# dynamodb-migrator
[](https://travis-ci.org/bblommers/dynamodb-migrator)
[](https://coveralls.io/github/bblommers/dynamodb-migrator?branch=master)
[](https://badge.fury.io/py/dynamodb-migrator)
A library that helps you create and migrate DynamoDB databases.
As performant DynamoDB is, that does come with the trade-off of being inflexible. Changing column names or adding secondary indexes is impossible.
The recommended approach is to create a new table with the desired properties, and migrate the existing data.
This library will help you do just that.
## Usage
- Write a migration script
- Execute the migration script as a step in the build pipeline
- Add to the migration-script as required
## Example Script
```python
from migrator.dynamodb_migrator import Migrator
migrator = Migrator()
@migrator.version(1)
@migrator.create(AttributeDefinitions=[{'AttributeName': 'hash_key', 'AttributeType': 'N'}],
TableName='my_new_table',
KeySchema=[{'AttributeName': 'hash_key', 'KeyType': 'HASH'}],
BillingMode='PAY_PER_REQUEST')
def v1(created_table):
print("Table created using the kwargs provided")
print("Note that the keyword-args are passed onto boto as is")
print(created_table)
@migrator.version(2)
@migrator.add_index(AttributeDefinitions=[{'AttributeName': 'postcode', 'AttributeType': 'S'}],
LocalSecondaryIndexes=[{'IndexName': 'string',
'KeySchema': [{'AttributeName': 'customer_nr', 'KeyType': 'HASH'},
{'AttributeName': 'postcode', 'KeyType': 'RANGE'}],
'Projection': {'ProjectionType': 'ALL'}}])
def v2(created_table):
print("Created a new table with the new index")
print("Created a DynamoDB stream that sends all updates to the old table to a custom Lambda-function")
print("The custom Lambda-function sends all updates to the new table")
print(created_table)
@NotYetImplemented
@migrator.version(3)
@migrator.delete_table("first_table")
def v3(migrate):
print("About to delete table")
print("Ensure that all upstream applications point to the new table, before adding this part to the pipeline!")
migrate()
print("Table deleted")
@NotYetImplemented
@migrator.version(4)
@migrator.convert(lambda item -> {'id': translate(item.id)})
def v4(migrate):
print("About to:")
print(" - Create new table (first_table_v4)")
print(" - Create a AWS Lambda script that will execute the above lambda, and write the result int he new table")
print(" - Create DynamoDB Stream on 'first_table' that triggers the new Lambda")
print(" - Execute a script that automatically updates all existing data")
print(" (This will trigger all data in 'first_table' to be converted and copied into the new table")
migrate()
print("Table with new data is ready to use")
```
## Examples
See the [examples](examples)-folder.
