feat: Make topLevelNode explainable (#737)

- Resolves #736

- Description: makes `topLevelNode` explainable without changing the `Source()` function to fetch child graphs.
 #626 will be done in a separate PR once `topLevelNode.Source()` is updated.

query/graphql/planner/top.go

@@ -115,6 +115,10 @@ func (n *topLevelNode) Source() planNode {
 	return nil
 }
 
+func (n *topLevelNode) Explain() (map[string]any, error) {
+	return map[string]any{}, nil
+}
+
 func (n *topLevelNode) Next() (bool, error) {
 	if n.isdone {
 		return false, nil

tests/integration/query/explain/top_with_average_test.go

@@ -0,0 +1,106 @@
+// Copyright 2022 Democratized Data Foundation
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+package test_explain
+
+import (
+	"testing"
+
+	testUtils "github.com/sourcenetwork/defradb/tests/integration"
+)
+
+func TestExplainTopLevelAverageQuery(t *testing.T) {
+	test := testUtils.QueryTestCase{
+		Description: "Explain top-level average query.",
+
+		Query: `query @explain {
+					_avg(
+						author: {
+							field: age
+						}
+					)
+				}`,
+
+		Docs: map[int][]string{
+			//authors
+			2: {
+				`{
+					"name": "John",
+					"verified": false,
+					"age": 28
+				}`,
+				`{
+					"name": "Bob",
+					"verified": true,
+					"age": 30
+				}`,
+			},
+		},
+
+		Results: []dataMap{
+			{
+				"explain": dataMap{
+					"topLevelNode": dataMap{},
+				},
+			},
+		},
+	}
+
+	executeTestCase(t, test)
+}
+
+func TestExplainTopLevelAverageQueryWithFilter(t *testing.T) {
+	test := testUtils.QueryTestCase{
+		Description: "Explain top-level average query with filter.",
+		Query: `query @explain {
+					_avg(
+						author: {
+							field: age,
+							filter: {
+								age: {
+									_gt: 26
+								}
+							}
+						}
+					)
+				}`,
+
+		Docs: map[int][]string{
+			//authors
+			2: {
+				`{
+					"name": "John",
+					"verified": false,
+					"age": 21
+				}`,
+				`{
+					"name": "Bob",
+					"verified": false,
+					"age": 30
+				}`,
+				`{
+					"name": "Alice",
+					"verified": false,
+					"age": 32
+				}`,
+			},
+		},
+
+		Results: []dataMap{
+			{
+				"explain": dataMap{
+					"topLevelNode": dataMap{},
+				},
+			},
+		},
+	}
+
+	executeTestCase(t, test)
+}

tests/integration/query/explain/top_with_count_test.go

@@ -0,0 +1,102 @@
+// Copyright 2022 Democratized Data Foundation
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+package test_explain
+
+import (
+	"testing"
+
+	testUtils "github.com/sourcenetwork/defradb/tests/integration"
+)
+
+func TestExplainTopLevelCountQuery(t *testing.T) {
+	test := testUtils.QueryTestCase{
+		Description: "Explain top-level count query.",
+
+		Query: `query @explain {
+					_count(author: {})
+				}`,
+
+		Docs: map[int][]string{
+			//authors
+			2: {
+				`{
+					"name": "John",
+					"verified": true,
+					"age": 21
+				}`,
+				`{
+					"name": "Bob",
+					"verified": false,
+					"age": 30
+				}`,
+			},
+		},
+
+		Results: []dataMap{
+			{
+				"explain": dataMap{
+					"topLevelNode": dataMap{},
+				},
+			},
+		},
+	}
+
+	executeTestCase(t, test)
+}
+
+func TestExplainTopLevelCountQueryWithFilter(t *testing.T) {
+	test := testUtils.QueryTestCase{
+		Description: "Explain top-level count query with filter.",
+
+		Query: `query @explain {
+					_count(
+						author: {
+							filter: {
+								age: {
+									_gt: 26
+								}
+							}
+						}
+					)
+				}`,
+
+		Docs: map[int][]string{
+			//authors
+			2: {
+				`{
+					"name": "John",
+					"verified": false,
+					"age": 21
+				}`,
+				`{
+					"name": "Bob",
+					"verified": false,
+					"age": 30
+				}`,
+				`{
+					"name": "Alice",
+					"verified": true,
+					"age": 32
+				}`,
+			},
+		},
+
+		Results: []dataMap{
+			{
+				"explain": dataMap{
+					"topLevelNode": dataMap{},
+				},
+			},
+		},
+	}
+
+	executeTestCase(t, test)
+}

tests/integration/query/explain/top_with_sum_test.go

@@ -0,0 +1,107 @@
+// Copyright 2022 Democratized Data Foundation
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+package test_explain
+
+import (
+	"testing"
+
+	testUtils "github.com/sourcenetwork/defradb/tests/integration"
+)
+
+func TestExplainTopLevelSumQuery(t *testing.T) {
+	test := testUtils.QueryTestCase{
+		Description: "Explain top-level sum query.",
+
+		Query: `query @explain {
+					_sum(
+						author: {
+							field: age
+						}
+					)
+				}`,
+
+		Docs: map[int][]string{
+			//authors
+			2: {
+				`{
+					"name": "John",
+					"verified": true,
+					"age": 21
+				}`,
+				`{
+					"name": "Bob",
+					"verified": true,
+					"age": 30
+				}`,
+			},
+		},
+
+		Results: []dataMap{
+			{
+				"explain": dataMap{
+					"topLevelNode": dataMap{},
+				},
+			},
+		},
+	}
+
+	executeTestCase(t, test)
+}
+
+func TestExplainTopLevelSumQueryWithFilter(t *testing.T) {
+	test := testUtils.QueryTestCase{
+		Description: "Explain top-level sum query with filter.",
+
+		Query: `query @explain {
+					_sum(
+						author: {
+							field: age,
+							filter: {
+								age: {
+									_gt: 26
+								}
+							}
+						}
+					)
+				}`,
+
+		Docs: map[int][]string{
+			//authors
+			2: {
+				`{
+					"name": "John",
+					"verified": false,
+					"age": 21
+				}`,
+				`{
+					"name": "Bob",
+					"verified": false,
+					"age": 30
+				}`,
+				`{
+					"name": "Alice",
+					"verified": true,
+					"age": 32
+				}`,
+			},
+		},
+
+		Results: []dataMap{
+			{
+				"explain": dataMap{
+					"topLevelNode": dataMap{},
+				},
+			},
+		},
+	}
+
+	executeTestCase(t, test)
+}