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https://issues.apache.org/jira/browse/BEAM-5918?focusedWorklogId=160713&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-160713
]
ASF GitHub Bot logged work on BEAM-5918:
----------------------------------------
Author: ASF GitHub Bot
Created on: 30/Oct/18 16:28
Start Date: 30/Oct/18 16:28
Worklog Time Spent: 10m
Work Description: kanterov commented on a change in pull request #6888:
[BEAM-5918] [WIP] Add Cast transform for Rows
URL: https://github.com/apache/beam/pull/6888#discussion_r229382088
##########
File path:
sdks/java/core/src/main/java/org/apache/beam/sdk/schemas/transforms/Cast.java
##########
@@ -0,0 +1,582 @@
+/*
+ * 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.sdk.schemas.Schema.TypeName.ARRAY;
+import static org.apache.beam.sdk.schemas.Schema.TypeName.INT16;
+import static org.apache.beam.sdk.schemas.Schema.TypeName.INT32;
+import static org.apache.beam.sdk.schemas.Schema.TypeName.INT64;
+import static org.apache.beam.sdk.schemas.Schema.TypeName.MAP;
+import static org.apache.beam.sdk.schemas.Schema.TypeName.ROW;
+
+import com.google.auto.value.AutoValue;
+import com.google.common.annotations.VisibleForTesting;
+import com.google.common.base.Joiner;
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.Maps;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+import org.apache.beam.sdk.annotations.Experimental;
+import org.apache.beam.sdk.schemas.FieldAccessDescriptor;
+import org.apache.beam.sdk.schemas.Schema;
+import org.apache.beam.sdk.schemas.Schema.TypeName;
+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.KV;
+import org.apache.beam.sdk.values.PCollection;
+import org.apache.beam.sdk.values.Row;
+
+/** Set of utilities for casting rows between schemas. */
+@Experimental(Experimental.Kind.SCHEMAS)
+@AutoValue
+public abstract class Cast<T> extends PTransform<PCollection<T>,
PCollection<Row>> {
+
+ public abstract Schema outputSchema();
+
+ public abstract Nullability nullability();
+
+ public abstract Type type();
+
+ public abstract Shape shape();
+
+ /** Builder for {@link Cast}. */
+ @AutoValue.Builder
+ public abstract static class Builder<T> {
+
+ public abstract Builder<T> outputSchema(Schema schema);
+
+ public abstract Builder<T> nullability(Nullability nullability);
+
+ public abstract Builder<T> type(Type type);
+
+ public abstract Builder<T> shape(Shape shape);
+
+ public abstract Cast<T> build();
+ }
+
+ public static <T> Builder<T> builder() {
+ return new AutoValue_Cast.Builder<T>();
+ }
+
+ public static <T> Cast<T> to(Schema outputSchema) {
+ return Cast.<T>builder()
+ .outputSchema(outputSchema)
+ .nullability(Nullability.IGNORE)
+ .type(Type.WIDEN)
+ .shape(Shape.PROJECTION)
+ .build();
+ }
+
+ public List<CompatibilityError> compatibility(Schema inputSchema) {
+ return Inference.compatibility(inputSchema, outputSchema(), nullability(),
type(), shape());
+ }
+
+ public void verifyCompatibility(Schema inputSchema) {
+ List<CompatibilityError> errors = compatibility(inputSchema);
+
+ if (!errors.isEmpty()) {
+ String reason =
+ errors
+ .stream()
+ .map(x -> Joiner.on('.').join(x.path()) + ": " + x.message())
+ .collect(Collectors.joining("\n\t"));
+
+ throw new IllegalArgumentException("Cast isn't compatible:\n\t" +
reason);
+ }
+ }
+
+ @Override
+ public PCollection<Row> expand(PCollection<T> input) {
+ Schema inputSchema = input.getSchema();
+
+ verifyCompatibility(inputSchema);
+
+ return input
+ .apply(
+ ParDo.of(
+ new DoFn<T, Row>() {
+ // TODO: This should be the same as resolved so that Beam
knows which fields
+ // are being accessed. Currently Beam only supports wildcard
descriptors.
+ // Once BEAM-4457 is fixed, fix this.
+ @FieldAccess("filterFields")
+ final FieldAccessDescriptor fieldAccessDescriptor =
+ FieldAccessDescriptor.withAllFields();
+
+ @ProcessElement
+ public void process(@FieldAccess("filterFields") Row row,
OutputReceiver<Row> r) {
+ r.output(castRow(row, inputSchema, outputSchema()));
+ }
+ }))
+ .setRowSchema(outputSchema());
+ }
+
+ @VisibleForTesting
+ static Row castRow(Row input, Schema inputSchema, Schema outputSchema) {
Review comment:
@kennknowles I was thinking about it, but I'm not sure it's stable enough.
What is the policy regarding version compatibility?
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Issue Time Tracking
-------------------
Worklog Id: (was: 160713)
Time Spent: 1h 10m (was: 1h)
> Add Cast transform for Rows
> ---------------------------
>
> Key: BEAM-5918
> URL: https://issues.apache.org/jira/browse/BEAM-5918
> Project: Beam
> Issue Type: Improvement
> Components: sdk-java-core
> Reporter: Gleb Kanterov
> Assignee: Kenneth Knowles
> Priority: Major
> Time Spent: 1h 10m
> Remaining Estimate: 0h
>
> There is a need for a generic transform that given two Row schemas will
> convert rows between them. There must be a possibility to opt-out from
> certain kind of conversions, for instance, converting ints to shorts can
> cause overflow. Another example, a schema could have a nullable field, but
> never have NULL value in practice, because it was filtered out.
> What is needed:
> - widening values (e.g., int -> long)
> - narrowwing (e.g., int -> short)
> - runtime check for overflow while narrowing
> - ignoring nullability (nullable=true -> nullable=false)
> - weakening nullability (nullable=false -> nullable=true)
> - projection (Schema(a: Int32, b: Int32) -> Schema(a: Int32))
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