mariadb/mysql-test
Rex Johnston 80ea16c620 MDEV-29360 Crash when pushing condition with always false IS NULL into derived
(Edited by Sergei Petrunia)

Problem: when the optimizer attempts to push a condition in form
"merged_view.not_null_column IS NULL" into a derived table other
than the merged_view itself, it may crash.

The cause is this scenario:
1. Condition pushdown code uses walk() with excl_dep_on_grouping_fields()
(or excl_dep_on_table()) to determine whether an Item expression can
be pushed. Item_args::excl_dep_on_table() assumes that any item with
const_item()==1 can be pushed anywhere.

2. Item_func_isnull(not_null_expr) will report const_item()=1 as it
will always evaluate false. However it will have non-const expression
as its argument. As described in #1, this item will be considered pushable.

3. Transformation of item for pushdown is done in "transformer function"
Item_XXX::{derived|grouping}_field_transformer_for_where().
This function will be called for Item_func_isnull's argument.
If the argument is an Item_direct_view_ref, its transformer function
will call find_matching_field_pair() (or find_producing_item())
to locate the origin of the item inside the SELECT we're pushing the
condition into. It will get a NULL pointer (origin not found) and crash.


== The fix ==
Let Item_func_is_null(not_null_expr) report const_item()==true but
let its used_tables() still report those from not_null_expr.

Then, in Item_args, make excl_dep_on_grouping_fields() and
excl_dep_on_table() to check the used tables/columns for items
that report const_item()==true but have non-zero used_tables().
2026-04-10 18:29:59 +03:00
..
collections
include Merge branch '10.6' into 10.11 2025-07-28 18:06:31 +02:00
lib Add MTR to verify TLS with chain of trust 2025-12-18 19:44:26 +02:00
main MDEV-29360 Crash when pushing condition with always false IS NULL into derived 2026-04-10 18:29:59 +03:00
std_data MDEV-18359, MDEV-26905: Fix invalid XML in charsets Index.xml 2026-03-31 16:01:05 +03:00
suite MDEV-39278 Validate .cfg file parser string lengths in InnoDB import 2026-04-08 15:45:24 +03:00
asan.supp
CMakeLists.txt Merge branch '10.5' into 10.6 2025-03-31 12:12:50 +02:00
dgcov.pl
lsan.supp
mariadb-stress-test.pl
mariadb-test-run.pl Merge 10.6 into 10.11 2026-03-31 11:48:18 +03:00
mtr.out-of-source
purify.supp
README
README-gcov
README.stress
suite.pm Add MTR to verify TLS with chain of trust 2025-12-18 19:44:26 +02:00
valgrind.supp

This directory contains test suites for the MariaDB server. To run
currently existing test cases, execute ./mysql-test-run in this directory.

Some tests are known to fail on some platforms or be otherwise unreliable.
In the file collections/smoke_test there is a list of tests that are
expected to be stable.

In general you do not have to have to do "make install", and you can have
a co-existing MariaDB installation, the tests will not conflict with it.
To run the tests in a source directory, you must do "make" first.

In Red Hat distributions, you should run the script as user "mysql".
The user is created with nologin shell, so the best bet is something like
  # su -
  # cd /usr/share/mysql-test
  # su -s /bin/bash mysql -c ./mysql-test-run

This will use the installed MariaDB executables, but will run a private
copy of the server process (using data files within /usr/share/mysql-test),
so you need not start the mysqld service beforehand.

You can omit --skip-test-list option if you want to check whether
the listed failures occur for you.

To clean up afterwards, remove the created "var" subdirectory, e.g.
  # su -s /bin/bash - mysql -c "rm -rf /usr/share/mysql-test/var"

If tests fail on your system, please read the following manual section
for instructions on how to report the problem:

https://mariadb.com/kb/en/reporting-bugs

If you want to use an already running MySQL server for specific tests,
use the --extern option to mysql-test-run. Please note that in this mode,
you are expected to provide names of the tests to run.

For example, here is the command to run the "alias" and "analyze" tests
with an external server:

  # mysql-test-run --extern socket=/tmp/mysql.sock alias analyze

To match your setup, you might need to provide other relevant options.

With no test names on the command line, mysql-test-run will attempt
to execute the default set of tests, which will certainly fail, because
many tests cannot run with an external server (they need to control the
options with which the server is started, restart the server during
execution, etc.)

You can create your own test cases. To create a test case, create a new
file in the main subdirectory using a text editor. The file should have a .test
extension. For example:

  # xemacs t/test_case_name.test

In the file, put a set of SQL statements that create some tables,
load test data, and run some queries to manipulate it.

Your test should begin by dropping the tables you are going to create and
end by dropping them again. This ensures that you can run the test over
and over again.

If you are using mysqltest commands in your test case, you should create
the result file as follows:

  # mysql-test-run --record test_case_name

  or

  # mysqltest --record < t/test_case_name.test

If you only have a simple test case consisting of SQL statements and
comments, you can create the result file in one of the following ways:

  # mysql-test-run --record test_case_name

  # mysql test < t/test_case_name.test > r/test_case_name.result

  # mysqltest --record --database test --result-file=r/test_case_name.result < t/test_case_name.test

When this is done, take a look at r/test_case_name.result.
If the result is incorrect, you have found a bug. In this case, you should
edit the test result to the correct results so that we can verify that
the bug is corrected in future releases.

If you want to submit your test case you can send it
to developers@lists.mariadb.org or attach it to a bug report on
http://mariadb.org/jira/.

If the test case is really big or if it contains 'not public' data,
then put your .test file and .result file(s) into a tar.gz archive,
add a README that explains the problem, ftp the archive to
ftp://ftp.mariadb.org/private and submit a report to
https://mariadb.org/jira about it.

The latest information about mysql-test-run can be found at:
https://mariadb.com/kb/en/mariadb/mysqltest/

If you want to create .rdiff files, check
https://mariadb.com/kb/en/mariadb/mysql-test-auxiliary-files/