johannaojeling commented on code in PR #24663: URL: https://github.com/apache/beam/pull/24663#discussion_r1058476211
########## sdks/go/pkg/beam/io/mongodbio/read.go: ########## @@ -0,0 +1,469 @@ +// Licensed to the Apache Software Foundation (ASF) under one or more +// contributor license agreements. See the NOTICE file distributed with +// this work for additional information regarding copyright ownership. +// The ASF licenses this file to You under the Apache License, Version 2.0 +// (the "License"); you may not use this file except in compliance with +// the License. You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +package mongodbio + +import ( + "context" + "fmt" + "math" + "reflect" + + "github.com/apache/beam/sdks/v2/go/pkg/beam" + "github.com/apache/beam/sdks/v2/go/pkg/beam/register" + "github.com/apache/beam/sdks/v2/go/pkg/beam/util/structx" + "go.mongodb.org/mongo-driver/bson" + "go.mongodb.org/mongo-driver/mongo" + "go.mongodb.org/mongo-driver/mongo/options" + "go.mongodb.org/mongo-driver/mongo/readpref" +) + +const ( + defaultReadBundleSize = 64 * 1024 * 1024 + + minSplitVectorChunkSize = 1024 * 1024 + maxSplitVectorChunkSize = 1024 * 1024 * 1024 + + maxBucketCount = math.MaxInt32 +) + +func init() { + register.DoFn3x1[context.Context, []byte, func(bson.M), error](&bucketAutoFn{}) + register.DoFn3x1[context.Context, []byte, func(bson.M), error](&splitVectorFn{}) + register.Emitter1[bson.M]() + + register.DoFn3x1[context.Context, bson.M, func(beam.Y), error](&readFn{}) + register.Emitter1[beam.Y]() +} + +// Read reads a MongoDB collection and returns a PCollection<T> for a given type T. T must be a +// struct with exported fields that should have a "bson" tag. By default, the transform uses the +// MongoDB internal splitVector command to split the collection into bundles. The transform can be +// configured to use the $bucketAuto aggregation instead to support reading from MongoDB Atlas +// where the splitVector command is not allowed. This is enabled by passing the ReadOptionFn +// WithReadBucketAuto(true). +// +// The Read transform has the required parameters: +// - s: the scope of the pipeline +// - uri: the MongoDB connection string +// - database: the MongoDB database to read from +// - collection: the MongoDB collection to read from +// - t: the type of the elements in the collection +// +// The Read transform takes a variadic number of ReadOptionFn which can set the ReadOption fields: +// - BucketAuto: whether to use the bucketAuto aggregation to split the collection into bundles. +// Defaults to false +// - Filter: a bson.M map that is used to filter the documents in the collection. Defaults to nil, +// which means no filter is applied +// - BundleSize: the size in bytes to bundle the documents into when reading. Defaults to +// 64 * 1024 * 1024 (64 MB) +func Read( + s beam.Scope, + uri string, + database string, + collection string, + t reflect.Type, + opts ...ReadOptionFn, +) beam.PCollection { + s = s.Scope("mongodbio.Read") + + option := &ReadOption{ + BundleSize: defaultReadBundleSize, + } + + for _, opt := range opts { + if err := opt(option); err != nil { + panic(fmt.Sprintf("mongodbio.Read: invalid option: %v", err)) + } + } + + imp := beam.Impulse(s) + + var bundled beam.PCollection + + if option.BucketAuto { + bundled = beam.ParDo(s, newBucketAutoFn(uri, database, collection, option), imp) + } else { + bundled = beam.ParDo(s, newSplitVectorFn(uri, database, collection, option), imp) + } + + return beam.ParDo( + s, + newReadFn(uri, database, collection, t, option), + bundled, + beam.TypeDefinition{Var: beam.YType, T: t}, + ) +} + +type bucketAutoFn struct { + mongoDBFn + BundleSize int64 +} + +func newBucketAutoFn( + uri string, + database string, + collection string, + option *ReadOption, +) *bucketAutoFn { + return &bucketAutoFn{ + mongoDBFn: mongoDBFn{ + URI: uri, + Database: database, + Collection: collection, + }, + BundleSize: option.BundleSize, + } +} + +func (fn *bucketAutoFn) ProcessElement( + ctx context.Context, + _ []byte, + emit func(bson.M), +) error { + collectionSize, err := fn.getCollectionSize(ctx) + if err != nil { + return err + } + + if collectionSize == 0 { + return nil + } + + bucketCount := calculateBucketCount(collectionSize, fn.BundleSize) + + buckets, err := fn.getBuckets(ctx, bucketCount) + if err != nil { + return err + } + + idFilters := idFiltersFromBuckets(buckets) + + for _, filter := range idFilters { + emit(filter) + } + + return nil +} + +type collStats struct { + Size int64 `bson:"size"` +} + +func (fn *bucketAutoFn) getCollectionSize(ctx context.Context) (int64, error) { + cmd := bson.M{"collStats": fn.Collection} + opts := options.RunCmd().SetReadPreference(readpref.Primary()) + + var stats collStats + if err := fn.collection.Database().RunCommand(ctx, cmd, opts).Decode(&stats); err != nil { + return 0, fmt.Errorf("error executing collStats command: %w", err) + } + + return stats.Size, nil +} + +func calculateBucketCount(collectionSize int64, bundleSize int64) int32 { + if bundleSize < 0 { + panic("monogdbio.calculateBucketCount: bundle size must be greater than 0") + } + + count := collectionSize / bundleSize + if collectionSize%bundleSize != 0 { + count++ + } + + if count > int64(maxBucketCount) { + count = maxBucketCount + } + + return int32(count) +} + +type bucket struct { + ID minMax `bson:"_id"` +} + +type minMax struct { + Min any `bson:"min"` + Max any `bson:"max"` +} + +func (fn *bucketAutoFn) getBuckets(ctx context.Context, count int32) ([]bucket, error) { + pipeline := mongo.Pipeline{bson.D{{ + Key: "$bucketAuto", + Value: bson.M{ + "groupBy": "$_id", + "buckets": count, + }, + }}} + + cursor, err := fn.collection.Aggregate(ctx, pipeline) + if err != nil { + return nil, fmt.Errorf("error executing bucketAuto aggregation: %w", err) + } + + var buckets []bucket + if err = cursor.All(ctx, &buckets); err != nil { + return nil, fmt.Errorf("error decoding buckets: %w", err) + } + + return buckets, nil +} + +func idFiltersFromBuckets(buckets []bucket) []bson.M { + idFilters := make([]bson.M, len(buckets)) + + for i := 0; i < len(buckets); i++ { + filter := bson.M{} + + if i != 0 { + filter["$gt"] = buckets[i].ID.Min + } + + if i != len(buckets)-1 { + filter["$lte"] = buckets[i].ID.Max + } + + if len(filter) == 0 { + idFilters[i] = filter + } else { + idFilters[i] = bson.M{"_id": filter} + } + } + + return idFilters +} + +type splitVectorFn struct { + mongoDBFn + BundleSize int64 +} + +func newSplitVectorFn( + uri string, + database string, + collection string, + option *ReadOption, +) *splitVectorFn { + return &splitVectorFn{ + mongoDBFn: mongoDBFn{ + URI: uri, + Database: database, + Collection: collection, + }, + BundleSize: option.BundleSize, + } +} + +func (fn *splitVectorFn) ProcessElement( + ctx context.Context, + _ []byte, + emit func(bson.M), +) error { + chunkSize := getChunkSize(fn.BundleSize) + + splitKeys, err := fn.getSplitKeys(ctx, chunkSize) + if err != nil { + return err + } + + idFilters := idFiltersFromSplits(splitKeys) + + for _, filter := range idFilters { + emit(filter) + } + + return nil +} + +func getChunkSize(bundleSize int64) int64 { + var chunkSize int64 + + if bundleSize < minSplitVectorChunkSize { + chunkSize = minSplitVectorChunkSize + } else if bundleSize > maxSplitVectorChunkSize { + chunkSize = maxSplitVectorChunkSize + } else { + chunkSize = bundleSize + } + + return chunkSize +} + +type splitVector struct { + SplitKeys []splitKey `bson:"splitKeys"` +} + +type splitKey struct { + ID any `bson:"_id"` +} + +func (fn *splitVectorFn) getSplitKeys(ctx context.Context, chunkSize int64) ([]splitKey, error) { + cmd := bson.D{ + {Key: "splitVector", Value: fmt.Sprintf("%s.%s", fn.Database, fn.Collection)}, + {Key: "keyPattern", Value: bson.D{{Key: "_id", Value: 1}}}, + {Key: "maxChunkSizeBytes", Value: chunkSize}, + } + + opts := options.RunCmd().SetReadPreference(readpref.Primary()) + + var vector splitVector + if err := fn.collection.Database().RunCommand(ctx, cmd, opts).Decode(&vector); err != nil { + return nil, fmt.Errorf("error executing splitVector command: %w", err) + } + + return vector.SplitKeys, nil +} + +func idFiltersFromSplits(splitKeys []splitKey) []bson.M { + idFilters := make([]bson.M, len(splitKeys)+1) + + for i := 0; i < len(splitKeys)+1; i++ { + filter := bson.M{} + + if i > 0 { + filter["$gt"] = splitKeys[i-1].ID + } + + if i < len(splitKeys) { + filter["$lte"] = splitKeys[i].ID + } + + if len(filter) == 0 { + idFilters[i] = filter + } else { + idFilters[i] = bson.M{"_id": filter} + } + } + + return idFilters +} + +type readFn struct { + mongoDBFn + Filter []byte Review Comment: Good point, updated -- This is an automated message from the Apache Git Service. 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