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


----- Original Message -----
> Hi Sergei!

Hi Vicentiu,

Thanks for fixing my reported bug :-)

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

> 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.

makes sense.

> 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.

That sounds like another bug that need to be fixed in ha_maria::index_init /  ha_myisam::index_init or the API is being used differently to usual.

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

The test case should also look at the result of the:

select * from mysql.index_stats where index_name='a' and table_name='t1';

> 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

more recent test cases include the area of the test failure in the filename or include the test with the general t/statistics.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;
> +
> +INSERT INTO t1 VALUES (REPEAT('a',27)),('foo');
> +drop table t1;

Can you please add a test case for innodb too as it supports FT in 10.0.

> 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)
> }
> + if (key_info->flags & HA_FULLTEXT) // skip if FULLTEXT index
> + DBUG_RETURN(rc);
> +

If this is the fix the if..return can go much earlier in collect_statistics_for_index, before Index_prefix_calc() even.

Daniel Black, Engineer @ Open Query (http://openquery.com.au)
Remote expertise & maintenance for MySQL/MariaDB server environments.

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