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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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‎google-cloud-bigquerystorage/src/main/java/com/google/cloud/bigquery/storage/v1alpha2/BQTableSchemaToProtoDescriptor.java

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/*
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* Copyright 2020 Google LLC
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.google.cloud.bigquery.storage.v1alpha2;
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import com.google.common.collect.ImmutableList;
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import com.google.common.collect.ImmutableMap;
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import com.google.protobuf.DescriptorProtos.DescriptorProto;
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import com.google.protobuf.DescriptorProtos.FieldDescriptorProto;
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import com.google.protobuf.DescriptorProtos.FileDescriptorProto;
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import com.google.protobuf.Descriptors;
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import com.google.protobuf.Descriptors.Descriptor;
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import com.google.protobuf.Descriptors.FileDescriptor;
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import java.util.ArrayList;
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import java.util.HashMap;
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import java.util.List;
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/**
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* Converts a BQ table schema to protobuf descriptor. The mapping between field types and field
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* modes are shown in the ImmutableMaps below.
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*/
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public class BQTableSchemaToProtoDescriptor {
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private static ImmutableMap<Table.TableFieldSchema.Mode, FieldDescriptorProto.Label>
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BQTableSchemaModeMap =
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ImmutableMap.of(
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Table.TableFieldSchema.Mode.NULLABLE, FieldDescriptorProto.Label.LABEL_OPTIONAL,
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Table.TableFieldSchema.Mode.REPEATED, FieldDescriptorProto.Label.LABEL_REPEATED,
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Table.TableFieldSchema.Mode.REQUIRED, FieldDescriptorProto.Label.LABEL_REQUIRED);
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private static ImmutableMap<Table.TableFieldSchema.Type, FieldDescriptorProto.Type>
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BQTableSchemaTypeMap =
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new ImmutableMap.Builder<Table.TableFieldSchema.Type, FieldDescriptorProto.Type>()
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.put(Table.TableFieldSchema.Type.BOOL, FieldDescriptorProto.Type.TYPE_BOOL)
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.put(Table.TableFieldSchema.Type.BYTES, FieldDescriptorProto.Type.TYPE_BYTES)
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.put(Table.TableFieldSchema.Type.DATE, FieldDescriptorProto.Type.TYPE_INT64)
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.put(Table.TableFieldSchema.Type.DATETIME, FieldDescriptorProto.Type.TYPE_INT64)
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.put(Table.TableFieldSchema.Type.DOUBLE, FieldDescriptorProto.Type.TYPE_DOUBLE)
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.put(Table.TableFieldSchema.Type.GEOGRAPHY, FieldDescriptorProto.Type.TYPE_BYTES)
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.put(Table.TableFieldSchema.Type.INT64, FieldDescriptorProto.Type.TYPE_INT64)
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.put(Table.TableFieldSchema.Type.NUMERIC, FieldDescriptorProto.Type.TYPE_BYTES)
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.put(Table.TableFieldSchema.Type.STRING, FieldDescriptorProto.Type.TYPE_STRING)
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.put(Table.TableFieldSchema.Type.STRUCT, FieldDescriptorProto.Type.TYPE_MESSAGE)
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.put(Table.TableFieldSchema.Type.TIME, FieldDescriptorProto.Type.TYPE_INT64)
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.put(Table.TableFieldSchema.Type.TIMESTAMP, FieldDescriptorProto.Type.TYPE_INT64)
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.build();
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/**
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* Converts Table.TableSchema to a Descriptors.Descriptor object.
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*
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* @param BQTableSchema
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* @throws Descriptors.DescriptorValidationException
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*/
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public static Descriptor ConvertBQTableSchemaToProtoDescriptor(Table.TableSchema BQTableSchema)
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throws Descriptors.DescriptorValidationException {
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return ConvertBQTableSchemaToProtoDescriptorImpl(
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BQTableSchema, "root", new HashMap<ImmutableList<Table.TableFieldSchema>, Descriptor>());
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}
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/**
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* Converts a Table.TableSchema to a Descriptors.Descriptor object.
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*
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* @param BQTableSchema
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* @param scope Keeps track of current scope to prevent repeated naming while constructing
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* descriptor.
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* @param dependencyMap Stores already constructed descriptors to prevent reconstruction
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* @throws Descriptors.DescriptorValidationException
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*/
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private static Descriptor ConvertBQTableSchemaToProtoDescriptorImpl(
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Table.TableSchema BQTableSchema,
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String scope,
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HashMap<ImmutableList<Table.TableFieldSchema>, Descriptor> dependencyMap)
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throws Descriptors.DescriptorValidationException {
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List<FileDescriptor> dependenciesList = new ArrayList<FileDescriptor>();
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List<FieldDescriptorProto> fields = new ArrayList<FieldDescriptorProto>();
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int index = 1;
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for (Table.TableFieldSchema BQTableField : BQTableSchema.getFieldsList()) {
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String currentScope = scope + "__" + BQTableField.getName();
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if (BQTableField.getType() == Table.TableFieldSchema.Type.STRUCT) {
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ImmutableList<Table.TableFieldSchema> fieldList =
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ImmutableList.copyOf(BQTableField.getFieldsList());
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if (dependencyMap.containsKey(fieldList)) {
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Descriptor descriptor = dependencyMap.get(fieldList);
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dependenciesList.add(descriptor.getFile());
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fields.add(ConvertBQTableFieldToProtoField(BQTableField, index++, descriptor.getName()));
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} else {
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Descriptor descriptor =
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ConvertBQTableSchemaToProtoDescriptorImpl(
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Table.TableSchema.newBuilder().addAllFields(fieldList).build(),
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currentScope,
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dependencyMap);
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dependenciesList.add(descriptor.getFile());
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dependencyMap.put(fieldList, descriptor);
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fields.add(ConvertBQTableFieldToProtoField(BQTableField, index++, currentScope));
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}
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} else {
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fields.add(ConvertBQTableFieldToProtoField(BQTableField, index++, currentScope));
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}
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}
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FileDescriptor[] dependenciesArray = new FileDescriptor[dependenciesList.size()];
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dependenciesArray = dependenciesList.toArray(dependenciesArray);
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DescriptorProto descriptorProto =
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DescriptorProto.newBuilder().setName(scope).addAllField(fields).build();
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FileDescriptorProto fileDescriptorProto =
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FileDescriptorProto.newBuilder().addMessageType(descriptorProto).build();
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FileDescriptor fileDescriptor =
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FileDescriptor.buildFrom(fileDescriptorProto, dependenciesArray);
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Descriptor descriptor = fileDescriptor.findMessageTypeByName(scope);
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return descriptor;
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}
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/**
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* Converts a BQTableField to ProtoField
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*
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* @param BQTableField BQ Field used to construct a FieldDescriptorProto
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* @param index Index for protobuf fields.
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* @param scope used to name descriptors
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*/
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private static FieldDescriptorProto ConvertBQTableFieldToProtoField(
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Table.TableFieldSchema BQTableField, int index, String scope) {
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Table.TableFieldSchema.Mode mode = BQTableField.getMode();
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String fieldName = BQTableField.getName();
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if (BQTableField.getType() == Table.TableFieldSchema.Type.STRUCT) {
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return FieldDescriptorProto.newBuilder()
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.setName(fieldName)
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.setTypeName(scope)
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.setLabel((FieldDescriptorProto.Label) BQTableSchemaModeMap.get(mode))
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.setNumber(index)
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.build();
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}
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return FieldDescriptorProto.newBuilder()
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.setName(fieldName)
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.setType((FieldDescriptorProto.Type) BQTableSchemaTypeMap.get(BQTableField.getType()))
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.setLabel((FieldDescriptorProto.Label) BQTableSchemaModeMap.get(mode))
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.setNumber(index)
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.build();
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}
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}

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