Problem: In a Scala application, you want to extract information from XML you receive, so you can use the data in your application. Use the methods of the Scala Elem and NodeSeq classes to extract the data. The most commonly used methods of the Elem class are shown here:. The label method returns the name of the current element. Element attributes are extracted with the attribute or attributes methods. The following examples demonstrate how to call these methods, and the values they return:.
These examples show how attribute and attributes work with multiple attributes:. The child method returns all child nodes of the current element. You can improve this result with the PrettyPrinter class. There are more ways to tackle these problems using XPath methods, which will be shown in subsequent chapters.
As a word of caution, be careful with the text method. If you need to extract text in this manner, a workaround is to extract the text components individually into a sequence, and then re-combine the sequence as desired. The following example demonstrates how to accomplish this with the childlabeland text methods. Given this XML literal:.
To get around this problem, you can allocate more heap space when starting the REPL with this command:. How to extract data from XML nodes in Scala. By Alvin Alexander. Last updated: January 15, Returns matching elements from child nodes at any depth of the XML tree. Returns a copy of the element, letting you replace data during the copy process. Use scala. PrettyPrinter to format the output, if desired.Got some examples to use spark xml utils as per the link.
There are some examples here. However can you guys also provide some sample code for this?
Also can you please mention the how and external package can be added from spark-shell and pyspark? We are looking for your guidance. Thanks, Rajdip. View solution in original post. Do I need to add the data bricks package in spark class path? As I am new to spark so struggling to understand how to use the package.
Of course to write your project code you will also need to add this package to your project maven pom dependency. If you build an uber jar for your project that includes this package then you dont need to change your command line for submission.
I work on HDP 2. I am trying to parse xml using pyspark code; manual parsing but I am having difficulty -when converting the list to a dataframe. Support Questions. Find answers, ask questions, and share your expertise. Turn on suggestions. Auto-suggest helps you quickly narrow down your search results by suggesting possible matches as you type. Showing results for. Search instead for. Did you mean:. Alert: Welcome to the Unified Cloudera Community. Former HCC members be sure to read and learn how to activate your account here.
All forum topics Previous Next.Here am pasting the sample JSON file. Your help would be appreciated. Please give an idea to parse the JSON file.
Use Nested FOR XML Queries
Any information that can be used to uniquely identify the vehicle, the vehicle owner or the officer issuing the violation will not be published. You simply need to read the file using the json method in sqlContext. I am going to take a quick example using a sample file compared to the behemoth of yours.
Assuming you are using scala for your operations and using shell for this example, when you fire your spark-shell, you will get an instance of SparkSession called spark. You can use it to access the methods that will help you solve your problem. The above statement will create a DataFrame for you. You can see the schema using the following statement. Now, I have taken a nested column and an array in my file to cover the two most common "complex datatypes" that you will get in your JSON documents.
You can access them specifically as shown below. Support Questions. Find answers, ask questions, and share your expertise.
Turn on suggestions. Auto-suggest helps you quickly narrow down your search results by suggesting possible matches as you type. Showing results for. Search instead for. Did you mean:. Alert: Welcome to the Unified Cloudera Community. Former HCC members be sure to read and learn how to activate your account here.Loading Nested XML data into HIVE table - Big data - Hadoop Tutorial - Session 12
All forum topics Previous Next. How to parse nested Json in spark2 Dataframe. Labels: Apache Spark. Reply 18, Views. Tags 4. Re: How to parse nested Json in spark2 Dataframe. Follows a quick example.GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together. If nothing happens, download GitHub Desktop and try again. If nothing happens, download Xcode and try again.
If nothing happens, download the GitHub extension for Visual Studio and try again. This package can be added to Spark using the --packages command line option. For example, to include it when starting the spark shell:.
Currently it supports the shortened name usage. You can use just xml instead of com. Although primarily used to convert portions of large XML documents into a DataFramefrom version 0. The functions above are exposed in the Scala API only, at the moment, as there is no separate Python package for spark-xml.
Note that handling attributes can be disabled with the option excludeAttribute. Attributes : Attributes are converted as fields with the heading prefix, attributePrefix. Value in an element that has no child elements but attributes : The value is put in a separate field, valueTag. This would not happen in reading and writing XML data but writing a DataFrame read from other sources.
How to deal with XML format in Apache Spark
Therefore, roundtrip in reading and writing XML files has the same structure but writing a DataFrame read from other sources is possible to have a different structure. These examples use a XML file available for download here :. Import com. You can also use. The library contains a Hadoop input format for reading XML files by a start tag and an end tag. This is similar with XmlInputFormat.
This library is built with SBT. To build a JAR file simply run sbt package from the project root. The build configuration includes support for both Scala 2. This project was initially created by HyukjinKwon and donated to Databricks.
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Thanks for the very helpful module. When its a simple struct then you can do something like df. PVAL from I have the same issue, i tried to define a nested custom schema but it's not possible i think.
Now this is a relatively simple transform that expand the current row into as many rows as you have items in the array. I guess its a learning curve issue. Thanks for the progress HyukjinKwon, I cant wait to see 0. Hi Bertrandbenj Is it possible to use the explode function in flatmap. Can you please tell me how do i flatten the below array structure. HyukjinKwon is this fixed? Hi kkarthik21 you can explode the df on chunk it will explode the whole df into every single entry of chunk array, then you can use the resultant df to select each column you want, thus flattening the whole df.
It seems there isn't one single and clean way to do this. I could have some answers about this from local Spark community. Hello enthusiasts, I am happy to note good activity here HiveContext" Any help appreciated!!!
Thanks Raj. I see a big discussion here for a similar problem I have in I iterated through the path and explode everything to eliminate arrays, but it is not the best way. Besides, I get an OOM error.The Apache Spark community has put a lot of effort into extending Spark.
Recently, we wanted to transform an XML dataset into something that was easier to query. We were mainly interested in doing data exploration on top of the billions of transactions that we get every day.
XML is a well-known format, but sometimes it can be complicated to work with. However, it was hard for us to keep up with the changes on the XML structure, so the previous option was discarded. We were using Spark Streaming capabilities to bring these transactions to our cluster, and we were thinking of doing the required transformations within Spark.
However, the same problem remained, as we had to change our Spark application every time the XML structure changed. There is an Apache Spark package from the community that we could use to solve these problems. In here, we just added the XML package to our Spark environment. This of course can be added when writing a Spark app and packaging it into a jar file.
When loading the DataFrame, we could specify the schema of our data, but this was our main concern in the first place, so we will let Spark infer it.
Going a step further, we could use tools that can read data in JSON format. Going a step further, we might want to use tools that read JSON format. As we could expect, with Spark we can do any kind of transformations, but there is no need to write a fancy JSON encoder because Spark already supports these features.
Then we save theRDD as a plain text file. We now can rest assured that XML schema changes are not going to affect us at all, we have removed ourselves from the burden of changing our application for every XML change, we can also use powerful tools to query our JSON dataset such as Apache Drill in a schema free fashion while our clients can report on our data using SQL.
If you have any questions about using this Apache Spark package to read XML files into a DataFrame, please ask them in the comments section below. Blog Apache Spark Current Post.
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The schema of semi-structured formats is not strict. Well, in CSV we may have column names in the first row, but this is not enough in most cases. The bigger datasets are, the longer you wait. Even if you need only the first record from the file, Spark by default reads its whole content to create a valid schema consisting of the superset of used fields and their types. If your datasets have mostly static schema, there is no need to read all the data.
You can speed up loading files with samplingRatio option for JSON and XML readers - the value is from range 0,1] and specifies what fraction of data will be loaded by scheme inferring job. Now the process of loading files is faster, but it still could be better. The solution to these problems already exists in spark codebase - all mentioned DataFrame readers take the schema parameter.
If you pass the schema, Spark context will not need to read underlying data to create DataFrames. Still, definifing schema is a very tedious job…. Fortunately, schemas are serializable objects and they serialize nicely to python dictionaries using standard pyspark library:. If you paste the JSON output compressed one, from schema. Using this trick you can easily store schemas on filesystem supported by spark HDFS, local, S3, … and load them into the applications using a very quick job.
Reading semi-structured files in Spark can be efficient if you know the schema before accesing the data. But defining the schema manually is hard and tedious…. All above code is pyspark 2. If you still codeg in pyspark 1.
X, replace spark with sqlContext. Some of above snippets may even work in scala. Hint 1: play with samplingRatio If your datasets have mostly static schema, there is no need to read all the data. JSON spark. Hint 2: define static schema The solution to these problems already exists in spark codebase - all mentioned DataFrame readers take the schema parameter. Still, definifing schema is a very tedious job… from pyspark. Getting it all together Reading semi-structured files in Spark can be efficient if you know the schema before accesing the data.
But defining the schema manually is hard and tedious… Next time you are building ETL application based on CSV, JSON or XML files, try the following approach: Locate a small, representative subset of input data so that it contains a superset of possible fields and their types.
For really big but consistent sources consider using samplingRatio parameter. Load the above dataset as dataframe and extract JSON representation of the schema into a file.
In your application add a code that reads schema file into a variable. Load your input dataset passing schema parameter pointing to the variable. And finally, a handy class that can simplify the procedure: import json from pyspark.