Introduction

Query rewriting in ProxySQL is a powerful feature that allows administrators to modify query behavior dynamically without altering application code. It is commonly used to optimize queries, enforc
e standard practices, and improve database security by controlling how queries are executed against the database server.

Importance of Query Rewrite

Implementing query rewrite mechanisms can significantly enhance database performance and security. By rewriting and optimizing queries, companies can:

  • Improve Performance: Optimizing query structures can reduce load times and improve the efficiency of database server operations.
  • Enforce Standards: Standardize queries automatically, ensuring consistency and adherence to database usage policies.
  • Enhanced Security: Reduce attack vectors by limiting query types and shapes that can be executed.
  • Reduction in Resource Utilization: Prevent over-fetching of data by transforming SELECT * into selective column queries.

These benefits make query rewrite a standard tool that should be a part of a robust database infrastructure strategy.

Connecting to ProxySQL Admin

To begin rewriting queries, connect to the ProxySQL admin interface. You can do this via a command-line interface using the default credentials (unless changed):

mysql -u admin -padmin -h 127.0.0.1 -P 6032

This command logs into the ProxySQL administrative interface, where you can manage query rules and other settings.

Creating Query Rewrite Rules

Example 1: Replace SELECT * with Specific Columns

Use case: Assume we have a table called users and we only want to fetch id, username, email.

Rule Creation:

INSERT INTO mysql_query_rules (rule_id, active, match_pattern, replace_pattern, apply)
VALUES (1, 1, '^SELECT \\* FROM users, 'SELECT id, username, email FROM users', 1);

Example 2: Add USE INDEX

Use case: Encourage use of a specific index for the username column in users table.

Rule Creation:

INSERT INTO mysql_query_rules (rule_id, active, match_pattern, replace_pattern, apply)
VALUES (2, 1, '^SELECT id, username FROM users, 'SELECT id, username FROM users USE INDEX (index_username)', 1);

Example 3: Add ORDER BY

Use case: Automatically add an ordering for queries fetching records from products.

Rule Creation:

INSERT INTO mysql_query_rules (rule_id, active, match_pattern, replace_pattern, apply)
VALUES (3, 1, '^SELECT id, name FROM products, 'SELECT id, name FROM products ORDER BY name ASC', 1);

Example 4: Redacting Information

Use case: Redact sensitive information (e.g., ssn) when queried from the users table.

Rule Creation:

INSERT INTO mysql_query_rules (rule_id, active, match_pattern, replace_pattern, apply)
VALUES (5, 1, '^SELECT (.*)ssn(.*) FROM users, 'SELECT \\"REDACTED\"\ FROM users', 1);

Verification

Confirm that the rules have been correctly applied:

SELECT rule_id, active, match_pattern, replace_pattern FROM mysql_query_rules;

Possible Output:

+---------+--------+-----------------------------------+-------------------------------------------+
| rule_id | active | match_pattern                     | replace_pattern                           |
+---------+--------+-----------------------------------+-------------------------------------------+
| 1       | 1      | ^SELECT \\* FROM users$           | SELECT id, username, email FROM users     |
| 2       | 1      | ^SELECT id, username FROM users$  | SELECT id, username FROM users USE INDEX  |
| 3       | 1      | ^SELECT id, name FROM product$    | SELECT id, name FROM products ORDER BY    |
| 5       | 1      | ^SELECT (.*)ssn(.*) FROM users$   | SELECT \\"REDACTED\"\ FROM users          |
+---------+--------+-----------------------------------+-------------------------------------------+

How Our Consultancy Can Help

Optimizing database queries with ProxySQL’s query rewrite is part of our extensive consultancy offerings in database management and performance tuning. Our team can assist in implementing these best practices to ensure that your databases are not only running efficiently but also securely. This service is included in our subscription offerings, designed to suit your specific enterprise needs, providing hands-on assistance and strategic implementation of ProxySQL features.

Implementing such tools and strategies maximizes database performance, minimizes downtime, and ensures data consistency throughout your application’s lifecycle.