away store v2

docs/architecture/adr-002-api-cleanup.md

@@ -1,4 +1,4 @@
-# ADR ADR-002: API Cleanup to Support Store V2
+# ADR ADR-002: API Cleanup to Improve Commit Performance
 
 ## Changelog
 
@@ -10,18 +10,17 @@ DRAFT
 
 ## Abstract
 
-This ADR proposes a cleanup of the API to support [Store V2](https://github.com/cosmos/cosmos-sdk/blob/main/docs/architecture/adr-065-store-v2.md).
-
-There are some proposals for the speedup of the `Commit` by the async writes. See the [Discussion](https://github.com/cosmos/cosmos-sdk/issues/16173) for more details.
+This ADR proposes a cleanup of the API to make more understandable and maintainable the codebase of `iavl`.
 
 There is a lot of legacy code in the SDK that is not used anymore and can be removed. See the [Discussion](https://github.com/cosmos/iavl/issues/737) for more details. 
 
+There are some proposals for the speedup of the `Commit` by the async writes. See the [Discussion](https://github.com/cosmos/cosmos-sdk/issues/16173) for more details.
+
 ## Context
 
-The introduction of `Store V2` separates SS (State Storage) and SC (State Commitment), where `iavl` is used for SC. The index of the `fast node` is not needed in `iavl` since SS allows key-value queries for a specific version.
-Additionally, `Store V2` introduces a new approach to `SaveVersion` that accepts a batch object for the atomicity of the commit and removes the usage of `dbm.Batch` in `nodeDB`.
+The current implementation of `iavl` suffers from performance issues due to synchronous writes during the `Commit` process. To address this, the proposed changes aim to finalize the current version in memory, parallelize hash calculations in `WorkingHash`, and introduce asynchronous writes in the background.
 
-The current implementation of `iavl` suffers from performance issues due to synchronous writes during the `Commit` process. To address this, the proposed changes aim to finalize the current version in memory, parallelize hash calculations in `WorkingHash`, and introduce asynchronous writes.
+It is also necessary to refactor the `Set` function to accept a batch object for the atomic commitments. 
 
 Moreover, the existing architecture of `iavl` lacks modularity and code organization:
 
@@ -30,12 +29,11 @@ Moreover, the existing architecture of `iavl` lacks modularity and code organiza
 
 ## Decision
 
-To support `Store V2` and improve `Commit` performance, we propose the following changes:
+To make the codebase more clear and improve `Commit` performance, we propose the following changes:
 
-### Support Store V2
+### Batch Set
 
-- Refactor the `SaveVersion` function to accept a batch object.
-- Remove the index of the `fast node` from `iavl`.
+- Refactor the `Set` function to accept a batch object.
 - Eliminate the usage of `dbm.Batch` in `nodeDB`.
 
 ### Async Commit
@@ -46,27 +44,30 @@ To support `Store V2` and improve `Commit` performance, we propose the following
 
 ### API Cleanup
 
-- Merge `ImmutableTree` and `MutableTree` into a single `Tree` structure.
-- Make `nodeDB` methods private.
+- Make `nodeDB` methods private and remove all unused methods.
+- Follow the naming convention of the `store` module.
 
 The modified API will have the following structure:
 
 ```go
-    Tree interface {
-        Has(key []byte) (bool, error)
-        Get(key []byte) ([]byte, error)
-        SaveVersion(cs *ChangeSet) ([]byte, int64, error)
-        Version() int64
-        Hash() []byte
+    MutableTree interface {
+        SaveChangeSet(cs *ChangeSet) ([]byte, error) // this is for batch set
         WorkingHash() []byte
-        VersionExists(version int64) bool
+        Commit() ([]byte, int64, error) // SaveVersion -> Commit
+        WaitForCommit() error // this is to make sure the async write is finished when shutdown
         DeleteVersionsTo(version int64) error
-        GetVersioned(key []byte, version int64) ([]byte, *cmtprotocrypto.ProofOps, error)
-        GetTree(version int64) (*iavl.Tree, error)
         SetInitialVersion(version uint64)
-        Iterator(start, end []byte, ascending bool) (types.Iterator, error)
         LoadVersionForOverwriting(targetVersion int64) error
-        WaitForCommit() error // this is for when gracefully shutdown
+        GetImmutableTree(version int64) (*ImmutableTree, error)
+    }
+
+    ImmutableTree interface {
+        Has(key []byte) (bool, error)
+        Get(key []byte) ([]byte, error)
+        Hash() []byte
+        Iterator(start, end []byte, ascending bool) (types.Iterator, error)
+        VersionExists(version int64) bool
+        GetVersionedProof(key []byte, version int64) ([]byte, *cmtprotocrypto.ProofOps, error)
     }
 ```
 ## Consequences
@@ -75,11 +76,11 @@ We expect the proposed changes to improve the performance of Commit through asyn
 
 ### Backwards Compatibility
 
-While this ADR will break the external API of `iavl`, it will not affect the internal state of nodeDB. Compatibility measures and migration steps will be necessary during the `Store V2` migration to handle the breaking changes.
+While this ADR will break the external API of `iavl`, it will not affect the internal state of nodeDB. Compatibility measures and migration steps will be necessary during the API cleanup to handle the breaking changes.
 
 ### Positive
 
-- Atomicity of the `Commit`.
+- Atomicity of the `Commitments`.
 - Improved Commit performance through async writes and parallelized hash calculations.
 - Increased flexibility and ease of modification and refactoring for iavl.
 
@@ -89,6 +90,5 @@ While this ADR will break the external API of `iavl`, it will not affect the int
 
 ## References
 
-- [Store V2](https://github.com/cosmos/cosmos-sdk/blob/main/docs/architecture/adr-065-store-v2.md)
 - https://github.com/cosmos/cosmos-sdk/issues/16173
 - https://github.com/cosmos/iavl/issues/737