MySQL Storage Engines and Index Implementation
MySQL Architecture Layers
MySQL's architecture comprises four interconnected layers:
- Network Connection Layer: Manages client connections via thread pooling
- Core Service Layer: Handles SQL parsing, optimization, and caching
- Storage Engine Layer: Plugin-based data managemnet system
- File System Layer: Stores configuration, data, and log files
Storage Engine Comparision
| Feature | InnoDB | MyISAM | MEMORY |
|---|---|---|---|
| Transactional Support | Yes | No | No |
| Locking Mechanism | Row/Table | Table | Table |
| Foreign Keys | Supported | Not Supported | Not Supported |
| Crash Recovery | ACID Compliant | Partial | None |
Storage Engine Operations
-- List supported engines
SHOW ENGINES;
-- Create table with specific engine
CREATE TABLE device_data(
device_id INT PRIMARY KEY AUTO_INCREMENT,
sensor_value DECIMAL(10,2)
) ENGINE = MEMORY;
-- Modify table engine
ALTER TABLE device_data ENGINE = INNODB;
Endex Implementation
Indexes accelerate data retrieval through optimized data structures:
- B-Tree: Balanced tree structure for efficient range queries
- B+Tree: Enhanced version with sequential leaf node pointers
- Hash: Key-value pairs for exact match lookups
Index Operations
-- Create composite index
CREATE INDEX idx_sensor_location
ON device_data(location_id, reading_time);
-- Display table indexes
SHOW INDEX FROM device_data;
-- Remove index
DROP INDEX idx_sensor_location ON device_data;
Locking Mechanisms
| Lock Type | Scope | Conflict Cases |
|---|---|---|
| Shared (Read) | Row/Table | Blocks write operations |
| Exclusive (Write) | Row/Table | Blocks read/write operations |
-- Acquire shared lock
SELECT * FROM network_logs
WHERE status = 'error' LOCK IN SHARE MODE;
-- Acquire exclusive lock
SELECT * FROM user_balance
FOR UPDATE;
Optimistic Locking Example
CREATE TABLE inventory(
item_id INT PRIMARY KEY,
quantity INT,
version INT DEFAULT 0
);
-- Concurrent update handling
UPDATE inventory
SET quantity = 95, version = version + 1
WHERE item_id = 101 AND version = 5;
Clustering with MyCat
Configuration for horizontal sharding:
<schema name="SHARDED_DB">
<table name="user_actions" dataNode="dn1,dn2" rule="shard_mod" />
</schema>
<dataNode name="dn1" dataHost="host1" database="shard1" />
<dataNode name="dn2" dataHost="host2" database="shard2" />
<function name="shard_mod" class="PartitionByMod">
<property name="count">2</property>
</function>
