Bug#32169848 THD_NDB TRANSACTION FUNCTIONALITY [#16]

Add counter for number of times table stats has been fetched from NDB.
Remove usage of execute, scan and purge counter from the function that
fetches table stats.
Keep counting one execute when fetching table stats.

Change-Id: I489babe9631e3c385ac8b49dfadc440cfe22fbaf

mysql-test/suite/ndb/r/ndb_basic.result

@@ -114,6 +114,7 @@ Ndb_conflict_trans_row_conflict_count	#
 Ndb_conflict_trans_row_reject_count	#
 Ndb_connect_count	#
 Ndb_execute_count	#
+Ndb_fetch_table_stats	#
 Ndb_index_stat_cache_clean	#
 Ndb_index_stat_cache_query	#
 Ndb_index_stat_event_count	#

mysql-test/suite/ndb/r/ndb_basic_3rpl.result

@@ -114,6 +114,7 @@ Ndb_conflict_trans_row_conflict_count	#
 Ndb_conflict_trans_row_reject_count	#
 Ndb_connect_count	#
 Ndb_execute_count	#
+Ndb_fetch_table_stats	#
 Ndb_index_stat_cache_clean	#
 Ndb_index_stat_cache_query	#
 Ndb_index_stat_event_count	#

mysql-test/suite/ndb/r/ndb_basic_4rpl.result

@@ -114,6 +114,7 @@ Ndb_conflict_trans_row_conflict_count	#
 Ndb_conflict_trans_row_reject_count	#
 Ndb_connect_count	#
 Ndb_execute_count	#
+Ndb_fetch_table_stats	#
 Ndb_index_stat_cache_clean	#
 Ndb_index_stat_cache_query	#
 Ndb_index_stat_event_count	#

mysql-test/suite/ndb/r/ndb_basic_ndbd.result

@@ -114,6 +114,7 @@ Ndb_conflict_trans_row_conflict_count	#
 Ndb_conflict_trans_row_reject_count	#
 Ndb_connect_count	#
 Ndb_execute_count	#
+Ndb_fetch_table_stats	#
 Ndb_index_stat_cache_clean	#
 Ndb_index_stat_cache_query	#
 Ndb_index_stat_event_count	#

mysql-test/suite/ndbcluster/fetch_table_stats_count.result

@@ -0,0 +1,29 @@
+#
+# Showing the "ndb_fetch_table_stats" counter
+#
+# Since fetching table stats incurs one roundtrip to NDB it should not
+# be done more than strictly required, the "ndb_fetch_table_stats"
+# counter provides a means to check when table stats are fetched.
+CREATE TABLE t1 (a int primary key) ENGINE = NDB;
+INSERT INTO t1 VALUES (1);
+SELECT * FROM t1;
+a
+1
+Table stats was fetched 1 time (expected 1)
+# Another query using an open handler instance should not cause
+# table stats to be fetched again
+SELECT * FROM t1;
+a
+1
+Table stats was fetched 0 times (expected 0)
+# Closing handler, should really not need to fetch
+# table stats again, but they seem to be
+FLUSH TABLES t1;
+Table stats was fetched 1 times (oops! expected 0)
+# Running query again, should cause
+# table stats to be fetched once again
+SELECT * FROM t1;
+a
+1
+Table stats was fetched 1 times (expected 1)
+DROP TABLE t1;

mysql-test/suite/ndbcluster/fetch_table_stats_count.test

@@ -0,0 +1,56 @@
+--source include/have_ndb.inc
+
+--echo #
+--echo # Showing the "ndb_fetch_table_stats" counter
+--echo #
+--echo # Since fetching table stats incurs one roundtrip to NDB it should not
+--echo # be done more than strictly required, the "ndb_fetch_table_stats"
+--echo # counter provides a means to check when table stats are fetched.
+
+CREATE TABLE t1 (a int primary key) ENGINE = NDB;
+
+let $count =
+  `SELECT VARIABLE_VALUE
+     FROM performance_schema.session_status
+       WHERE variable_name = 'NDB_FETCH_TABLE_STATS'`;
+
+INSERT INTO t1 VALUES (1);
+SELECT * FROM t1;
+
+let $count =
+  `SELECT VARIABLE_VALUE-$count
+     FROM performance_schema.session_status
+       WHERE variable_name = 'NDB_FETCH_TABLE_STATS'`;
+echo Table stats was fetched $count time (expected 1);
+
+--echo # Another query using an open handler instance should not cause
+--echo # table stats to be fetched again
+SELECT * FROM t1;
+
+let $count =
+  `SELECT VARIABLE_VALUE-$count
+     FROM performance_schema.session_status
+       WHERE variable_name = 'NDB_FETCH_TABLE_STATS'`;
+echo Table stats was fetched $count times (expected 0);
+
+--echo # Closing handler, should really not need to fetch
+--echo # table stats again, but they seem to be
+FLUSH TABLES t1;
+
+let $count =
+  `SELECT VARIABLE_VALUE-$count
+     FROM performance_schema.session_status
+       WHERE variable_name = 'NDB_FETCH_TABLE_STATS'`;
+echo Table stats was fetched $count times (oops! expected 0);
+
+--echo # Running query again, should cause
+--echo # table stats to be fetched once again
+SELECT * FROM t1;
+
+let $count =
+  `SELECT VARIABLE_VALUE-$count
+     FROM performance_schema.session_status
+       WHERE variable_name = 'NDB_FETCH_TABLE_STATS'`;
+echo Table stats was fetched $count times (expected 1);
+
+DROP TABLE t1;

storage/ndb/plugin/ha_ndbcluster.cc

@@ -630,6 +630,7 @@ static int update_status_variables(Thd_ndb *thd_ndb, st_ndb_status *ns,
       ns->api_client_stats[i] = thd_ndb->ndb->getClientStat(i);
     }
     ns->schema_locks_count = thd_ndb->schema_locks_count;
+    ns->fetch_table_stats = thd_ndb->m_fetch_table_stats;
   }
   return 0;
 }
@@ -746,6 +747,8 @@ static SHOW_VAR ndb_status_vars_dynamic[] = {
      SHOW_SCOPE_GLOBAL},
     {"system_name", (char *)&g_ndb_status.system_name, SHOW_CHAR_PTR,
      SHOW_SCOPE_GLOBAL},
+    {"fetch_table_stats", (char *)&g_ndb_status.fetch_table_stats, SHOW_LONG,
+     SHOW_SCOPE_GLOBAL},
     {NullS, NullS, SHOW_LONG, SHOW_SCOPE_GLOBAL}};
 
 static SHOW_VAR ndb_status_vars_slave[] = {
@@ -12881,6 +12884,11 @@ int ha_ndbcluster::update_stats(THD *thd, bool do_read_stat, uint part_id) {
     table_stats = m_share->cached_table_stats;
     mysql_mutex_unlock(&m_share->mutex);
   } else {
+    // Count number of table stat fetches
+    thd_ndb->m_fetch_table_stats++;
+    // Count one execute for fetch of stats
+    thd_ndb->m_execute_count++;
+
     // Request stats from NDB
     NdbError ndb_error;
     if (ndb_get_table_statistics(thd, thd_ndb->ndb, m_table, &table_stats,

storage/ndb/plugin/ha_ndbcluster.h

@@ -155,6 +155,7 @@ struct st_ndb_status {
   long long last_commit_epoch_session;
   long long api_client_stats[Ndb::NumClientStatistics];
   const char *system_name;
+  long fetch_table_stats;
 };
 
 int ndbcluster_commit(handlerton *, THD *thd, bool all);

storage/ndb/plugin/ndb_stats.cc

@@ -31,7 +31,6 @@
 #include "storage/ndb/include/ndbapi/NdbTransaction.hpp"
 #include "storage/ndb/plugin/ndb_sleep.h"
 #include "storage/ndb/plugin/ndb_thd.h"
-#include "storage/ndb/plugin/ndb_thd_ndb.h"
 
 // Empty mask for reading no attributes using NdbRecord, will be initialized
 // to all zeros by linker.
@@ -41,8 +40,6 @@ bool ndb_get_table_statistics(THD *thd, Ndb *ndb,
                               const NdbDictionary::Table *ndbtab,
                               Ndb_table_stats *stats, NdbError &ndb_error,
                               Uint32 part_id) {
-  Thd_ndb *thd_ndb = get_thd_ndb(thd);
-
   DBUG_TRACE;
 
   Uint64 rows, fixed_mem, var_mem, ext_space, free_ext_space;
@@ -108,14 +105,6 @@ bool ndb_get_table_statistics(THD *thd, Ndb *ndb,
       goto retry;
     }
 
-    // NOTE! Updating scan and execute counters here when reading statistics is
-    // a little bit unusual, probably better not to count here or use separate
-    // "fetch stats" counter.
-    thd_ndb->m_scan_count++;
-    thd_ndb->m_pruned_scan_count += (pOp->getPruned() ? 1 : 0);
-
-    thd_ndb->m_execute_count++;
-    DBUG_PRINT("info", ("execute_count: %u", thd_ndb->m_execute_count));
     if (trans->execute(NdbTransaction::NoCommit, NdbOperation::AbortOnError,
                        1 /* force send */) == -1) {
       ndb_error = trans->getNdbError();

storage/ndb/plugin/ndb_thd_ndb.h

@@ -223,6 +223,9 @@ class Thd_ndb {
   void increment_hinted_trans_count() { m_hinted_trans_count++; }
   uint hinted_trans_count() const { return m_hinted_trans_count; }
 
+  // Number of times that table stats has been fetched from NDB
+  uint m_fetch_table_stats{0};
+
   NdbTransaction *global_schema_lock_trans;
   uint global_schema_lock_count;
   uint global_schema_lock_error;