Database Drivers¶

Trysil supports four relational databases. All drivers use FireDAC internally for database connectivity.

Supported Databases¶

Database	Connection Class	Unit	Delphi Edition
SQLite	`TTSQLiteConnection`	`Trysil.Data.FireDAC.SQLite`	Community
SQL Server	`TTSqlServerConnection`	`Trysil.Data.FireDAC.SqlServer`	Enterprise
PostgreSQL	`TTPostgreSQLConnection`	`Trysil.Data.FireDAC.PostgreSQL`	Community
Firebird	`TTFirebirdConnection`	`Trysil.Data.FireDAC.FirebirdSQL`	Community

Note

SQL Server support requires the Enterprise edition of Delphi. All other databases work with the Community edition.

Connection Pattern¶

Every driver follows the same two-step pattern:

Register the connection definition (class method, called once at startup).
Create connection instances as needed.

// Step 1: Register (once, at application startup)
TTSQLiteConnection.RegisterConnection('Main', 'database.db');

// Step 2: Create (as many times as needed)
LConnection := TTSQLiteConnection.Create('Main');
try
  LContext := TTContext.Create(LConnection);
  try
    // Use the context...
  finally
    LContext.Free;
  end;
finally
  LConnection.Free;
end;

The connection name ('Main' in the example) is a logical identifier. You can register multiple connections with different names to connect to different databases simultaneously.

Connection Pooling¶

Connection pooling is managed by FireDAC through a global singleton:

uses
  Trysil.Data.FireDAC.ConnectionPool;

// Enable pooling (recommended for server applications)
TTFireDACConnectionPool.Instance.Config.Enabled := True;

// Disable pooling (suitable for desktop applications)
TTFireDACConnectionPool.Instance.Config.Enabled := False;

When pooling is enabled, calling Create on a connection class borrows a connection from the pool instead of opening a new one. The connection is returned to the pool when freed.

Update Mode¶

TTUpdateMode controls the WHERE clause generated for UPDATE and DELETE statements:

Mode	WHERE Clause	Use Case
`KeyAndVersionColumn`	Primary key + version column	Default. Enables optimistic locking.
`KeyOnly`	Primary key only	Tables without a `[TVersionColumn]` field.

LConnection := TTSQLiteConnection.Create('Main');
LConnection.UpdateMode := TTUpdateMode.KeyOnly;

With KeyAndVersionColumn (the default), an UPDATE includes the current version in the WHERE clause. If another transaction has modified the row, the version will not match and ETConcurrentUpdateException is raised.

SQL Syntax Generation¶

Database-specific SQL (pagination, sequences, identity columns) is auto-generated per database engine via TTSyntaxClasses -- a pluggable strategy pattern. Each driver registers its own syntax classes at startup.

The SQL syntax implementations live in the Trysil/Data/SqlSyntax/ directory:

Database	Syntax Unit
SQLite	`Trysil.Data.SqlSyntax.SQLite`
SQL Server	`Trysil.Data.SqlSyntax.SqlServer`
PostgreSQL	`Trysil.Data.SqlSyntax.PostgreSQL`
Firebird	`Trysil.Data.SqlSyntax.FirebirdSQL`

You do not need to interact with these units directly. The correct syntax is selected automatically based on the connection class you use.

Connection Hierarchy¶

All connection classes inherit from TTConnection (defined in Trysil.Data.pas), which declares the full contract: transaction management, CreateReader, CreateInsertCommand, CreateUpdateCommand, CreateDeleteCommand, GetSequenceID, SelectCount, and CheckRelations.

TTGenericConnection (defined in Trysil.Data.Connection.pas) extends TTConnection and adds:

A UUID-based ConnectionID for log correlation across threads.
TTSyntaxClasses -- the pluggable SQL-generation strategy.

All four FireDAC drivers extend TTGenericConnection.