REP-5319 Only create partition-verification tasks in generation 0.

internal/verifier/migration_verifier.go

@@ -1082,22 +1082,25 @@ func (verifier *Verifier) verifyMetadataAndPartitionCollection(ctx context.Conte
 		task.Status = verificationTaskMetadataMismatch
 	}
 
-	partitions, shardKeys, docsCount, bytesCount, err := verifier.partitionAndInspectNamespace(ctx, srcNs)
-	if err != nil {
-		task.Status = verificationTaskFailed
-		verifier.logger.Error().Msgf("[Worker %d] Error partitioning collection: %+v", workerNum, err)
-		return
-	}
-	verifier.logger.Debug().Msgf("[Worker %d] split collection “%s” into %d partitions", workerNum, srcNs, len(partitions))
-
-	task.SourceDocumentCount = docsCount
-	task.SourceByteCount = bytesCount
-
-	for _, partition := range partitions {
-		_, err := verifier.InsertPartitionVerificationTask(partition, shardKeys, dstNs)
+	if task.Generation == 0 {
+		partitions, shardKeys, docsCount, bytesCount, err := verifier.partitionAndInspectNamespace(ctx, srcNs)
 		if err != nil {
 			task.Status = verificationTaskFailed
-			verifier.logger.Error().Msgf("[Worker %d] Error inserting verifier tasks: %+v", workerNum, err)
+
+			verifier.logger.Error().Msgf("[Worker %d] Error partitioning collection: %+v", workerNum, err)
+			return
+		}
+		verifier.logger.Debug().Msgf("[Worker %d] split collection “%s” into %d partitions", workerNum, srcNs, len(partitions))
+
+		task.SourceDocumentCount = docsCount
+		task.SourceByteCount = bytesCount
+
+		for _, partition := range partitions {
+			_, err := verifier.InsertPartitionVerificationTask(partition, shardKeys, dstNs)
+			if err != nil {
+				task.Status = verificationTaskFailed
+				verifier.logger.Error().Msgf("[Worker %d] Error inserting verifier tasks: %+v", workerNum, err)
+			}
 		}
 	}
 

internal/verifier/migration_verifier_test.go

@@ -18,6 +18,7 @@ import (
 
 	"github.com/10gen/migration-verifier/internal/partitions"
 	"github.com/10gen/migration-verifier/internal/testutil"
+	"github.com/10gen/migration-verifier/mslices"
 	"github.com/cespare/permute/v2"
 	"github.com/rs/zerolog"
 	"github.com/samber/lo"
@@ -1283,6 +1284,68 @@ func (suite *IntegrationTestSuite) TestVerificationStatus() {
 	suite.Equal(1, status.CompletedTasks, "completed tasks not equal")
 }
 
+func (suite *IntegrationTestSuite) TestMetadataMismatchAndPartitioning() {
+	ctx := suite.Context()
+
+	srcColl := suite.srcMongoClient.Database(suite.DBNameForTest()).Collection("coll")
+	dstColl := suite.dstMongoClient.Database(suite.DBNameForTest()).Collection("coll")
+
+	verifier := suite.BuildVerifier()
+
+	ns := srcColl.Database().Name() + "." + srcColl.Name()
+	verifier.SetSrcNamespaces([]string{ns})
+	verifier.SetDstNamespaces([]string{ns})
+	verifier.SetNamespaceMap()
+
+	for _, coll := range mslices.Of(srcColl, dstColl) {
+		_, err := coll.InsertOne(ctx, bson.M{"_id": 1, "x": 42})
+		suite.Require().NoError(err)
+	}
+
+	_, err := srcColl.Indexes().CreateOne(
+		ctx,
+		mongo.IndexModel{
+			Keys: bson.D{{"foo", 1}},
+		},
+	)
+	suite.Require().NoError(err)
+
+	runner := RunVerifierCheck(ctx, suite.T(), verifier)
+	runner.AwaitGenerationEnd()
+
+	cursor, err := verifier.verificationTaskCollection().Find(
+		ctx,
+		bson.M{"generation": 0},
+		options.Find().SetSort(bson.M{"type": 1}),
+	)
+	suite.Require().NoError(err)
+
+	var tasks []VerificationTask
+	suite.Require().NoError(cursor.All(ctx, &tasks))
+
+	suite.Require().Len(tasks, 2)
+	suite.Require().Equal(verificationTaskVerifyDocuments, tasks[0].Type)
+	suite.Require().Equal(verificationTaskCompleted, tasks[0].Status)
+	suite.Require().Equal(verificationTaskVerifyCollection, tasks[1].Type)
+	suite.Require().Equal(verificationTaskMetadataMismatch, tasks[1].Status)
+
+	runner.StartNextGeneration()
+	runner.AwaitGenerationEnd()
+
+	cursor, err = verifier.verificationTaskCollection().Find(
+		ctx,
+		bson.M{"generation": 1},
+		options.Find().SetSort(bson.M{"type": 1}),
+	)
+	suite.Require().NoError(err)
+
+	suite.Require().NoError(cursor.All(ctx, &tasks))
+
+	suite.Require().Len(tasks, 1, "generation 1 should only have done 1 task")
+	suite.Require().Equal(verificationTaskVerifyCollection, tasks[0].Type)
+	suite.Require().Equal(verificationTaskMetadataMismatch, tasks[0].Status)
+}
+
 func (suite *IntegrationTestSuite) TestGenerationalRechecking() {
 	zerolog.SetGlobalLevel(zerolog.DebugLevel)
 	verifier := suite.BuildVerifier()

mslices/slices.go

@@ -0,0 +1,11 @@
+package mslices
+
+// This package complements the Go standard library’s package of the
+// same name with broadly-useful tools that the standard library lacks.
+
+// Of returns a slice out of the given arguments. It’s syntactic sugar
+// to capitalize on Go’s type inference, similar to
+// [this declined feature proposal](https://github.com/golang/go/issues/47709).
+func Of[T any](pieces ...T) []T {
+	return append([]T{}, pieces...)
+}

mslices/slices_test.go

@@ -0,0 +1,27 @@
+package mslices
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/suite"
+)
+
+type mySuite struct {
+	suite.Suite
+}
+
+func TestUnitTestSuite(t *testing.T) {
+	suite.Run(t, &mySuite{})
+}
+
+func (s *mySuite) Test_Of() {
+	slc := Of(12, 23, 34)
+
+	s.Assert().IsType([]int{}, slc, "expected type")
+
+	a := []int{1, 2, 3}
+	b := Of(a...)
+	a[0] = 4
+
+	s.Assert().Equal(1, b[0], "should copy slice")
+}