Implement SPLIT keyword in SELECT statement

db/iterator.go

@@ -54,6 +54,7 @@ type iterator struct {
 	expr  sql.Fields
 	what  sql.Exprs
 	cond  sql.Expr
+	split sql.Idents
 	group sql.Groups
 	order sql.Orders
 	limit int
@@ -133,6 +134,7 @@ func (i *iterator) Close() {
 	i.expr = nil
 	i.what = nil
 	i.cond = nil
+	i.split = nil
 	i.group = nil
 	i.order = nil
 	i.limit = -1
@@ -149,8 +151,10 @@ func (i *iterator) setupState(ctx context.Context) {
 	i.expr = nil
 	i.what = nil
 	i.cond = nil
+	i.split = nil
 	i.group = nil
 	i.order = nil
+	i.split = nil
 	i.limit = -1
 	i.start = -1
 	i.versn = math.MaxInt64
@@ -160,6 +164,7 @@ func (i *iterator) setupState(ctx context.Context) {
 		i.expr = stm.Expr
 		i.what = stm.What
 		i.cond = stm.Cond
+		i.split = stm.Split
 		i.group = stm.Group
 		i.order = stm.Order
 		i.tasks = stm.Parallel
@@ -865,6 +870,10 @@ func (i *iterator) Yield(ctx context.Context) (out []interface{}, err error) {
 		}
 	}
 
+	if len(i.split) > 0 {
+		i.res = i.Split(ctx, i.res)
+	}
+
 	if len(i.group) > 0 {
 		i.res = i.Group(ctx, i.res)
 	}
@@ -887,6 +896,42 @@ func (i *iterator) Yield(ctx context.Context) (out []interface{}, err error) {
 
 }
 
+func (i *iterator) Split(ctx context.Context, arr []interface{}) (out []interface{}) {
+
+	for _, s := range i.split {
+
+		out = make([]interface{}, 0)
+
+		for _, a := range arr {
+
+			doc := data.Consume(a)
+
+			pth := make([]string, 0)
+
+			switch doc.Get(s.VA).Data().(type) {
+			case []interface{}:
+				pth = append(pth, s.VA, "*")
+			default:
+				pth = append(pth, s.VA)
+			}
+
+			doc.Walk(func(key string, val interface{}, exi bool) error {
+				doc := doc.Copy()
+				doc.Set(val, s.VA)
+				out = append(out, doc.Data())
+				return nil
+			}, pth...)
+
+		}
+
+		arr = out
+
+	}
+
+	return out
+
+}
+
 func (i *iterator) Group(ctx context.Context, arr []interface{}) (out []interface{}) {
 
 	var grp []*groupable

sql/ast.go

@@ -170,6 +170,7 @@ type SelectStatement struct {
 	Expr     Fields
 	What     Exprs
 	Cond     Expr
+	Split    Idents
 	Group    Groups
 	Order    Orders
 	Limit    Expr

sql/select.go

@@ -39,6 +39,10 @@ func (p *parser) parseSelectStatement() (stmt *SelectStatement, err error) {
 		return nil, err
 	}
 
+	if stmt.Split, err = p.parseSplit(); err != nil {
+		return nil, err
+	}
+
 	if stmt.Group, err = p.parseGroup(); err != nil {
 		return nil, err
 	}
@@ -142,6 +146,26 @@ func (p *parser) parseFields() (mul Fields, err error) {
 
 }
 
+func (p *parser) parseSplit() (Idents, error) {
+
+	// The next token that we expect to see is a
+	// SPLIT token, and if we don't find one then
+	// return nil, with no error.
+
+	if _, _, exi := p.mightBe(SPLIT); !exi {
+		return nil, nil
+	}
+
+	// We don't need to have a ON token, but we
+	// allow it so that the SQL query would read
+	// better when compared to english.
+
+	_, _, _ = p.mightBe(ON)
+
+	return p.parseIdioms()
+
+}
+
 func (p *parser) parseGroup() (mul Groups, err error) {
 
 	// The next token that we expect to see is a

sql/string.go

@@ -225,10 +225,11 @@ func (this KillStatement) String() string {
 }
 
 func (this SelectStatement) String() string {
-	return print("SELECT %v FROM %v%v%v%v%v%v%v%v%v",
+	return print("SELECT %v FROM %v%v%v%v%v%v%v%v%v%v",
 		this.Expr,
 		this.What,
 		maybe(this.Cond != nil, print(" WHERE %v", this.Cond)),
+		maybe(this.Split != nil, print(" SPLIT %v", this.Split)),
 		this.Group,
 		this.Order,
 		maybe(this.Limit != nil, print(" LIMIT %v", this.Limit)),

sql/tokens.go

@@ -183,6 +183,7 @@ const (
 	SIGNIN
 	SIGNUP
 	SOMECONTAINEDIN
+	SPLIT
 	START
 	TABLE
 	THEN
@@ -360,6 +361,7 @@ var tokens = [...]string{
 	SIGNIN:          "SIGNIN",
 	SIGNUP:          "SIGNUP",
 	SOMECONTAINEDIN: "SOMECONTAINEDIN",
+	SPLIT:           "SPLIT",
 	START:           "START",
 	TABLE:           "TABLE",
 	THEN:            "THEN",