Partial JOIN implementation

parsers/models.go

@@ -3,6 +3,7 @@ package parsers
 type SelectStmt struct {
 	SelectItems      []SelectItem
 	Table            Table
+	JoinItems        []JoinItem
 	Filters          interface{}
 	Distinct         bool
 	Count            int
@@ -16,6 +17,11 @@ type Table struct {
 	Value string
 }
 
+type JoinItem struct {
+	Table      Table
+	SelectItem SelectItem
+}
+
 type SelectItemType int
 
 const (

parsers/nosql/join_test.go

@@ -0,0 +1,57 @@
+package nosql_test
+
+import (
+	"testing"
+
+	"github.com/pikami/cosmium/parsers"
+)
+
+func Test_Parse_Join(t *testing.T) {
+
+	t.Run("Should parse simple JOIN", func(t *testing.T) {
+		testQueryParse(
+			t,
+			`SELECT c.id, c["pk"] FROM c JOIN cc IN c["tags"]`,
+			parsers.SelectStmt{
+				SelectItems: []parsers.SelectItem{
+					{Path: []string{"c", "id"}},
+					{Path: []string{"c", "pk"}},
+				},
+				Table: parsers.Table{Value: "c"},
+				JoinItems: []parsers.JoinItem{
+					{
+						Table: parsers.Table{
+							Value: "cc",
+						},
+						SelectItem: parsers.SelectItem{
+							Path: []string{"c", "tags"},
+						},
+					},
+				},
+			},
+		)
+	})
+
+	t.Run("Should parse JOIN VALUE", func(t *testing.T) {
+		testQueryParse(
+			t,
+			`SELECT VALUE cc FROM c JOIN cc IN c["tags"]`,
+			parsers.SelectStmt{
+				SelectItems: []parsers.SelectItem{
+					{Path: []string{"cc"}, IsTopLevel: true},
+				},
+				Table: parsers.Table{Value: "c"},
+				JoinItems: []parsers.JoinItem{
+					{
+						Table: parsers.Table{
+							Value: "cc",
+						},
+						SelectItem: parsers.SelectItem{
+							Path: []string{"c", "tags"},
+						},
+					},
+				},
+			},
+		)
+	})
+}

parsers/nosql/nosql.peg

@@ -4,7 +4,7 @@ package nosql
 import "github.com/pikami/cosmium/parsers"
 
 func makeSelectStmt(
-	columns, table,
+	columns, table, joinItems,
 	whereClause interface{}, distinctClause interface{},
 	count interface{}, groupByClause interface{}, orderList interface{},
 	offsetClause interface{},
@@ -14,6 +14,13 @@ func makeSelectStmt(
 		Table:       table.(parsers.Table),
 	}
 
+    if joinItemsArray, ok := joinItems.([]interface{}); ok && len(joinItemsArray) > 0 {
+		selectStmt.JoinItems = make([]parsers.JoinItem, len(joinItemsArray))
+		for i, joinItem := range joinItemsArray {
+			selectStmt.JoinItems[i] = joinItem.(parsers.JoinItem)
+		}
+	}
+
 	switch v := whereClause.(type) {
 	case parsers.ComparisonExpression, parsers.LogicalExpression, parsers.Constant, parsers.SelectItem:
 		selectStmt.Filters = v
@@ -48,6 +55,13 @@ func makeSelectStmt(
 	return selectStmt, nil
 }
 
+func makeJoin(table interface{}, column interface{}) (parsers.JoinItem, error) {
+    return parsers.JoinItem{
+        Table:      table.(parsers.Table),
+        SelectItem: column.(parsers.SelectItem),
+    }, nil
+}
+
 func makeSelectItem(name interface{}, path interface{}, selectItemType parsers.SelectItemType) (parsers.SelectItem, error) {
 	ps := path.([]interface{})
 
@@ -161,13 +175,15 @@ Input <- selectStmt:SelectStmt {
 
 SelectStmt <- Select ws
     distinctClause:DistinctClause? ws
-    topClause:TopClause? ws columns:Selection ws
+    topClause:TopClause? ws
+    columns:Selection ws
     From ws table:TableName ws
+    joinClauses:JoinClause* ws
     whereClause:(ws Where ws condition:Condition { return condition, nil })?
     groupByClause:(ws GroupBy ws columns:ColumnList { return columns, nil })?
     orderByClause:OrderByClause?
     offsetClause:OffsetClause? {
-    return makeSelectStmt(columns, table, whereClause,
+    return makeSelectStmt(columns, table, joinClauses, whereClause,
         distinctClause, topClause, groupByClause, orderByClause, offsetClause)
 }
 
@@ -177,6 +193,10 @@ TopClause <- Top ws count:Integer {
     return count, nil
 }
 
+JoinClause <- Join ws table:TableName ws "IN"i ws column:SelectItem {
+    return makeJoin(table, column)
+}
+
 OffsetClause <- "OFFSET"i ws offset:IntegerLiteral ws "LIMIT"i ws limit:IntegerLiteral {
     return []interface{}{offset.(parsers.Constant).Value, limit.(parsers.Constant).Value}, nil
 }
@@ -300,6 +320,8 @@ As <- "AS"i
 
 From <- "FROM"i
 
+Join <- "JOIN"i
+
 Where <- "WHERE"i
 
 And <- "AND"i

query_executors/memory_executor/aggregate_functions.go

@@ -11,7 +11,7 @@ func (c memoryExecutorContext) aggregate_Avg(arguments []interface{}, row RowTyp
 	sum := 0.0
 	count := 0
 
-	if array, isArray := row.([]RowType); isArray {
+	if array, isArray := row.([]RowWithJoins); isArray {
 		for _, item := range array {
 			value := c.getFieldValue(selectExpression, item)
 			if numericValue, ok := value.(float64); ok {
@@ -35,7 +35,7 @@ func (c memoryExecutorContext) aggregate_Count(arguments []interface{}, row RowT
 	selectExpression := arguments[0].(parsers.SelectItem)
 	count := 0
 
-	if array, isArray := row.([]RowType); isArray {
+	if array, isArray := row.([]RowWithJoins); isArray {
 		for _, item := range array {
 			value := c.getFieldValue(selectExpression, item)
 			if value != nil {
@@ -52,7 +52,7 @@ func (c memoryExecutorContext) aggregate_Max(arguments []interface{}, row RowTyp
 	max := 0.0
 	count := 0
 
-	if array, isArray := row.([]RowType); isArray {
+	if array, isArray := row.([]RowWithJoins); isArray {
 		for _, item := range array {
 			value := c.getFieldValue(selectExpression, item)
 			if numericValue, ok := value.(float64); ok {
@@ -81,7 +81,7 @@ func (c memoryExecutorContext) aggregate_Min(arguments []interface{}, row RowTyp
 	min := math.MaxFloat64
 	count := 0
 
-	if array, isArray := row.([]RowType); isArray {
+	if array, isArray := row.([]RowWithJoins); isArray {
 		for _, item := range array {
 			value := c.getFieldValue(selectExpression, item)
 			if numericValue, ok := value.(float64); ok {
@@ -110,7 +110,7 @@ func (c memoryExecutorContext) aggregate_Sum(arguments []interface{}, row RowTyp
 	sum := 0.0
 	count := 0
 
-	if array, isArray := row.([]RowType); isArray {
+	if array, isArray := row.([]RowWithJoins); isArray {
 		for _, item := range array {
 			value := c.getFieldValue(selectExpression, item)
 			if numericValue, ok := value.(float64); ok {

query_executors/memory_executor/join_test.go

@@ -0,0 +1,86 @@
+package memoryexecutor_test
+
+import (
+	"testing"
+
+	"github.com/pikami/cosmium/parsers"
+	memoryexecutor "github.com/pikami/cosmium/query_executors/memory_executor"
+)
+
+func Test_Execute_Joins(t *testing.T) {
+	mockData := []memoryexecutor.RowType{
+		map[string]interface{}{
+			"id": 1,
+			"tags": []map[string]interface{}{
+				{"name": "a"},
+				{"name": "b"},
+			},
+		},
+		map[string]interface{}{
+			"id": 2,
+			"tags": []map[string]interface{}{
+				{"name": "b"},
+				{"name": "c"},
+			},
+		},
+	}
+
+	t.Run("Should execute JOIN on 'tags'", func(t *testing.T) {
+		testQueryExecute(
+			t,
+			parsers.SelectStmt{
+				SelectItems: []parsers.SelectItem{
+					{Path: []string{"c", "id"}},
+					{Path: []string{"cc", "name"}},
+				},
+				Table: parsers.Table{Value: "c"},
+				JoinItems: []parsers.JoinItem{
+					{
+						Table: parsers.Table{
+							Value: "cc",
+						},
+						SelectItem: parsers.SelectItem{
+							Path: []string{"c", "tags"},
+						},
+					},
+				},
+			},
+			mockData,
+			[]memoryexecutor.RowType{
+				map[string]interface{}{"id": 1, "name": "a"},
+				map[string]interface{}{"id": 1, "name": "b"},
+				map[string]interface{}{"id": 2, "name": "b"},
+				map[string]interface{}{"id": 2, "name": "c"},
+			},
+		)
+	})
+
+	t.Run("Should execute JOIN VALUE on 'tags'", func(t *testing.T) {
+		testQueryExecute(
+			t,
+			parsers.SelectStmt{
+				SelectItems: []parsers.SelectItem{
+					{Path: []string{"cc"}, IsTopLevel: true},
+				},
+				Table: parsers.Table{Value: "c"},
+				JoinItems: []parsers.JoinItem{
+					{
+						Table: parsers.Table{
+							Value: "cc",
+						},
+						SelectItem: parsers.SelectItem{
+							Path: []string{"c", "tags"},
+						},
+					},
+				},
+			},
+			mockData,
+			[]memoryexecutor.RowType{
+				map[string]interface{}{"name": "a"},
+				map[string]interface{}{"name": "b"},
+				map[string]interface{}{"name": "b"},
+				map[string]interface{}{"name": "c"},
+			},
+		)
+	})
+}

query_executors/memory_executor/memory_executor.go

@@ -13,6 +13,7 @@ import (
 )
 
 type RowType interface{}
+type RowWithJoins map[string]RowType
 type ExpressionType interface{}
 
 type memoryExecutorContext struct {
@@ -24,24 +25,52 @@ func Execute(query parsers.SelectStmt, data []RowType) []RowType {
 		parameters: query.Parameters,
 	}
 
-	result := make([]RowType, 0)
+	joinedRows := make([]RowWithJoins, 0)
-
-	// Apply Filter
 	for _, row := range data {
-		if ctx.evaluateFilters(query.Filters, row) {
+		// Perform joins
-			result = append(result, row)
+		dataTables := map[string][]RowType{}
+
+		for _, join := range query.JoinItems {
+			joinedData := ctx.getFieldValue(join.SelectItem, row)
+			if joinedDataArray, isArray := joinedData.([]map[string]interface{}); isArray {
+				var rows []RowType
+				for _, m := range joinedDataArray {
+					rows = append(rows, RowType(m))
+				}
+				dataTables[join.Table.Value] = rows
+			}
 		}
+
+		// Generate flat rows
+		flatRows := []RowWithJoins{
+			{query.Table.Value: row},
+		}
+		for joinedTableName, joinedTable := range dataTables {
+			flatRows = zipRows(flatRows, joinedTableName, joinedTable)
+		}
+
+		// Apply filters
+		filteredRows := []RowWithJoins{}
+		for _, rowWithJoins := range flatRows {
+			if ctx.evaluateFilters(query.Filters, rowWithJoins) {
+				filteredRows = append(filteredRows, rowWithJoins)
+			}
+		}
+
+		joinedRows = append(joinedRows, filteredRows...)
 	}
 
 	// Apply order
 	if query.OrderExpressions != nil && len(query.OrderExpressions) > 0 {
-		ctx.orderBy(query.OrderExpressions, result)
+		ctx.orderBy(query.OrderExpressions, joinedRows)
 	}
 
+	result := make([]RowType, 0)
+
 	// Apply group
 	isGroupSelect := query.GroupBy != nil && len(query.GroupBy) > 0
 	if isGroupSelect {
-		result = ctx.groupBy(query, result)
+		result = ctx.groupBy(query, joinedRows)
 	}
 
 	// Apply select
@@ -50,9 +79,9 @@ func Execute(query parsers.SelectStmt, data []RowType) []RowType {
 		if hasAggregateFunctions(query.SelectItems) {
 			// When can have aggregate functions without GROUP BY clause,
 			// we should aggregate all rows in that case
-			selectedData = append(selectedData, ctx.selectRow(query.SelectItems, result))
+			selectedData = append(selectedData, ctx.selectRow(query.SelectItems, joinedRows))
 		} else {
-			for _, row := range result {
+			for _, row := range joinedRows {
 				selectedData = append(selectedData, ctx.selectRow(query.SelectItems, row))
 			}
 		}
@@ -79,7 +108,7 @@ func Execute(query parsers.SelectStmt, data []RowType) []RowType {
 	return result
 }
 
-func (c memoryExecutorContext) selectRow(selectItems []parsers.SelectItem, row RowType) interface{} {
+func (c memoryExecutorContext) selectRow(selectItems []parsers.SelectItem, row interface{}) interface{} {
 	// When the first value is top level, select it instead
 	if len(selectItems) > 0 && selectItems[0].IsTopLevel {
 		return c.getFieldValue(selectItems[0], row)
@@ -103,7 +132,7 @@ func (c memoryExecutorContext) selectRow(selectItems []parsers.SelectItem, row R
 	return newRow
 }
 
-func (c memoryExecutorContext) evaluateFilters(expr ExpressionType, row RowType) bool {
+func (c memoryExecutorContext) evaluateFilters(expr ExpressionType, row RowWithJoins) bool {
 	if expr == nil {
 		return true
 	}
@@ -164,7 +193,7 @@ func (c memoryExecutorContext) evaluateFilters(expr ExpressionType, row RowType)
 	return false
 }
 
-func (c memoryExecutorContext) getFieldValue(field parsers.SelectItem, row RowType) interface{} {
+func (c memoryExecutorContext) getFieldValue(field parsers.SelectItem, row interface{}) interface{} {
 	if field.Type == parsers.SelectItemTypeArray {
 		arrayValue := make([]interface{}, 0)
 		for _, selectItem := range field.SelectItems {
@@ -200,7 +229,8 @@ func (c memoryExecutorContext) getFieldValue(field parsers.SelectItem, row RowTy
 	}
 
 	rowValue := row
-	if array, isArray := row.([]RowType); isArray {
+	// Used for aggregates
+	if array, isArray := row.([]RowWithJoins); isArray {
 		rowValue = array[0]
 	}
 
@@ -374,6 +404,9 @@ func (c memoryExecutorContext) getFieldValue(field parsers.SelectItem, row RowTy
 	}
 
 	value := rowValue
+	if joinedRow, isRowWithJoins := value.(RowWithJoins); isRowWithJoins {
+		value = joinedRow[field.Path[0]]
+	}
 
 	if len(field.Path) > 1 {
 		for _, pathSegment := range field.Path[1:] {
@@ -381,6 +414,8 @@ func (c memoryExecutorContext) getFieldValue(field parsers.SelectItem, row RowTy
 			switch nestedValue := value.(type) {
 			case map[string]interface{}:
 				value = nestedValue[pathSegment]
+			case RowWithJoins:
+				value = nestedValue[pathSegment]
 			case []int, []string, []interface{}:
 				slice := reflect.ValueOf(nestedValue)
 				if arrayIndex, err := strconv.Atoi(pathSegment); err == nil && slice.Len() > arrayIndex {
@@ -398,7 +433,7 @@ func (c memoryExecutorContext) getFieldValue(field parsers.SelectItem, row RowTy
 
 func (c memoryExecutorContext) getExpressionParameterValue(
 	parameter interface{},
-	row RowType,
+	row RowWithJoins,
 ) interface{} {
 	switch typedParameter := parameter.(type) {
 	case parsers.SelectItem:
@@ -410,7 +445,7 @@ func (c memoryExecutorContext) getExpressionParameterValue(
 	return nil
 }
 
-func (c memoryExecutorContext) orderBy(orderBy []parsers.OrderExpression, data []RowType) {
+func (c memoryExecutorContext) orderBy(orderBy []parsers.OrderExpression, data []RowWithJoins) {
 	less := func(i, j int) bool {
 		for _, order := range orderBy {
 			val1 := c.getFieldValue(order.SelectItem, data[i])
@@ -430,8 +465,8 @@ func (c memoryExecutorContext) orderBy(orderBy []parsers.OrderExpression, data [
 	sort.SliceStable(data, less)
 }
 
-func (c memoryExecutorContext) groupBy(selectStmt parsers.SelectStmt, data []RowType) []RowType {
+func (c memoryExecutorContext) groupBy(selectStmt parsers.SelectStmt, data []RowWithJoins) []RowType {
-	groupedRows := make(map[string][]RowType)
+	groupedRows := make(map[string][]RowWithJoins)
 	groupedKeys := make([]string, 0)
 
 	// Group rows by group by columns
@@ -454,7 +489,7 @@ func (c memoryExecutorContext) groupBy(selectStmt parsers.SelectStmt, data []Row
 	return aggregatedRows
 }
 
-func (c memoryExecutorContext) generateGroupKey(groupByFields []parsers.SelectItem, row RowType) string {
+func (c memoryExecutorContext) generateGroupKey(groupByFields []parsers.SelectItem, row RowWithJoins) string {
 	var keyBuilder strings.Builder
 	for _, column := range groupByFields {
 		fieldValue := c.getFieldValue(column, row)
@@ -465,7 +500,7 @@ func (c memoryExecutorContext) generateGroupKey(groupByFields []parsers.SelectIt
 	return keyBuilder.String()
 }
 
-func (c memoryExecutorContext) aggregateGroup(selectStmt parsers.SelectStmt, groupRows []RowType) RowType {
+func (c memoryExecutorContext) aggregateGroup(selectStmt parsers.SelectStmt, groupRows []RowWithJoins) RowType {
 	aggregatedRow := c.selectRow(selectStmt.SelectItems, groupRows)
 
 	return aggregatedRow
@@ -553,3 +588,27 @@ func hasAggregateFunctions(selectItems []parsers.SelectItem) bool {
 
 	return false
 }
+
+func zipRows(current []RowWithJoins, joinedTableName string, rowsToZip []RowType) []RowWithJoins {
+	resultMap := make([]RowWithJoins, 0)
+
+	for _, currentRow := range current {
+		for _, rowToZip := range rowsToZip {
+			newRow := copyMap(currentRow)
+			newRow[joinedTableName] = rowToZip
+			resultMap = append(resultMap, newRow)
+		}
+	}
+
+	return resultMap
+}
+
+func copyMap(originalMap map[string]RowType) map[string]RowType {
+	targetMap := make(map[string]RowType)
+
+	for k, v := range originalMap {
+		targetMap[k] = v
+	}
+
+	return targetMap
+}