Fixed bug mdev-4019.

The bug could cause a crash when several connections needed
persistent statistics for the same table.

Also added a missing call of set_statistics_for_table() in the code
of the function mysql_update.

mysql-test/r/stat_tables_par.result

@@ -219,4 +219,24 @@ set debug_sync='RESET';
 set global use_stat_tables=@save_global_use_stat_tables;
 DROP DATABASE dbt3_s001;
 use test;
+set @save_global_use_stat_tables=@@global.use_stat_tables;
+set global use_stat_tables='preferably';
+set debug_sync='RESET';
+create table t1 (a int, b int, key(a));
+insert t1 values (1,1),(2,2);
+analyze table t1;
+Table	Op	Msg_type	Msg_text
+test.t1	analyze	status	OK
+SET debug_sync='after_open_table_ignore_flush WAIT_FOR go';
+select * from information_schema.statistics where table_schema='test';
+select * from t1;
+a	b
+1	1
+2	2
+SET DEBUG_SYNC= "now SIGNAL go";
+TABLE_CATALOG	TABLE_SCHEMA	TABLE_NAME	NON_UNIQUE	INDEX_SCHEMA	INDEX_NAME	SEQ_IN_INDEX	COLUMN_NAME	COLLATION	CARDINALITY	SUB_PART	PACKED	NULLABLE	INDEX_TYPE	COMMENT	INDEX_COMMENT
+def	test	t1	1	test	a	1	a	A	2	NULL	NULL	YES	BTREE		
+set debug_sync='RESET';
+drop table t1;
+set global use_stat_tables=@save_global_use_stat_tables;
 set use_stat_tables=@save_use_stat_tables;

mysql-test/r/stat_tables_par_innodb.result

@@ -228,6 +228,26 @@ set debug_sync='RESET';
 set global use_stat_tables=@save_global_use_stat_tables;
 DROP DATABASE dbt3_s001;
 use test;
+set @save_global_use_stat_tables=@@global.use_stat_tables;
+set global use_stat_tables='preferably';
+set debug_sync='RESET';
+create table t1 (a int, b int, key(a));
+insert t1 values (1,1),(2,2);
+analyze table t1;
+Table	Op	Msg_type	Msg_text
+test.t1	analyze	status	OK
+SET debug_sync='after_open_table_ignore_flush WAIT_FOR go';
+select * from information_schema.statistics where table_schema='test';
+select * from t1;
+a	b
+1	1
+2	2
+SET DEBUG_SYNC= "now SIGNAL go";
+TABLE_CATALOG	TABLE_SCHEMA	TABLE_NAME	NON_UNIQUE	INDEX_SCHEMA	INDEX_NAME	SEQ_IN_INDEX	COLUMN_NAME	COLLATION	CARDINALITY	SUB_PART	PACKED	NULLABLE	INDEX_TYPE	COMMENT	INDEX_COMMENT
+def	test	t1	1	test	a	1	a	A	2	NULL	NULL	YES	BTREE		
+set debug_sync='RESET';
+drop table t1;
+set global use_stat_tables=@save_global_use_stat_tables;
 set use_stat_tables=@save_use_stat_tables;
 set optimizer_switch=@save_optimizer_switch_for_stat_tables_test;
 SET SESSION STORAGE_ENGINE=DEFAULT;

mysql-test/t/stat_tables_par.test

@@ -242,4 +242,37 @@ DROP DATABASE dbt3_s001;
 
 use test;
 
+#
+# Bug mdev-4019: crash when executing in parallel ANALYZE and 
+#                SELECT * FROM information_schema.statistics
+# 
+
+set @save_global_use_stat_tables=@@global.use_stat_tables;
+set global use_stat_tables='preferably';
+set debug_sync='RESET';
+
+create table t1 (a int, b int, key(a));
+insert t1 values (1,1),(2,2);
+
+analyze table t1;
+
+SET debug_sync='after_open_table_ignore_flush WAIT_FOR go';
+send select * from information_schema.statistics where table_schema='test';
+
+connect(con1, localhost, root);
+connection con1;
+select * from t1;
+SET DEBUG_SYNC= "now SIGNAL go";
+
+connection default;
+reap;
+
+connection default;
+disconnect con1;
+set debug_sync='RESET';
+
+drop table t1;
+set global use_stat_tables=@save_global_use_stat_tables;
+
+
 set use_stat_tables=@save_use_stat_tables;

sql/sql_base.cc

@@ -4654,6 +4654,7 @@ open_and_process_table(THD *thd, LEX *lex, TABLE_LIST *tables,
           Field **table_field_ptr= tables->table->field;
           for ( ; *field_ptr; field_ptr++, table_field_ptr++)
             (*table_field_ptr)->read_stats= (*field_ptr)->read_stats;
+          tables->table->stats_is_read= table_share->stats_cb.stats_is_read;
         }
       }	
     }

sql/sql_statistics.cc

@@ -2501,6 +2501,8 @@ int read_statistics_for_table(THD *thd, TABLE *table, TABLE_LIST *stat_tables)
     }
   }
       
+  table->stats_is_read= TRUE;
+
   DBUG_RETURN(0);
 }
 
@@ -2559,6 +2561,8 @@ bool statistics_for_tables_is_needed(THD *thd, TABLE_LIST *tables)
           table_share->stats_cb.stats_can_be_read &&
           !table_share->stats_cb.stats_is_read)
         return TRUE;
+      if (table_share->stats_cb.stats_is_read)
+        tl->table->stats_is_read= TRUE;
     } 
   }
 
@@ -2618,6 +2622,8 @@ int read_statistics_for_tables_if_needed(THD *thd, TABLE_LIST *tables)
         (void) read_statistics_for_table(thd, tl->table, stat_tables);
         table_share->stats_cb.stats_is_read= TRUE;
       }
+      if (table_share->stats_cb.stats_is_read)
+        tl->table->stats_is_read= TRUE;
     }
   }  
 
@@ -3045,7 +3051,7 @@ void set_statistics_for_table(THD *thd, TABLE *table)
   Use_stat_tables_mode use_stat_table_mode= get_use_stat_tables_mode(thd);
   table->used_stat_records= 
     (use_stat_table_mode <= COMPLEMENTARY ||
-     !stats_cb->stats_is_read || read_stats->cardinality_is_null) ?
+     !table->stats_is_read || read_stats->cardinality_is_null) ?
     table->file->stats.records : read_stats->cardinality;
   KEY *key_info, *key_info_end;
   for (key_info= table->key_info, key_info_end= key_info+table->s->keys;
@@ -3053,7 +3059,7 @@ void set_statistics_for_table(THD *thd, TABLE *table)
   {
     key_info->is_statistics_from_stat_tables=
       (use_stat_table_mode > COMPLEMENTARY &&
-       stats_cb->stats_is_read &&
+       table->stats_is_read &&
        key_info->read_stats->avg_frequency_is_inited() &&
        key_info->read_stats->get_avg_frequency(0) > 0.5);
   }

sql/sql_update.cc

@@ -32,6 +32,7 @@
 #include "sql_view.h"                           // check_key_in_view
 #include "sp_head.h"
 #include "sql_trigger.h"
+#include "sql_statistics.h"
 #include "probes_mysql.h"
 #include "debug_sync.h"
 #include "key.h"                                // is_key_used
@@ -404,6 +405,7 @@ int mysql_update(THD *thd,
 #endif
   /* Update the table->file->stats.records number */
   table->file->info(HA_STATUS_VARIABLE | HA_STATUS_NO_LOCK);
+  set_statistics_for_table(thd, table);
 
   select= make_select(table, 0, 0, conds, 0, &error);
   if (error || !limit || thd->is_error() ||

sql/table.h

@@ -1189,6 +1189,7 @@ struct TABLE
   bool no_partitions_used; /* If true, all partitions have been pruned away */
 #endif
   uint max_keys; /* Size of allocated key_info array. */
+  bool stats_is_read;     /* Persistent statistics is read for the table */
   MDL_ticket *mdl_ticket;
 
   void init(THD *thd, TABLE_LIST *tl);