Transactions¶

TTTransaction wraps explicit transaction management in Trysil. It is defined in Trysil.Transaction.pas.

Basic Usage¶

var LTransaction := LContext.CreateTransaction;
try
  LContext.Insert<TOrder>(LOrder);
  LContext.Insert<TOrderLine>(LLine1);
  LContext.Insert<TOrderLine>(LLine2);
  // Auto-commits when LTransaction is freed
finally
  LTransaction.Free;
end;

The transaction starts automatically on construction (AfterConstruction) and commits automatically on destruction (BeforeDestruction). There is no need to call a Commit method explicitly.

Rollback¶

To abort a transaction, call Rollback before the transaction is freed:

var LTransaction := LContext.CreateTransaction;
try
  try
    LContext.Insert<TOrder>(LOrder);
    LContext.Insert<TOrderLine>(LLine);
    // Something fails...
  except
    LTransaction.Rollback;
    raise;
  end;
finally
  LTransaction.Free;
end;

After Rollback is called, the auto-commit on destruction is skipped.

Behavior¶

Auto-start: The transaction starts in AfterConstruction. If the connection already has an active transaction, a new local transaction is not started (nested transaction support depends on the database driver).
Auto-commit: The transaction commits in BeforeDestruction, unless Rollback was called or the connection does not support transactions.
Internal use: The resolver uses TTTransaction internally for write operations (Insert, Update, Delete). When you use InsertAll, UpdateAll, DeleteAll, or ApplyAll, the context wraps the batch in a transaction automatically.

Checking Transaction State¶

if LContext.InTransaction then
  WriteLn('Transaction is active');

if LContext.SupportTransaction then
  WriteLn('Connection supports transactions');

Property	Description
`InTransaction`	`True` if the write connection currently has an active transaction
`SupportTransaction`	`True` if the write connection supports transaction management

Transaction with Session¶

When using TTSession<T>.ApplyChanges, the session creates its own transaction if one is not already active. You can wrap the session in an explicit transaction to combine it with other operations:

var LTransaction := LContext.CreateTransaction;
try
  try
    LSession.ApplyChanges;
    LContext.Insert<TAuditLog>(LAuditEntry);
  except
    LTransaction.Rollback;
    raise;
  end;
finally
  LTransaction.Free;
end;