Hi everyone.

I am trying to run the following simple query on a table with 500K records.

SELECT COUNT(*) AS impressionCount
            FROM impression
            WHERE 0 = 0
                AND impressionObjectId1 = 'C69A54B8-B828-E2E4-2319A93011DF4120'
                AND impressionObjectId2 = '1';

This query is taking 10 seconds to run. I have tried creating individual indexes for the impressionObjectId1 and impressionObjectId2 columns, as well as a composite index using both. The composite worked well for a while, but now it is also slow.

Here is my table structure:

DROP TABLE IF EXISTS `impression`;
CREATE TABLE `impression` (
  `impressionId` varchar(50) NOT NULL,
  `impressionObjectId1` varchar(50) NOT NULL,
  `impressionObjectId2` varchar(50) default NULL,
  `impressionStampDate` datetime NOT NULL,
  PRIMARY KEY  (`impressionId`),
  KEY `IX_object` (`impressionObjectId1`,`impressionObjectId2`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 ROW_FORMAT=DYNAMIC COMMENT='InnoDB free: 191488 kB';

Any advice would be greatly appreciated. Thanks

EDIT: When adding an EXPLAIN, this is the output:

1, 'SIMPLE', 'impression', 'ref', 'IX_object', 'IX_object', '105', 'const,const', 304499, 'Using where; Using index'