GODRIVER-3412 Add index hint support for distinct command.

internal/integration/unified/collection_operation_execution.go

@@ -523,6 +523,8 @@ func executeDistinct(ctx context.Context, operation *operation) (*operationResul
 		val := elem.Value()
 
 		switch key {
+		case "hint":
+			opts.SetHint(val)
 		case "collation":
 			collation, err := createCollation(val.Document())
 			if err != nil {

mongo/collection.go

@@ -1281,6 +1281,13 @@ func (coll *Collection) Distinct(
 		}
 		op.Comment(comment)
 	}
+	if args.Hint != nil {
+		hint, err := marshalValue(args.Hint, coll.bsonOpts, coll.registry)
+		if err != nil {
+			return &DistinctResult{err: err}
+		}
+		op.Hint(hint)
+	}
 	retry := driver.RetryNone
 	if coll.client.retryReads {
 		retry = driver.RetryOncePerCommand

mongo/options/distinctoptions.go

@@ -13,6 +13,7 @@ package options
 type DistinctOptions struct {
 	Collation *Collation
 	Comment   interface{}
+	Hint      interface{}
 }
 
 // DistinctOptionsBuilder contains options to configure distinct operations. Each
@@ -60,3 +61,17 @@ func (do *DistinctOptionsBuilder) SetComment(comment interface{}) *DistinctOptio
 
 	return do
 }
+
+// SetHint sets the value for the Comment field. Specifies a string or document that
+// will be included in server logs, profiling logs, and currentOp queries to help trace
+// the operation. The default value is nil, which means that no comment will be included
+// in the logs.
+func (do *DistinctOptionsBuilder) SetHint(hint interface{}) *DistinctOptionsBuilder {
+	do.Opts = append(do.Opts, func(opts *DistinctOptions) error {
+		opts.Hint = hint
+
+		return nil
+	})
+
+	return do
+}

testdata/crud/unified/distinct-hint.json

@@ -0,0 +1,139 @@
+{
+  "description": "distinct-hint",
+  "schemaVersion": "1.0",
+  "runOnRequirements": [
+    {
+      "minServerVersion": "7.1.0"
+    }
+  ],
+  "createEntities": [
+    {
+      "client": {
+        "id": "client0",
+        "observeEvents": [
+          "commandStartedEvent"
+        ]
+      }
+    },
+    {
+      "database": {
+        "id": "database0",
+        "client": "client0",
+        "databaseName": "distinct-hint-tests"
+      }
+    },
+    {
+      "collection": {
+        "id": "collection0",
+        "database": "database0",
+        "collectionName": "coll0"
+      }
+    }
+  ],
+  "initialData": [
+    {
+      "collectionName": "coll0",
+      "databaseName": "distinct-hint-tests",
+      "documents": [
+        {
+          "_id": 1,
+          "x": 11
+        },
+        {
+          "_id": 2,
+          "x": 22
+        },
+        {
+          "_id": 3,
+          "x": 33
+        }
+      ]
+    }
+  ],
+  "tests": [
+    {
+      "description": "distinct with hint string",
+      "operations": [
+        {
+          "name": "distinct",
+          "object": "collection0",
+          "arguments": {
+            "fieldName": "x",
+            "filter": {
+              "_id": 1
+            },
+            "hint": "_id_"
+          },
+          "expectResult": [
+            11
+          ]
+        }
+      ],
+      "expectEvents": [
+        {
+          "client": "client0",
+          "events": [
+            {
+              "commandStartedEvent": {
+                "command": {
+                  "distinct": "coll0",
+                  "key": "x",
+                  "query": {
+                    "_id": 1
+                  },
+                  "hint": "_id_"
+                },
+                "commandName": "distinct",
+                "databaseName": "distinct-hint-tests"
+              }
+            }
+          ]
+        }
+      ]
+    },
+    {
+      "description": "distinct with hint document",
+      "operations": [
+        {
+          "name": "distinct",
+          "object": "collection0",
+          "arguments": {
+            "fieldName": "x",
+            "filter": {
+              "_id": 1
+            },
+            "hint": {
+              "_id": 1
+            }
+          },
+          "expectResult": [
+            11
+          ]
+        }
+      ],
+      "expectEvents": [
+        {
+          "client": "client0",
+          "events": [
+            {
+              "commandStartedEvent": {
+                "command": {
+                  "distinct": "coll0",
+                  "key": "x",
+                  "query": {
+                    "_id": 1
+                  },
+                  "hint": {
+                    "_id": 1
+                  }
+                },
+                "commandName": "distinct",
+                "databaseName": "distinct-hint-tests"
+              }
+            }
+          ]
+        }
+      ]
+    }
+  ]
+}

testdata/crud/unified/distinct-hint.yml

@@ -0,0 +1,73 @@
+description: "distinct-hint"
+
+schemaVersion: "1.0"
+runOnRequirements:
+  # https://jira.mongodb.org/browse/SERVER-14227
+  # Server supports distinct with hint starting from 7.1.0.
+  - minServerVersion: "7.1.0"
+
+createEntities:
+  - client:
+      id: &client0 client0
+      observeEvents: [ commandStartedEvent ]
+  - database:
+      id: &database0 database0
+      client: *client0
+      databaseName: &database0Name distinct-hint-tests
+  - collection:
+      id: &collection0 collection0
+      database: *database0
+      collectionName: &collection0Name coll0
+
+initialData:
+  - collectionName: *collection0Name
+    databaseName: *database0Name
+    documents:
+      - { _id: 1, x: 11 }
+      - { _id: 2, x: 22 }
+      - { _id: 3, x: 33 }
+
+tests:
+  - description: "distinct with hint string"
+    operations:
+      - name: distinct
+        object: *collection0
+        arguments:
+          fieldName: &fieldName x
+          filter: &filter { _id: 1 }
+          hint: _id_
+        expectResult: [ 11 ]
+    expectEvents:
+      - client: *client0
+        events:
+          - commandStartedEvent:
+              command:
+                distinct: *collection0Name
+                key: *fieldName
+                query: *filter
+                hint: _id_
+              commandName: distinct
+              databaseName: *database0Name
+
+  - description: "distinct with hint document"
+    operations:
+      - name: distinct
+        object: *collection0
+        arguments:
+          fieldName: *fieldName
+          filter: *filter
+          hint:
+            _id: 1
+        expectResult: [ 11 ]
+    expectEvents:
+      - client: *client0
+        events:
+          - commandStartedEvent:
+              command:
+                distinct: *collection0Name
+                key: *fieldName
+                query: *filter
+                hint:
+                  _id: 1
+              commandName: distinct
+              databaseName: *database0Name

x/mongo/driver/operation/distinct.go

@@ -31,6 +31,7 @@ type Distinct struct {
 	clock          *session.ClusterClock
 	collection     string
 	comment        bsoncore.Value
+	hint           bsoncore.Value
 	monitor        *event.CommandMonitor
 	crypt          driver.Crypt
 	database       string
@@ -120,6 +121,9 @@ func (d *Distinct) command(dst []byte, desc description.SelectedServer) ([]byte,
 	if d.comment.Type != bsoncore.Type(0) {
 		dst = bsoncore.AppendValueElement(dst, "comment", d.comment)
 	}
+	if d.hint.Type != bsoncore.Type(0) {
+		dst = bsoncore.AppendValueElement(dst, "hint", d.hint)
+	}
 	if d.key != nil {
 		dst = bsoncore.AppendStringElement(dst, "key", *d.key)
 	}
@@ -199,6 +203,16 @@ func (d *Distinct) Comment(comment bsoncore.Value) *Distinct {
 	return d
 }
 
+// Hint sets a value to help trace an operation.
+func (d *Distinct) Hint(hint bsoncore.Value) *Distinct {
+	if d == nil {
+		d = new(Distinct)
+	}
+
+	d.hint = hint
+	return d
+}
+
 // CommandMonitor sets the monitor to use for APM events.
 func (d *Distinct) CommandMonitor(monitor *event.CommandMonitor) *Distinct {
 	if d == nil {