Added support for TOP statement

parsers/models.go

@@ -28,6 +28,7 @@ type SelectStmt struct {
 	SelectItems []SelectItem
 	Table       Table
 	Filters     interface{}
+	Count       int
 }
 
 type Table struct {

parsers/nosql/nosql.peg

@@ -3,7 +3,7 @@ package nosql
 
 import "github.com/pikami/cosmium/parsers"
 
-func makeSelectStmt(columns, table, whereClause interface{}) (parsers.SelectStmt, error) {
+func makeSelectStmt(columns, table, whereClause interface{}, count interface{}) (parsers.SelectStmt, error) {
 	selectStmt := parsers.SelectStmt{
 		SelectItems: columns.([]parsers.SelectItem),
 		Table:       table.(parsers.Table),
@@ -15,6 +15,10 @@ func makeSelectStmt(columns, table, whereClause interface{}) (parsers.SelectStmt
 		selectStmt.Filters = filters
 	}
 
+	if n, ok := count.(int); ok {
+		selectStmt.Count = n
+	}
+
 	return selectStmt, nil
 }
 
@@ -98,10 +102,14 @@ Input <- selectStmt:SelectStmt {
     return selectStmt, nil
 }
 
-SelectStmt <- Select ws columns:Selection ws
+SelectStmt <- Select ws topClause:TopClause? ws columns:Selection ws
     From ws table:TableName ws
     whereClause:(ws Where ws condition:Condition { return condition, nil })? {
-    return makeSelectStmt(columns, table, whereClause)
+    return makeSelectStmt(columns, table, whereClause, topClause)
+}
+
+TopClause <- Top ws count:Integer {
+    return count, nil
 }
 
 Selection <- SelectValueSpec / ColumnList
@@ -178,6 +186,8 @@ ComparisonExpression <- left:(Literal / SelectItem) ws op:ComparisonOperator ws
 
 Select <- ("select" / "SELECT")
 
+Top <- ("top" / "TOP")
+
 As <- ("as" / "AS")
 
 From <- ("from" / "FROM")
@@ -190,9 +200,8 @@ ComparisonOperator <- "=" / "!=" / "<" / "<=" / ">" / ">=" {
 
 Literal <- FloatLiteral / IntegerLiteral / StringLiteral / BooleanLiteral
 
-IntegerLiteral <- [0-9]+ {
-    intValue, _ := strconv.Atoi(string(c.text))
-    return parsers.Constant{Type: parsers.ConstantTypeInteger, Value: intValue}, nil
+IntegerLiteral <- number:Integer {
+    return parsers.Constant{Type: parsers.ConstantTypeInteger, Value: number.(int)}, nil
 }
 StringLiteral <- "\"" chars:StringCharacter* "\"" {
     return parsers.Constant{Type: parsers.ConstantTypeString,Value: joinStrings(chars.([]interface{}))}, nil
@@ -206,6 +215,10 @@ BooleanLiteral <- ("true" / "false") {
     return parsers.Constant{Type: parsers.ConstantTypeBoolean, Value: boolValue}, nil
 }
 
+Integer <- [0-9]+ {
+    return strconv.Atoi(string(c.text))
+}
+
 StringCharacter <- !('"' / "\\") . { return string(c.text), nil }
   / "\\" seq:EscapeSequenceCharacter { return seq, nil }
 

parsers/nosql/nosql_test.go

@@ -52,6 +52,20 @@ func Test_Parse(t *testing.T) {
 		)
 	})
 
+	t.Run("Should parse SELECT TOP", func(t *testing.T) {
+		testQueryParse(
+			t,
+			`SELECT TOP 1 c.id FROM c`,
+			parsers.SelectStmt{
+				SelectItems: []parsers.SelectItem{
+					{Path: []string{"c", "id"}},
+				},
+				Table: parsers.Table{Value: "c"},
+				Count: 1,
+			},
+		)
+	})
+
 	t.Run("Should parse SELECT VALUE", func(t *testing.T) {
 		testQueryParse(
 			t,

query_executors/memory_executor/memory_executor.go

@@ -18,6 +18,17 @@ func Execute(query parsers.SelectStmt, data []RowType) []RowType {
 		}
 	}
 
+	// Apply result limit
+	if query.Count > 0 {
+		count := func() int {
+			if len(result) < query.Count {
+				return len(result)
+			}
+			return query.Count
+		}()
+		result = result[:count]
+	}
+
 	return result
 }
 

query_executors/memory_executor/memory_executor_test.go

@@ -45,6 +45,24 @@ func Test_Execute(t *testing.T) {
 		)
 	})
 
+	t.Run("Should execute SELECT TOP", func(t *testing.T) {
+		testQueryExecute(
+			t,
+			parsers.SelectStmt{
+				SelectItems: []parsers.SelectItem{
+					{Path: []string{"c", "id"}},
+					{Path: []string{"c", "pk"}},
+				},
+				Table: parsers.Table{Value: "c"},
+				Count: 1,
+			},
+			mockData,
+			[]memoryexecutor.RowType{
+				map[string]interface{}{"id": "12345", "pk": 123},
+			},
+		)
+	})
+
 	t.Run("Should execute SELECT VALUE", func(t *testing.T) {
 		testQueryExecute(
 			t,