rpc: Fix tx.height range queries (#2899)

Modify lookForHeight to return a height only there's a equal operator.
Previously, it was returning a height even for range conditions: "height
< 10000".

Fixes #2759

CHANGELOG_PENDING.md

@@ -37,4 +37,5 @@ 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
+- [rpc] \#2759 fix tx.height range queries
 - [rpc] \#2811 Allow integer IDs in JSON-RPC requests

rpc/client/rpc_test.go

@@ -370,20 +370,27 @@ func TestTxSearch(t *testing.T) {
 		}
 
 		// query by height
-		result, err = c.TxSearch(fmt.Sprintf("tx.height >= %d", txHeight), true, 1, 30)
+		result, err = c.TxSearch(fmt.Sprintf("tx.height=%d", txHeight), true, 1, 30)
 		require.Nil(t, err, "%+v", err)
 		require.Len(t, result.Txs, 1)
 
-		// we query for non existing tx
+		// query for non existing tx
 		result, err = c.TxSearch(fmt.Sprintf("tx.hash='%X'", anotherTxHash), false, 1, 30)
 		require.Nil(t, err, "%+v", err)
 		require.Len(t, result.Txs, 0)
 
-		// we query using a tag (see kvstore application)
+		// query using a tag (see kvstore application)
 		result, err = c.TxSearch("app.creator='Cosmoshi Netowoko'", false, 1, 30)
 		require.Nil(t, err, "%+v", err)
 		if len(result.Txs) == 0 {
 			t.Fatal("expected a lot of transactions")
 		}
+
+		// query using a tag (see kvstore application) and height
+		result, err = c.TxSearch("app.creator='Cosmoshi Netowoko' AND tx.height<10000", true, 1, 30)
+		require.Nil(t, err, "%+v", err)
+		if len(result.Txs) == 0 {
+			t.Fatal("expected a lot of transactions")
+		}
 	}
 }

state/txindex/kv/kv.go

@@ -225,9 +225,10 @@ func lookForHash(conditions []query.Condition) (hash []byte, err error, ok bool)
 	return
 }
 
+// lookForHeight returns a height if there is an "height=X" condition.
 func lookForHeight(conditions []query.Condition) (height int64) {
 	for _, c := range conditions {
-		if c.Tag == types.TxHeightKey {
+		if c.Tag == types.TxHeightKey && c.Op == query.OpEqual {
 			return c.Operand.(int64)
 		}
 	}