[indexer] order results by index if height is the same (#2900)

Fixes #2775

CHANGELOG_PENDING.md

@@ -37,5 +37,6 @@ program](https://hackerone.com/tendermint).
 - [blockchain] \#2731 Retry both blocks if either is bad to avoid getting stuck during fast sync (@goolAdapter)
 - [log] \#2868 fix module=main setting overriding all others
 - [rpc] \#2808 RPC validators calls IncrementAccum if necessary
+- [kv indexer] \#2775 order results by index if height is the same
 - [rpc] \#2759 fix tx.height range queries
 - [rpc] \#2811 Allow integer IDs in JSON-RPC requests

state/txindex/kv/kv.go

@@ -207,8 +207,11 @@ func (txi *TxIndex) Search(q *query.Query) ([]*types.TxResult, error) {
 		i++
 	}
 
-	// sort by height by default
+	// sort by height & index by default
 	sort.Slice(results, func(i, j int) bool {
+		if results[i].Height == results[j].Height {
+			return results[i].Index < results[j].Index
+		}
 		return results[i].Height < results[j].Height
 	})
 

state/txindex/kv/kv_test.go

@@ -133,6 +133,7 @@ func TestTxSearchMultipleTxs(t *testing.T) {
 	})
 	txResult.Tx = types.Tx("Bob's account")
 	txResult.Height = 2
+	txResult.Index = 1
 	err := indexer.Index(txResult)
 	require.NoError(t, err)
 
@@ -142,14 +143,26 @@ func TestTxSearchMultipleTxs(t *testing.T) {
 	})
 	txResult2.Tx = types.Tx("Alice's account")
 	txResult2.Height = 1
+	txResult2.Index = 2
+
 	err = indexer.Index(txResult2)
 	require.NoError(t, err)
 
+	// indexed third (to test the order of transactions)
+	txResult3 := txResultWithTags([]cmn.KVPair{
+		{Key: []byte("account.number"), Value: []byte("3")},
+	})
+	txResult3.Tx = types.Tx("Jack's account")
+	txResult3.Height = 1
+	txResult3.Index = 1
+	err = indexer.Index(txResult3)
+	require.NoError(t, err)
+
 	results, err := indexer.Search(query.MustParse("account.number >= 1"))
 	assert.NoError(t, err)
 
-	require.Len(t, results, 2)
+	require.Len(t, results, 3)
-	assert.Equal(t, []*types.TxResult{txResult2, txResult}, results)
+	assert.Equal(t, []*types.TxResult{txResult3, txResult2, txResult}, results)
 }
 
 func TestIndexAllTags(t *testing.T) {