Range¶
Application Scenarios¶
This algorithm applies to routing data in different ranges to different shards. Less-than signs (<), greater-than signs (>), and BETWEEN ... AND ... are frequently used in SQL queries.
Instructions¶
The sharding key can only be an integer, a date, or used in combination with a date function. If a date function is used, the sharding key must be DATE, DATETIME, or TIMESTAMP.
Data Routing¶
Data is routed to different shards by the sharding key value based on algorithm metadata rules.
Metadata needs to be set when a table is created. For example, if there are eight shards in one schema, the metadata range can be [1-2]=0, [3-4]=1, [5-6]=2, [7-8]=3, [9-10]=4, [11-12]=5, [13-14]=6, and default=7. Data is routed to shards by the sharding key value based on the range.
Calculation Method¶
Method 1: Use an Integer as the Sharding Key
Condition | Calculation Method | Example |
|---|---|---|
Integer sharding keys | Database routing result: Data is routed to different shards based on the sharding key and the preset metadata range. | Data is routed to shard1 if the sharding key value is 3 and the preset metadata range is [3-4]. |
Method 2: Use a Date as the Sharding Key
Date Function | Calculation Method | Example |
|---|---|---|
year() | year(yyyy-MM-dd)=yyyy | year('2019-10-11')=2019 |
month() | month(yyyy-MM-dd)=MM | month('2019-10-11')=10 |
weekofyear() | weekofyear(yyyy-MM-dd)=Week number of the current year Note The Weekofyear() function is used to return the week number of a specific date represented by the date parameter in a year. For details, see WEEK. | weekofyear ('2019-10-11')=41 |
day() | day(yyyy-MM-dd)=dd | day ('2019-10-11')=11 |
Condition | Calculation Method | Example |
|---|---|---|
Date sharding key | Database routing: Data is routed to different database shards based on the date function (database sharding key value) and the preset metadata range. | Data is routed to shard 4 based on the metadata range 9-10 when the sharding key value is 10: month(2019-10-11)=10 belongs to [9-10]=4. |
Syntax for Creating Tables¶
create table range_tb(
id int,
name varchar(30) DEFAULT NULL,
create_time datetime DEFAULT NULL,
primary key(id)
)
dbpartition by range(id)
{
1-2=0,
3-4=1,
5-6=2,
7-8=3,
9-10=4,
11-12=5,
13-14=6,
default=7
};
Precautions¶
None