Spark Rename Dataset Column

com Example 1 rename allows you to change. Part Operations; The syntax dataset [[parts]] or Part [dataset, parts] can be used to extract parts of a Dataset. Hi, I have a dataset in MDX using an OLE DB connexion. Apache Spark is the next-generation processing engine for big data. Dataset Joins Joining Datasets is done with joinWith , and this behaves similarly to a regular relational join, except the result is a tuple of the different record types as shown in Example 4-11. I'm not sure if you need to rename the API name for this use case to work, or just the label. I am trying to get rid of white spaces from column names - because otherwise the DF cannot be saved as parquet file - and did not find any usefull method for renaming. That means, I can safely remove all these four columns whose names start with ‘assignee’ after the ‘rename’ step. See the Cloud Dataproc Quickstarts for instructions on creating a clus. AgilData / Blog / Engineering / Apache Spark: RDD, DataFrame or Dataset? Apache Spark: RDD, DataFrame or Dataset? January 15, 2016. In this case, it will join the data in the row level instead of aggregating it. This assignment works when the list has the same number of elements as the row and column labels. Spark dataframe split one column into multiple columns using split function April 23, 2018 adarsh 4d Comments Lets say we have dataset as below and we want to split a single column into multiple columns using withcolumn and split functions of dataframe. Well, in CSV we may have column names in the first row, but this is not enough in most cases. Note that, before Spark 2. HoloViews defines an extensible system of interfaces to load, manipulate, and visualize this kind of data,. Well first of all you cannot add columns to dataset, but to datatables but i get your point. Topics to be covered : 1. We are going to load this data, which is in a CSV format, into a DataFrame and then we. Reshaping Data with Pivot in Spark February 16th, 2016. autoBroadcastJoinThreshold to determine if a table should be broadcast. Using rename to change column names is a much better way than before. Using Spark withColumnRenamed – To rename DataFrame column name Spark has a withColumnRenamed function on DataFrame to change a column name. Dataset operations can also be untyped, through various domain-specific-language (DSL) functions defined in: Dataset (this class), Column, and functions. Rate this: Please Sign up or sign in to vote. Renaming SAS Data Sets. The more Spark knows about the data initially, the more optimizations are available for you. 6 saw a new DataSet API. Remember that the main advantage to using Spark DataFrames vs those other programs is that Spark can handle data across many RDDs, huge data sets that would never fit on a single computer. py to examples/ml and rename to dataframe_example. 3, and Spark 1. The rows and column values may be scalar values, lists, slice objects or boolean. To change column names using rename function in Pandas, one needs to specify a mapper, a dictionary with old name as keys and new name as values. We have to use the FORCE option because the base data set no longer exists after the rename. Multi-Column Key and Value – Reduce a Tuple in Spark Posted on February 12, 2015 by admin In many tutorials key-value is typically a pair of single scalar values, for example (‘Apple’, 7). Project Information. _ Create a data frame by reading README. The two configuration parameters for caching are. Join the world's most active Tech Community! Welcome back to the World's most active Tech Community!. To change column names using rename function in Pandas, one needs to specify a mapper, a dictionary with old name as keys and new name as values. We often need to rename one or multiple columns on Spark DataFrames, especially when columns are nested it becomes complicated. The path to the file. Spark SQL - Column of Dataframe as a List - Databricks. Initializing SparkSession A SparkSession can be used create DataFrame, register DataFrame as tables, execute SQL over tables, cache tables, and read parquet files. PROJECT NAME. Spark – Add new column to Dataset A new column could be added to an existing Dataset using Dataset. Hi, I have a dataset in MDX using an OLE DB connexion. You can vote up the examples you like and your votes will be used in our system to generate more good examples. That’s why each time you open a JSON/CSV/XML dataset in Spark using the simplest API, you wait some time and see jobs executed in WebUI:. Indeed, the sequence of when statements is very repetitive and can be refactored. Temporary columns do not filter any column in the. however can this be accomplished using a procedure like proc datasets? I see the rename option in the proc datasets but apparently this is only used for renaming columns not for the dataset name. AgilData / Blog / Engineering / Apache Spark: RDD, DataFrame or Dataset? Apache Spark: RDD, DataFrame or Dataset? January 15, 2016. To select a column from the Dataset, use apply method in Scala and col in Java. Introduction. These examples are extracted from open source projects. It also creates an accompanying reduced Experimental Design Data Set (EDDS). Flexible Data Ingestion. K-Means only supports numeric columns. union() method to append a Dataset to another with same number of columns. Using StructType — To rename nested elements in Spark Dataframe Changing a column name on nested data is not straight forward and we can do this by creating new schema (with new columns) and using. The flights dataset and a new dataset called airports are already in your workspace. Predicting Song Listens Using Apache Spark. ) and colon (:) yield errors on querying, so they are disallowed in Hive 1. Spreadsheets, relational databases, CSV files, and many other typical data sources fit naturally into this format. Temporary columns do not filter any column in the. In a DataSet with multiple DataTable objects, you can use DataRelation Objects to relate one table to another, to navigate through the tables, and to return child or parent rows from a related table. The major challenge with renaming columns in R is that there is several different ways to do it. As Spark becomes more widely adopted, we have focused on creating higher-level APIs that provide increased opportunities for automatic optimization. SPARK-11895 finished the work of Scala example, here we focus on the Python one. You can define a Dataset JVM objects and then manipulate them using functional transformations ( map , flatMap , filter , and so on) similar to an RDD. Part Operations; The syntax dataset [[parts]] or Part [dataset, parts] can be used to extract parts of a Dataset. One of its features is the unification of the DataFrame and Dataset APIs. Spark SQL - DataFrames - A DataFrame is a distributed collection of data, which is organized into named columns. In our case, the label column (Category) will be encoded to label indices, from 0 to 32; the most frequent label (LARCENY/THEFT) will be indexed as 0. If you wish to rename your columns while displaying it to the user or if you are using tables in joins then you may need to have alias for table names. This has so far been missing in Dataframe API which was restricted you to manipulate data easily at compile time. The input to this code is a csv file which contains 3 columns. 3 introduced the radically different DataFrame API and the recently released Spark 1. The names of the key column(s) must be the same in each table. Define Query parameter with multiple value for MDX query and assign parameter name same as SSRS report parameter. ) and colon (:) yield errors on querying, so they are disallowed in Hive 1. Flexible Data Ingestion. And all those things needs to be carried out without touching the data residing in that dataset. withColumn accepts two arguments: the column name to be added, and the Column and returns a new Dataset. Unnamed rows and columns correspond to lists at those levels. The new Spark DataFrames API is designed to make big data processing on tabular data easier. Other than making column names or table names more readable, alias also helps in making developer life better by writing smaller table names in join conditions. Dataset is a strongly typed data structure dictated by a case class. 6 release introduces a preview of the new Dataset API. Reshaping Data with Pivot in Spark February 16th, 2016. labeling a SAS data set. You can also create free column references from $ -prefixed strings. For example, the Scala code below defines a DataFrame from an RDD of User objects. We've also added some practice exercises that you can try for yourself. GitHub Gist: instantly share code, notes, and snippets. If your data set is large, you will see only a subset of the rows even though the operations will run on the entire data set. How to rename multiple columns of Dataframe in Spark Scala? If you need to select only some columns and rename it this is the another option. In this tutorial we will learn how to rename the column of dataframe in pandas. Easiest way I have found to mass rename dataset columns is by going to the dataset -> explore -> fields link in top left -> find field and click dropdwon arrow -> rename -> input new label for the field. Also see[D] rename group for renaming groups of variables. All, I would like to request your help in guiding me in my attempt to rename all the columns in a SAS dataset. Remember, you already have SparkSession spark and people_df DataFrames available in your workspace. By Andy Grove. rename (name_dict=None, inplace=None, **names) ¶ Returns a new object with renamed variables and dimensions. The caching functionality can be tuned using the setConf method in the SQLContext or HiveContext class. Renaming datasets and columns From time to time, you may need to rename a dataset or individual column header title to make it easier later to build your reports and dashboards. In this case, it will join the data in the row level instead of aggregating it. Solved: Hello I would like to add a new column to the existing data set in Excel and refresh my dashboard. BTW, I find the way suggested by the official documentation to rename columns (i. Hi I have a dataframe (loaded CSV) where the inferredSchema filled the column names from the file. cacheTable("people") Dataset. 6 release introduces a preview of the new Dataset API. 3 introduced the radically different DataFrame API and the recently released Spark 1. Spark; SPARK-13822 Follow-ups of DataFrame/Dataset API unification; SPARK-13880; Rename DataFrame. This includes any datasets in your workspace and datasets in shared workspaces. Using a spreadsheet to clean up a dataset This recipe was created for the School of Data by Tactical Technology Collective. i am making a simple program to create a mysql table from vb. It's also possible to use R's string search-and-replace functions to rename columns. Spark Tutorials. These examples are extracted from open source projects. Last Updated. but in practice renaming is simply not meaningful on statically typed Dataset. The DataFrame API was introduced in Spark 1. When you apply the select and filter methods on DataFrames and Datasets, the MapR Database OJAI Connector for Apache Spark pushes these elements to MapR Database where possible. 1 online graduate program in Texas. Create( How to remove duplicate column from DataSet?. v201907300820 by KNIME AG, Zurich, Switzerland Renames all columns based on a regular expression search & replace pattern. Spark DataFrame expand on a lot of these concepts, allowing you to transfer that knowledge easily by understanding the simple syntax of Spark DataFrames. login’ column like before. How to rename a column. In this Spark Tutorial - Concatenate two Datasets, we have learnt to use Dataset. Below is a sample code which helps to do the same. Lets begin the tutorial and discuss about the SparkSQL and DataFrames Operations using Spark 1. Sample use case: Use the LTRIM function in the SQL interface to remove numbers, special characters from the left end of the source string. expressions. Use the CHANGE statement in the DATASETS procedure to rename one or more data sets in the same library. Note that the ^ and $ surrounding alpha are there to ensure that the entire string matches. We will prepare a data frame so that we can practice renaming its columns in the below sections. Chapter 10 Data Manipulation with SparkR Now that we have our two datasets saved as Spark DataFrames, we can conduct standard data manipulation techniques to visualize and explore our data. Move dataset_example. This includes any datasets in your workspace and datasets in shared workspaces. Rename The Columns Of A MDX Dataset Mar 5, 2008. The problem is that using kryo leads to Spark just storing every row in the dataset as a flat binary object. In our case, the label column (Category) will be encoded to label indices, from 0 to 32; the most frequent label (LARCENY/THEFT) will be indexed as 0. Here is the query: Code Snippet WITH MEMBER [Number Proposal Issued] as. Chapter 10 Data Manipulation with SparkR Now that we have our two datasets saved as Spark DataFrames, we can conduct standard data manipulation techniques to visualize and explore our data. Spark createDataFrame() has another signature which takes the RDD[Row] type and schema for column names as arguments. The Mongo Spark Connector provides the com. As we know that we can use SP_RENAME system stored procedure to rename user created objects like tables, procedures, functions, views, indexes, columns, user defined types, CLR user defined types etc in current database. TiddlyWiki MarkDown → Rename DataFrame Column. Since `Dataset` has a new meaning in Spark 1. Renaming SAS Data Sets. Along the way we tell SAS exactly which variables to keep/drop. It also creates an accompanying reduced Experimental Design Data Set (EDDS). Dataset Column. The flights dataset and a new dataset called airports are already in your workspace. When you apply the select and filter methods on DataFrames and Datasets, the MapR Database OJAI Connector for Apache Spark pushes these elements to MapR Database where possible. autoBroadcastJoinThreshold to determine if a table should be broadcast. Sometimes we will wish to delete a column from an existing table in SQL. $\endgroup$ - ultron Nov 18 '16 at 15:02. In this post “SP_RENAME table with schema change” I will share a trick to rename a table using sp_rename and then transfer it schema. This is the default value to use if you haven't specified a value for the data type requested by DataTables. In this talk I given an overview of some of the exciting new API's available in Spark 2. Spark DataFrame expand on a lot of these concepts, allowing you to transfer that knowledge easily by understanding the simple syntax of Spark DataFrames. toPandas calls collect on the dataframe and brings the entire dataset into memory on the driver, so you will be moving data across network and holding locally in memory, so this should only be called if the DF is small enough to store locally. Along the way we tell SAS exactly which variables to keep/drop. createOrReplaceTempView("people") spark. It works for data processing and during aggregation. The syntax of withColumn() is provided below. I would like to add another column to the dataframe by two columns, perform an operation on, and then report back the result into the new column (specifically, I have a column that is latitude and one that is longitude and I would like to convert those two to the Geotrellis Point class and return the point). 13 and later, column names can contain any Unicode character (see HIVE-6013 ), however, dot (. In this article, we'd like to show you how to rename column of data frame by using R base functions or other libraries. Does Spark actually generate an intermediate data set with that many columns, or does it just consider this an intermediate step that individual items pass through transiently (or indeed does it optimise this away step entirely when it sees that the only use of these columns is to be assembled into a vector)?. Warning: R will allow a field to be named with a space but you won't be able to easily refer to that column after the name change. The syntax of withColumn() is provided below. You can however select the columns you want to display: when viewing a dataset, click the "Display" button in the upper right corner, then "Select displayed columns". RENAME {DATABASE | SCHEMA} db_name TO new_db_name; But it was removed on the MySQL version 5. Our dataset has five total columns, one of which isn't populated at all (video_release_date) and two that are missing some values (release_date and imdb_url). This example modifies two SAS data sets using the MODIFY statement and statements subordinate to it. Below is a sample code which helps to do the same. Should be easy, but I can't do it. Inspecting the schema for d2 or d3, you see there is just one binary column:. withColumn() method. Apache Spark : RDD vs DataFrame vs Dataset With Spark2. There will be one column for each unique value of the ID variable (or if multiple ID variables are present, one column for each unique combination of values). data() - append the string :name to indicate to DataTables that it should perform a column name selector operation. Azure Databricks - Transforming Data Frames in Spark Posted on 01/31/2018 02/27/2018 by Vincent-Philippe Lauzon In previous weeks, we've looked at Azure Databricks , Azure's managed Spark cluster service. The new Spark DataFrames API is designed to make big data processing on tabular data easier. If you want to rename the column name on the report, follow Ville's response. I am trying to get rid of white spaces from column names - because otherwise the DF cannot be saved as parquet file - and did not find any usefull method for renaming. rename all variables in a dataset. We’ll also show how to remove columns from a data frame. Once it's been created, i want to rename the table to something else so. The DataFrame API was introduced in Spark 1. Needs to be accessible from the cluster. Tons of companies are adapting Apache Spark to extract meaning from massive data sets, today you have access to that same big data technology right on your desktop. This includes any datasets in your workspace and datasets in shared workspaces. Spark Dataset union & column order. This is the default value to use if you haven't specified a value for the data type requested by DataTables. 03/30/2017; 2 minutes to read +5; In this article. The two configuration parameters for caching are. I want to rename the name of the output file by a specif column at the same time I want to fix the sheet. index, columns: scalar, list-like, dict-like or function, optional A scalar, list-like, dict-like or functions transformations to apply to that axis' values. To rename a dataframe using Spark, you just have to make use of the withColumnRenamed() method. The two configuration parameters for caching are. Change of DF column type of string to date. Saving DataFrames. To change column names using rename function in Pandas, one needs to specify a mapper, a dictionary with old name as keys and new name as values. Therefore the Spark statistics node doesn't recognize any usable columns. i am making a simple program to create a mysql table from vb. This can be done easily using the function rename() [dplyr package]. Once it's been created, i want to rename the table to something else so. The following examples gets the ColumnName for every column in every table in a DataSet. Here are a few examples of parsing nested data structures in JSON using Spark DataFrames (examples here done with Spark 1. If there are additional common variables, SAS saves only the last values encountered. You can also find that Spark SQL uses the following two families of joins: joinWith creates a Dataset with two columns _1 and _2 that each contain records for. Easiest way I have found to mass rename dataset columns is by going to the dataset -> explore -> fields link in top left -> find field and click dropdwon arrow -> rename -> input new label for the field. So Datasets and DataFrames, we go through these optimizers, and in the end, we have RDDs that we're actually running. There are multiple ways to rename row and column labels. Working with these things is a bit more manual than one might think and for your purpose i don't think you need merge functionality, made a scaffolding sample here:. Apache Spark is becoming a must tool for big data engineers and data scientists. spark dataset api with examples - tutorial 20 November 8, 2017 adarsh Leave a comment A Dataset is a strongly typed collection of domain-specific objects that can be transformed in parallel using functional or relational operations. For example, the Scala code below defines a DataFrame from an RDD of User objects. Migrations are like version control for your database, allowing your team to easily modify and share the application's database schema. Apache Spark : RDD vs DataFrame vs Dataset Published on August 3, 2016 August 3, Which means it gives us a view of data as columns with column name and types info, We can think data in data. For managed tables, renaming a table moves the table location; for unmanaged (external) tables, renaming a table does not move the table location. HOW TO: Rename Columns. In this blog, we will learn the advantages that the dataset API in Spark 2. SPARK-11895 finished the work of Scala example, here we focus on the Python one. Spark using Python Notes: The columns with data issues have been removed—State, Phone, zip and all charges The target variable has been converted to 0,1 and must be the last column The other two flag columns (IntlPlan and Vmail Plan) have been set to 0,1 as well Headings removed. The names of the key column(s) must be the same in each table. Click Add a step (+) , and select Rename Columns. I was trying to remove empty columns using SAS, R or Excel but it doesn't work. Describing a SAS Data Set shows the modifications to the GROUP data set. Transform/change value of an existing column. For the sales productivity reports and dashboard, let's rename the dataset and update a few column header titles in the OpportunitySet dataset. spark, and must also pass in a table and zkUrl parameter to specify which table and server to persist the DataFrame to. So, in this post, we will walk through how we can add some additional columns with the source data. Load gapminder data set. There are two methods for altering the column labels: the columns method and the rename method. It's also possible to subset your data based on row position. BUT, the dataset fields take the name of the returned columns and in this case, the [Time Key Issuing Date] values. There are multiple ways to rename row and column labels. Well, in CSV we may have column names in the first row, but this is not enough in most cases. Using the Columns Method If we have our labeled DataFrame already created, the simplest method for overwriting the column labels is to call the columns method on the DataFrame object and provide the new list of names we'd like to specify. Should be easy, but I can't do it. Note that an _ option must be specified. scala spark statistical-data-exploration. Reshaping Data with Pivot in Spark February 16th, 2016. As R user you will agree: To rename column names is one of the most often applied data manipulations in R. Table functions in DAX expressions can create temporary columns that are not tied to any column in the model. How can I filter them out within Spark(I found only one approach to turn Spark to table, use rename nodes and then turn table to spark, but that is not an real option)? Kind regard. Remember, you already have SparkSession spark and people_df DataFrames available in your workspace. $\begingroup$ a function that takes the columns of a dataframe that I give as an input and maps the new values onto old values,just in those columns ,is what I'm trying to figure out ,without using loops. R first appeared in 1993. Using the Columns Method If we have our labeled DataFrame already created, the simplest method for overwriting the column labels is to call the columns method on the DataFrame object and provide the new list of names we’d like to specify. It is conceptually equivalent to a table in a relational database or a data frame in R/Python, but with richer optimizations under the hood. We often need to rename one or multiple columns on Spark DataFrames, especially when columns are nested it becomes complicated. I've found myself working with large CSV files quite frequently and realising that my existing toolset didn't let me explore them quickly I thought I'd spend a bit of time looking at Spark to see if it could help. • Spark SQL automatically selects a compression codec for each column based on data statistics. This can make working with columns in the API very easy - for example to access the data from the column named location you would use table. RStudio is an active member of the R community. Use this parameter to select the column that you want to rename. If you use this LTRIM in the data set API, the trim source will be the first parameter. In this post “SP_RENAME table with schema change” I will share a trick to rename a table using sp_rename and then transfer it schema. Sometimes we will wish to delete a column from an existing table in SQL. Below is a sample code which helps to do the same. Move dataset_example. Then, let’s see some ways in which we can do. baahu June 16, 2018 No Comments on SPARK : How to generate Nested Json using Dataset Tweet I have come across requirements where in I am supposed to generate the output in nested Json format. In this course, Developing Spark Applications Using Scala & Cloudera, you’ll learn how to process data at scales you previously thought were out of your reach. Often while working with a big data frame in pandas, you might have a column with string/characters and you want to find the number of unique elements present in the column. Unnamed rows and columns correspond to lists at those levels. private void PrintColumnNames(DataSet dataSet) { // For each DataTable, print the ColumnName. In Hive 0. Using rename to change column names is a much better way than before. It’s also possible to use R base functions, but they require more typing. Today we will talk how do you can easily rename a database in MySQL. Explore degrees available through the No. 6, we should rename it to avoid confusion. It was inspired from SQL. I have a huge dataset with 405 columns and 12,000 rows. How to rename all the columns of a dataset with names coming from another one? 0 votes I have a first dataset with no column names (it appears col_0, Col_1) and a text file "dictionary" in which I have the names of the columns. Conceptually, it is equivalent to relational tables with good optimizati. Pandarize your Spark DataFrames. My question is once the file is created I can look at it and see how many diag columns were generated. dataset[All,KeyMap[Replace["old" -> "New"]]] This approach essentially conducts the idea of OP and reserves the names of other columns. Describing a SAS Data Set shows the modifications to the GROUP data set. Spark DataFrames provide an API to operate on tabular data. data normally does. How to rename multiple columns of Dataframe in Spark Scala? If you need to select only some columns and rename it this is the another option. Currently we only allow dynamic partition columns to be the last column(s) in the partition clause because the partition column order indicates its hierarchical order (meaning dt is the root partition, and country is the child partition). If the destination table name already exists, an exception is thrown. It works for data processing and during aggregation. Before sorting, the Spark's engine tries to discard data that will not be used in the join like nulls and useless columns. I have already built a dashboard based on. Spark A friend of mine (he would ask this question but his computer is down) has an input folder that contains over 100,000 files. The last datatypes of each column, but not necessarily in the corresponding order to the listed columns. Because the returned data type isn’t always consistent with matrix indexing, it’s generally safer to use list-style indexing, or the drop=FALSE op. Rename an existing table or view. 6 release introduces a preview of the new Dataset API. In Apache Spark, a DataFrame is a distributed collection of rows under named columns. A group of “renaming” macros will be created, which perform different renaming jobs, i. Having a good deal of experience capturing and evaluating damped radio oscillations for a Spark Gap transmitter, I immediately saw the utility of the circuit for a simple Q determination based on the waveform itself. Using a spreadsheet to clean up a dataset This recipe was created for the School of Data by Tactical Technology Collective. When performing joins in Spark, one question keeps coming up: When joining multiple dataframes, how do you prevent ambiguous column name errors? 1) Let's start off by preparing a couple of simple example dataframes // Create first example dataframe val firstDF = spark. The BigQuery connector can be used with Apache Spark to read and write data from/to BigQuery. 0, a DataFrame is represented by a Dataset of Rows and is now an alias of Dataset[Row]. however can this be accomplished using a procedure like proc datasets? I see the rename option in the proc datasets but apparently this is only used for renaming columns not for the dataset name. SQL: ALTER TABLE Statement. Using combineByKey in Apache-Spark. Let us get started with some examples from a real world data set. SparkSession import org. For wide-to-long transposes, you typically do not need an ID variable. v201907300820 by KNIME AG, Zurich, Switzerland Renames all columns based on a regular expression search & replace pattern. Rename datasets, params, locations, and columns. I have a dataset that is being created from an XML file. Here's an easy example of how to rename all columns in an Apache Spark DataFrame. I will be comparing the R dataframe capabilities with spark ones. 5, with more than 100 built-in functions introduced in Spark 1. Adding Multiple Columns to Spark DataFrames Jan 8, 2017 I have been using spark's dataframe API for quite sometime and often I would want to add many columns to a dataframe(for ex : Creating more features from existing features for a machine learning model) and find it hard to write many withColumn statements. Specifically, the RENAME= and KEEP= options are used to modify the back8 data set. Define Query parameter with multiple value for MDX query and assign parameter name same as SSRS report parameter. Derive new column from an existing column. In pandas the index is just a special column,. Tasks include modifying SAS files. You can also find that Spark SQL uses the following two families of joins: joinWith creates a Dataset with two columns _1 and _2 that each contain records for. Suppose we have a dataset which is in CSV format. AgilData / Blog / Engineering / Apache Spark: RDD, DataFrame or Dataset? Apache Spark: RDD, DataFrame or Dataset? January 15, 2016. Spark SQL interfaces provide Spark with an insight into both the structure of the data as well as the processes being performed. Note: In the Spark SQL interface, the first parameter is trim characters, the second is the trim source. Core Spark Joins. labeling a SAS data set. While we use the same columnar representation as Dataframe (Dataset[Row]) semantics is completely different here. Changing column name for a dataset. SparkSession import org. Download; Upload; Applets. New in Spark 2. To create a Dataset we need: a.