docs: Storage compatibility matrix

Added a document that lists what storage providers we have implemented and what functionality is implemented. Also made some small additions to the storage interface documentation.

Signed-off-by: Derek Trider <Derek.Trider@securekey.com>

docs/storage_compatibility_matrix.md

@@ -0,0 +1,68 @@
+# Storage Compatibility Matrix
+
+Aries-Framework-Go (this repo) and [Aries-Framework-Go-Ext](https://github.com/hyperledger/aries-framework-go-ext) have a number of storage providers that implement the [Aries storage interfaces](../spi/storage/storage.go).
+
+This document lists the storage provider implementations we have and what functionality is currently implemented/supported.
+
+The functions defined in the interfaces can be categorized as either "core" or "extended" functionality.
+
+✓ = Implemented
+
+X = Not implemented (but could be)
+
+Unsupported = Not implemented (and not currently supported by the underlying database/technology/spec)
+
+## Core Functionality
+
+These are the functions that the Aries agent currently uses. For a storage provider implementation to work in an Aries agent, it needs to support the functions below.
+
+|                           | MongoDB | CouchDB | EDV | MySQL | IndexedDB | LevelDB | In-Memory | PostgreSQL |
+|---------------------------|---------|---------|-----|-------|-----------|---------|-----------|------------|
+| Provider - OpenStore      | ✓       | ✓       | ✓   | ✓     | ✓         | ✓       | ✓         | ✓          |
+| Provider - SetStoreConfig | ✓       | ✓       | ✓*  | ✓**   | ✓***      | ✓       | ✓         | ✓****      |
+| Provider - Close          | ✓       | ✓       | ✓   | ✓     | ✓         | ✓       | ✓         | ✓          |
+| Store - Put               | ✓       | ✓       | ✓   | ✓**   | ✓***      | ✓       | ✓         | ✓****      |
+| Store - Get               | ✓       | ✓       | ✓   | ✓     | ✓         | ✓       | ✓         | ✓          |
+| Store - Query Using 1 Tag | ✓       | ✓       | ✓   | ✓**   | ✓***      | ✓       | ✓         | X*****     |
+| Store - Delete            | ✓       | ✓       | ✓   | ✓     | ✓         | ✓       | ✓         | ✓          |
+| Store - Close             | ✓       | ✓       | ✓   | ✓     | ✓         | ✓       | ✓         | ✓          |
+| Iterator - Next           | ✓       | ✓       | ✓   | ✓     | ✓         | ✓       | ✓         | ✓          |
+| Iterator - Key            | ✓       | ✓       | ✓   | ✓     | ✓         | ✓       | ✓         | ✓          |
+| Iterator - Value          | ✓       | ✓       | ✓   | ✓     | ✓         | ✓       | ✓         | ✓          |
+| Iterator - Close          | ✓       | ✓       | ✓   | ✓     | ✓         | ✓       | ✓         | ✓          |
+
+\* This method is more or less a no-op since EDV doesn't need this. Store config is just stored in-memory for now - see [here](https://github.com/hyperledger/aries-framework-go-ext/issues/2492) for more info. Since the Aries agent doesn't currently use GetStoreConfig, this isn't an issue for Aries usages.
+
+\*\* Current tagging/querying mechanism is unoptimized and not recommended for production use as-is. See [here](https://github.com/hyperledger/aries-framework-go-ext/issues/67) for more info.
+
+\*\*\* Current tagging/querying mechanism is unoptimized and not recommended for production use as-is. See [here](https://github.com/hyperledger/aries-framework-go-ext/issues/2540) for more info.
+
+\*\*\*\* There are some limitations with the current implementation of these methods. See [here](https://github.com/hyperledger/aries-framework-go-ext/issues/229) for more info.
+
+\*\*\*\*\* Tag name only queries have been implemented, but not tag name + value queries. Both types of queries are used by an Aries agent. See [here](https://github.com/hyperledger/aries-framework-go-ext/issues/229) for more info.
+
+## Extended Functionality
+
+The Aries agent does not currently make use of these functions, but they may be useful in building your own application.
+
+|                                       | MongoDB | CouchDB | EDV         | MySQL | IndexedDB | LevelDB | In-Memory | PostgreSQL |
+|---------------------------------------|---------|---------|-------------|-------|-----------|---------|-----------|------------|
+| Provider - GetStoreConfig             | ✓       | ✓       | ✓*          | ✓**   | ✓***      | ✓***    | ✓         | X          |
+| Provider - GetOpenStores              | ✓       | ✓       | ✓           | X     | X         | ✓       | ✓         | X          |
+| Store - GetTags                       | ✓       | ✓       | ✓           | ✓     | ✓         | ✓       | ✓         | X          |
+| Store - GetBulk                       | ✓       | ✓       | ✓           | X     | X         | ✓****   | ✓         | X          |
+| Store - Query Using Multiple Tags     | ✓       | X       | X           | X     | X         | X       | X         | X          |
+| Store - Query Using Custom Pagination | ✓       | ✓       | Unsupported | X     | X         | X       | X         | X          |
+| Store - Query Using Custom Sorting    | ✓       | ✓       | Unsupported | X     | X         | X       | X         | X          |
+| Store - Batch                         | ✓       | ✓       | ✓           | ✓     | ✓         | ✓****   | ✓         | X          |
+| Store - Flush                         | ✓       | ✓       | ✓           | ✓     | ✓         | ✓       | ✓         | ✓          |
+| Iterator - Tags                       | ✓       | ✓       | ✓           | ✓     | ✓         | ✓       | ✓         | X          |
+| Iterator - TotalItems                 | ✓       | ✓       | ✓           | ✓     | ✓         | ✓       | ✓         | X          |
+
+\* Only returns store config if it's still in memory. Can't be used to report whether the underlying database exists.
+
+\*\* Doesn't currently check the underlying data for existence (looks at in-memory stores instead). See [here](https://github.com/hyperledger/aries-framework-go-ext/issues/167) for more info.
+
+\*\*\* Doesn't currently check the underlying data for existence (looks at in-memory stores instead). See [here](https://github.com/hyperledger/aries-framework-go/issues/2948) for more info.
+
+\*\*\*\* Unoptimized implementation. See [here](https://github.com/hyperledger/aries-framework-go/issues/2605) for more info.

spi/storage/storage.go

@@ -194,6 +194,7 @@ type Store interface {
 	// GetTags fetches all tags associated with the given key.
 	// If key cannot be found, then an error wrapping ErrDataNotFound will be returned.
 	// If key is empty, then an error will be returned.
+	// As of writing, aries-framework-go code does not use this, but it may be useful for custom solutions.
 	GetTags(key string) ([]Tag, error)
 
 	// GetBulk fetches the values associated with the given keys.
@@ -225,6 +226,7 @@ type Store interface {
 	// enabled and a key is used that already exists in the database.
 	// Depending on the implementation, this method may be faster than repeated Put and/or Delete calls.
 	// If any of the given keys are empty, or the operations slice is empty or nil, then an error will be returned.
+	// As of writing, aries-framework-go code does not use this, but it may be useful for custom solutions.
 	Batch(operations []Operation) error
 
 	// Flush forces any queued up Put and/or Delete operations to execute.