DuckDB（嵌入式 OLAP）

介绍

DuckDB 是一款进程内分析数据库，它可以在无需维护分布式多服务器系统的情况下处理出人意料的大型数据集。

DuckDB has two configurable options for concurrency:

• One process can both read and write to the database.
• Multiple processes can read from the database, but no processes can write (access_mode = 'READ_ONLY').

DuckDB | 官网

安装包

FreeSql.Provider.Duckdb

.NET CLI

dotnet add package FreeSql.Provider.Duckdb

Package Manager

Install-Package FreeSql.Provider.Duckdb

声明

static IFreeSql fsql = new FreeSql.FreeSqlBuilder()
    .UseConnectionString(FreeSql.DataType.DuckDB, "DataSource = train_services.db")
    .UseMonitorCommand(cmd => Console.WriteLine($"Sql：{cmd.CommandText}"))
    .UseAutoSyncStructure(true) //自动创建表
    .Build();

依赖的第三方 ado.net 驱动源代码：https://github.com/Giorgi/DuckDB.NET

Connection String	Description
DataSource = :memory:	Connect to a new in-memory database
DataSource = :memory:?cache=shared	Connect to a shared, in-memory database
DataSource = train_services.db	Connect to train_services.db
DataSource = train_services.db;ACCESS_MODE=READ_ONLY	Connect to train_services.db, make connection read-only
DataSource = :memory:;threads=8;ACCESS_MODE=READ_ONLY	Connect to a new in-memory database, limit threads to 8, make connection read-only
DataSource = train_services.db;ACCESS_MODE=READ_ONLY;memory_limit=10GB	Connect to train_services.db, make connection read-only, limit RAM usage to 10GB

类型映射

CSharp	DuckDB	说明
bool/bool?	BOOLEAN	logical boolean (true/false)
sbyte/sbyte?	TINYINT	signed one-byte integer
short/short?	SMALLINT	signed two-byte integer
int/int?	INTEGER	signed four-byte integer
long/long?	BIGINT	signed eight-byte integer
byte/byte?	UTINYINT
ushort/ushort?	USMALLINT
uint/uint?	UINTEGER
ulong/ulong?	UBIGINT
double/double?	DOUBLE	double precision floating-point number (8 bytes)
float/float?	FLOAT	single precision floating-point number (4 bytes)
decimal/decimal?	DECIMAL(10,2)	fixed-precision number with the given width (precision) and scale
TimeSpan/TimeSpan?	TIME	time of day (no time zone)
DateTime/DateTime?	TIMESTAMP	combination of time and date
TimeOnly/TimeOnly?	TIME
DateOnly/DateOnly?	DATE	calendar date (year, month day)
byte[]	BLOB	variable-length binary data
string	VARCHAR(255)	variable-length character string
char	CHAR(1)
Guid/Guid?	UUID	UUID data type
BitArray	BIT	string of 1s and 0s
BigInteger/BigInteger?	HUGEINT	signed sixteen-byte integer
T[]	ARRAY/LIST	如 int[]、string[]，不能是可空 int?[]
class + JsonMap	STRUCT	{'i': 42, 'j': 'a'}
Dictionary<TKey, TValue>	MAP	map([1, 2], ['a', 'b'])

自定义映射，请移步【类型映射】文档。