diff --git a/pg_stat_monitor.c b/pg_stat_monitor.c
index 19f9b45e..a2729cf6 100644
--- a/pg_stat_monitor.c
+++ b/pg_stat_monitor.c
@@ -1999,7 +1999,7 @@ IsBucketValid(uint64 bucketid)
 
 	TimestampDifference(pgsm->bucket_start_time[bucketid], current_tz, &secs, &microsecs);
 
-	if (secs > (pgsm_bucket_time * pgsm_max_buckets))
+	if (secs > ((int64)pgsm_bucket_time * pgsm_max_buckets))
 		return false;
 	return true;
 }
diff --git a/pg_stat_monitor.h b/pg_stat_monitor.h
index 339f6474..9cd590d1 100644
--- a/pg_stat_monitor.h
+++ b/pg_stat_monitor.h
@@ -93,8 +93,8 @@
 /* the assumption of query max nested level */
 #define DEFAULT_MAX_NESTED_LEVEL	10
 
-#define MAX_QUERY_BUF						(pgsm_query_shared_buffer * 1024 * 1024)
-#define MAX_BUCKETS_MEM 					(pgsm_max * 1024 * 1024)
+#define MAX_QUERY_BUF						((int64)pgsm_query_shared_buffer * 1024 * 1024)
+#define MAX_BUCKETS_MEM 					((int64)pgsm_max * 1024 * 1024)
 #define BUCKETS_MEM_OVERFLOW() 				((hash_get_num_entries(pgsm_hash) * sizeof(pgsmEntry)) >= MAX_BUCKETS_MEM)
 #define MAX_BUCKET_ENTRIES 					(MAX_BUCKETS_MEM / sizeof(pgsmEntry))
 #define QUERY_BUFFER_OVERFLOW(x,y)  		((x + y + sizeof(uint64) + sizeof(uint64)) > MAX_QUERY_BUF)
diff --git a/t/007_settings_pgsm_query_shared_buffer.pl b/t/007_settings_pgsm_query_shared_buffer.pl
index 432e8799..35ab0a68 100644
--- a/t/007_settings_pgsm_query_shared_buffer.pl
+++ b/t/007_settings_pgsm_query_shared_buffer.pl
@@ -20,7 +20,7 @@
 open my $conf, '>>', "$pgdata/postgresql.conf";
 print $conf "shared_preload_libraries = 'pg_stat_monitor'\n";
 print $conf "pg_stat_monitor.pgsm_bucket_time = 360000\n";
-print $conf "pg_stat_monitor.pgsm_query_shared_buffer = 1\n";
+print $conf "pg_stat_monitor.pgsm_query_shared_buffer = 1\n"; # Min possible value
 print $conf "pg_stat_monitor.pgsm_normalized_query = 'yes'\n";
 close $conf;
 
@@ -109,6 +109,29 @@
 ok($cmdret == 0, "SELECT XXX FROM pg_stat_monitor");
 PGSM::append_to_file($stdout);
 
+$node->append_conf('postgresql.conf', "pg_stat_monitor.pgsm_query_shared_buffer = 2048\n");
+$node->restart();
+
+($cmdret, $stdout, $stderr) = $node->psql('postgres', 'SELECT pg_stat_monitor_reset();', extra_params => ['-a', '-Pformat=aligned','-Ptuples_only=off']);
+ok($cmdret == 0, "Reset PGSM EXTENSION");
+PGSM::append_to_file($stdout);
+
+($cmdret, $stdout, $stderr) = $node->psql('postgres', "SELECT name, setting, unit, context, vartype, source, min_val, max_val, enumvals, boot_val, reset_val, pending_restart FROM pg_settings WHERE name='pg_stat_monitor.pgsm_query_shared_buffer';", extra_params => ['-a', '-Pformat=aligned','-Ptuples_only=off']);
+ok($cmdret == 0, "Print PGSM EXTENSION Settings");
+PGSM::append_to_file($stdout);
+
+$out = system ("pgbench -i -s 10 -p $port example");
+print " out: $out \n";
+ok($cmdret == 0, "Perform pgbench init");
+
+$out = system ("pgbench -c 10 -j 2 -t 1000 -p $port example");
+print " out: $out \n";
+ok($cmdret == 0, "Run pgbench");
+
+($cmdret, $stdout, $stderr) = $node->psql('postgres', 'SELECT datname, substr(query,0,150) AS query, SUM(calls) AS calls FROM pg_stat_monitor GROUP BY datname, query ORDER BY datname, query, calls DESC Limit 20;', extra_params => ['-a', '-Pformat=aligned','-Ptuples_only=off']);
+ok($cmdret == 0, "SELECT XXX FROM pg_stat_monitor");
+PGSM::append_to_file($stdout);
+
 # DROP EXTENSION
 $stdout = $node->safe_psql('postgres', 'DROP EXTENSION pg_stat_monitor;', extra_params => ['-a']);
 ok($cmdret == 0, "DROP PGSM EXTENSION");
diff --git a/t/016_settings_pgsm_max.pl b/t/016_settings_pgsm_max.pl
index ba673108..7a7fb46f 100644
--- a/t/016_settings_pgsm_max.pl
+++ b/t/016_settings_pgsm_max.pl
@@ -19,7 +19,7 @@
 # UPDATE postgresql.conf to include/load pg_stat_monitor library
 open my $conf, '>>', "$pgdata/postgresql.conf";
 print $conf "shared_preload_libraries = 'pg_stat_monitor'\n";
-print $conf "pg_stat_monitor.pgsm_max = 1000\n";
+print $conf "pg_stat_monitor.pgsm_max = 2048\n";
 close $conf;
 
 # Start server
@@ -62,7 +62,7 @@
 ok($cmdret == 0, "Print PGSM EXTENSION Settings");
 PGSM::append_to_file($stdout);
 
-$node->append_conf('postgresql.conf', "pg_stat_monitor.pgsm_max = 10\n");
+$node->append_conf('postgresql.conf', "pg_stat_monitor.pgsm_max = 10\n"); # Min possible value
 $node->restart();
 
 ($cmdret, $stdout, $stderr) = $node->psql('postgres', 'SELECT pg_stat_monitor_reset();', extra_params => ['-a', '-Pformat=aligned','-Ptuples_only=off']);
diff --git a/t/031_query_stat.pl b/t/031_query_stat.pl
new file mode 100644
index 00000000..7490ffef
--- /dev/null
+++ b/t/031_query_stat.pl
@@ -0,0 +1,63 @@
+#!/usr/bin/perl
+
+use strict;
+use warnings;
+use File::Basename;
+use File::Compare;
+use File::Copy;
+use Test::More;
+use lib 't';
+use pgsm;
+
+# Get file name and CREATE out file name and dirs WHERE requried
+PGSM::setup_files_dir(basename($0));
+
+# CREATE new PostgreSQL node and do initdb
+my $node = PGSM->pgsm_init_pg();
+my $pgdata = $node->data_dir;
+
+# UPDATE postgresql.conf to include/load pg_stat_monitor library
+open my $conf, '>>', "$pgdata/postgresql.conf";
+print $conf "shared_preload_libraries = 'pg_stat_monitor'\n";
+print $conf "pg_stat_monitor.pgsm_bucket_time = 2147483647\n"; # Max value for this parameter 
+print $conf "pg_stat_monitor.pgsm_max_buckets = 20000\n"; # Max value for this parameter
+close $conf;
+
+# Start server
+my $rt_value = $node->start;
+ok($rt_value == 1, "Start Server");
+
+# CREATE EXTENSION and change out file permissions
+my ($cmdret, $stdout, $stderr) = $node->psql('postgres', 'CREATE EXTENSION pg_stat_monitor;', extra_params => ['-a']);
+ok($cmdret == 0, "CREATE PGSM EXTENSION");
+PGSM::append_to_file($stdout);
+
+# Run required commands/queries and dump output to out file.
+($cmdret, $stdout, $stderr) = $node->psql('postgres', 'SELECT pg_stat_monitor_reset();', extra_params => ['-a', '-Pformat=aligned','-Ptuples_only=off']);
+ok($cmdret == 0, "Reset PGSM EXTENSION");
+PGSM::append_to_file($stdout);
+
+($cmdret, $stdout, $stderr) = $node->psql('postgres', "SELECT 1 AS num;", extra_params => ['-a', '-Pformat=aligned','-Ptuples_only=off']);
+ok($cmdret == 0, "Print results of a test query");
+PGSM::append_to_file($stdout);
+
+($cmdret, $stdout, $stderr) = $node->psql('postgres', 'SELECT query, comments FROM pg_stat_monitor ORDER BY query COLLATE "C";', extra_params => ['-a', '-Pformat=aligned','-Ptuples_only=off']);
+ok($cmdret == 0, "Check query stats");
+PGSM::append_to_file($stdout);
+
+# DROP EXTENSION
+$stdout = $node->safe_psql('postgres', 'DROP EXTENSION pg_stat_monitor;', extra_params => ['-a']);
+ok($cmdret == 0, "DROP PGSM EXTENSION");
+PGSM::append_to_file($stdout);
+
+# Stop the server
+$node->stop;
+
+# compare the expected and out file
+my $compare = PGSM->compare_results();
+
+# Test/check if expected and result/out file match. If Yes, test passes.
+is($compare,0,"Compare Files: $PGSM::expected_filename_with_path and $PGSM::out_filename_with_path files.");
+
+# Done testing for this testcase file.
+done_testing();
diff --git a/t/expected/007_settings_pgsm_query_shared_buffer.out b/t/expected/007_settings_pgsm_query_shared_buffer.out
index ff813114..8e7687aa 100644
--- a/t/expected/007_settings_pgsm_query_shared_buffer.out
+++ b/t/expected/007_settings_pgsm_query_shared_buffer.out
@@ -111,4 +111,41 @@ SELECT datname, substr(query,0,150) AS query, SUM(calls) AS calls FROM pg_stat_m
  example | insert into pgbench_tellers(tid,bid,tbalance) values ($1,$2,$3)                                               |   100
 (20 rows)
 
+SELECT pg_stat_monitor_reset();
+ pg_stat_monitor_reset 
+-----------------------
+ 
+(1 row)
+
+SELECT name, setting, unit, context, vartype, source, min_val, max_val, enumvals, boot_val, reset_val, pending_restart FROM pg_settings WHERE name='pg_stat_monitor.pgsm_query_shared_buffer';
+                   name                   | setting | unit |  context   | vartype |       source       | min_val | max_val | enumvals | boot_val | reset_val | pending_restart 
+------------------------------------------+---------+------+------------+---------+--------------------+---------+---------+----------+----------+-----------+-----------------
+ pg_stat_monitor.pgsm_query_shared_buffer | 2048    | MB   | postmaster | integer | configuration file | 1       | 10000   |          | 20       | 2048      | f
+(1 row)
+
+SELECT datname, substr(query,0,150) AS query, SUM(calls) AS calls FROM pg_stat_monitor GROUP BY datname, query ORDER BY datname, query, calls DESC Limit 20;
+ datname |                                                     query                                                     | calls 
+---------+---------------------------------------------------------------------------------------------------------------+-------
+ example | BEGIN                                                                                                         | 10000
+ example | END                                                                                                           | 10000
+ example | INSERT INTO pgbench_history (tid, bid, aid, delta, mtime) VALUES ($1, $2, $3, $4, CURRENT_TIMESTAMP)          | 10000
+ example | SELECT abalance FROM pgbench_accounts WHERE aid = $1                                                          | 10000
+ example | UPDATE pgbench_accounts SET abalance = abalance + $1 WHERE aid = $2                                           | 10000
+ example | UPDATE pgbench_branches SET bbalance = bbalance + $1 WHERE bid = $2                                           | 10000
+ example | UPDATE pgbench_tellers SET tbalance = tbalance + $1 WHERE tid = $2                                            | 10000
+ example | alter table pgbench_accounts add primary key (aid)                                                            |     1
+ example | alter table pgbench_branches add primary key (bid)                                                            |     1
+ example | alter table pgbench_tellers add primary key (tid)                                                             |     1
+ example | begin                                                                                                         |     1
+ example | commit                                                                                                        |     1
+ example | copy pgbench_accounts from stdin                                                                              |     1
+ example | create table pgbench_accounts(aid    int not null,bid int,abalance int,filler char(84)) with (fillfactor=100) |     1
+ example | create table pgbench_branches(bid int not null,bbalance int,filler char(88)) with (fillfactor=100)            |     1
+ example | create table pgbench_history(tid int,bid int,aid    int,delta int,mtime timestamp,filler char(22))            |     1
+ example | create table pgbench_tellers(tid int not null,bid int,tbalance int,filler char(84)) with (fillfactor=100)     |     1
+ example | drop table if exists pgbench_accounts, pgbench_branches, pgbench_history, pgbench_tellers                     |     1
+ example | insert into pgbench_branches(bid,bbalance) values($1,$2)                                                      |    10
+ example | insert into pgbench_tellers(tid,bid,tbalance) values ($1,$2,$3)                                               |   100
+(20 rows)
+
 DROP EXTENSION pg_stat_monitor;
diff --git a/t/expected/007_settings_pgsm_query_shared_buffer.out.15 b/t/expected/007_settings_pgsm_query_shared_buffer.out.15
index cf8e9948..c01b7f26 100755
--- a/t/expected/007_settings_pgsm_query_shared_buffer.out.15
+++ b/t/expected/007_settings_pgsm_query_shared_buffer.out.15
@@ -111,4 +111,41 @@ SELECT datname, substr(query,0,150) AS query, SUM(calls) AS calls FROM pg_stat_m
  example | insert into pgbench_tellers(tid,bid,tbalance) values ($1,$2,$3)                                               |   100
 (20 rows)
 
+SELECT pg_stat_monitor_reset();
+ pg_stat_monitor_reset 
+-----------------------
+ 
+(1 row)
+
+SELECT name, setting, unit, context, vartype, source, min_val, max_val, enumvals, boot_val, reset_val, pending_restart FROM pg_settings WHERE name='pg_stat_monitor.pgsm_query_shared_buffer';
+                   name                   | setting | unit |  context   | vartype |       source       | min_val | max_val | enumvals | boot_val | reset_val | pending_restart 
+------------------------------------------+---------+------+------------+---------+--------------------+---------+---------+----------+----------+-----------+-----------------
+ pg_stat_monitor.pgsm_query_shared_buffer | 2048    | MB   | postmaster | integer | configuration file | 1       | 10000   |          | 20       | 2048      | f
+(1 row)
+
+SELECT datname, substr(query,0,150) AS query, SUM(calls) AS calls FROM pg_stat_monitor GROUP BY datname, query ORDER BY datname, query, calls DESC Limit 20;
+ datname |                                                     query                                                     | calls 
+---------+---------------------------------------------------------------------------------------------------------------+-------
+ example | BEGIN                                                                                                         | 10000
+ example | END                                                                                                           | 10000
+ example | INSERT INTO pgbench_history (tid, bid, aid, delta, mtime) VALUES ($1, $2, $3, $4, CURRENT_TIMESTAMP)          | 10000
+ example | SELECT abalance FROM pgbench_accounts WHERE aid = $1                                                          | 10000
+ example | UPDATE pgbench_accounts SET abalance = abalance + $1 WHERE aid = $2                                           | 10000
+ example | UPDATE pgbench_branches SET bbalance = bbalance + $1 WHERE bid = $2                                           | 10000
+ example | UPDATE pgbench_tellers SET tbalance = tbalance + $1 WHERE tid = $2                                            | 10000
+ example | alter table pgbench_accounts add primary key (aid)                                                            |     1
+ example | alter table pgbench_branches add primary key (bid)                                                            |     1
+ example | alter table pgbench_tellers add primary key (tid)                                                             |     1
+ example | begin                                                                                                         |     1
+ example | commit                                                                                                        |     1
+ example | copy pgbench_accounts from stdin with (freeze on)                                                             |     1
+ example | create table pgbench_accounts(aid    int not null,bid int,abalance int,filler char(84)) with (fillfactor=100) |     1
+ example | create table pgbench_branches(bid int not null,bbalance int,filler char(88)) with (fillfactor=100)            |     1
+ example | create table pgbench_history(tid int,bid int,aid    int,delta int,mtime timestamp,filler char(22))            |     1
+ example | create table pgbench_tellers(tid int not null,bid int,tbalance int,filler char(84)) with (fillfactor=100)     |     1
+ example | drop table if exists pgbench_accounts, pgbench_branches, pgbench_history, pgbench_tellers                     |     1
+ example | insert into pgbench_branches(bid,bbalance) values($1,$2)                                                      |    10
+ example | insert into pgbench_tellers(tid,bid,tbalance) values ($1,$2,$3)                                               |   100
+(20 rows)
+
 DROP EXTENSION pg_stat_monitor;
diff --git a/t/expected/007_settings_pgsm_query_shared_buffer.out.16 b/t/expected/007_settings_pgsm_query_shared_buffer.out.16
index 6dc840fd..ae39e46c 100644
--- a/t/expected/007_settings_pgsm_query_shared_buffer.out.16
+++ b/t/expected/007_settings_pgsm_query_shared_buffer.out.16
@@ -111,4 +111,41 @@ SELECT datname, substr(query,0,150) AS query, SUM(calls) AS calls FROM pg_stat_m
  example | select o.n, p.partstrat, pg_catalog.count(i.inhparent) from pg_catalog.pg_class as c join pg_catalog.pg_namespace as n on (n.oid = c.relnamespace) cr |     1
 (20 rows)
 
+SELECT pg_stat_monitor_reset();
+ pg_stat_monitor_reset 
+-----------------------
+ 
+(1 row)
+
+SELECT name, setting, unit, context, vartype, source, min_val, max_val, enumvals, boot_val, reset_val, pending_restart FROM pg_settings WHERE name='pg_stat_monitor.pgsm_query_shared_buffer';
+                   name                   | setting | unit |  context   | vartype |       source       | min_val | max_val | enumvals | boot_val | reset_val | pending_restart 
+------------------------------------------+---------+------+------------+---------+--------------------+---------+---------+----------+----------+-----------+-----------------
+ pg_stat_monitor.pgsm_query_shared_buffer | 2048    | MB   | postmaster | integer | configuration file | 1       | 10000   |          | 20       | 2048      | f
+(1 row)
+
+SELECT datname, substr(query,0,150) AS query, SUM(calls) AS calls FROM pg_stat_monitor GROUP BY datname, query ORDER BY datname, query, calls DESC Limit 20;
+ datname |                                                                         query                                                                         | calls 
+---------+-------------------------------------------------------------------------------------------------------------------------------------------------------+-------
+ example | INSERT INTO pgbench_history (tid, bid, aid, delta, mtime) VALUES ($1, $2, $3, $4, CURRENT_TIMESTAMP)                                                  | 10000
+ example | SELECT abalance FROM pgbench_accounts WHERE aid = $1                                                                                                  | 10000
+ example | UPDATE pgbench_accounts SET abalance = abalance + $1 WHERE aid = $2                                                                                   | 10000
+ example | UPDATE pgbench_branches SET bbalance = bbalance + $1 WHERE bid = $2                                                                                   | 10000
+ example | UPDATE pgbench_tellers SET tbalance = tbalance + $1 WHERE tid = $2                                                                                    | 10000
+ example | alter table pgbench_accounts add primary key (aid)                                                                                                    |     1
+ example | alter table pgbench_branches add primary key (bid)                                                                                                    |     1
+ example | alter table pgbench_tellers add primary key (tid)                                                                                                     |     1
+ example | begin                                                                                                                                                 | 10001
+ example | commit                                                                                                                                                | 10001
+ example | copy pgbench_accounts from stdin with (freeze on)                                                                                                     |     1
+ example | create table pgbench_accounts(aid    int not null,bid int,abalance int,filler char(84)) with (fillfactor=100)                                         |     1
+ example | create table pgbench_branches(bid int not null,bbalance int,filler char(88)) with (fillfactor=100)                                                    |     1
+ example | create table pgbench_history(tid int,bid int,aid    int,delta int,mtime timestamp,filler char(22))                                                    |     1
+ example | create table pgbench_tellers(tid int not null,bid int,tbalance int,filler char(84)) with (fillfactor=100)                                             |     1
+ example | drop table if exists pgbench_accounts, pgbench_branches, pgbench_history, pgbench_tellers                                                             |     1
+ example | insert into pgbench_branches(bid,bbalance) values($1,$2)                                                                                              |    10
+ example | insert into pgbench_tellers(tid,bid,tbalance) values ($1,$2,$3)                                                                                       |   100
+ example | select count(*) from pgbench_branches                                                                                                                 |     1
+ example | select o.n, p.partstrat, pg_catalog.count(i.inhparent) from pg_catalog.pg_class as c join pg_catalog.pg_namespace as n on (n.oid = c.relnamespace) cr |     1
+(20 rows)
+
 DROP EXTENSION pg_stat_monitor;
diff --git a/t/expected/016_settings_pgsm_max.out b/t/expected/016_settings_pgsm_max.out
index 111ad5fe..1bb29437 100644
--- a/t/expected/016_settings_pgsm_max.out
+++ b/t/expected/016_settings_pgsm_max.out
@@ -8,7 +8,7 @@ SELECT pg_stat_monitor_reset();
 SELECT name, setting, unit, context, vartype, source, min_val, max_val, enumvals, boot_val, reset_val, pending_restart FROM pg_settings WHERE name='pg_stat_monitor.pgsm_max';
            name           | setting | unit |  context   | vartype |       source       | min_val | max_val | enumvals | boot_val | reset_val | pending_restart 
 --------------------------+---------+------+------------+---------+--------------------+---------+---------+----------+----------+-----------+-----------------
- pg_stat_monitor.pgsm_max | 1000    | MB   | postmaster | integer | configuration file | 10      | 10240   |          | 256      | 1000      | f
+ pg_stat_monitor.pgsm_max | 2048    | MB   | postmaster | integer | configuration file | 10      | 10240   |          | 256      | 2048      | f
 (1 row)
 
 SELECT pg_stat_monitor_reset();
diff --git a/t/expected/031_query_stat.out b/t/expected/031_query_stat.out
new file mode 100644
index 00000000..4790121f
--- /dev/null
+++ b/t/expected/031_query_stat.out
@@ -0,0 +1,21 @@
+CREATE EXTENSION pg_stat_monitor;
+SELECT pg_stat_monitor_reset();
+ pg_stat_monitor_reset 
+-----------------------
+ 
+(1 row)
+
+SELECT 1 AS num;
+ num 
+-----
+   1
+(1 row)
+
+SELECT query, comments FROM pg_stat_monitor ORDER BY query COLLATE "C";
+             query              | comments 
+--------------------------------+----------
+ SELECT 1 AS num                | 
+ SELECT pg_stat_monitor_reset() | 
+(2 rows)
+
+DROP EXTENSION pg_stat_monitor;