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Displaying posts with tag: persistent statistics (reset)
Some Notes on Index Statistics in InnoDB

In MySQL 5.6 we introduced a huge improvement in the way that index and table statistics are gathered by InnoDB and subsequently used by the Optimizer during query optimization: Persistent Statistics. Some aspects of the way that Persistent Statistics work could be improved further though, and we’d really like your input on that.

How much to sample?

The statistics are gathered by picking some pages semi-randomly, analyzing them, and deriving some conclusions about the entire table and/or index from those analyzed pages. The number of pages sampled can be specified on a per-table basis with the STATS_SAMPLE_PAGES clause. For example:

ALTER TABLE t STATS_SAMPLE_PAGES=500;


This …

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Persistent statistics and partitions

Today when I was studying for the MySQL 5.6 exams.

I was studying for these two items:

  • Create and utilize table partitioning
  • Obtain MySQL metadata from INFORMATION_SCHEMA tables


The first step is to create a table, partition it with a hash.

mysql> CREATE TABLE pfoo (id INT AUTO_INCREMENT PRIMARY KEY, name VARCHAR(255))
-> PARTITION BY HASH(id) PARTITIONS 4;
Query OK, 0 rows affected (0.04 sec)

mysql> INSERT INTO pfoo(name) VALUES('test01'),('test02'),('test03'),('test04'),
-> ('test05'),('test06'),('test07'),('test08'),('test09'),('test10'),('test11');
Query OK, 11 rows affected (0.00 sec)
Records: 11 Duplicates: 0 Warnings: 0

mysql> SELECT * FROM pfoo;
+----+--------+
| id | name |
+----+--------+
| 4 | test04 |
| 8 | test08 |
| 1 | test01 |
| 5 | test05 …
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