co.cask.hydrator.common.HiveSchemaConverter Maven / Gradle / Ivy
/*
* Copyright © 2014-2016 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 co.cask.hydrator.common;
import co.cask.cdap.api.data.schema.Schema;
import co.cask.cdap.api.data.schema.UnsupportedTypeException;
import java.util.Iterator;
import java.util.Map;
/**
* Helper class for converting a {@link Schema} into a hive schema.
*/
public final class HiveSchemaConverter {
private HiveSchemaConverter() { }
/**
* Translate the given schema into a hive schema. Assumes the input schema is not recursive.
*
* @param schema schema to translate.
* @return hive schema that can be used in a create statement.
*/
public static String toHiveSchema(Schema schema) throws UnsupportedTypeException {
if (schema.getType() != Schema.Type.RECORD || schema.getFields().size() < 1) {
throw new UnsupportedTypeException("Schema must be of type record and have at least one field.");
}
StringBuilder builder = new StringBuilder();
builder.append("(");
// schema is guaranteed to have at least one field, and all field names are guaranteed to be unique.
Iterator fieldIter = schema.getFields().iterator();
appendField(builder, fieldIter.next(), false);
while (fieldIter.hasNext()) {
builder.append(", ");
appendField(builder, fieldIter.next(), false);
}
builder.append(")");
return builder.toString();
}
public static void appendType(StringBuilder builder, Schema schema) throws UnsupportedTypeException {
switch (schema.getType()) {
case NULL:
break;
case ENUM:
builder.append("string");
break;
case BOOLEAN:
builder.append("boolean");
break;
case INT:
builder.append("int");
break;
case LONG:
builder.append("bigint");
break;
case FLOAT:
builder.append("float");
break;
case DOUBLE:
builder.append("double");
break;
case BYTES:
builder.append("binary");
break;
case STRING:
builder.append("string");
break;
case ARRAY:
// array
builder.append("array<");
appendType(builder, schema.getComponentSchema());
builder.append(">");
break;
case MAP:
// map
builder.append("map<");
Map.Entry mapSchema = schema.getMapSchema();
appendType(builder, mapSchema.getKey());
builder.append(",");
appendType(builder, mapSchema.getValue());
builder.append(">");
break;
case RECORD:
//struct>
builder.append("struct<");
Iterator fieldIter = schema.getFields().iterator();
appendField(builder, fieldIter.next(), true);
while (fieldIter.hasNext()) {
builder.append(",");
appendField(builder, fieldIter.next(), true);
}
builder.append(">");
break;
case UNION:
// if something is nullable, it is a union of null and the other type.
if (schema.isNullable()) {
appendType(builder, schema.getNonNullable());
} else {
// TODO: support hive unions
throw new UnsupportedTypeException("Unions are currently not supported");
}
}
}
private static void appendField(StringBuilder builder, Schema.Field field, boolean inStruct)
throws UnsupportedTypeException {
String name = field.getName();
builder.append(name);
// structs look like "struct>"
// outside a struct fields look like "name1 string, name2 array"
builder.append(inStruct ? ":" : " ");
appendType(builder, field.getSchema());
}
}
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