Hi Sergei!

I've implemented a fix for the bug described in MDEV-7362, that also fixes MDEV-7380. The test case also covers MDEV-7380. With the following fix,the 

I've spent a bit of time trying to figure out the architecture of things there. I am not confident my fix is complete, or if this is the way we want to go about fixing it. The fix does what we discussed over IRC, that we are not interested in computing statistics for a FULLTEXT index.

What I think would be the root cause of the problem is calling ha_index_init() on an index that does not support this. By calling table->file->ha_index_init(), the table->field array gets corrupted and that ultimately leads to a crash in the function using it afterwards.

Then again, this module is completely new to me, so any comments are appreciated. Here is the diff of the first changes.

diff --git a/mysql-test/t/mdev-7362.test b/mysql-test/t/mdev-7362.test

new file mode 100644

index 0000000..6551893

--- /dev/null

+++ b/mysql-test/t/mdev-7362.test

@@ -0,0 +1,14 @@

+CREATE TABLE t1 (a longtext, FULLTEXT KEY (`a`)) ENGINE=MyISAM;

+insert into t1 values (unhex('3E0D0A4141414142334E7A6143317963324541414141424977414141674541726D'));

+analyze table t1 persistent for all;

+drop table t1;

+

+CREATE TABLE t1 (a longtext, FULLTEXT KEY (`a`)) ENGINE=MyISAM;

+insert into t1 values (unhex('3E0D0A4141414142334E7A6143317963324541414141424977414141674541'));

+analyze table t1 persistent for all;

+drop table t1;

+

+CREATE TABLE t1 (f longtext NOT NULL, FULLTEXT KEY f (f)) ENGINE=MyISAM;

+INSERT INTO t1 VALUES (REPEAT('a',27)),('foo');

+ANALYZE TABLE t1 PERSISTENT FOR ALL;

+drop table t1;

diff --git a/sql/sql_statistics.cc b/sql/sql_statistics.cc

index d368145..2c1cccf 100644

--- a/sql/sql_statistics.cc

+++ b/sql/sql_statistics.cc

@@ -2367,6 +2367,9 @@ int collect_statistics_for_index(THD *thd, TABLE *table, uint index)

     DBUG_RETURN(rc);

   }

 

+  if (key_info->flags & HA_FULLTEXT) // skip if FULLTEXT index

+    DBUG_RETURN(rc);

+

   table->key_read= 1;

   table->file->extra(HA_EXTRA_KEYREAD);

 

Regards,

Vicențiu