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131 lines
3.6 KiB
Crystal
131 lines
3.6 KiB
Crystal
module DB
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# Transactions should be started from `DB#transaction`, `Connection#transaction`
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# or `Connection#begin_transaction`.
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#
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# Use `Transaction#connection` to submit statements to the database.
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#
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# Use `Transaction#commit` or `Transaction#rollback` to close the ongoing transaction
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# explicitly. Or refer to `BeginTransaction#transaction` for documentation on how to
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# use `#transaction(&block)` methods in `DB` and `Connection`.
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#
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# Nested transactions are supported by using sql `SAVEPOINT`. To start a nested
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# transaction use `Transaction#transaction` or `Transaction#begin_transaction`.
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#
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abstract class Transaction
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include Disposable
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include BeginTransaction
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abstract def connection : Connection
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# commits the current transaction
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def commit
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close!
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end
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# rollbacks the current transaction
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def rollback
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close!
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end
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private def close!
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raise DB::Error.new("Transaction already closed") if closed?
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close
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end
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abstract def release_from_nested_transaction
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end
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class TopLevelTransaction < Transaction
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getter connection : Connection
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# :nodoc:
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property savepoint_name : String? = nil
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def initialize(@connection : Connection)
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@nested_transaction = false
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@connection.perform_begin_transaction
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end
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def commit
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@connection.perform_commit_transaction
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super
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end
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def rollback
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@connection.perform_rollback_transaction
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super
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end
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protected def do_close
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connection.release_from_transaction
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end
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def begin_transaction : Transaction
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raise DB::Error.new("There is an existing nested transaction in this transaction") if @nested_transaction
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@nested_transaction = true
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create_save_point_transaction(self)
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end
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# :nodoc:
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def create_save_point_transaction(parent : Transaction) : SavePointTransaction
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# TODO should we wrap this in a mutex?
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previous_savepoint = @savepoint_name
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savepoint_name = if previous_savepoint
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previous_savepoint.succ
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else
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# random prefix to avoid determinism
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"cr_#{@connection.object_id}_#{Random.rand(10_000)}_00001"
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end
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@savepoint_name = savepoint_name
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create_save_point_transaction(parent, savepoint_name)
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end
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protected def create_save_point_transaction(parent : Transaction, savepoint_name : String) : SavePointTransaction
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SavePointTransaction.new(parent, savepoint_name)
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end
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# :nodoc:
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def release_from_nested_transaction
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@nested_transaction = false
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end
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end
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class SavePointTransaction < Transaction
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getter connection : Connection
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def initialize(@parent : Transaction, @savepoint_name : String)
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@nested_transaction = false
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@connection = @parent.connection
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@connection.perform_create_savepoint(@savepoint_name)
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end
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def commit
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@connection.perform_release_savepoint(@savepoint_name)
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super
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end
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def rollback
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@connection.perform_rollback_savepoint(@savepoint_name)
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super
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end
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protected def do_close
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@parent.release_from_nested_transaction
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end
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def begin_transaction : Transaction
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raise DB::Error.new("There is an existing nested transaction in this transaction") if @nested_transaction
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@nested_transaction = true
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create_save_point_transaction(self)
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end
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def create_save_point_transaction(parent : Transaction)
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@parent.create_save_point_transaction(parent)
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end
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def release_from_nested_transaction
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@nested_transaction = false
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end
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end
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end
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