Transaction Function

This function allows you to execute a block of code within a transaction. If auto_commit is TRUE (default), the transaction will be committed automatically upon successful execution. If auto_commit is FALSE, you must explicitly commit or rollback within the transaction block.

Usage

# S3 method for class 'Engine'
with(engine, expr, auto_commit = TRUE)

Arguments

engine

An Engine object that manages the database connection

expr

An expression to be evaluated within the transaction

auto_commit

Logical. Whether to automatically commit if no errors occur (default: TRUE)

Value

The result of evaluating the expression

Details

Within the transaction block, the following special functions are available:

• commit(): Explicitly commits the current transaction. After calling this function, no further changes will be made to the database within the current transaction block.

• rollback(): Explicitly rolls back (cancels) the current transaction. This undoes all changes made within the transaction block up to this point.

If auto_commit = TRUE (the default), the transaction will be automatically committed when the block completes without errors. If an error occurs, the transaction is automatically rolled back.

If auto_commit = FALSE, you must explicitly call commit() within the block to save your changes. If neither commit() nor rollback() is called, the transaction will be rolled back by default and a warning will be issued.

Examples

if (FALSE) { # \dontrun{
# With auto-commit (default)
with.Engine(engine, {
  User$record(name = "Alice")$create()
  User$record(name = "Bob")$create()
  # Transaction automatically committed if no errors
})

# With manual commit
with.Engine(engine, {
  User$record(name = "Alice")$create()
  User$record(name = "Bob")$create()
  
  # Explicitly commit the transaction
  commit()
}, auto_commit = FALSE)

# With conditional commit/rollback
with.Engine(engine, {
  User$record(name = "Alice")$create()
  
  # Check a condition
  if (some_validation_check()) {
    User$record(name = "Bob")$create()
    commit()
  } else {
    # Discard all changes if validation fails
    rollback()
  }
}, auto_commit = FALSE)

# Error handling with explicit rollback
with.Engine(engine, {
  tryCatch({
    User$record(name = "Alice")$create()
    # Some operation that might fail
    problematic_operation()
    commit()
  }, error = function(e) {
    # Custom error handling
    message("Operation failed: ", e$message)
    rollback()
  })
}, auto_commit = FALSE)
} # }