diff --git a/influxql/ast.go b/influxql/ast.go
index 9fd1e69bac..dfa0398e69 100644
--- a/influxql/ast.go
+++ b/influxql/ast.go
@@ -1737,6 +1737,83 @@ type rewriterFunc func(Node) Node
 
 func (fn rewriterFunc) Rewrite(n Node) Node { return fn(n) }
 
+// Eval evaluates expr against a map.
+func Eval(expr Expr, m map[string]interface{}) interface{} {
+	if expr == nil {
+		return nil
+	}
+
+	switch expr := expr.(type) {
+	case *BinaryExpr:
+		return evalBinaryExpr(expr, m)
+	case *BooleanLiteral:
+		return expr.Val
+	case *NumberLiteral:
+		return expr.Val
+	case *ParenExpr:
+		return Eval(expr.Expr, m)
+	case *StringLiteral:
+		return expr.Val
+	case *VarRef:
+		return m[expr.Val]
+	default:
+		return nil
+	}
+}
+
+func evalBinaryExpr(expr *BinaryExpr, m map[string]interface{}) interface{} {
+	lhs := Eval(expr.LHS, m)
+	rhs := Eval(expr.RHS, m)
+
+	// Evaluate if both sides are simple types.
+	switch lhs := lhs.(type) {
+	case bool:
+		rhs, _ := rhs.(bool)
+		switch expr.Op {
+		case AND:
+			return lhs && rhs
+		case OR:
+			return lhs || rhs
+		}
+	case float64:
+		rhs, _ := rhs.(float64)
+		switch expr.Op {
+		case EQ:
+			return lhs == rhs
+		case NEQ:
+			return lhs != rhs
+		case LT:
+			return lhs < rhs
+		case LTE:
+			return lhs <= rhs
+		case GT:
+			return lhs > rhs
+		case GTE:
+			return lhs >= rhs
+		case ADD:
+			return lhs + rhs
+		case SUB:
+			return lhs - rhs
+		case MUL:
+			return lhs * rhs
+		case DIV:
+			if rhs == 0 {
+				return float64(0)
+			}
+			return lhs / rhs
+		}
+	case string:
+		rhs, _ := rhs.(string)
+		switch expr.Op {
+		case EQ:
+			return lhs == rhs
+		case NEQ:
+			return lhs != rhs
+		}
+	}
+	return nil
+}
+
 // Reduce evaluates expr using the available values in valuer.
 // References that don't exist in valuer are ignored.
 func Reduce(expr Expr, valuer Valuer) Expr {
diff --git a/influxql/ast_test.go b/influxql/ast_test.go
index 261d975c57..33872e9082 100644
--- a/influxql/ast_test.go
+++ b/influxql/ast_test.go
@@ -1,6 +1,7 @@
 package influxql_test
 
 import (
+	"reflect"
 	"strings"
 	"testing"
 
@@ -165,6 +166,50 @@ func TestRewrite(t *testing.T) {
 	}
 }
 
+// Ensure an expression can be reduced.
+func TestEval(t *testing.T) {
+	for i, tt := range []struct {
+		in   string
+		out  interface{}
+		data map[string]interface{}
+	}{
+		// Number literals.
+		{in: `1 + 2`, out: float64(3)},
+		{in: `(foo*2) + ( (4/2) + (3 * 5) - 0.5 )`, out: float64(26.5), data: map[string]interface{}{"foo": float64(5)}},
+		{in: `foo / 2`, out: float64(2), data: map[string]interface{}{"foo": float64(4)}},
+		{in: `4 = 4`, out: true},
+		{in: `4 <> 4`, out: false},
+		{in: `6 > 4`, out: true},
+		{in: `4 >= 4`, out: true},
+		{in: `4 < 6`, out: true},
+		{in: `4 <= 4`, out: true},
+		{in: `4 AND 5`, out: nil},
+
+		// Boolean literals.
+		{in: `true AND false`, out: false},
+		{in: `true OR false`, out: true},
+
+		// String literals.
+		{in: `'foo' = 'bar'`, out: false},
+		{in: `'foo' = 'foo'`, out: true},
+
+		// Variable references.
+		{in: `foo`, out: "bar", data: map[string]interface{}{"foo": "bar"}},
+		{in: `foo = 'bar'`, out: true, data: map[string]interface{}{"foo": "bar"}},
+		{in: `foo = 'bar'`, out: nil, data: map[string]interface{}{"foo": nil}},
+		{in: `foo <> 'bar'`, out: true, data: map[string]interface{}{"foo": "xxx"}},
+	} {
+		// Evaluate expression.
+		out := influxql.Eval(MustParseExpr(tt.in), tt.data)
+
+		// Compare with expected output.
+		if !reflect.DeepEqual(tt.out, out) {
+			t.Errorf("%d. %s: unexpected output:\n\nexp=%#v\n\ngot=%#v\n\n", i, tt.in, tt.out, out)
+			continue
+		}
+	}
+}
+
 // Ensure an expression can be reduced.
 func TestReduce(t *testing.T) {
 	now := mustParseTime("2000-01-01T00:00:00Z")
diff --git a/tx_test.go b/tx_test.go
index 9a93b81483..fe97f3148e 100644
--- a/tx_test.go
+++ b/tx_test.go
@@ -34,7 +34,7 @@ func TestTx_CreateIterators(t *testing.T) {
 	stmt := MustParseSelectStatement(`
 		SELECT value
 		FROM "db"."raw"."cpu"
-		WHERE (service = 'redis' AND (value > 10 OR value < 5)) AND (time >= '2000-01-01' AND time < '2000-01-02')
+		WHERE (service = 'redis' AND value < 100) AND (time >= '2000-01-01' AND time < '2000-01-02')
 		GROUP BY time(1h), region`)
 
 	// Retrieve iterators from server.
@@ -60,7 +60,6 @@ func TestTx_CreateIterators(t *testing.T) {
 
 	// Iterate over each one.
 	if data := slurp(itrs); !reflect.DeepEqual(data, []keyValue{
-		{key: 946684800000000000, value: float64(100), tags: "\x00\aus-east"},
 		{key: 946684800000000000, value: float64(2), tags: "\x00\aus-west"},
 		{key: 946684810000000000, value: float64(90), tags: "\x00\aus-east"},
 		{key: 946684830000000000, value: float64(70), tags: "\x00\aus-east"},