Expectation Store
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Overview
Definition
An Expectation Store is a connector to store and retrieve information about collections of verifiable assertions about data.
Features and promises
Expectation Stores allow you to store and retrieve
Expectation SuitesA collection of verifiable assertions about
data.. These Stores can be accessed and configured through
the
Data ContextThe primary entry point for a Great Expectations
deployment, with configurations and methods for
all supporting components., but entries are added to them when you save an
Expectation Suite (typically through a convenience
method available from your Data Context). A configured
Expectation Store is required in order to work with
Great Expectations. A local configuration for an
Expectation Store will be added automatically to
great_expectations.yml when you
initialize your Data Context for the first time.
Generally speaking, while working with Great Expectations to ValidateThe act of applying an Expectation Suite to a Batch. data you will not need to interact with an Expectation Store directly outside configuring the StoreA connector to store and retrieve information about metadata in Great Expectations.. Instead, your Data Context will use an Expectation Store to store and retrieve Expectation Suites behind the scenes, and the objects you will directly work with will be those suites.
Relationship to other objects
Expectation Stores can be used to store and retrieve Expectation Suites. This means that Expectation Stores may also come into play when working with CheckpointsThe primary means for validating data in a production deployment of Great Expectations. and ValidatorsUsed to run an Expectation Suite against data., which can take Expectation Suites as input (rather than having a set Expectation Suite pre-defined in their configuration).
Use cases
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Setup |
When you initialize your Data Context for the first
time, a configuration for a local Expectation Store
will automatically be added to
great_expectations.yml. You may change
this configuration to work with different
environments.
- For more information on configuring an Expectation Store for a specific environment, please refer to our in-depth guides on Expectation Store configurations.
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Create Expectations |
Most workflows for creating Expectations automatically bundle them into an Expectation Suite. When you save the resultant Expectation Suite, your Data Context will use an Expectation Store to do so. Likewise, to edit an existing Expectation Suite, you will use your Data Context to retrieve it through an Expectation Store. This process is available through a convenience method in the Data Context, so you will not have to directly instantiate and interact with the Expectation Store.
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Validate Data |
When Validating Data it is possible to have Checkpoints configured to require an Expectation Suite as a parameter, or to have an Expectation Suite pre-defined in the Checkpoint's configuration. In either case, your Expectation Store will be used behind the scenes to retrieve the Expectation Suite in question (unless you are providing an Expectation Suite that still exists in memory from the Create Expectations step).
API basics
How to access
You will not typically need direct access to your
Expectation Store. Instead, your Data Context will use
your Expectation Store behind the scenes when storing
or retrieving Expectation Suites. Most of your direct
interaction with the Expectation Store will take place
during Setup, if you have need to configure your
Expectation Store beyond the default that is provided
when you initialize your Data Context. The rest of the
time you will most likely use convenience methods in
your Data Context to retrieve Expectation Suites, and
the save_expectation_suite method of a
Validator to save newly created Expectation Suites.
Both of these methods will make use of your
Expectation Store behind the scenes.
Configuration
For details on how to configure an Expectation Store, please reference the relevant how-to guide: