Implement OFFSET LIMIT

docs/COMPATIBILITY.md

@@ -36,7 +36,7 @@ Cosmium strives to support the core features of Cosmos DB, including:
 | WHERE        | Yes         |
 | ORDER BY     | Yes         |
 | GROUP BY     | Yes         |
-| OFFSET LIMIT | No          |
+| OFFSET LIMIT | Yes         |
 
 ### Keywords
 | Keyword  | Implemented |

parsers/models.go

@@ -6,6 +6,7 @@ type SelectStmt struct {
 	Filters          interface{}
 	Distinct         bool
 	Count            int
+	Offset           int
 	Parameters       map[string]interface{}
 	OrderExpressions []OrderExpression
 	GroupBy          []SelectItem

parsers/nosql/nosql.peg

@@ -7,6 +7,7 @@ func makeSelectStmt(
 	columns, table,
 	whereClause interface{}, distinctClause interface{},
 	count interface{}, groupByClause interface{}, orderList interface{},
+	offsetClause interface{},
 ) (parsers.SelectStmt, error) {
 	selectStmt := parsers.SelectStmt{
 		SelectItems: columns.([]parsers.SelectItem),
@@ -26,13 +27,23 @@ func makeSelectStmt(
 		selectStmt.Count = n
 	}
 
+	if offsetArr, ok := offsetClause.([]interface{}); ok && len(offsetArr) == 2 {
+		if n, ok := offsetArr[0].(int); ok {
+			selectStmt.Offset = n
+		}
+
+		if n, ok := offsetArr[1].(int); ok {
+			selectStmt.Count = n
+		}
+	}
+
 	if orderExpressions, ok := orderList.([]parsers.OrderExpression); ok {
 		selectStmt.OrderExpressions = orderExpressions
 	}
 
-    if groupByClause != nil {
+	if groupByClause != nil {
-        selectStmt.GroupBy = groupByClause.([]parsers.SelectItem)
+		selectStmt.GroupBy = groupByClause.([]parsers.SelectItem)
-    }
+	}
 
 	return selectStmt, nil
 }
@@ -154,9 +165,10 @@ SelectStmt <- Select ws
     From ws table:TableName ws
     whereClause:(ws Where ws condition:Condition { return condition, nil })?
     groupByClause:(ws GroupBy ws columns:ColumnList { return columns, nil })?
-    orderByClause:OrderByClause? {
+    orderByClause:OrderByClause?
+    offsetClause:OffsetClause? {
     return makeSelectStmt(columns, table, whereClause,
-        distinctClause, topClause, groupByClause, orderByClause)
+        distinctClause, topClause, groupByClause, orderByClause, offsetClause)
 }
 
 DistinctClause <- "DISTINCT"i
@@ -165,6 +177,10 @@ TopClause <- Top ws count:Integer {
     return count, nil
 }
 
+OffsetClause <- "OFFSET"i ws offset:IntegerLiteral ws "LIMIT"i ws limit:IntegerLiteral {
+    return []interface{}{offset.(parsers.Constant).Value, limit.(parsers.Constant).Value}, nil
+}
+
 Selection <- SelectValueSpec / ColumnList / SelectAsterisk
 
 SelectAsterisk <- "*" {

parsers/nosql/select_test.go

@@ -50,6 +50,21 @@ func Test_Parse_Select(t *testing.T) {
 		)
 	})
 
+	t.Run("Should parse SELECT OFFSET", func(t *testing.T) {
+		testQueryParse(
+			t,
+			`SELECT c.id FROM c OFFSET 3 LIMIT 5`,
+			parsers.SelectStmt{
+				SelectItems: []parsers.SelectItem{
+					{Path: []string{"c", "id"}},
+				},
+				Table:  parsers.Table{Value: "c"},
+				Count:  5,
+				Offset: 3,
+			},
+		)
+	})
+
 	t.Run("Should parse SELECT VALUE", func(t *testing.T) {
 		testQueryParse(
 			t,

query_executors/memory_executor/select_test.go

@@ -71,6 +71,32 @@ func Test_Execute_Select(t *testing.T) {
 		)
 	})
 
+	t.Run("Should execute SELECT OFFSET", 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:  2,
+				Offset: 1,
+				OrderExpressions: []parsers.OrderExpression{
+					{
+						SelectItem: parsers.SelectItem{Path: []string{"c", "id"}},
+						Direction:  parsers.OrderDirectionDesc,
+					},
+				},
+			},
+			mockData,
+			[]memoryexecutor.RowType{
+				map[string]interface{}{"id": "67890", "pk": 456},
+				map[string]interface{}{"id": "456", "pk": 456},
+			},
+		)
+	})
+
 	t.Run("Should execute SELECT VALUE", func(t *testing.T) {
 		testQueryExecute(
 			t,