1 files changed, 69 insertions, 0 deletions
diff --git a/core/vm/sqlvm/ast/printer.go b/core/vm/sqlvm/ast/printer.go
new file mode 100644
index 000000000..25f04e863
--- /dev/null
+++ b/core/vm/sqlvm/ast/printer.go
@@ -0,0 +1,69 @@
+package ast
+
+import (
+	"fmt"
+	"reflect"
+)
+
+// PrintAST prints ast to stdout.
+func PrintAST(n interface{}, indent string) {
+	if n == nil {
+		fmt.Printf("%snil\n", indent)
+		return
+	}
+	typeOf := reflect.TypeOf(n)
+	valueOf := reflect.ValueOf(n)
+	name := ""
+	if typeOf.Kind() == reflect.Ptr {
+		if valueOf.IsNil() {
+			fmt.Printf("%snil\n", indent)
+			return
+		}
+		name = "*"
+		valueOf = valueOf.Elem()
+		typeOf = typeOf.Elem()
+	}
+	name = name + typeOf.Name()
+
+	if op, ok := n.(Optional); ok {
+		fmt.Printf("%s%s", indent, name)
+		m := op.GetOption()
+		if m == nil {
+			fmt.Printf("\n")
+			return
+		}
+		fmt.Printf(":\n")
+		for k := range m {
+			fmt.Printf("%s  %s:\n", indent, k)
+			PrintAST(m[k], indent+"    ")
+		}
+		return
+	}
+	if op, ok := n.(UnaryOperator); ok {
+		fmt.Printf("%s%s:\n", indent, name)
+		fmt.Printf("%s  Target:\n", indent)
+		PrintAST(op.GetTarget(), indent+"    ")
+		return
+	}
+	if op, ok := n.(BinaryOperator); ok {
+		fmt.Printf("%s%s:\n", indent, name)
+		fmt.Printf("%s  Object:\n", indent)
+		PrintAST(op.GetObject(), indent+"    ")
+		fmt.Printf("%s  Subject:\n", indent)
+		PrintAST(op.GetSubject(), indent+"    ")
+		return
+	}
+	if arr, ok := n.([]interface{}); ok {
+		fmt.Printf("%s[\n", indent)
+		for idx := range arr {
+			PrintAST(arr[idx], indent+"  ")
+		}
+		fmt.Printf("%s]\n", indent)
+		return
+	}
+	if stringer, ok := n.(fmt.Stringer); ok {
+		fmt.Printf("%s%s: %s\n", indent, name, stringer.String())
+		return
+	}
+	fmt.Printf("%s%s: %+v\n", indent, name, valueOf.Interface())
+}