MDEV-7362: ANALYZE TABLES crash with table-independent-statistics gathering

FULLTEXT indexes do not permit index first lookups. By calling:
ha_index_first() with a garbage parameter, random data gets overwritten
that causes the table->field array to be corrupted. Subsequently, when
the field array is accessed, a segfault occurs.

By not allowing index statistics for FULLTEXT indexes, the problem is
resolved.

mysql-test/r/statistics_index_crash-7362.result

+CREATE TABLE t1 (a longtext, FULLTEXT KEY (`a`)) ENGINE=InnoDB;
+INSERT INTO t1 VALUES (unhex('3E0D0A4141414142334E7A6143317963324541414141424977414141674541726D'));
+ANALYZE TABLE t1 PERSISTENT FOR ALL;
+Table	Op	Msg_type	Msg_text
+test.t1	analyze	status	Engine-independent statistics collected
+test.t1	analyze	status	OK
+SELECT * FROM mysql.index_stats WHERE index_name='a' AND table_name='t1';
+db_name	table_name	index_name	prefix_arity	avg_frequency
+test	t1	a	1	NULL
+DROP TABLE t1;
+CREATE TABLE t1 (a longtext, FULLTEXT KEY (`a`)) ENGINE=MyISAM;
+INSERT INTO t1 VALUES (unhex('3E0D0A4141414142334E7A6143317963324541414141424977414141674541726D'));
+ANALYZE TABLE t1 PERSISTENT FOR ALL;
+Table	Op	Msg_type	Msg_text
+test.t1	analyze	status	Engine-independent statistics collected
+test.t1	analyze	status	OK
+SELECT * FROM mysql.index_stats WHERE index_name='a' AND table_name='t1';
+db_name	table_name	index_name	prefix_arity	avg_frequency
+test	t1	a	1	NULL
+DROP TABLE t1;
+CREATE TABLE geom (g GEOMETRY NOT NULL, SPATIAL INDEX(g)) ENGINE=MyISAM;
+INSERT INTO geom VALUES
+(MultiPolygonFromText('MULTIPOLYGON(((28 26,28 0,84 0,84 42,28 26),(52 18,66 23,73 9,48 6,52 18)),((59 18,67 18,67 13,59 13,59 18)))')),
+(MPolyFromText('MULTIPOLYGON(((28 26,28 0,84 0,84 42,28 26),(52 18,66 23,73 9,48 6,52 18)),((59 18,67 18,67 13,59 13,59 18)))')),
+(MPolyFromWKB(AsWKB(MultiPolygon(Polygon(LineString(Point(0, 3), Point(3, 3), Point(3, 0), Point(0, 3)))))));
+ANALYZE TABLE geom PERSISTENT FOR ALL;
+Table	Op	Msg_type	Msg_text
+test.geom	analyze	status	Engine-independent statistics collected
+test.geom	analyze	status	OK
+SELECT * FROM mysql.index_stats WHERE index_name='g' AND table_name='geom';
+db_name	table_name	index_name	prefix_arity	avg_frequency
+test	geom	g	1	NULL
+DROP TABLE geom;

mysql-test/t/statistics_index_crash-7362.test

+# Test cases that cover the crashes within:
+# MDEV-7362 ANALYZE TABLES crash with table-independent-statistics gathering
+# MDEV-7380 engine-independent stats SEGV on ANALYZE TABLE (#2)
+
+--source include/have_stat_tables.inc
+--source include/have_innodb.inc
+
+CREATE TABLE t1 (a longtext, FULLTEXT KEY (`a`)) ENGINE=InnoDB;
+INSERT INTO t1 VALUES (unhex('3E0D0A4141414142334E7A6143317963324541414141424977414141674541726D'));
+ANALYZE TABLE t1 PERSISTENT FOR ALL;
+--sorted_result
+SELECT * FROM mysql.index_stats WHERE index_name='a' AND table_name='t1';
+DROP TABLE t1;
+
+CREATE TABLE t1 (a longtext, FULLTEXT KEY (`a`)) ENGINE=MyISAM;
+INSERT INTO t1 VALUES (unhex('3E0D0A4141414142334E7A6143317963324541414141424977414141674541726D'));
+ANALYZE TABLE t1 PERSISTENT FOR ALL;
+--sorted_result
+SELECT * FROM mysql.index_stats WHERE index_name='a' AND table_name='t1';
+DROP TABLE t1;
+
+CREATE TABLE geom (g GEOMETRY NOT NULL, SPATIAL INDEX(g)) ENGINE=MyISAM;
+INSERT INTO geom VALUES
+    (MultiPolygonFromText('MULTIPOLYGON(((28 26,28 0,84 0,84 42,28 26),(52 18,66 23,73 9,48 6,52 18)),((59 18,67 18,67 13,59 13,59 18)))')),
+    (MPolyFromText('MULTIPOLYGON(((28 26,28 0,84 0,84 42,28 26),(52 18,66 23,73 9,48 6,52 18)),((59 18,67 18,67 13,59 13,59 18)))')),
+    (MPolyFromWKB(AsWKB(MultiPolygon(Polygon(LineString(Point(0, 3), Point(3, 3), Point(3, 0), Point(0, 3)))))));
+ANALYZE TABLE geom PERSISTENT FOR ALL;
+--sorted_result
+SELECT * FROM mysql.index_stats WHERE index_name='g' AND table_name='geom';
+DROP TABLE geom;

sql/sql_statistics.cc

@@ -2355,9 +2355,15 @@ int collect_statistics_for_index(THD *thd, TABLE *table, uint index)
   int rc= 0;
   KEY *key_info= &table->key_info[index];
   ha_rows rows= 0;
-  Index_prefix_calc index_prefix_calc(table, key_info);
+
   DBUG_ENTER("collect_statistics_for_index");
 
+  /* No statistics for FULLTEXT indexes. */
+  if (key_info->flags & HA_FULLTEXT)
+    DBUG_RETURN(rc);
+
+  Index_prefix_calc index_prefix_calc(table, key_info);
+
   DEBUG_SYNC(table->in_use, "statistics_collection_start1");
   DEBUG_SYNC(table->in_use, "statistics_collection_start2");
 
@@ -2391,7 +2397,7 @@ int collect_statistics_for_index(THD *thd, TABLE *table, uint index)
   if (!rc)
     index_prefix_calc.get_avg_frequency();
 
-  DBUG_RETURN(rc);            
+  DBUG_RETURN(rc);
 }