MDEV-16711 Crash in Field_blob::store() while reading statistics

          for the small InnoDB table

This bug was introduced by the patch 6c414fcf.
The patch has not taken into account that some objects of the Field_* types
are created only for TABLE_SHARE and the field 'table' is set to NULL
for them. In particular such are objects created to store statistical
min/max values for columns.

mysql-test/r/stat_tables.result

@@ -539,6 +539,10 @@ SELECT * FROM mysql.column_stats;
 db_name	table_name	column_name	min_value	max_value	nulls_ratio	avg_length	avg_frequency	hist_size	hist_type	histogram
 test	t1	pk	1	2	0.0000	4.0000	1.0000	0	NULL	NULL
 test	t1	t	bar	foo	0.0000	3.0000	1.0000	0	NULL	NULL
+SELECT pk FROM t1;
+pk
+1
+2
 DROP TABLE t1;
 set use_stat_tables=@save_use_stat_tables;
 #
@@ -566,3 +570,19 @@ SELECT * FROM mysql.column_stats;
 db_name	table_name	column_name	min_value	max_value	nulls_ratio	avg_length	avg_frequency	hist_size	hist_type	histogram
 DROP TABLE t1;
 set use_stat_tables=@save_use_stat_tables;
+#
+# MDEV-16711:CREATE OR REPLACE TABLE introducing BLOB column
+#
+SET use_stat_tables= PREFERABLY;
+CREATE TABLE t1 (pk INT PRIMARY KEY, t CHAR(60));
+INSERT INTO t1 VALUES (1,'foo'),(2,'bar');
+ANALYZE TABLE t1;
+Table	Op	Msg_type	Msg_text
+test.t1	analyze	status	Engine-independent statistics collected
+test.t1	analyze	status	OK
+CREATE OR REPLACE TABLE t1 (pk INT PRIMARY KEY, t TEXT);
+SELECT MAX(pk) FROM t1;
+MAX(pk)
+NULL
+DROP TABLE t1;
+set use_stat_tables=@save_use_stat_tables;

mysql-test/r/stat_tables_innodb.result

@@ -566,6 +566,10 @@ SELECT * FROM mysql.column_stats;
 db_name	table_name	column_name	min_value	max_value	nulls_ratio	avg_length	avg_frequency	hist_size	hist_type	histogram
 test	t1	pk	1	2	0.0000	4.0000	1.0000	0	NULL	NULL
 test	t1	t	bar	foo	0.0000	3.0000	1.0000	0	NULL	NULL
+SELECT pk FROM t1;
+pk
+1
+2
 DROP TABLE t1;
 set use_stat_tables=@save_use_stat_tables;
 #
@@ -593,5 +597,21 @@ SELECT * FROM mysql.column_stats;
 db_name	table_name	column_name	min_value	max_value	nulls_ratio	avg_length	avg_frequency	hist_size	hist_type	histogram
 DROP TABLE t1;
 set use_stat_tables=@save_use_stat_tables;
+#
+# MDEV-16711:CREATE OR REPLACE TABLE introducing BLOB column
+#
+SET use_stat_tables= PREFERABLY;
+CREATE TABLE t1 (pk INT PRIMARY KEY, t CHAR(60));
+INSERT INTO t1 VALUES (1,'foo'),(2,'bar');
+ANALYZE TABLE t1;
+Table	Op	Msg_type	Msg_text
+test.t1	analyze	status	Engine-independent statistics collected
+test.t1	analyze	status	OK
+CREATE OR REPLACE TABLE t1 (pk INT PRIMARY KEY, t TEXT);
+SELECT MAX(pk) FROM t1;
+MAX(pk)
+NULL
+DROP TABLE t1;
+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.test

@@ -325,7 +325,7 @@ INSERT INTO mysql.column_stats VALUES
 --sorted_result
 SELECT * FROM mysql.column_stats;
 
-# SELECT pk FROM t1;
+SELECT pk FROM t1;
 
 DROP TABLE t1;
 
@@ -350,3 +350,21 @@ SELECT * FROM mysql.column_stats;
 DROP TABLE t1;
 
 set use_stat_tables=@save_use_stat_tables;
+
+
+--echo #
+--echo # MDEV-16711:CREATE OR REPLACE TABLE introducing BLOB column
+--echo #
+
+SET use_stat_tables= PREFERABLY;
+
+CREATE TABLE t1 (pk INT PRIMARY KEY, t CHAR(60));
+INSERT INTO t1 VALUES (1,'foo'),(2,'bar');
+ANALYZE TABLE t1;
+CREATE OR REPLACE TABLE t1 (pk INT PRIMARY KEY, t TEXT);
+
+SELECT MAX(pk) FROM t1;
+
+DROP TABLE t1;
+
+set use_stat_tables=@save_use_stat_tables;

sql/field.cc

@@ -7942,7 +7942,13 @@ int Field_blob::store(const char *from,uint length,CHARSET_INFO *cs)
     return 0;
   }
 
-  if (table->blob_storage)    // GROUP_CONCAT with ORDER BY | DISTINCT
+  /*
+    For min/max fields of statistical data 'table' is set to NULL.
+    It could not be otherwise as this data is shared by many instances
+    of the same base table.
+  */
+
+  if (table && table->blob_storage)    // GROUP_CONCAT with ORDER BY | DISTINCT
   {
     DBUG_ASSERT(!f_is_hex_escape(flags));
     DBUG_ASSERT(field_charset == cs);