PyOrient Transactions - begin()

This method initiates a transaction.

Beginning Transactions

When you initialize a transaction through the tx_commit() client method, the return object provides you with several methods used in controlling the transaction process. Using the begin() method, you can initiate a transaction on this object.

Beginning a transactions effectively saves the database state. In the event that there is a problem with operations made after this point, you can revert the database back to this point using the rollback() method. Alternatively, you can commit the changes to the database using the commit() method.




For instance, say for a web application you want to create a series of new records on the database through a transaction. This ensures that, in the event that something goes wrong in the process, you can revert the database to its earlier state rather than committing an incomplete operation.

# Initialize Transaction Control Object
tx = client.tx_commit()

# Begin Transaction

   # Create Records
   for record in records:
      new = client.record_create(cluster_id, record)

# Commit Changes

Here, your application has an array of records stored in the records object. It initializes a transaction object with the tx_commit() client method, then begins the transaction with begin(). Within a try statement, it loops through this array, using the record_create() method to create new records. After it creates the record, it attaches the operations to the open transaction.

In the event that there is a problem, Python executes the except statement, which calls rollback(), reverting the database to its earlier state. If it's able to create all the records in the array, it issues the commit() method to commit the changes to the database.

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