sql: add minimal sql support

This patch adds the support of SQL in connector.
Added all required constants in const.go for encoding SQL in msgpack.

Fixes #62

Author: vr009

connector.go

@@ -17,6 +17,7 @@ type Connector interface {
 	Call(functionName string, args interface{}) (resp *Response, err error)
 	Call17(functionName string, args interface{}) (resp *Response, err error)
 	Eval(expr string, args interface{}) (resp *Response, err error)
+	Execute(expr string, args interface{}) (resp *Response, err error)
 
 	GetTyped(space, index interface{}, key interface{}, result interface{}) (err error)
 	SelectTyped(space, index interface{}, offset, limit, iterator uint32, key interface{}, result interface{}) (err error)

const.go

@@ -11,6 +11,7 @@ const (
 	EvalRequest      = 8
 	UpsertRequest    = 9
 	Call17Request    = 10
+	ExecuteRequest   = 11
 	PingRequest      = 64
 	SubscribeRequest = 66
 
@@ -29,6 +30,10 @@ const (
 	KeyDefTuple     = 0x28
 	KeyData         = 0x30
 	KeyError        = 0x31
+	KeyMetaData     = 0x32
+	KeySQLText      = 0x40
+	KeySQLBind      = 0x41
+	KeySQLInfo      = 0x42
 
 	// https://github.com/fl00r/go-tarantool-1.6/issues/2
 

multi/multi.go

@@ -294,6 +294,10 @@ func (connMulti *ConnectionMulti) Eval(expr string, args interface{}) (resp *tar
 	return connMulti.getCurrentConnection().Eval(expr, args)
 }
 
+func (connMulti *ConnectionMulti) Execute(expr string, args interface{}) (resp *tarantool.Response, err error) {
+	return connMulti.getCurrentConnection().Execute(expr, args)
+}
+
 func (connMulti *ConnectionMulti) GetTyped(space, index interface{}, key interface{}, result interface{}) (err error) {
 	return connMulti.getCurrentConnection().GetTyped(space, index, key, result)
 }

request.go

@@ -2,6 +2,7 @@ package tarantool
 
 import (
 	"errors"
+	"reflect"
 	"time"
 
 	"gopkg.in/vmihailenco/msgpack.v2"
@@ -120,6 +121,13 @@ func (conn *Connection) Eval(expr string, args interface{}) (resp *Response, err
 	return conn.EvalAsync(expr, args).Get()
 }
 
+// Execute passes sql expression for execution.
+//
+// It is equal to conn.ExecuteAsync(space, tuple).Get().
+func (conn *Connection) Execute(expr string, args interface{}) (resp *Response, err error) {
+	return conn.ExecuteAsync(expr, args).Get()
+}
+
 // single used for conn.GetTyped for decode one tuple
 type single struct {
 	res   interface{}
@@ -346,10 +354,39 @@ func (conn *Connection) EvalAsync(expr string, args interface{}) *Future {
 	})
 }
 
+// ExecuteAsync sends a sql expression for execution and returns Future.
+func (conn *Connection) ExecuteAsync(expr string, args interface{}) *Future {
+	future := conn.newFuture(ExecuteRequest)
+	bind := makeSQLBind(args)
+	return future.send(conn, func(enc *msgpack.Encoder) error {
+		enc.EncodeMapLen(2)
+		enc.EncodeUint64(KeySQLText)
+		enc.EncodeString(expr)
+		enc.EncodeUint64(KeySQLBind)
+		return enc.Encode(bind)
+	})
+}
+
 //
 // private
 //
 
+func makeSQLBind(from interface{}) interface{} {
+	val := reflect.ValueOf(from)
+	arr := []map[string]interface{}{}
+
+	if val.Kind() == reflect.Map {
+		for _, e := range val.MapKeys() {
+			mp := map[string]interface{}{}
+			v := val.MapIndex(e)
+			t := v.Interface()
+			mp[":"+e.String()] = t
+			arr = append(arr, mp)
+		}
+	}
+	return arr
+}
+
 func (fut *Future) pack(h *smallWBuf, enc *msgpack.Encoder, body func(*msgpack.Encoder) error) (err error) {
 	rid := fut.requestId
 	hl := h.Len()