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Mysql optimizer cost model software#
Mysql optimizer cost model code#

–Materialized cache for complex conditionsĬREATE TABLE order_lines (order integer, lineno integer, price decimal(10,2), qty integer, sum_price decimal(10,2) GENERATED ALWAYS AS (qty * price) STORED ) –Functional index: create a stored column, add a secondary index

STORED: computed when inserted/updated, stored in SE, indexable.

VIRTUAL: computed when read, not stored, not indexable.

Applicable to SELECT/INSERT/DELETE/UPDATE.Plan isn’t available when query plan is under creation.Useful for diagnostic on long running queries.–Cost of generating query + reparsing max ~5% performance overheadĮXPLAIN FOR Cost of queries to be rewritten is insignificant compared to performance gain.–Statement digest computed for performance schema anyway ~ Zero cost for queries not to be rewritten.Designed for rewriting problematic queries only!.

MySQL 5.7 Query Rewrite Plugin: Performance Impact

In case match, the query is rewritten.

In case rules table has changed, refresh rules.

–Plugin(s) is asked if it wants digests (It does) MySQL 5.7 Query Rewrite Plug-in: Server’s POV Parse error in replacement …near … at line 1 SELECT name, department_name FROXM employee STRAIGHT JOIN department USING ( department_id ) WHERE salary > ? Parse error in pattern:……near ……at line 1 SELECT name, department_name FROXM employee JOIN department USING ( department_id ) WHERE salary > ?įROM employee STRAIGHT JOIN department USING ( department_id ) WHERE salary > ? SELECT name, department_name FROM employee STRAIGHT JOIN department USING ( department_id ) WHERE salary > ? SELECT name, department_name FROM employee JOIN department USING ( department_id ) WHERE salary > ? – Will not detect differences in literals ON t1.keycol = t2.keycol WHERE col1 = 42 AND col2 = 2ġ.Hash lookup using query digest computed during parsing Replace parameter markers in Replacement with actual literals:įROM t1 STRAIGHT_JOIN t2 FORCE INDEX (col1) SELECT * FROM t1 JOIN t2 ON t1.keycol = t2.keycol WHERE col1 = 42 AND col2 = 2

~Zero performance overhead for queries not to be rewritten.

Improve problematic queries from ORMs, third party apps, etc.

–Rewrite problematic queries without the need to make application changes

New pre and post parse query rewrite APIs.

Mysql optimizer cost model code#

– However, dabase application code cannot be changed – Users can change the query plan by adding hints or rewrite the MySQL 5.7 Visual Explain in MySQL Workbench Mysql> EXPLAIN FORMAT=JSON SELECT SUM(o_totalprice) FROM orders WHERE o_orderdate BETWEEN '' AND '' MySQL 5.7 Additional Cost Data in JSON Explain

MySQL 5.7 Improved Record Estimation for JOIN Performance Improvements: DBT-3 (SF 10)Įxecution Time Relative to 5.6 in Percentageĥ out of 22 queries get an improved query plan SELECT office_name FROM office JOIN employee ON office.id = employee.office WHERE employee.name LIKE “John” AND hire_date BETWEEN “” AND “” Įxplain for 5.7: Total Cost = cost(scan emp) + 9991*1.23% * cost(eq_ref_access office) 100 rows with first_name=”John” AND hire_date BETWEEN “2012-01- 01″ AND “″ĬREATE TABLE emp ( id INTEGER NOT NULL PRIMARY KEY, office_id INTEGER NOT NULL, first_name VARCHAR(20), hire_date DATE NOT NULL, KEY office (office_id) ) ENGINE=InnoDB ĬREATE TABLE office ( id INTEGER NOT NULL PRIMARY KEY, officename VARCHAR(20) ) ENGINE=InnoDB Įxplain for 5.6: Total Cost = cost(scan office) + 100 * cost(ref_access emp).Prefix_rows_t1 Records passing the table conditions on t1 –More accurate record estimate -> improved JOIN order Prefix_rows_t1 Takes into account the entire query condition.MySQL 5.7 Improved Record Estimates for JOIN The development, release, and timing of any features or functionality described for Oracle’s products remains at the sole discretion of Oracle. It is not a commitment to deliver any material, code, or functionality, and should not be relied upon in making purchasing decisions. It is intended for information purposes only, and may not be incorporated into any contract. The following is intended to outline our general product direction. MySQL 5.7: What’s New in the Parser and the Optimizer?

Mysql optimizer cost model code#

Mysql optimizer cost model software#