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https://issues.apache.org/jira/browse/BEAM-7174?focusedWorklogId=240725&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-240725
]
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_r281871409
##########
File path:
sdks/java/core/src/main/java/org/apache/beam/sdk/schemas/transforms/DropFields.java
##########
@@ -0,0 +1,144 @@
+/*
+ * 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 java.util.Map;
+import java.util.Set;
+import java.util.stream.Collectors;
+import org.apache.beam.sdk.schemas.FieldAccessDescriptor;
+import org.apache.beam.sdk.schemas.Schema;
+import org.apache.beam.sdk.schemas.Schema.Field;
+import org.apache.beam.sdk.schemas.Schema.FieldType;
+import org.apache.beam.sdk.transforms.PTransform;
+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.Maps;
+import org.apache.beam.vendor.guava.v20_0.com.google.common.collect.Sets;
+
+/**
+ * A transform to drop fields from a schema.
+ *
+ * <p>This transform acts as the inverse of the {@link Select} transform. A
list of fields to drop
+ * is specified, and all fields in the schema that are not specified are
selected. For example:
+ *
+ * <pre>{@code @DefaultSchema(JavaFieldSchema.class)
+ * public class UserEvent {
+ * public String userId;
+ * public String eventId;
+ * public int eventType;
+ * public Location location;
+ * }}</pre>
+ *
+ * <pre>{@code @DefaultSchema(JavaFieldSchema.class)
+ * public class Location {
+ * public double latitude;
+ * public double longtitude;
+ * }
+ *
+ * PCollection<UserEvent> events = readUserEvents();
+ * // Drop the location field.
+ * PCollection<Row> noLocation = events.apply(DropFields.fields("location"));
+ * // Drop the latitude field.
+ * PCollection<Row> noLatitude =
events.apply(DropFields.fields("location.latitude"));
+ * }</pre>
+ */
+public class DropFields {
+ public static <T> Inner<T> fields(String... fields) {
+ return fields(FieldAccessDescriptor.withFieldNames(fields));
+ }
+
+ public static <T> Inner<T> fields(Integer... fieldIds) {
+ return fields(FieldAccessDescriptor.withFieldIds(fieldIds));
+ }
+
+ public static <T> Inner<T> fields(FieldAccessDescriptor fieldsToDrop) {
+ return new Inner<>(fieldsToDrop);
+ }
+
+ /** Implementation class for DropFields. */
+ public static class Inner<T> extends PTransform<PCollection<T>,
PCollection<Row>> {
+ private final FieldAccessDescriptor fieldsToDrop;
+
+ private Inner(FieldAccessDescriptor fieldsToDrop) {
+ this.fieldsToDrop = fieldsToDrop;
+ }
+
+ FieldAccessDescriptor complement(Schema inputSchema, FieldAccessDescriptor
input) {
+ Set<String> fieldNamesToSelect = Sets.newHashSet();
+ Map<FieldAccessDescriptor.FieldDescriptor, FieldAccessDescriptor>
nestedFieldsToSelect =
+ Maps.newHashMap();
+ for (int i = 0; i < inputSchema.getFieldCount(); ++i) {
+ if (input.fieldIdsAccessed().contains(i)) {
+ // This field is selected, so exclude it from the complement.
+ continue;
+ }
+ Field field = inputSchema.getField(i);
+ Map<Integer, FieldAccessDescriptor.FieldDescriptor> nestedFields =
+ input.getNestedFieldsAccessed().entrySet().stream()
+ .map(Map.Entry::getKey)
+ .collect(Collectors.toMap(k -> k.getFieldId(), k -> k));
+
+ FieldAccessDescriptor.FieldDescriptor fieldDescriptor =
nestedFields.get(i);
+ if (fieldDescriptor != null) {
+ // Some subfields are selected, so recursively calculate the
complementary subfields to
+ // select.
+ FieldType fieldType = inputSchema.getField(i).getType();
+ for (FieldAccessDescriptor.FieldDescriptor.Qualifier qualifier :
+ fieldDescriptor.getQualifiers()) {
+ switch (qualifier.getKind()) {
+ case LIST:
+ fieldType = fieldType.getCollectionElementType();
+ break;
+ case MAP:
+ fieldType = fieldType.getMapValueType();
+ break;
+ default:
+ throw new RuntimeException("Unexpected field descriptor
type.");
+ }
+ }
+ checkArgument(fieldType.getTypeName().isCompositeType());
+ FieldAccessDescriptor nestedDescriptor =
+ input.getNestedFieldsAccessed().get(fieldDescriptor);
+ nestedFieldsToSelect.put(
+ fieldDescriptor, complement(fieldType.getRowSchema(),
nestedDescriptor));
+ } else {
+ // Neither the field nor the subfield is selected. This means we
should select it.
+ fieldNamesToSelect.add(field.getName());
+ }
+ }
+
+ FieldAccessDescriptor fieldAccess =
FieldAccessDescriptor.withFieldNames(fieldNamesToSelect);
+ for (Map.Entry<FieldAccessDescriptor.FieldDescriptor,
FieldAccessDescriptor> entry :
+ nestedFieldsToSelect.entrySet()) {
+ fieldAccess = fieldAccess.withNestedField(entry.getKey(),
entry.getValue());
+ }
+ return fieldAccess.resolve(inputSchema);
+ }
+
+ @Override
+ public PCollection<Row> expand(PCollection<T> input) {
+ Schema inputSchema = input.getSchema();
+ FieldAccessDescriptor selectDescriptor =
+ complement(inputSchema, fieldsToDrop.resolve(inputSchema));
+
+ return Select.<T>fieldAccess(selectDescriptor).expand(input);
Review comment:
Is there a reason why we call the `expand` function here explicitly, instead
of doing
`return input.apply(Select.<T>fieldAccess(selectDescriptor));`
as usual?
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Issue Time Tracking
-------------------
Worklog Id: (was: 240725)
Time Spent: 1.5h (was: 1h 20m)
> 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: 1.5h
> Remaining Estimate: 0h
>
> We need transforms to add fields, remove fields, and rename fields.
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