proc = NULL;
                MyWorkerInfo->wi_launchtime = 0;
+               MyWorkerInfo->wi_dobalance = false;
                MyWorkerInfo->wi_cost_delay = 0;
                MyWorkerInfo->wi_cost_limit = 0;
                MyWorkerInfo->wi_cost_limit_base = 0;
@@ -1776,17 +1779,19 @@ autovac_balance_cost(void)
        if (vac_cost_limit <= 0 || vac_cost_delay <= 0)
                return;
 
-       /* caculate the total base cost limit of active workers */
+       /* calculate the total base cost limit of participating active workers */
        cost_total = 0.0;
        dlist_foreach(iter, &AutoVacuumShmem->av_runningWorkers)
        {
                WorkerInfo      worker = dlist_container(WorkerInfoData, wi_links, iter.cur);
 
                if (worker->wi_proc != NULL &&
+                       worker->wi_dobalance &&
                        worker->wi_cost_limit_base > 0 && worker->wi_cost_delay > 0)
                        cost_total +=
                                (double) worker->wi_cost_limit_base / worker->wi_cost_delay;
        }
+
        /* there are no cost limits -- nothing to do */
        if (cost_total <= 0)
                return;
@@ -1801,6 +1806,7 @@ autovac_balance_cost(void)
                WorkerInfo      worker = dlist_container(WorkerInfoData, wi_links, iter.cur);
 
                if (worker->wi_proc != NULL &&
+                       worker->wi_dobalance &&
                        worker->wi_cost_limit_base > 0 && worker->wi_cost_delay > 0)
                {
                        int                     limit = (int)
@@ -1815,12 +1821,14 @@ autovac_balance_cost(void)
                        worker->wi_cost_limit = Max(Min(limit,
                                                                                        worker->wi_cost_limit_base),
                                                                                1);
+               }
 
-                       elog(DEBUG2, "autovac_balance_cost(pid=%u db=%u, rel=%u, cost_limit=%d, cost_limit_base=%d, cost_delay=%d)",
+               if (worker->wi_proc != NULL)
+                       elog(DEBUG2, "autovac_balance_cost(pid=%u db=%u, rel=%u, dobalance=%s cost_limit=%d, cost_limit_base=%d, cost_delay=%d)",
                                 worker->wi_proc->pid, worker->wi_dboid, worker->wi_tableoid,
+                                worker->wi_dobalance ? "yes" : "no",
                                 worker->wi_cost_limit, worker->wi_cost_limit_base,
                                 worker->wi_cost_delay);
-               }
        }
 }
 
@@ -2284,6 +2292,7 @@ do_autovacuum(void)
                LWLockAcquire(AutovacuumLock, LW_EXCLUSIVE);
 
                /* advertise my cost delay parameters for the balancing algorithm */
+               MyWorkerInfo->wi_dobalance = tab->at_dobalance;
                MyWorkerInfo->wi_cost_delay = tab->at_vacuum_cost_delay;
                MyWorkerInfo->wi_cost_limit = tab->at_vacuum_cost_limit;
                MyWorkerInfo->wi_cost_limit_base = tab->at_vacuum_cost_limit;
@@ -2579,6 +2588,14 @@ table_recheck_autovac(Oid relid, HTAB *table_toast_map,
                tab->at_relname = NULL;
                tab->at_nspname = NULL;
                tab->at_datname = NULL;
+
+               /*
+                * If any of the cost delay parameters has been set individually for
+                * this table, disable the balancing algorithm.
+                */
+               tab->at_dobalance =
+                       !(avopts && (avopts->vacuum_cost_limit > 0 ||
+                                                avopts->vacuum_cost_delay > 0));
        }
 
        heap_freetuple(classTup);