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https://issues.apache.org/jira/browse/BEAM-5918?focusedWorklogId=161320&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-161320
]
ASF GitHub Bot logged work on BEAM-5918:
----------------------------------------
Author: ASF GitHub Bot
Created on: 31/Oct/18 21:21
Start Date: 31/Oct/18 21:21
Worklog Time Spent: 10m
Work Description: kanterov commented on a change in pull request #6888:
[BEAM-5918] Add Cast transform for Rows
URL: https://github.com/apache/beam/pull/6888#discussion_r229872246
##########
File path:
sdks/java/core/src/main/java/org/apache/beam/sdk/schemas/transforms/Cast.java
##########
@@ -0,0 +1,440 @@
+/*
+ * 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 com.google.auto.value.AutoValue;
+import com.google.common.base.Joiner;
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.Maps;
+import java.io.Serializable;
+import java.math.BigDecimal;
+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 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.Field;
+import org.apache.beam.sdk.schemas.Schema.FieldType;
+import org.apache.beam.sdk.schemas.Schema.TypeName;
+import org.apache.beam.sdk.schemas.utils.SchemaZipFold;
+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;
+
+/** 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 Validator validator();
+
+ public static <T> Cast<T> of(Schema outputSchema, Validator validator) {
+ return new AutoValue_Cast<>(outputSchema, validator);
+ }
+
+ public static <T> Cast<T> widening(Schema outputSchema) {
+ return new AutoValue_Cast<>(outputSchema, Widening.of());
+ }
+
+ public static <T> Cast<T> narrowing(Schema outputSchema) {
+ return new AutoValue_Cast<>(outputSchema, Narrowing.of());
+ }
+
+ /** Describes compatibility errors during casting. */
+ @AutoValue
+ public abstract static class CompatibilityError implements Serializable {
+
+ public abstract List<String> path();
+
+ public abstract String message();
+
+ public static CompatibilityError create(List<String> path, String message)
{
+ return new AutoValue_Cast_CompatibilityError(path, message);
+ }
+ }
+
+ /** Interface for statically validating casts. */
+ public interface Validator extends Serializable {
+ List<CompatibilityError> apply(Schema input, Schema output);
+ }
+
+ /**
+ * Widening changes to type that can represent any possible value of the
original type.
+ *
+ * <p>Standard widening conversions:
+ *
+ * <ul>
+ * <li>BYTE to INT16, INT32, INT64, FLOAT, DOUBLE, DECIMAL
+ * <li>INT16 to INT32, INT64, FLOAT, DOUBLE, DECIMAL
+ * <li>INT32 to INT64, FLOAT, DOUBLE, DECIMAL
+ * <li>INT64 to FLOAT, DOUBLE, DECIMAL
+ * <li>FLOAT to DOUBLE, DECIMAL
+ * <li>DOUBLE to DECIMAL
+ * </ul>
+ *
+ * <p>Row widening:
+ *
+ * <ul>
+ * <li>wider schema to schema with a subset of fields
Review comment:
Doesn't match with the definition of widening, probably should be only in
narrowing.
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Issue Time Tracking
-------------------
Worklog Id: (was: 161320)
Time Spent: 3.5h (was: 3h 20m)
> 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: Gleb Kanterov
> Priority: Major
> Time Spent: 3.5h
> 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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