Github user shivaram commented on a diff in the pull request: https://github.com/apache/spark/pull/4173#discussion_r23627816 --- Diff: sql/core/src/main/scala/org/apache/spark/sql/DataFrame.scala --- @@ -0,0 +1,606 @@ +/* +* 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.spark.sql + +import scala.language.implicitConversions +import scala.reflect.ClassTag +import scala.collection.JavaConversions._ + +import java.util.{ArrayList, List => JList} + +import com.fasterxml.jackson.core.JsonFactory +import net.razorvine.pickle.Pickler + +import org.apache.spark.annotation.Experimental +import org.apache.spark.rdd.RDD +import org.apache.spark.api.java.JavaRDD +import org.apache.spark.api.python.SerDeUtil +import org.apache.spark.storage.StorageLevel +import org.apache.spark.sql.catalyst.ScalaReflection +import org.apache.spark.sql.catalyst.analysis.UnresolvedRelation +import org.apache.spark.sql.catalyst.expressions._ +import org.apache.spark.sql.catalyst.expressions.{Literal => LiteralExpr} +import org.apache.spark.sql.catalyst.plans.{JoinType, Inner} +import org.apache.spark.sql.catalyst.plans.logical._ +import org.apache.spark.sql.execution.{LogicalRDD, EvaluatePython} +import org.apache.spark.sql.json.JsonRDD +import org.apache.spark.sql.types.{NumericType, StructType} +import org.apache.spark.util.Utils + + +/** + * A collection of rows that have the same columns. + * + * A [[DataFrame]] is equivalent to a relational table in Spark SQL, and can be created using + * various functions in [[SQLContext]]. + * {{{ + * val people = sqlContext.parquetFile("...") + * }}} + * + * Once created, it can be manipulated using the various domain-specific-language (DSL) functions + * defined in: [[DataFrame]] (this class), [[Column]], and [[dsl]] for Scala DSL. + * + * To select a column from the data frame, use the apply method: + * {{{ + * val ageCol = people("age") // in Scala + * Column ageCol = people.apply("age") // in Java + * }}} + * + * Note that the [[Column]] type can also be manipulated through its various functions. + * {{ + * // The following creates a new column that increases everybody's age by 10. + * people("age") + 10 // in Scala + * }} + * + * A more concrete example: + * {{{ + * // To create DataFrame using SQLContext + * val people = sqlContext.parquetFile("...") + * val department = sqlContext.parquetFile("...") + * + * people.filter("age" > 30) + * .join(department, people("deptId") === department("id")) + * .groupBy(department("name"), "gender") + * .agg(avg(people("salary")), max(people("age"))) + * }}} + */ +// TODO: Improve documentation. +class DataFrame protected[sql]( + val sqlContext: SQLContext, + private val baseLogicalPlan: LogicalPlan, + operatorsEnabled: Boolean) + extends DataFrameSpecificApi with RDDApi[Row] { + + protected[sql] def this(sqlContext: Option[SQLContext], plan: Option[LogicalPlan]) = + this(sqlContext.orNull, plan.orNull, sqlContext.isDefined && plan.isDefined) + + protected[sql] def this(sqlContext: SQLContext, plan: LogicalPlan) = this(sqlContext, plan, true) + + @transient protected[sql] lazy val queryExecution = sqlContext.executePlan(baseLogicalPlan) + + @transient protected[sql] val logicalPlan: LogicalPlan = baseLogicalPlan match { + // For various commands (like DDL) and queries with side effects, we force query optimization to + // happen right away to let these side effects take place eagerly. + case _: Command | _: InsertIntoTable | _: CreateTableAsSelect[_] |_: WriteToFile => + LogicalRDD(queryExecution.analyzed.output, queryExecution.toRdd)(sqlContext) + case _ => + baseLogicalPlan + } + + /** + * An implicit conversion function internal to this class for us to avoid doing + * "new DataFrame(...)" everywhere. + */ + private[this] implicit def toDataFrame(logicalPlan: LogicalPlan): DataFrame = { + new DataFrame(sqlContext, logicalPlan, true) + } + + /** Return the list of numeric columns, useful for doing aggregation. */ + protected[sql] def numericColumns: Seq[Expression] = { + schema.fields.filter(_.dataType.isInstanceOf[NumericType]).map { n => + logicalPlan.resolve(n.name, sqlContext.analyzer.resolver).get + } + } + + /** Resolve a column name into a Catalyst [[NamedExpression]]. */ + protected[sql] def resolve(colName: String): NamedExpression = { + logicalPlan.resolve(colName, sqlContext.analyzer.resolver).getOrElse( + throw new RuntimeException(s"""Cannot resolve column name "$colName"""")) + } + + /** Left here for compatibility reasons. */ + @deprecated("1.3.0", "use toDataFrame") + def toSchemaRDD: DataFrame = this + + /** + * Return the object itself. Used to force an implicit conversion from RDD to DataFrame in Scala. + */ + def toDF: DataFrame = this + + /** Return the schema of this [[DataFrame]]. */ + override def schema: StructType = queryExecution.analyzed.schema --- End diff -- Can we add a new higher-level type for `schema` as well ? It is painful as a user to dig into `StructType` etc. -- Similarly while applying a schema to an RDD it would be good to have a higher-level type / constructor.
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