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https://issues.apache.org/jira/browse/BEAM-7174?focusedWorklogId=240712&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-240712
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ASF GitHub Bot logged work on BEAM-7174:
----------------------------------------
Author: ASF GitHub Bot
Created on: 12/May/19 06:37
Start Date: 12/May/19 06:37
Worklog Time Spent: 10m
Work Description: robinyqiu commented on pull request #8425: [BEAM-7174]
Add schema modification transforms
URL: https://github.com/apache/beam/pull/8425#discussion_r283121044
##########
File path:
sdks/java/core/src/main/java/org/apache/beam/sdk/schemas/transforms/AddFields.java
##########
@@ -0,0 +1,432 @@
+/*
+ * 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 org.apache.beam.sdk.schemas.transforms;
+
+import static
org.apache.beam.vendor.guava.v20_0.com.google.common.base.Preconditions.checkArgument;
+import static
org.apache.beam.vendor.guava.v20_0.com.google.common.base.Preconditions.checkNotNull;
+
+import com.google.auto.value.AutoValue;
+import java.io.Serializable;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Collectors;
+import javax.annotation.Nullable;
+import org.apache.beam.sdk.schemas.FieldAccessDescriptor;
+import
org.apache.beam.sdk.schemas.FieldAccessDescriptor.FieldDescriptor.Qualifier;
+import
org.apache.beam.sdk.schemas.FieldAccessDescriptor.FieldDescriptor.Qualifier.Kind;
+import org.apache.beam.sdk.schemas.Schema;
+import org.apache.beam.sdk.schemas.Schema.FieldType;
+import org.apache.beam.sdk.transforms.DoFn;
+import org.apache.beam.sdk.transforms.PTransform;
+import org.apache.beam.sdk.transforms.ParDo;
+import org.apache.beam.sdk.values.PCollection;
+import org.apache.beam.sdk.values.Row;
+import
org.apache.beam.vendor.guava.v20_0.com.google.common.collect.ImmutableList;
+import org.apache.beam.vendor.guava.v20_0.com.google.common.collect.Iterables;
+import org.apache.beam.vendor.guava.v20_0.com.google.common.collect.Lists;
+import org.apache.beam.vendor.guava.v20_0.com.google.common.collect.Maps;
+import org.apache.beam.vendor.guava.v20_0.com.google.common.collect.Multimap;
+import org.apache.beam.vendor.guava.v20_0.com.google.common.collect.Multimaps;
+
+/**
+ * A transform to add new nullable fields to a PCollection's schema. Elements
are extended to have
+ * the new schema. By default new fields are nullable, and input rows will be
extended to the new
+ * schema by inserting null values. However explicit default values for new
fields can be set using
+ * {@link Inner#field(String, Schema.FieldType, Object)}. Nested fields can be
added as well.
+ *
+ * <p>Example use:
+ *
+ * <pre>{@code PCollection<Event> events = readEvents();
+ * PCollection<Row> augmentedEvents =
+ * events.apply(AddFields.<Event>create()
+ * .field("userId", FieldType.STRING)
+ * .field("location.zipcode", FieldType.INT32)
+ * .field("userDetails.isSpecialUser", "FieldType.BOOLEAN", false));
+ * }</pre>
+ */
+public class AddFields {
+ public static <T> Inner<T> create() {
+ return new Inner<>();
+ }
+
+ /** Inner PTransform for AddFields. */
+ public static class Inner<T> extends PTransform<PCollection<T>,
PCollection<Row>> {
+ /** Internal object representing a new field added. */
+ @AutoValue
+ abstract static class NewField implements Serializable {
+ abstract String getName();
+
+ abstract FieldAccessDescriptor getDescriptor();
+
+ abstract Schema.FieldType getFieldType();
+
+ @Nullable
+ abstract Object getDefaultValue();
+
+ @AutoValue.Builder
+ abstract static class Builder {
+ abstract Builder setName(String name);
+
+ abstract Builder setDescriptor(FieldAccessDescriptor descriptor);
+
+ abstract Builder setFieldType(Schema.FieldType fieldType);
+
+ abstract Builder setDefaultValue(@Nullable Object defaultValue);
+
+ abstract NewField build();
+ }
+
+ abstract Builder toBuilder();
+
+ static NewField of(
+ FieldAccessDescriptor fieldAccessDescriptor,
+ Schema.FieldType fieldType,
+ Object defaultValue) {
+ return new AutoValue_AddFields_Inner_NewField.Builder()
+ .setName(getName(fieldAccessDescriptor))
+ .setDescriptor(fieldAccessDescriptor)
+ .setFieldType(fieldType)
+ .setDefaultValue(defaultValue)
+ .build();
+ }
+
+ // If this field represents a nested value, pop the
FieldAccessDescriptor one level down.
+ NewField descend() {
+ FieldAccessDescriptor descriptor =
+
Iterables.getOnlyElement(getDescriptor().getNestedFieldsAccessed().values());
+ return
toBuilder().setDescriptor(descriptor).setName(getName(descriptor)).build();
+ }
+
+ static String getName(FieldAccessDescriptor descriptor) {
+ if (!descriptor.getFieldsAccessed().isEmpty()) {
+ return Iterables.getOnlyElement(descriptor.fieldNamesAccessed());
+ } else {
+ return
Iterables.getOnlyElement(descriptor.nestedFieldsByName().keySet());
+ }
+ }
+
+ FieldAccessDescriptor.FieldDescriptor getFieldDescriptor() {
+ if (!getDescriptor().getFieldsAccessed().isEmpty()) {
+ return Iterables.getOnlyElement(getDescriptor().getFieldsAccessed());
+ } else {
+ return
Iterables.getOnlyElement(getDescriptor().getNestedFieldsAccessed().keySet());
+ }
+ }
+ }
+
+ /** This class encapsulates all data needed to add a a new field to the
schema. */
+ @AutoValue
+ abstract static class AddFieldsInformation implements Serializable {
+ // The new output fieldtype after adding the new field.
+ @Nullable
+ abstract Schema.FieldType getOutputFieldType();
+
+ // A list of default values corresponding to this level of the schema.
+ abstract List<Object> getDefaultValues();
+
+ // A list of nested values. This list corresponds to the output schema
fields, and is
+ // populated for fields that
+ // have new nested values. For other fields, the list contains a null
value.
+ abstract List<AddFieldsInformation> getNestedNewValues();
+
+ @AutoValue.Builder
+ abstract static class Builder {
+ abstract AddFieldsInformation.Builder
setOutputFieldType(Schema.FieldType outputFieldType);
+
+ abstract AddFieldsInformation.Builder setDefaultValues(List<Object>
defaultValues);
+
+ abstract AddFieldsInformation.Builder setNestedNewValues(
+ List<AddFieldsInformation> nestedNewValues);
+
+ abstract AddFieldsInformation build();
+ }
+
+ abstract AddFieldsInformation.Builder toBuilder();
+
+ static AddFieldsInformation of(
+ Schema.FieldType outputFieldType,
+ List<Object> defaultValues,
+ List<AddFieldsInformation> nestedNewValues) {
+ return new AutoValue_AddFields_Inner_AddFieldsInformation.Builder()
+ .setOutputFieldType(outputFieldType)
+ .setDefaultValues(defaultValues)
+ .setNestedNewValues(nestedNewValues)
+ .build();
+ }
+ }
+
+ private final List<NewField> newFields;
+
+ private Inner() {
+ this.newFields = Collections.emptyList();
+ }
+
+ private Inner(List<NewField> newFields) {
+ this.newFields = newFields;
+ }
+
+ /**
+ * Add a new field of the specified type. The new field will be nullable
and will be filled in
+ * with null values.
+ */
+ public Inner<T> field(String fieldName, Schema.FieldType fieldType) {
+ return field(fieldName, fieldType.withNullable(true), null);
+ }
+
+ /**
+ * Add a new field of the specified type. The new field will be filled in
with the specified
+ * value.
+ */
+ public Inner<T> field(String fieldName, Schema.FieldType fieldType, Object
defaultValue) {
+ if (defaultValue == null) {
+ checkArgument(fieldType.getNullable());
+ }
+
+ FieldAccessDescriptor descriptor =
FieldAccessDescriptor.withFieldNames(fieldName);
+ checkArgument(descriptor.referencesSingleField());
+ List<NewField> fields =
+ ImmutableList.<NewField>builder()
+ .addAll(newFields)
+ .add(NewField.of(descriptor, fieldType, defaultValue))
+ .build();
+ return new Inner<>(fields);
+ }
+
+ private AddFieldsInformation getAddFieldsInformation(
+ Schema inputSchema, Collection<NewField> fieldsToAdd) {
+ List<NewField> newTopLevelFields =
+ fieldsToAdd.stream()
+ .filter(n -> !n.getDescriptor().getFieldsAccessed().isEmpty())
+ .collect(Collectors.toList());
+ List<NewField> newNestedFields =
+ fieldsToAdd.stream()
+ .filter(n ->
!n.getDescriptor().getNestedFieldsAccessed().isEmpty())
+ .collect(Collectors.toList());
+ // Group all nested fields together by the field at the current level.
For example, if adding
+ // a.b, a.c, a.d
+ // this map will contain a -> {a.b, a.c, a.d}/
+ Multimap<String, NewField> newNestedFieldsMap =
+ Multimaps.index(newNestedFields, NewField::getName);
+
+ Map<Integer, AddFieldsInformation> resolvedNestedNewValues =
Maps.newHashMap();
+ Schema.Builder builder = Schema.builder();
+ for (int i = 0; i < inputSchema.getFieldCount(); ++i) {
+ Schema.Field field = inputSchema.getField(i);
+ Collection<NewField> nestedFields =
newNestedFieldsMap.get(field.getName());
+
+ // If this field is a nested field and new subfields are added further
down the tree, add
+ // those subfields before
+ // adding to the current schema. Otherwise we just add this field as
is to the new schema.
+ if (!nestedFields.isEmpty()) {
+ nestedFields =
nestedFields.stream().map(NewField::descend).collect(Collectors.toList());
+
+ AddFieldsInformation nestedInformation =
+ getAddFieldsInformation(field.getType(), nestedFields);
+ field = field.withType(nestedInformation.getOutputFieldType());
+ resolvedNestedNewValues.put(i, nestedInformation);
+ }
+ builder.addField(field);
+ }
+
+ // Add any new fields at this level.
Review comment:
By reading the implementation code here, I see that top-level fields are
added before nested fields. Can we document this in the class level javadoc?
Otherwise this may be confusing to users, e.g. after calling
`pc.apply(AddFields.create().field("new1.nested",
FieldType.STRING).field("new2", FieldType.INT32)`
users may expect a new schema in which `new1` appears before `new2`, which
is not the case.
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Issue Time Tracking
-------------------
Worklog Id: (was: 240712)
Time Spent: 20m (was: 10m)
> Add transforms for modifying schemas
> ------------------------------------
>
> Key: BEAM-7174
> URL: https://issues.apache.org/jira/browse/BEAM-7174
> Project: Beam
> Issue Type: Sub-task
> Components: sdk-java-core
> Reporter: Reuven Lax
> Assignee: Reuven Lax
> Priority: Major
> Time Spent: 20m
> Remaining Estimate: 0h
>
> We need transforms to add fields, remove fields, and rename fields.
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