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111 changes: 111 additions & 0 deletions
111
wrangler-core/src/main/java/io/cdap/wrangler/utils/DirectiveOutputSchemaGenerator.java
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| /* | ||
| * Copyright © 2023 Cask Data, Inc. | ||
| * | ||
| * Licensed 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 io.cdap.wrangler.utils; | ||
|
|
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| import io.cdap.cdap.api.data.schema.Schema; | ||
| import io.cdap.wrangler.api.Directive; | ||
| import io.cdap.wrangler.api.Pair; | ||
| import io.cdap.wrangler.api.Row; | ||
|
|
||
| import java.util.LinkedHashMap; | ||
| import java.util.LinkedList; | ||
| import java.util.List; | ||
| import java.util.Map; | ||
| import javax.annotation.Nullable; | ||
|
|
||
| /** | ||
| * This class can be used to generate the output schema for the output data of a directive. It maintains a map of | ||
| * output fields present across all output rows after applying a directive. This map is used to generate the schema | ||
| * if the directive does not return a custom output schema. | ||
| */ | ||
| public class DirectiveOutputSchemaGenerator { | ||
| private final SchemaConverter schemaGenerator; | ||
| private final Map<String, Object> outputFieldMap; | ||
| private final Directive directive; | ||
|
|
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| public DirectiveOutputSchemaGenerator(Directive directive, SchemaConverter schemaGenerator) { | ||
| this.directive = directive; | ||
| this.schemaGenerator = schemaGenerator; | ||
| outputFieldMap = new LinkedHashMap<>(); | ||
| } | ||
|
|
||
| /** | ||
| * Method to add new fields from the given output to the map of fieldName --> value maintained for schema generation. | ||
| * A value is added to the map only if it is absent (or) if the existing value is null and given value is non-null | ||
| * @param output list of output {@link Row}s after applying directive. | ||
| */ | ||
| public void addNewOutputFields(List<Row> output) { | ||
| for (Row row : output) { | ||
| for (Pair<String, Object> field : row.getFields()) { | ||
| String fieldName = field.getFirst(); | ||
| Object fieldValue = field.getSecond(); | ||
| if (outputFieldMap.containsKey(fieldName)) { | ||
| // If existing value is null, override with this non-null value | ||
| if (fieldValue != null && outputFieldMap.get(fieldName) == null) { | ||
| outputFieldMap.put(fieldName, fieldValue); | ||
| } | ||
| } else { | ||
| outputFieldMap.putIfAbsent(fieldName, fieldValue); | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
|
||
| /** | ||
| * Method to get the output schema of the directive. Returns a generated schema based on maintained map of fields | ||
| * only if directive does not return a custom output schema. | ||
| * @param inputSchema input {@link Schema} of the data before applying the directive | ||
| * @return {@link Schema} corresponding to the output data | ||
| */ | ||
| public Schema getDirectiveOutputSchema(Schema inputSchema) throws RecordConvertorException { | ||
| Schema directiveOutputSchema = directive.getOutputSchema(inputSchema); | ||
| return directiveOutputSchema != null ? directiveOutputSchema : generateDirectiveOutputSchema(inputSchema); | ||
| } | ||
|
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| // Given the schema from previous step and output of current directive, generates the directive output schema. | ||
| private Schema generateDirectiveOutputSchema(Schema inputSchema) | ||
| throws RecordConvertorException { | ||
| List<Schema.Field> outputFields = new LinkedList<>(); | ||
| for (String fieldName : outputFieldMap.keySet()) { | ||
| Object fieldValue = outputFieldMap.get(fieldName); | ||
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| Schema existing = inputSchema.getField(fieldName) != null ? inputSchema.getField(fieldName).getSchema() : null; | ||
| Schema generated = fieldValue != null && !isValidSchemaForValue(existing, fieldValue) ? | ||
| schemaGenerator.getSchema(fieldValue, fieldName) : null; | ||
|
|
||
| if (generated != null) { | ||
| outputFields.add(Schema.Field.of(fieldName, generated)); | ||
| } else if (existing != null) { | ||
| outputFields.add(Schema.Field.of(fieldName, existing)); | ||
| } else { | ||
| outputFields.add(Schema.Field.of(fieldName, Schema.of(Schema.Type.NULL))); | ||
| } | ||
| } | ||
| return Schema.recordOf("output", outputFields); | ||
| } | ||
|
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| // Checks whether the provided input schema is of valid type for given object | ||
| private boolean isValidSchemaForValue(@Nullable Schema schema, Object value) throws RecordConvertorException { | ||
| if (schema == null) { | ||
| return false; | ||
| } | ||
| Schema generated = schemaGenerator.getSchema(value, "temp_field_name"); | ||
| generated = generated.isNullable() ? generated.getNonNullable() : generated; | ||
| schema = schema.isNullable() ? schema.getNonNullable() : schema; | ||
| return generated.getLogicalType() == schema.getLogicalType() && generated.getType() == schema.getType(); | ||
| } | ||
| } |
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wrangler-core/src/main/java/io/cdap/wrangler/utils/OutputSchemaGenerator.java
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