MySQL partitioned table works slower than equivalent unpartitioned table

Question

Help! I have a table in MySql (without partitioning) with ~4 500 000 rows:

CREATE TABLE stat_accounts_history (
  id bigint(20) NOT NULL AUTO_INCREMENT,
  accountId bigint(20) DEFAULT NULL,
  month varchar(255) DEFAULT NULL,
  purchase decimal(19, 2) DEFAULT NULL,
  purchaseCard decimal(19, 2) DEFAULT NULL,
  requiredPurchase decimal(19, 2) DEFAULT NULL,
  PRIMARY KEY (id),
  INDEX IDX_stat_accounts_history_accountId (accountId),
  INDEX IDX_stat_accounts_history_month (month)
)
ENGINE = INNODB
AUTO_INCREMENT = 4707631
AVG_ROW_LENGTH = 241
CHARACTER SET utf8
COLLATE utf8_general_ci;

I exported all data from this table and imported it to equivalent partitioned table:

CREATE TABLE stat_accounts_history_part (
  accountId bigint(20) NOT NULL,
  month varchar(255) NOT NULL DEFAULT '',
  purchase decimal(19, 2) DEFAULT NULL,
  purchaseCard decimal(19, 2) DEFAULT NULL,
  requiredPurchase decimal(19, 2) DEFAULT NULL,
  monthRef bigint(20) NOT NULL DEFAULT 0,
  PRIMARY KEY (accountId, monthRef),
  INDEX IDX_stat_accounts_history_part10_monthRef (monthRef),
  UNIQUE INDEX UK_stat_accounts_history_part1 (id, monthRef)
)
ENGINE = INNODB
AVG_ROW_LENGTH = 242
CHARACTER SET utf8
COLLATE utf8_general_ci
PARTITION BY LIST (monthRef)
(
PARTITION p2013_01 VALUES IN (9)
ENGINE = INNODB,
PARTITION p2013_02 VALUES IN (10)
ENGINE = INNODB,
PARTITION p2013_03 VALUES IN (11)
ENGINE = INNODB,
PARTITION p2013_04 VALUES IN (12)
ENGINE = INNODB,
PARTITION p2013_05 VALUES IN (13)
ENGINE = INNODB,
PARTITION p2013_06 VALUES IN (14)
ENGINE = INNODB,
PARTITION p2013_07 VALUES IN (15)
ENGINE = INNODB,
PARTITION p2013_08 VALUES IN (16)
ENGINE = INNODB,
PARTITION p2013_09 VALUES IN (17)
ENGINE = INNODB
);

In my web-application (Java+Spring+Hibernate) I wrote method to test queries to this tables:

for(int i = 0; i < 100; i++){
    long timeIter = System.nanoTime();
    dao.createSQLQuery("select count(accountId) from stat_accounts_history_part where monthRef=9 and (purchase+purchaseCard)>=requiredPurchase").list();
    System.out.print((long)((System.nanoTime() - timeIter)/1000000) + "\t");

    timeIter = System.nanoTime();
    dao.createSQLQuery("select count(accountId) from stat_accounts_history_part where monthRef=17 and (purchase+purchaseCard)>=requiredPurchase").list();
    System.out.print((long)((System.nanoTime() - timeIter)/1000000) + "\t");

    timeIter = System.nanoTime();
    dao.createSQLQuery("select count(id) from stat_accounts_history where month='2013.01' and (purchase+purchaseCard)>=requiredPurchase").list();
    System.out.print((long)((System.nanoTime() - timeIter)/1000000) + "\t");

    timeIter = System.nanoTime();
    dao.createSQLQuery("select count(id) from stat_accounts_history where month='2013.09' and (purchase+purchaseCard)>=requiredPurchase").list();
    System.out.print((long)((System.nanoTime() - timeIter)/1000000) + "\t");

    System.out.println();
}

And what I see is (1-2 cols - partitioned table, 3-4 cols - unpartitioned table):

1894   479   9   541    
436    442   2   2  
447    458   2   2  
469    469   2   2  
439    451   2   2  
468    453   3   2

I tried execute queries both with Hibernate and JDBC connection - same result.

Why queries to partitioned table works slower?

Answer 1

I resolved this problem by myself.

1. You should set innodb_file_per_table = 1 in my.cnf.
2. Query cache is not supported for partitioned tables in MySQL - http://dev.mysql.com/doc/refman/5.5/en/partitioning-limitations.html