[GitHub] [beam] lostluck commented on a diff in pull request #17347: [BEAM-14304] implement parquetio to read/write parquet files

[GitBox <gi...@apache.org>]

lostluck commented on code in PR #17347:
URL: https://github.com/apache/beam/pull/17347#discussion_r853292786


##########
sdks/go/pkg/beam/io/parquetio/parquetio.go:
##########
@@ -0,0 +1,159 @@
+// 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.
+// This module contains all Go code used for Beam's SDKs. This file is placed

Review Comment:
   Please add a line break between the license and the package doc. 



##########
sdks/go/pkg/beam/io/parquetio/parquetio.go:
##########
@@ -0,0 +1,159 @@
+// 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.
+// This module contains all Go code used for Beam's SDKs. This file is placed
+// in this directory in order to cover the go code required for Java and Python
+// containers, as well as the entire Go SDK. Placing this file in the repository
+// root is not possible because it causes conflicts with a pre-existing vendor
+// directory.
+package parquetio
+
+import (
+	"context"
+	"io/ioutil"
+	"reflect"
+	"strings"
+
+	"github.com/apache/beam/sdks/v2/go/pkg/beam"
+	"github.com/apache/beam/sdks/v2/go/pkg/beam/io/filesystem"
+	"github.com/xitongsys/parquet-go-source/buffer"
+	"github.com/xitongsys/parquet-go/reader"
+	"github.com/xitongsys/parquet-go/writer"
+)
+
+func init() {
+	beam.RegisterFunction(expandFn)
+	beam.RegisterType(reflect.TypeOf((*parquetReadFn)(nil)).Elem())
+	beam.RegisterType(reflect.TypeOf((*parquetWriteFn)(nil)).Elem())
+}
+
+// Read reads a set of files and returns lines as a PCollection<elem>
+// based on the internal avro schema of the file.
+// A type - reflect.TypeOf( YourType{} ) -  with
+// JSON tags can be defined or if you wish to return the raw JSON string,
+// use - reflect.TypeOf("") -
+func Read(s beam.Scope, glob string, t reflect.Type) beam.PCollection {
+	s = s.Scope("parquetio.Read")
+	filesystem.ValidateScheme(glob)
+	return read(s, t, beam.Create(s, glob))
+}
+
+func read(s beam.Scope, t reflect.Type, col beam.PCollection) beam.PCollection {
+	files := beam.ParDo(s, expandFn, col)
+	return beam.ParDo(s,
+		&parquetReadFn{Type: beam.EncodedType{T: t}},
+		files,
+		beam.TypeDefinition{Var: beam.XType, T: t},
+	)
+}
+
+func expandFn(ctx context.Context, glob string, emit func(string)) error {
+	if strings.TrimSpace(glob) == "" {
+		return nil // ignore empty string elements here
+	}
+
+	fs, err := filesystem.New(ctx, glob)
+	if err != nil {
+		return err
+	}
+	defer fs.Close()
+
+	files, err := fs.List(ctx, glob)
+	if err != nil {
+		return err
+	}
+	for _, filename := range files {
+		emit(filename)
+	}
+	return nil
+}
+
+type parquetReadFn struct {
+	Type beam.EncodedType
+}
+
+func (a *parquetReadFn) ProcessElement(ctx context.Context, filename string, emit func(beam.X)) error {
+	fs, err := filesystem.New(ctx, filename)
+	if err != nil {
+		return err
+	}
+	defer fs.Close()
+
+	fd, err := fs.OpenRead(ctx, filename)
+	if err != nil {
+		return err
+	}
+	defer fd.Close()
+
+	data, err := ioutil.ReadAll(fd)
+	if err != nil {
+		return err
+	}
+
+	bufferReader := buffer.NewBufferFileFromBytes(data)
+	parquetReader, err := reader.NewParquetReader(bufferReader, reflect.New(a.Type.T).Interface(), 4)
+	if err != nil {
+		return err
+	}
+
+	vals, err := parquetReader.ReadByNumber(int(parquetReader.GetNumRows()))
+	if err != nil {
+		return err
+	}
+	for _, v := range vals {
+		emit(v)
+	}
+
+	return nil
+}
+
+func Write(s beam.Scope, filename string, t reflect.Type, col beam.PCollection) {

Review Comment:
   Please add a doc comment here, making it explicit this will only write a single file.



##########
sdks/go/pkg/beam/io/parquetio/parquetio_test.go:
##########
@@ -0,0 +1,126 @@
+// 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.
+// This module contains all Go code used for Beam's SDKs. This file is placed
+// in this directory in order to cover the go code required for Java and Python
+// containers, as well as the entire Go SDK. Placing this file in the repository
+// root is not possible because it causes conflicts with a pre-existing vendor
+// directory.
+package parquetio

Review Comment:
   The test files don't need to have a package doc, and the license should be disconnected from the `package` line, so they don't get interpreted as one.
   
   ```suggestion
   // limitations under the License.
   
   package parquetio
   ```



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