reuvenlax commented on a change in pull request #11290: [BEAM-9670] Fix nullability widening in CoGroup key resolution URL: https://github.com/apache/beam/pull/11290#discussion_r402457753
########## File path: sdks/java/core/src/main/java/org/apache/beam/sdk/schemas/SchemaUtils.java ########## @@ -0,0 +1,101 @@ +/* + * 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; + +import org.apache.beam.sdk.schemas.Schema.FieldType; + +/** A set of utility functions for schemas. */ +public class SchemaUtils { + /** + * Given two schema that have matching types, return a nullable-widened schema. + * + * <p>The schemas must have matching types, except for field names which can differ. The returned + * schema will contain the field names in the first schema. All field types will be nullable if + * the corresponding field type is nullable in either of the input schemas. + */ + public static Schema mergeWideningNullable(Schema schema1, Schema schema2) { + if (schema1.getFieldCount() != schema2.getFieldCount()) { + throw new IllegalArgumentException( + "Cannot merge schemas with different numbers of fields. " + + "schema1: " + + schema1 + + " schema2: " + + schema2); + } + Schema.Builder builder = Schema.builder(); + for (int i = 0; i < schema1.getFieldCount(); ++i) { + String name = schema1.getField(i).getName(); + builder.addField( + name, widenNullableTypes(schema1.getField(i).getType(), schema2.getField(i).getType())); + } + return builder.build(); + } + + static FieldType widenNullableTypes(FieldType fieldType1, FieldType fieldType2) { + if (fieldType1.getTypeName() != fieldType2.getTypeName()) { + throw new IllegalArgumentException( + "Cannot merge two types: " + + fieldType1.getTypeName() + + " and " + + fieldType2.getTypeName()); + } + + FieldType result; + switch (fieldType1.getTypeName()) { + case ROW: + result = + FieldType.row( + mergeWideningNullable(fieldType1.getRowSchema(), fieldType2.getRowSchema())); + break; + case ARRAY: + FieldType arrayElementType = + widenNullableTypes( + fieldType1.getCollectionElementType(), fieldType2.getCollectionElementType()); + result = FieldType.array(arrayElementType); + break; + case ITERABLE: + FieldType iterableElementType = + widenNullableTypes( + fieldType1.getCollectionElementType(), fieldType2.getCollectionElementType()); + result = FieldType.iterable(iterableElementType); + break; + case MAP: + FieldType keyType = + widenNullableTypes(fieldType1.getMapKeyType(), fieldType2.getMapKeyType()); + FieldType valueType = + widenNullableTypes(fieldType1.getMapValueType(), fieldType2.getMapValueType()); + result = FieldType.map(keyType, valueType); + break; + case LOGICAL_TYPE: + if (!fieldType1 + .getLogicalType() + .getIdentifier() + .equals(fieldType2.getLogicalType().getIdentifier())) { + throw new IllegalArgumentException( + "Logical types don't match and cannot be merged: " + + fieldType1.getLogicalType().getIdentifier() + + ".v.s" + + fieldType2.getLogicalType().getIdentifier()); + } + // fall through + default: + result = fieldType1; + } + return result.withNullable(fieldType1.getNullable() || fieldType2.getNullable()); Review comment: Maybe? I'm not sure visitor per se, as we don't require double dispatch. However we might consider generalizing the recursive tree walk. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: [email protected] With regards, Apache Git Services
