mariadb/mysql-test
Dave Gosselin 16f2b7e3df MDEV-36125 [NO_]INDEX_MERGE Hint
Introduces NO_INDEX_MERGE and INDEX_MERGE, which control whether or
not index merge strategies are used during query optimization.  Here
is an example query from the tests:

  SET optimizer_switch='index_merge_intersection=off';
  EXPLAIN SELECT /*+ INDEX_MERGE(t1 f4, f2) */ COUNT(*) FROM t1
  WHERE f4 = 'h' AND f2 = 2;

with the hint in place, the query plan will employ the index_merge
intersect strategy (abbreviated EXPLAIN output):

  type		Extra
  index_merge	Using intersect(f2,f4); Using where; Using index

The presence of the [NO_]INDEX_MERGE hint overrides the optimizer's
choice of keys during the index merge optimization.  As we see in
the above example, keys f2 and f4 and given and the optimizer will
consider only those keys for this query.

When the hint is given without any particular keys, as in
INDEX_MERGE(table), then all keys are considered.  In this case, the
cheapest index merge among the keys should be used.  When
NO_INDEX_MERGE(table) is given, then index merge is disabled for
that table.

When the hint is given with one or more keys, then only those keys
are considered.  In the case of NO_INDEX_MERGE, those keys are
excluded.  This can lead to no merged indexes at all, because
there may not be sufficient row-ordered read columns available for
consideration.

The index merge strategies of intersection, union, and sort union
cannot themselves be directly controlled via the hints.  In combination
with the optimizer switches for the same, the strategy may be
indirectly controlled but this is not guaranteed.

When the hint directs the optimizer such that insufficient ROR scans
are available, thus leading to a situation where the INDEX_MERGE hint
cannot be honored, the server will emit a warning to that effect.

In the hints module (opt_hints*{cc,h}), this commit adds some
index merge-specific functionality to make interpreting hint state
at callsites in the optimizer cleaner and more intuitive.
Particularly, we add a bit field to the table hints class which
indicates the keys that are marked by an [NO_]INDEX_MERGE hint, if
present.  A new function, index_merge_hint (and associated new
helper functions) relies on this field when interpreting index merge
hint state for the optimizer.

If there are no index merges available prior to attemping to find
a suitable union/sort union, then the optimizer will not attempt
it.  This change results in optimizer trace output which does not
include the 'analyzing_index_merge_union' block when there are no
merges.

Parts of this implementation based on MySQL commit
ebcb981807e3d91a64782e89d48e1a25622eafea
2025-09-05 15:10:13 +03:00
..
collections MDEV-9804 Implement a caching_sha2_password plugin 2025-07-27 13:57:06 +02:00
include Merge branch '12.0' into 12.1 2025-08-03 15:01:09 +02:00
lib Merge branch '11.8' into 12.0 2025-05-22 09:22:55 +02:00
main MDEV-36125 [NO_]INDEX_MERGE Hint 2025-09-05 15:10:13 +03:00
std_data Merge branch '11.8' into 12.0 2025-06-18 07:50:39 +02:00
suite 12.2 branch 2025-08-04 21:28:16 +02:00
asan.supp
CMakeLists.txt
dgcov.pl
lsan.supp
mariadb-stress-test.pl Fix typos in mysql-test/ 2025-04-29 13:53:16 +10:00
mariadb-test-run.pl Merge branch '11.8' into 12.0 2025-07-31 20:55:47 +02:00
mtr.out-of-source
purify.supp
README
README-gcov
README.stress
suite.pm
valgrind.supp Fix typos in mysql-test/ 2025-04-29 13:53:16 +10:00

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 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/mariadb-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/mariadb-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/mariadb-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:

  # mariadb-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:

  # mariadb-test-run --record test_case_name

  or

  # mariadb-test --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:

  # mariadb-test-run --record test_case_name

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

  # mariadb-test --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/