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Commit364509a

Browse files
pg_upgrade: Retrieve subscription count more efficiently.
Presently, pg_upgrade obtains the number of subscriptions in theto-be-upgraded cluster by first querying pg_subscription in everydatabase for the number of subscriptions in only that database.Then, in count_old_cluster_subscriptions(), it adds all the valuescollected in the first step. This is expensive, especially whenthere are many databases.Fortunately, there is a better way to retrieve the subscriptioncount. Since pg_subscription is a shared catalog, we only need toconnect to a single database and query it once. This commitmodifies pg_upgrade to use that approach, which also allows us totrim several lines of code. In passing, move the call toget_db_subscription_count(), which has been renamed toget_subscription_count(), from get_db_rel_and_slot_infos() to thededicated >= v17 section in check_and_dump_old_cluster().We may be able to make similar improvements toget_old_cluster_logical_slot_infos(), but that is left as a futureexercise.Reviewed-by: Michael Paquier, Amit KapilaDiscussion:https://postgr.es/m/ZprQJv_TxccN3tkr%40nathanBackpatch-through: 17
1 parent9f21482 commit364509a

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3 files changed

+15
-53
lines changed

3 files changed

+15
-53
lines changed

‎src/bin/pg_upgrade/check.c

Lines changed: 6 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -609,8 +609,10 @@ check_and_dump_old_cluster(bool live_check)
609609

610610
/*
611611
* Subscriptions and their dependencies can be migrated since PG17.
612-
* See comments atop get_db_subscription_count().
612+
* Before that the logical slots are not upgraded, so we will not be
613+
* able to upgrade the logical replication clusters completely.
613614
*/
615+
get_subscription_count(&old_cluster);
614616
check_old_cluster_subscription_state();
615617
}
616618

@@ -1797,17 +1799,14 @@ check_new_cluster_subscription_configuration(void)
17971799
{
17981800
PGresult*res;
17991801
PGconn*conn;
1800-
intnsubs_on_old;
18011802
intmax_replication_slots;
18021803

18031804
/* Subscriptions and their dependencies can be migrated since PG17. */
18041805
if (GET_MAJOR_VERSION(old_cluster.major_version)<1700)
18051806
return;
18061807

1807-
nsubs_on_old=count_old_cluster_subscriptions();
1808-
18091808
/* Quick return if there are no subscriptions to be migrated. */
1810-
if (nsubs_on_old==0)
1809+
if (old_cluster.nsubs==0)
18111810
return;
18121811

18131812
prep_status("Checking for new cluster configuration for subscriptions");
@@ -1821,10 +1820,10 @@ check_new_cluster_subscription_configuration(void)
18211820
pg_fatal("could not determine parameter settings on new cluster");
18221821

18231822
max_replication_slots=atoi(PQgetvalue(res,0,0));
1824-
if (nsubs_on_old>max_replication_slots)
1823+
if (old_cluster.nsubs>max_replication_slots)
18251824
pg_fatal("\"max_replication_slots\" (%d) must be greater than or equal to the number of "
18261825
"subscriptions (%d) on the old cluster",
1827-
max_replication_slots,nsubs_on_old);
1826+
max_replication_slots,old_cluster.nsubs);
18281827

18291828
PQclear(res);
18301829
PQfinish(conn);

‎src/bin/pg_upgrade/info.c

Lines changed: 7 additions & 44 deletions
Original file line numberDiff line numberDiff line change
@@ -28,7 +28,6 @@ static void print_db_infos(DbInfoArr *db_arr);
2828
staticvoidprint_rel_infos(RelInfoArr*rel_arr);
2929
staticvoidprint_slot_infos(LogicalSlotInfoArr*slot_arr);
3030
staticvoidget_old_cluster_logical_slot_infos(DbInfo*dbinfo,boollive_check);
31-
staticvoidget_db_subscription_count(DbInfo*dbinfo);
3231

3332

3433
/*
@@ -293,15 +292,8 @@ get_db_rel_and_slot_infos(ClusterInfo *cluster, bool live_check)
293292

294293
get_rel_infos(cluster,pDbInfo);
295294

296-
/*
297-
* Retrieve the logical replication slots infos and the subscriptions
298-
* count for the old cluster.
299-
*/
300295
if (cluster==&old_cluster)
301-
{
302296
get_old_cluster_logical_slot_infos(pDbInfo,live_check);
303-
get_db_subscription_count(pDbInfo);
304-
}
305297
}
306298

307299
if (cluster==&old_cluster)
@@ -748,54 +740,25 @@ count_old_cluster_logical_slots(void)
748740
}
749741

750742
/*
751-
* get_db_subscription_count()
752-
*
753-
* Gets the number of subscriptions in the database referred to by "dbinfo".
743+
* get_subscription_count()
754744
*
755-
* Note: This function will not do anything if the old cluster is pre-PG17.
756-
* This is because before that the logical slots are not upgraded, so we will
757-
* not be able to upgrade the logical replication clusters completely.
745+
* Gets the number of subscriptions in the cluster.
758746
*/
759-
staticvoid
760-
get_db_subscription_count(DbInfo*dbinfo)
747+
void
748+
get_subscription_count(ClusterInfo*cluster)
761749
{
762750
PGconn*conn;
763751
PGresult*res;
764752

765-
/* Subscriptions can be migrated since PG17. */
766-
if (GET_MAJOR_VERSION(old_cluster.major_version)<1700)
767-
return;
768-
769-
conn=connectToServer(&old_cluster,dbinfo->db_name);
753+
conn=connectToServer(cluster,"template1");
770754
res=executeQueryOrDie(conn,"SELECT count(*) "
771-
"FROM pg_catalog.pg_subscription WHERE subdbid = %u",
772-
dbinfo->db_oid);
773-
dbinfo->nsubs=atoi(PQgetvalue(res,0,0));
755+
"FROM pg_catalog.pg_subscription");
756+
cluster->nsubs=atoi(PQgetvalue(res,0,0));
774757

775758
PQclear(res);
776759
PQfinish(conn);
777760
}
778761

779-
/*
780-
* count_old_cluster_subscriptions()
781-
*
782-
* Returns the number of subscriptions for all databases.
783-
*
784-
* Note: this function always returns 0 if the old_cluster is PG16 and prior
785-
* because we gather subscriptions only for cluster versions greater than or
786-
* equal to PG17. See get_db_subscription_count().
787-
*/
788-
int
789-
count_old_cluster_subscriptions(void)
790-
{
791-
intnsubs=0;
792-
793-
for (intdbnum=0;dbnum<old_cluster.dbarr.ndbs;dbnum++)
794-
nsubs+=old_cluster.dbarr.dbs[dbnum].nsubs;
795-
796-
returnnsubs;
797-
}
798-
799762
staticvoid
800763
free_db_and_rel_infos(DbInfoArr*db_arr)
801764
{

‎src/bin/pg_upgrade/pg_upgrade.h

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -197,7 +197,6 @@ typedef struct
197197
* path */
198198
RelInfoArrrel_arr;/* array of all user relinfos */
199199
LogicalSlotInfoArrslot_arr;/* array of all LogicalSlotInfo */
200-
intnsubs;/* number of subscriptions */
201200
}DbInfo;
202201

203202
/*
@@ -296,6 +295,7 @@ typedef struct
296295
charmajor_version_str[64];/* string PG_VERSION of cluster */
297296
uint32bin_version;/* version returned from pg_ctl */
298297
constchar*tablespace_suffix;/* directory specification */
298+
intnsubs;/* number of subscriptions */
299299
}ClusterInfo;
300300

301301

@@ -430,7 +430,7 @@ FileNameMap *gen_db_file_maps(DbInfo *old_db,
430430
constchar*new_pgdata);
431431
voidget_db_rel_and_slot_infos(ClusterInfo*cluster,boollive_check);
432432
intcount_old_cluster_logical_slots(void);
433-
intcount_old_cluster_subscriptions(void);
433+
voidget_subscription_count(ClusterInfo*cluster);
434434

435435
/* option.c */
436436

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