Configuration Rules

MyCat sharding requires defining table rules and functions in configuration files.

Table Rule Structure

<tableRule name="custom-sharding-long">
    <rule>
        <columns>user_id</columns>
        <algorithm>range-long</algorithm>
    </rule>
</tableRule>

Function Definition

<function name="range-long" class="io.mycat.route.function.AutoPartitionByLong">
    <property name="mapFile">range-partition.txt</property>
</function>

Continuous Sharding Methods

Numeric Range Sharding

Partitions data based on predefined numeric ranges in configuraiton files.

# range start-end , node index
0-50000=0
50001-100000=1
100001-200000=2

Date-Based Sharding

Distributes data across partitions using date intervals.

<function name="date-partition" class="io.mycat.route.function.PartitionByDate">
    <property name="dateFormat">yyyy-MM-dd</property>
    <property name="startDate">2023-01-01</property>
    <property name="partitionDays">30</property>
</function>

Discrete Sharding Approaches

Enumeration Sharding

Maps specific values to designated partitions using configuration files.

# value = node index
100=0
200=1
300=2

Modulo Sharding

Distributes data using modulo arithmetic on numeric values.

<function name="mod-partition" class="io.mycat.route.function.PartitionByMod">
    <property name="count">4</property>
</function>

Consistent Hashing

Uses murmur hash algorithm for improved data distribution during scaling.

<function name="consistent-hash" class="io.mycat.route.function.PartitionByMurmurHash">
    <property name="seed">0</property>
    <property name="count">3</property>
    <property name="virtualBucketTimes">160</property>
</function>

Composite Sharding Strategies

Range-Modulo Combination

Combines range partitioning with modulo distribution within ranges.

# range start-end, modulo divisor
0-1000000=4
1000001-2000000=2

Date Range with Hash

Groups data by date ranges and applies hashing within each group.

<function name="date-range-hash" class="io.mycat.route.function.PartitionByRangeDateHash">
    <property name="dateFormat">yyyy-MM-dd HH:mm:ss</property>
    <property name="startDate">2023-01-01 00:00:00</property>
    <property name="rangeDays">30</property>
    <property name="groupSize">5</property>
</function>

Sharding Strategy Considerations

• Evaluate table size - target ~10M rows per shard after partitioning
• Select sharding key based on most frequent query patterns
• Consiedr data migration requirements during scaling operations
• Apply consistent sharding rules to related tables for join operations
• Use global tables for rarely updated configuration data