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feat: Added BQSchemaToProtoDescriptor.java (#395)
Add class that converts from BQ Table Schema to Protocol Buffer Descriptor.
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allenc3 committed Jul 7, 2020
1 parent dab15da commit c3a9542b146c2a95bd69e6bb940e02f72354141c
@@ -0,0 +1,149 @@
/*
* Copyright 2020 Google LLC
*
* Licensed 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 com.google.cloud.bigquery.storage.v1alpha2;

import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableMap;
import com.google.protobuf.DescriptorProtos.DescriptorProto;
import com.google.protobuf.DescriptorProtos.FieldDescriptorProto;
import com.google.protobuf.DescriptorProtos.FileDescriptorProto;
import com.google.protobuf.Descriptors;
import com.google.protobuf.Descriptors.Descriptor;
import com.google.protobuf.Descriptors.FileDescriptor;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

/**
* Converts a BQ table schema to protobuf descriptor. The mapping between field types and field
* modes are shown in the ImmutableMaps below.
*/
public class BQTableSchemaToProtoDescriptor {
private static ImmutableMap<Table.TableFieldSchema.Mode, FieldDescriptorProto.Label>
BQTableSchemaModeMap =
ImmutableMap.of(
Table.TableFieldSchema.Mode.NULLABLE, FieldDescriptorProto.Label.LABEL_OPTIONAL,
Table.TableFieldSchema.Mode.REPEATED, FieldDescriptorProto.Label.LABEL_REPEATED,
Table.TableFieldSchema.Mode.REQUIRED, FieldDescriptorProto.Label.LABEL_REQUIRED);

private static ImmutableMap<Table.TableFieldSchema.Type, FieldDescriptorProto.Type>
BQTableSchemaTypeMap =
new ImmutableMap.Builder<Table.TableFieldSchema.Type, FieldDescriptorProto.Type>()
.put(Table.TableFieldSchema.Type.BOOL, FieldDescriptorProto.Type.TYPE_BOOL)
.put(Table.TableFieldSchema.Type.BYTES, FieldDescriptorProto.Type.TYPE_BYTES)
.put(Table.TableFieldSchema.Type.DATE, FieldDescriptorProto.Type.TYPE_INT64)
.put(Table.TableFieldSchema.Type.DATETIME, FieldDescriptorProto.Type.TYPE_INT64)
.put(Table.TableFieldSchema.Type.DOUBLE, FieldDescriptorProto.Type.TYPE_DOUBLE)
.put(Table.TableFieldSchema.Type.GEOGRAPHY, FieldDescriptorProto.Type.TYPE_BYTES)
.put(Table.TableFieldSchema.Type.INT64, FieldDescriptorProto.Type.TYPE_INT64)
.put(Table.TableFieldSchema.Type.NUMERIC, FieldDescriptorProto.Type.TYPE_BYTES)
.put(Table.TableFieldSchema.Type.STRING, FieldDescriptorProto.Type.TYPE_STRING)
.put(Table.TableFieldSchema.Type.STRUCT, FieldDescriptorProto.Type.TYPE_MESSAGE)
.put(Table.TableFieldSchema.Type.TIME, FieldDescriptorProto.Type.TYPE_INT64)
.put(Table.TableFieldSchema.Type.TIMESTAMP, FieldDescriptorProto.Type.TYPE_INT64)
.build();

/**
* Converts Table.TableSchema to a Descriptors.Descriptor object.
*
* @param BQTableSchema
* @throws Descriptors.DescriptorValidationException
*/
public static Descriptor ConvertBQTableSchemaToProtoDescriptor(Table.TableSchema BQTableSchema)
throws Descriptors.DescriptorValidationException {
return ConvertBQTableSchemaToProtoDescriptorImpl(
BQTableSchema, "root", new HashMap<ImmutableList<Table.TableFieldSchema>, Descriptor>());
}

/**
* Converts a Table.TableSchema to a Descriptors.Descriptor object.
*
* @param BQTableSchema
* @param scope Keeps track of current scope to prevent repeated naming while constructing
* descriptor.
* @param dependencyMap Stores already constructed descriptors to prevent reconstruction
* @throws Descriptors.DescriptorValidationException
*/
private static Descriptor ConvertBQTableSchemaToProtoDescriptorImpl(
Table.TableSchema BQTableSchema,
String scope,
HashMap<ImmutableList<Table.TableFieldSchema>, Descriptor> dependencyMap)
throws Descriptors.DescriptorValidationException {
List<FileDescriptor> dependenciesList = new ArrayList<FileDescriptor>();
List<FieldDescriptorProto> fields = new ArrayList<FieldDescriptorProto>();
int index = 1;
for (Table.TableFieldSchema BQTableField : BQTableSchema.getFieldsList()) {
String currentScope = scope + "__" + BQTableField.getName();
if (BQTableField.getType() == Table.TableFieldSchema.Type.STRUCT) {
ImmutableList<Table.TableFieldSchema> fieldList =
ImmutableList.copyOf(BQTableField.getFieldsList());
if (dependencyMap.containsKey(fieldList)) {
Descriptor descriptor = dependencyMap.get(fieldList);
dependenciesList.add(descriptor.getFile());
fields.add(ConvertBQTableFieldToProtoField(BQTableField, index++, descriptor.getName()));
} else {
Descriptor descriptor =
ConvertBQTableSchemaToProtoDescriptorImpl(
Table.TableSchema.newBuilder().addAllFields(fieldList).build(),
currentScope,
dependencyMap);
dependenciesList.add(descriptor.getFile());
dependencyMap.put(fieldList, descriptor);
fields.add(ConvertBQTableFieldToProtoField(BQTableField, index++, currentScope));
}
} else {
fields.add(ConvertBQTableFieldToProtoField(BQTableField, index++, currentScope));
}
}
FileDescriptor[] dependenciesArray = new FileDescriptor[dependenciesList.size()];
dependenciesArray = dependenciesList.toArray(dependenciesArray);
DescriptorProto descriptorProto =
DescriptorProto.newBuilder().setName(scope).addAllField(fields).build();
FileDescriptorProto fileDescriptorProto =
FileDescriptorProto.newBuilder().addMessageType(descriptorProto).build();
FileDescriptor fileDescriptor =
FileDescriptor.buildFrom(fileDescriptorProto, dependenciesArray);
Descriptor descriptor = fileDescriptor.findMessageTypeByName(scope);
return descriptor;
}

/**
* Converts a BQTableField to ProtoField
*
* @param BQTableField BQ Field used to construct a FieldDescriptorProto
* @param index Index for protobuf fields.
* @param scope used to name descriptors
*/
private static FieldDescriptorProto ConvertBQTableFieldToProtoField(
Table.TableFieldSchema BQTableField, int index, String scope) {
Table.TableFieldSchema.Mode mode = BQTableField.getMode();
String fieldName = BQTableField.getName();
if (BQTableField.getType() == Table.TableFieldSchema.Type.STRUCT) {
return FieldDescriptorProto.newBuilder()
.setName(fieldName)
.setTypeName(scope)
.setLabel((FieldDescriptorProto.Label) BQTableSchemaModeMap.get(mode))
.setNumber(index)
.build();
}
return FieldDescriptorProto.newBuilder()
.setName(fieldName)
.setType((FieldDescriptorProto.Type) BQTableSchemaTypeMap.get(BQTableField.getType()))
.setLabel((FieldDescriptorProto.Label) BQTableSchemaModeMap.get(mode))
.setNumber(index)
.build();
}
}

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