Table of Contents
- What is Apache Drill?
- Needed For This Tutorial
- Installing Prerequisites
- Installing Apache Drill
- Running Queries with Apache Drill
- Installing Virtual Box (links)
- Installing Ubuntu (links)
- Sources and Links
What is Apache Drill?
Inspired by Google’s Dremel, Apache Drill is a distributed, low-latency system that supports interactive ad-hoc analysis for large-scale datasets. It’s key features include full SQL, nested data support, optional schema, and flexible and extensive architecture. The design goal of Drill is to quickly respond to queries involving petabytes of data. Drill is not a database; it is a query layer on top of data, and it is supported by full table scans. It provides frameworks for parallel processing and flexible query execution. Drill is still relatively new, so documentation and support is limited, information is inconsistent, and bugs are still present. In my case, troubleshooting errors or figuring out proper syntax can go on for hours or days because of lack of information and support.
Let us take a look at how Apache Drill gains its querying flexibility. Drill takes a query written in natural, readable language such as SQL and transforms it into a logical plan, and then into a physical plan before executing it.
( Hausenblas & Nadeau, 2013)
Drill takes the source query and transforms it into a logical plan using an interface such as an JDBC or ODBC library. The logical plan consists of Java objects and a text form, and is usually stored in memory. The logical plan runs through a optimizer and a physical plan is produced, which represents the structure if computation. After the physical plan is produced, the query is ready for execution in Drill.
Each node, called Drillbits, is designed to maximize data locality. Coordination, query planning, execution, etc. are all distributed. By default, Drillbits hold all roles. Why? Because we want speed!
Needed For This Tutorial
I assume most would know how to set up Virtual Box and Ubuntu, but if not, I have included links to setup tutorials towards the end of the report. I am new to Linux systems, so I have written this report so that it is easy for beginners to follow as well. To the experienced users, bear with me.
Ubuntu 12.04.4 (I am using Oracle’s Virtual Box)
Ctrl+Alt+T to open a terminal:
sudo apt-get update
Enter in your password. Now, check your Java version:
Note: Whenever you use “sudo”, you will likely be prompted for your password.
If Java has not yet been installed, the terminal will return “the program ‘java’ can be found in the following packages: …” We will need JDK 7. Install it:
sudo apt-get install openjdk-7-jdk
Note: Whenever you are asked if you want to continue, either enter in y or press enter.
Try the java version command again, and you should see something similar to:
Now that Java 1.7 is installed, we will need Maven. Go to maven.apache.org/download.cgi and download apache-maven-3.2.1-bin.tar.gz. The Drill Wiki page says that any Maven 3.0+ will work, but this is not true. There is a bug that will cause a build error when installing Drill, and it is only avoidable with the current Maven (3.2.1). The information on the Drill’s wiki page is often out dated and there doesn’t seem to be anyone actively managing it.
Check to make sure Maven is not already installed:
If you’ve just freshly installed Ubuntu, it shouldn’t be installed. If it is, you could try uninstalling it with:
sudo apt-get purge <package name>
In this case, <package name> is most likely “maven” or “maven2″. Next, I installed the downloaded maven package with these steps:
sudo tar –zxvf apache-maven-3.2.1-bin.tar.gz sudo mkdir –p /usr/local/apache-maven sudo mv apache-maven-3.2.1 /usr/local/apache-maven gedit ~/.profile
gedit will open, append to the bottom:
export M2_HOME=/usr/local/apache-maven/apache-maven-3.2.1 export M2=$M2_HOME/bin export MAVEN_OPTS="-Xms256m -Xmx512m" export PATH=$M2:$PATH
Save and close. Back at the terminal:
sudo ln -s /usr/local/apache-maven/apache-maven-3.2.1/bin/mvn /usr/bin/mvn mvn -version
“mvn –version” will return something similar to:
Now that JDK 1.7 and Maven 3.2.1 is installed, we are ready to install Apache Drill.
Installing Apache Drill
You can either install Apache Drill by installing the binaries or compiling the source files. According to Drill’s Wiki page, the quickest way to get started is to install the binaries, which I found out after two days, just doesn’t work. When there are updates, the binaries are not updated in sync with the source files. The only option is to compile the source files (this is why Maven 3.2.1 is a prerequisite).
sudo apt-get install git-all
Grab the Drill files:
git clone https://github.com/apache/incubator-drill.git
cd incubator-drill mvn clean install -DskipTests
Note: System may hang if you leave out “-DskipTests” or take an absurd amount of time to complete. Mine never completed without this option.
After it is finished buildling, feed the terminal these commands:
mkdir drill sudo tar xvzf distribution/target/*.tar.gz --strip=1 -C drill
Running Queries with Apache Drill
If there are no errors up until now, Drill should be installed and we are ready to try some queries:
cd drill bin/sqlline –u jdbc:drill:zk=local –n admin –p admin
<more info on shell>
Note: You may get some permission denied errors. These are the log files being denied permission, which you can avoid by putting sudo before the command. You can ignore this if you want to.
select * from cp.`employee.json`;
Note: employee.json is already included in the source files somewhere, so try that command as it is.
The interesting thing about Drill is that you can query your noSQL data in natural SQL language, meaning you can run queries such as:
select * from cp.`employee.json` where position_id=13; select employee_id as id, full_name as name from cp.`employee.json` where position_id=13 and first_name=’Michael’;
Let us try running queries on some of our own data. The data I am going to use is from my other project, Lower Orbit – Yelp Challenge/FourSquare Dataset. In particular, I am going to try running some queries on the user.json, which contains user data that you might see on a user profile such as name, review count, friends, etc.
First, I moved the data into the “sample-data” folder in “drill” by opening a new terminal (Ctrl+Shift+N)
sudo mv <source> <destination>
In my case:
sudo mv user.json incubator-drill/drill/sample-data
Close the terminal.
Note: This step gets very tedious to do when I was troubleshooting the json file for errors caused by nested data. An easier approach is to change the folder permissions with “sudo chown <username> <path to directory>”.
Unfortunately, I’ve ran into some errors that I cannot solve yet. First, I cannot seem to run queries on a large data set on my local machine.
select name from cp.`sample/data-user.json`;
I created a snippet of the data set containing 300 objects instead of 70,000 to at least see what kind of operations I can perform on my own data set:
select name, review_count from cp.`sample-data/user-short.json`;
I am able to execute “select” and “from” clauses, but not the “where” clause. I took 10 user objects out of the 70,000 user objects and found that it was the nested data under the “friends” field that was causing an error when I use the “where” clause.
After playing around some more with the data, I found that the failures seem to be coming from two things. A “BatchExceededException: [ Batch exceeded in size. Capacity: 262145, Attempted: 22 ]” occurs with the user.json, which I suspect may have to do with the file size of the file. Secondly, I couldn’t query the data when the field “average_stars” contained a combination of floats and ints. For example, one object may have average_star: 3 and another object average_star: 3.6. This will cause a cast exception and the query will not be executed.
In order to get Drill to accept my data, I had to remove a few fields (average_stars, elite, and friends). I am not entirely sure why yet, but it seems that Drill is not very stable at handling my nested data.
select name, review_count from cp.`sample-data/user.json` where review_count > 2500 order by review_count;
Here I was able to query the entire user.json file (instead of a shortened version of it) and get these fields.
- Cluster mode
Installing Virtual Box
virtual box manual: http://www.virtualbox.org/manual/ch01.html
installing Ubuntu on Virtual Box: http://www.wikihow.com/Install-Ubuntu-on-VirtualBox
youtube video: https://www.youtube.com/watch?v=rt8wrKBKrt0