fix(store): handle nil end in cachekv/iterator (cosmos#12945)

Closes: cosmos#12661

Adds support for nil end semantics to iterators in cachekv store, addressing [this workaround](https://github.com/osmosis-labs/osmosis/blob/4176b287d48338870bfda3029bfa20a6e45ac126/osmoutils/store_helper.go#L37-L41).

Note that this has the effect of sorting the dirty cache into the BTree cache store in the bounds `[startIndex, end-of-cache-space]`

---

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CHANGELOG.md

@@ -56,6 +56,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 ### Bug Fixes
 
 * (store) [#13516](https://github.com/cosmos/cosmos-sdk/pull/13516) Fix state listener that was observing writes at wrong time.
+* (store) [#12945](https://github.com/cosmos/cosmos-sdk/pull/12945) Fix nil end semantics in store/cachekv/iterator when iterating a dirty cache.
 
 ## v0.45.11 - 2022-11-09
 

store/cachekv/store.go

@@ -281,7 +281,7 @@ const minSortSize = 1024
 // Constructs a slice of dirty items, to use w/ memIterator.
 func (store *Store) dirtyItems(start, end []byte) {
 	startStr, endStr := conv.UnsafeBytesToStr(start), conv.UnsafeBytesToStr(end)
-	if startStr > endStr {
+	if end != nil && startStr > endStr {
 		// Nothing to do here.
 		return
 	}
@@ -296,6 +296,7 @@ func (store *Store) dirtyItems(start, end []byte) {
 	// than just not having the cache.
 	if n < minSortSize {
 		for key := range store.unsortedCache {
+			// dbm.IsKeyInDomain is nil safe and returns true iff key is greater than start
 			if dbm.IsKeyInDomain(conv.UnsafeStrToBytes(key), start, end) {
 				cacheValue := store.cache[key]
 				unsorted = append(unsorted, &kv.Pair{Key: []byte(key), Value: cacheValue.value})
@@ -313,7 +314,7 @@ func (store *Store) dirtyItems(start, end []byte) {
 	}
 	sort.Strings(strL)
 
-	startIndex, endIndex := findStartEndIndex(strL, startStr, endStr)
+	startIndex, endIndex := findStartEndIndex(strL, startStr, endStr, end)
 
 	// Since we spent cycles to sort the values, we should process and remove a reasonable amount
 	// ensure start to end is at least minSortSize in size
@@ -337,18 +338,24 @@ func (store *Store) dirtyItems(start, end []byte) {
 	store.clearUnsortedCacheSubset(kvL, stateAlreadySorted)
 }
 
-func findStartEndIndex(strL []string, startStr, endStr string) (int, int) {
+func findStartEndIndex(strL []string, startStr, endStr string, end []byte) (int, int) {
 	// Now find the values within the domain
 	//  [start, end)
 	startIndex := findStartIndex(strL, startStr)
-	endIndex := findEndIndex(strL, endStr)
+	if startIndex < 0 {
+		startIndex = 0
+	}
 
-	if endIndex < 0 {
+	var endIndex int
+	if end == nil {
 		endIndex = len(strL) - 1
+	} else {
+		endIndex = findEndIndex(strL, endStr)
 	}
-	if startIndex < 0 {
-		startIndex = 0
+	if endIndex < 0 {
+		endIndex = len(strL) - 1
 	}
+
 	return startIndex, endIndex
 }