Table of Contents

DataLinq + MySQL & MariaDB

DataLinq provides unified support for both MySQL and MariaDB through the DataLinq.MySql NuGet package. It uses the MySqlConnector ADO.NET driver.

What This Provider Actually Covers

This provider does three distinct jobs:

  • runtime access through DataLinq.MySql
  • metadata introspection from information_schema
  • SQL generation for MySQL and MariaDB

That matters because MariaDB-specific behavior only appears when the connection type and factory selection are actually MariaDB-aware.

Schema Introspection and Type Mapping

create-models reads schema metadata from information_schema and maps backend types to C# types. The mapping is aware of signedness, length, defaults, foreign keys, indices, and enum definitions.

MySQL/MariaDB Type Maps to C# Type
INT UNSIGNED uint
INT int
BIGINT UNSIGNED ulong
BIGINT long
SMALLINT short
TINYINT sbyte
TINYINT UNSIGNED byte
BIT(1) bool
DECIMAL decimal
DOUBLE, FLOAT double, float
VARCHAR, TEXT, CHAR, etc. string
DATE DateOnly
DATETIME, TIMESTAMP DateTime
TIME TimeOnly
ENUM generated C# enum
BINARY(16) Guid
BLOB, VARBINARY, etc. byte[]
JSON string
UUID (MariaDB only) Guid

Additional notes:

  • SET is treated as string
  • BINARY(16) is the normal Guid representation
  • enums are emitted as generated C# enums with value metadata

Default Value Handling

create-models imports MySQL and MariaDB defaults into DataLinq metadata instead of treating them as raw schema text.

That includes:

  • quoted string defaults
  • quoted numeric defaults such as DEFAULT '0', converted to the actual C# property type instead of being treated as strings
  • enum defaults, including enum labels reported from schema metadata
  • CURRENT_DATE, CURRENT_TIME, CURRENT_TIMESTAMP
  • MySQL/MariaDB temporal aliases such as NOW(), LOCALTIME, and LOCALTIMESTAMP
  • parenthesized defaults such as (0) and ('abc')

This matters because MySQL and MariaDB are loose about how defaults are represented in schema metadata. DataLinq normalizes the SQL literal first, then converts it according to the target property type.

Examples:

  • INT DEFAULT '0' -> C# int default 0
  • BIGINT DEFAULT '0' -> C# long default 0L
  • ENUM('standard','premium') DEFAULT 'premium' -> generated enum member default
  • VARCHAR DEFAULT '""' -> C# string default containing two double-quote characters, not leaked SQL quoting syntax

Unsupported or Dangerous Defaults

Zero-date defaults such as 0000-00-00 and 0000-00-00 00:00:00 are not generated into typed date properties.

DataLinq warns and skips those defaults instead of emitting broken C# or pretending that invalid MySQL date garbage is fine.

MariaDB-Specific Features

MariaDB can use a native UUID type. DataLinq supports that, but only when you actually use MariaDB-specific type metadata.

Native UUID Type

  • Reading schema: A MariaDB UUID column maps to Guid.
  • Generating schema: To emit a native MariaDB UUID, use [Type(DatabaseType.MariaDB, "uuid")].
  • Default behavior: MariaDB SQL generation prefers native UUID for plain Guid properties.

Provider Configuration

To leverage MariaDB-specific behavior, make sure your datalinq.json connection is marked as MariaDB:

"Connections": [
  {
    "Type": "MariaDB",
    "DataSourceName": "my_mariadb_database",
    "ConnectionString": "..."
  }
]

If you mark the connection as MySQL, you are asking DataLinq to behave like MySQL even if the server happens to be MariaDB.

Important Guid Caveat

Guid values stored as BINARY(16) depend on MySqlConnector GuidFormat=LittleEndianBinary16 behaving the way the tests expect.

Native MariaDB UUID avoids that pain. BINARY(16) does not. This is a real caveat, not a theoretical one.

SQL Generation

When generating a schema from your DataLinq models:

  • MySQL maps Guid to BINARY(16) by default
  • MariaDB maps Guid to native UUID by default
  • view definitions use CREATE OR REPLACE VIEW

Default SQL generation is typed, not stringly:

  • string and char defaults are SQL-quoted and escaped correctly
  • bit defaults are emitted as b'0' and b'1'
  • numeric defaults use invariant formatting
  • DateOnly, TimeOnly, DateTime, and related values are emitted as provider-safe SQL literals
  • MariaDB uuid defaults and MySQL binary(16) Guid defaults are emitted differently because they are genuinely different storage shapes

If DataLinq can parse a supported MySQL/MariaDB default and represent it in metadata, it should also be able to emit it back out correctly in generated SQL. That roundtrip is now something the test suite actually checks.

Transaction Behavior

The current MySQL and MariaDB transaction implementation opens transactions with IsolationLevel.ReadCommitted.

That is relevant when comparing provider behavior to SQLite. Do not write cross-provider transaction visibility tests that assume they behave the same.

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