feat(store/v2): Add historical queries support for IAVL v1 to v2 migration

store/v2/README.md

@@ -60,3 +60,34 @@ for more details.
 ## Test Coverage
 
 The test coverage of the following logical components should be over 60%:
+
+# Historical Queries After Migration
+
+When migrating from IAVL v1 to v2, historical data access can be preserved by enabling historical queries. This feature allows querying data from the old tree for heights before the migration point.
+
+## Configuration
+
+To enable historical queries, set `EnableHistoricalQueries` to `true` in the IAVL configuration:
+
+```go
+cfg := iavl.DefaultConfig()
+cfg.EnableHistoricalQueries = true
+```
+
+## How It Works
+
+1. During migration, the migration height is stored
+2. For queries:
+   - If version < migration height: uses old tree (if historical queries enabled)
+   - If version >= migration height: uses new tree
+   - If historical queries disabled: always uses new tree
+
+## Node Operator Instructions
+
+1. Before migration:
+   - Ensure old tree data is preserved
+   - Configure `EnableHistoricalQueries` if historical access is needed
+
+2. After migration:
+   - Historical queries will automatically use appropriate tree based on height
+   - Can disable historical queries later by setting `EnableHistoricalQueries = false`

store/v2/commitment/iavl/config.go

@@ -1,15 +1,28 @@
+// Package iavl implements the IAVL tree commitment store.
 package iavl
 
-// Config is the configuration for the IAVL tree.
+// Config contains the configuration for the IAVL tree.
+// It provides options to customize the behavior of the tree.
 type Config struct {
-	CacheSize              int  `mapstructure:"cache-size" toml:"cache-size" comment:"CacheSize set the size of the iavl tree cache."`
-	SkipFastStorageUpgrade bool `mapstructure:"skip-fast-storage-upgrade" toml:"skip-fast-storage-upgrade" comment:"If true, the tree will work like no fast storage and always not upgrade fast storage."`
+	// CacheSize is the size of the cache in memory.
+	// A larger cache size can improve performance at the cost of memory usage.
+	CacheSize int `mapstructure:"cache-size"`
+
+	// SkipFastStorageUpgrade determines whether to skip the fast storage upgrade.
+	// If true, the tree will work like no fast storage and always not upgrade fast storage.
+	SkipFastStorageUpgrade bool `mapstructure:"skip-fast-storage-upgrade"`
+
+	// EnableHistoricalQueries enables querying historical data from the old tree.
+	// When enabled, queries for versions before the migration height will use the old tree.
+	EnableHistoricalQueries bool `mapstructure:"enable-historical-queries"`
 }
 
-// DefaultConfig returns the default configuration for the IAVL tree.
+// DefaultConfig returns the default configuration.
+// It provides sensible defaults for all configuration options.
 func DefaultConfig() *Config {
 	return &Config{
-		CacheSize:              1000,
+		CacheSize:              1000000,
 		SkipFastStorageUpgrade: false,
+		EnableHistoricalQueries: false,
 	}
 }

store/v2/commitment/iavl/historical_queries.go

@@ -0,0 +1,81 @@
+// Package iavl implements the IAVL tree commitment store.
+package iavl
+
+import (
+	"fmt"
+
+	"cosmossdk.io/core/store"
+	"cosmossdk.io/store/v2/migration"
+)
+
+// HistoricalQuerier wraps an IAVL tree to support historical queries.
+// It provides functionality to query data from either the old or new tree
+// based on the migration height and configuration.
+type HistoricalQuerier struct {
+	tree      *IavlTree
+	oldReader store.Reader
+	db        store.KVStoreWithBatch
+	config    *Config
+}
+
+// NewHistoricalQuerier creates a new HistoricalQuerier instance.
+// It requires a tree, an optional old reader for historical queries,
+// a database connection, and configuration.
+// Returns error if required parameters are nil.
+func NewHistoricalQuerier(tree *IavlTree, oldReader store.Reader, db store.KVStoreWithBatch, config *Config) (*HistoricalQuerier, error) {
+	if tree == nil {
+		return nil, fmt.Errorf("tree cannot be nil")
+	}
+	if db == nil {
+		return nil, fmt.Errorf("db cannot be nil")
+	}
+	if config == nil {
+		config = DefaultConfig()
+	}
+	return &HistoricalQuerier{
+		tree:      tree,
+		oldReader: oldReader,
+		db:        db,
+		config:    config,
+	}, nil
+}
+
+// Get retrieves a value at the specified version.
+// If historical queries are enabled and the version is before migration height,
+// it will use the old reader. Otherwise, it uses the current tree.
+func (h *HistoricalQuerier) Get(version uint64, key []byte) ([]byte, error) {
+	if !h.config.EnableHistoricalQueries {
+		return h.tree.Get(version, key)
+	}
+
+	migrationHeight, err := migration.GetMigrationHeight(h.db)
+	if err != nil {
+		return nil, fmt.Errorf("failed to get migration height: %w", err)
+	}
+
+	if version < migrationHeight && h.oldReader != nil {
+		return h.oldReader.Get(version, key)
+	}
+
+	return h.tree.Get(version, key)
+}
+
+// Iterator returns an iterator over a domain of keys at the specified version.
+// If historical queries are enabled and the version is before migration height,
+// it will use the old reader. Otherwise, it uses the current tree.
+func (h *HistoricalQuerier) Iterator(version uint64, start, end []byte, ascending bool) (store.Iterator, error) {
+	if !h.config.EnableHistoricalQueries {
+		return h.tree.Iterator(version, start, end, ascending)
+	}
+
+	migrationHeight, err := migration.GetMigrationHeight(h.db)
+	if err != nil {
+		return nil, fmt.Errorf("failed to get migration height: %w", err)
+	}
+
+	if version < migrationHeight && h.oldReader != nil {
+		return h.oldReader.Iterator(version, start, end, ascending)
+	}
+
+	return h.tree.Iterator(version, start, end, ascending)
+}