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DynamoDB Single Table Library

Project description

Dokklib-DB

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Dokklib-DB is a Python library for the DynamoDB single table pattern.

Features

  • Simple, Pythonic query interface on top of Boto3. No more nested dict literals!
  • Type safety for primary keys and indices (for documentation and data integrity).
  • Easy error handling.
  • Full type hint & unit test coverage + integration testing.

Documentation

Install

Install with:

pip install "boto3>=1.10.34,<2" dokklib-db

Requires Python 3.6 or later.

Note that Boto3 is not specified as an installation requirement for Dokklib-DB, so you have to install it separately (like in the example command above). The reason for this is to make Dokklib-DB easier to use in AWS Lambda where Boto3 is part of the default environment. The earliest supported Boto3 version is 1.10.34 which is the same version as the Boto3 package in the Python 3 AWS Lambda environments.

Example usage

import dokklib_db as db


class User(db.EntityName):
    """User entity name.

    Key value: unique user name, eg. 'alice'.
    Example key: 'USER#alice'.

    """


class Group(db.EntityName):
    """Group entity name.

    Key value: unique group name, eg. 'my-group'.
    Example key: 'GROUP#my-group'.

    """


table = db.Table('SingleTable')

# Construct entity keys.
pk_alice = db.PartitionKey(User, 'alice')
pk_bob = db.PartitionKey(User, 'bob')
sk_group1 = db.SortKey(Group, 'group1')

# Add users to group one.
# Insert is a `PutItem` operation that fails if the item already exists.
table.insert(pk_alice, sk_group1)
table.insert(pk_bob, sk_group1)

# Get all users in group one.
pk_group = db.PartitionKey(Group, 'group1')
user_prefix = db.PrefixSortKey(User)
group_members = table.query_prefix(pk_group, user_prefix, 
    global_index=db.InversePrimaryIndex())

print(group_members)
# [{'PK': 'alice'}, {'PK': 'bob'}]

# Move users from group one to group two atomically.
sk_group2 = db.SortKey(Group, 'group2')
table.transact_write_items([
    db.DeleteArg(pk_alice, sk_group1),
    db.DeleteArg(pk_bob, sk_group1),
    db.InsertArg(pk_alice, sk_group2),
    db.InsertArg(pk_bob, sk_group2)
])

Status

The library is in beta and under heavy development as I'm working on it while building a serverless project that relies on it. I have only implemented parts of the DynamoDB API that I needed so far, but I'm planning on achieving full coverage. Feature and pull requests are welcome. (Please open an issue, before starting work on a pull request to avoid wasted effort.)

Project details


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