[Solved] MySQL - Change index on myIsam table

EverSQL Database Performance Knowledge Base

MySQL - Change index on myIsam table

Database type:

I have a table where two columns are used in a where condition.

This is a MyIsam table and both columns hold text and use FULLTEXT as index.

The values in both columns are not unique.

The select statement works pretty slow.

Question is: can I simply remove the FULLTEXT index and use another index instead?

The query that is used is just as simple as possbile:

SELECT * FROM tbl WHERE col1=X AND col2=y and col3=z


How to optimize this SQL query?

The following recommendations will help you in your SQL tuning process.
You'll find 3 sections below:

  1. Description of the steps you can take to speed up the query.
  2. The optimal indexes for this query, which you can copy and create in your database.
  3. An automatically re-written query you can copy and execute in your database.
The optimization process and recommendations:
  1. Avoid Selecting Unnecessary Columns (query line: 2): Avoid selecting all columns with the '*' wildcard, unless you intend to use them all. Selecting redundant columns may result in unnecessary performance degradation.
  2. Create Optimal Indexes (modified query below): The recommended indexes are an integral part of this optimization effort and should be created before testing the execution duration of the optimized query.
Optimal indexes for this query:
ALTER TABLE `tbl` ADD INDEX `tbl_idx_col1_x_col2_y_col3_z` (`col1`,`X`,`col2`,`y`,`col3`,`z`);
The optimized query:
        tbl.col1 = tbl.X 
        AND tbl.col2 = tbl.y 
        AND tbl.col3 = tbl.z

Related Articles

* original question posted on StackOverflow here.