This includes all test changes from
"Changing all cost calculation to be given in milliseconds"
and forwards.
Some of the things that caused changes in the result files:
- As part of fixing tests, I added 'echo' to some comments to be able to
easier find out where things where wrong.
- MATERIALIZED has now a higher cost compared to X than before. Because
of this some MATERIALIZED types have changed to DEPENDEND SUBQUERY.
- Some test cases that required MATERIALIZED to repeat a bug was
changed by adding more rows to force MATERIALIZED to happen.
- 'Filtered' in SHOW EXPLAIN has in many case changed from 100.00 to
something smaller. This is because now filtered also takes into
account the smallest possible ref access and filters, even if they
where not used. Another reason for 'Filtered' being smaller is that
we now also take into account implicit filtering done for subqueries
using FIRSTMATCH.
(main.subselect_no_exists_to_in)
This is caluculated in best_access_path() and stored in records_out.
- Table orders has changed because more accurate costs.
- 'index' and 'ALL' for small tables has changed to use 'range' or
'ref' because of optimizer_scan_setup_cost.
- index can be changed to 'range' as 'range' optimizer assumes we don't
have to read the blocks from disk that range optimizer has already read.
This can be confusing in the case where there is no obvious where clause
but instead there is a hidden 'key_column > NULL' added by the optimizer.
(main.subselect_no_exists_to_in)
- Scan on primary clustered key does not report 'Using Index' anymore
(It's a table scan, not an index scan).
- For derived tables, the number of rows is now 100 instead of 2,
which can be seen in EXPLAIN.
- More tests have "Using index for group by" as the cost of this
optimization is now more correct (lower).
- A primary key could be preferred for a normal key, even if it would
access more rows, as it's faster to do 1 lokoup and 3 'index_next' on a
clustered primary key than one lookup trough a secondary.
(main.stat_tables_innodb)
Notes:
- There was a 4.7% more calls to best_extension_by_limited_search() in
the main.greedy_optimizer test. However examining the test results
it looked that the plans where slightly better (eq_ref where more
chained together) so I assume this is ok.
- I have verified a few test cases where there was notable/unexpected
changes in the plan and in all cases the new optimizer plans where
faster. (main.greedy_optimizer and some others)
The original code was mostly rule based and preferred clustered or
covering indexed independent of cost.
There where a few test changes:
- Some test changed from using filesort to index or table scan. This
happened when most of the rows had to be sorted and the ORDER BY could
use covering or a clustered index (innodb_mysql, create_spatial_index).
- Some test changed range to filesort. This where mainly because the range
was scanning most of the rows or using index scan + row lookup and
filesort with table scan is cheaper. (order_by).
- Change in join_cache was because sorting 2 rows is faster than retrieving
10 rows.
- In selectivity_innodb.test one test changed to use a cheaper index.
This feature adds the functionality of ignorability for indexes.
Indexes are not ignored be default.
To control index ignorability explicitly for a new index,
use IGNORE or NOT IGNORE as part of the index definition for
CREATE TABLE, CREATE INDEX, or ALTER TABLE.
Primary keys (explicit or implicit) cannot be made ignorable.
The table INFORMATION_SCHEMA.STATISTICS get a new column named IGNORED that
would store whether an index needs to be ignored or not.
Similar to the tables SYS_FOREIGN and SYS_FOREIGN_COLS,
the tables mysql.innodb_table_stats and mysql.innodb_index_stats
are updated by the InnoDB internal SQL parser, which fails to
enforce the size limits of the data. Due to this, it is possible
for InnoDB to hang when there are persistent statistics defined on
partitioned tables where the total length of table name,
partition name and subpartition name exceeds the incorrectly
defined limit VARCHAR(64). That column should have been defined
as VARCHAR(199).
btr_node_ptr_max_size(): Interpret the VARCHAR(64) as VARCHAR(199),
to prevent a hang in the case that the upgrade script has not been
run.
dict_table_schema_check(): Ignore difference in the length of the
table_name column.
ha_innobase::max_supported_key_length(): For innodb_page_size=4k,
return a larger value so that the table mysql.innodb_index_stats
can be created. This could allow "impossible" tables to be created,
such that it is not possible to insert anything into a secondary
index when both the secondary key and the primary key are long,
but this is the easiest and most consistent way. The Oracle fix
would only ignore the maximum length violation for the two
statistics tables.
os_file_get_status_posix(), os_file_get_status_win32(): Handle
ENAMETOOLONG as well.
This patch is based on the following change in MySQL 5.7.23.
Not all changes were applied, and our variant allows persistent
statistics to work without hangs even if the table definitions
were not upgraded.
From fdbdce701ab8145ae234c9d401109dff4e4106cb Mon Sep 17 00:00:00 2001
From: Aditya A <aditya.a@oracle.com>
Date: Thu, 17 May 2018 16:11:43 +0530
Subject: [PATCH] Bug #26390736 THE FIELD TABLE_NAME (VARCHAR(64)) FROM
MYSQL.INNODB_TABLE_STATS CAN OVERFLOW.
In mysql.innodb_index_stats and mysql.innodb_table_stats
tables the table name column didn't take into consideration
partition names which can be more than varchar(64).
