Fix Bug#16400412 UNNECESSARY DICT_UPDATE_STATISTICS DURING CONCURRENT

UPDATES

After checking that the table has changed too much in
row_update_statistics_if_needed() and calling dict_update_statistics(),
also check if the same condition holds after acquiring the table stats
latch. This is to avoid multiple threads concurrently entering and
executing the stats update code.

Approved by:	Marko (rb:2186)

storage/innobase/dict/dict0dict.c

@@ -770,8 +770,10 @@ dict_table_get(
 		/* If table->ibd_file_missing == TRUE, this will
 		print an error message and return without doing
 		anything. */
-		dict_update_statistics(table, TRUE /* only update stats
-				       if they have not been initialized */);
+		dict_update_statistics(
+			table,
+			TRUE, /* only update stats if not initialized */
+			FALSE /* update even if not changed too much */);
 	}
 
 	return(table);
@@ -4340,10 +4342,14 @@ void
 dict_update_statistics(
 /*===================*/
 	dict_table_t*	table,		/*!< in/out: table */
-	ibool		only_calc_if_missing_stats)/*!< in: only
+	ibool		only_calc_if_missing_stats,/*!< in: only
 					update/recalc the stats if they have
 					not been initialized yet, otherwise
 					do nothing */
+	ibool		only_calc_if_changed_too_much)/*!< in: only
+					update/recalc the stats if the table
+					has been changed too much since the
+					last stats update/recalc */
 {
 	dict_index_t*	index;
 	ulint		sum_of_index_sizes	= 0;
@@ -4373,7 +4379,10 @@ dict_update_statistics(
 
 	dict_table_stats_lock(table, RW_X_LATCH);
 
-	if (only_calc_if_missing_stats && table->stat_initialized) {
+	if ((only_calc_if_missing_stats && table->stat_initialized)
+	    || (only_calc_if_changed_too_much
+		&& !DICT_TABLE_CHANGED_TOO_MUCH(table))) {
+
 		dict_table_stats_unlock(table, RW_X_LATCH);
 		return;
 	}
@@ -4532,7 +4541,10 @@ dict_table_print_low(
 
 	ut_ad(mutex_own(&(dict_sys->mutex)));
 
-	dict_update_statistics(table, FALSE /* update even if initialized */);
+	dict_update_statistics(
+		table,
+		FALSE, /* update even if initialized */
+		FALSE /* update even if not changed too much */);
 
 	dict_table_stats_lock(table, RW_S_LATCH);
 

storage/innobase/dict/dict0load.c

 /*****************************************************************************
 
-Copyright (c) 1996, 2010, Innobase Oy. All Rights Reserved.
+Copyright (c) 1996, 2013, Innobase Oy. All Rights Reserved.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -352,8 +352,10 @@ dict_process_sys_tables_rec(
 
 		/* Update statistics if DICT_TABLE_UPDATE_STATS
 		is set */
-		dict_update_statistics(*table, FALSE /* update even if
-				       initialized */);
+		dict_update_statistics(
+			*table,
+			FALSE, /* update even if initialized */
+			FALSE /* update even if not changed too much */);
 	}
 
 	return(NULL);

storage/innobase/handler/ha_innodb.cc

@@ -8122,9 +8122,10 @@ ha_innobase::info_low(
 
 			prebuilt->trx->op_info = "updating table statistics";
 
-			dict_update_statistics(ib_table,
-					       FALSE /* update even if stats
-						     are initialized */);
+			dict_update_statistics(
+				ib_table,
+				FALSE, /* update even if initialized */
+				FALSE /* update even if not changed too much */);
 
 			prebuilt->trx->op_info = "returning various info to MySQL";
 		}

storage/innobase/include/dict0dict.h

 /*****************************************************************************
 
-Copyright (c) 1996, 2012, Oracle and/or its affiliates. All Rights Reserved.
+Copyright (c) 1996, 2013, Oracle and/or its affiliates. All Rights Reserved.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -1124,6 +1124,18 @@ ulint
 dict_index_calc_min_rec_len(
 /*========================*/
 	const dict_index_t*	index);	/*!< in: index */
+
+/** Calculate new statistics if 1 / 16 of table has been modified
+since the last time a statistics batch was run.
+We calculate statistics at most every 16th round, since we may have
+a counter table which is very small and updated very often.
+@param t table
+@return true if the table has changed too much and stats need to be
+recalculated
+*/
+#define DICT_TABLE_CHANGED_TOO_MUCH(t) \
+	((ib_int64_t) (t)->stat_modified_counter > 16 + (t)->stat_n_rows / 16)
+
 /*********************************************************************//**
 Calculates new estimates for table and index statistics. The statistics
 are used in query optimization. */
@@ -1132,10 +1144,14 @@ void
 dict_update_statistics(
 /*===================*/
 	dict_table_t*	table,		/*!< in/out: table */
-	ibool		only_calc_if_missing_stats);/*!< in: only
+	ibool		only_calc_if_missing_stats,/*!< in: only
 					update/recalc the stats if they have
 					not been initialized yet, otherwise
 					do nothing */
+	ibool		only_calc_if_changed_too_much);/*!< in: only
+					update/recalc the stats if the table
+					has been changed too much since the
+					last stats update/recalc */
 /********************************************************************//**
 Reserves the dictionary system mutex for MySQL. */
 UNIV_INTERN

storage/innobase/include/dict0mem.h

 /*****************************************************************************
 
-Copyright (c) 1996, 2012, Oracle and/or its affiliates. All Rights Reserved.
+Copyright (c) 1996, 2013, Oracle and/or its affiliates. All Rights Reserved.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -607,7 +607,13 @@ struct dict_table_struct{
 				/*!< flag: TRUE if the maximum length of
 				a single row exceeds BIG_ROW_SIZE;
 				initialized in dict_table_add_to_cache() */
-				/** Statistics for query optimization */
+				/** Statistics for query optimization.
+				The following stat_* members are usually
+				protected by dict_table_stats_lock(). In
+				some exceptional cases (performance critical
+				code paths) we access or modify stat_n_rows
+				and stat_modified_counter without any
+				protection. */
 				/* @{ */
 	unsigned	stat_initialized:1; /*!< TRUE if statistics have
 				been calculated the first time

storage/innobase/row/row0mysql.c

 /*****************************************************************************
 
-Copyright (c) 2000, 2012, Oracle and/or its affiliates. All Rights Reserved.
+Copyright (c) 2000, 2013, Oracle and/or its affiliates. All Rights Reserved.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -962,17 +962,12 @@ row_update_statistics_if_needed(
 
 	table->stat_modified_counter = counter + 1;
 
-	/* Calculate new statistics if 1 / 16 of table has been modified
-	since the last time a statistics batch was run, or if
-	stat_modified_counter > 2 000 000 000 (to avoid wrap-around).
-	We calculate statistics at most every 16th round, since we may have
-	a counter table which is very small and updated very often. */
+	if (DICT_TABLE_CHANGED_TOO_MUCH(table)) {
 
-	if (counter > 2000000000
-	    || ((ib_int64_t)counter > 16 + table->stat_n_rows / 16)) {
-
-		dict_update_statistics(table, FALSE /* update even if stats
-						    are initialized */);
+		dict_update_statistics(
+			table,
+			FALSE, /* update even if stats are initialized */
+			TRUE /* only update if stats changed too much */);
 	}
 }
 
@@ -3050,8 +3045,10 @@ next_rec:
 	dict_table_autoinc_lock(table);
 	dict_table_autoinc_initialize(table, 1);
 	dict_table_autoinc_unlock(table);
-	dict_update_statistics(table, FALSE /* update even if stats are
-					    initialized */);
+	dict_update_statistics(
+		table,
+		FALSE, /* update even if stats are initialized */
+		FALSE /* update even if not changed too much */);
 
 	trx_commit_for_mysql(trx);