Apache Drill - Query using JSON

Apache Drill supports JSON format for querying data. Drill treats a JSON object as SQL record. One object equals one row in a Drill table.

Querying JSON File

Let us query the sample file, “employee.json” packaged as part of the drill. This sample file is Foodmart data packaged as JAR in Drill's classpath: ./jars/3rdparty/foodmart-data-json.0.4.jar. The sample file can be accessed using namespace, cp.

Start the Drill shell, and select the first row of data from the “employee.json” file installed.

Query

0: jdbc:drill:zk = local> select * from cp.`employee.json` limit 1;

Result

+--------------+--------------+------------+------------+--------------+----------------+-----------+----------------+------------+-----------------------+---------+---------------+-----------------+----------------+--------+-------------------+
| employee_id  |   full_name  | first_name | last_name  | position_id  | position_title | store_id  | department_id  | birth_date |       hire_date       | salary  | supervisor_id | education_level | marital_status | gender |  management_role  |
+--------------+--------------+------------+------------+--------------+----------------+-----------+----------------+------------+-----------------------+---------+---------------+-----------------+----------------+--------+-------------------+
|       1      | Sheri Nowmer |    Sheri   |   Nowmer   |       1      |   President    |     0     |       1        | 1961-08-26 | 1994-12-01 00:00:00.0 | 80000.0 |       0       | Graduate Degree |        S       |    F   | Senior Management |
+--------------+--------------+------------+------------+--------------+----------------+-----------+----------------+------------+-----------------------+---------+---------------+-----------------+----------------+--------+-------------------+

The same result can be viewed in the web console as −

Storage Plugin Configuration

You can connect Drill to a file system through a storage plugin. On the Storage tab of the Drill Web Console (http://localhost:8047), you can view and reconfigure a storage plugin.

The Drill installation contains the following default storage plugin configurations.

cp − Points to the JAR files in the Drill classpath.
dfs − Points to the local file system, but you can configure this storage plugin to point to any distributed file system, such as a Hadoop or S3 file system.
hbase − Provides a connection to the HBase.
hive − Integrates Drill with the Hive metadata abstraction of files, HBase, and libraries to read data and operate on SerDes and UDFs.
mongo − Provides a connection to MongoDB data.

Storage Plugin Configuration Persistence

Embedded mode − Apache Drill saves the storage plugin configurations in a temporary directory. The temporary directory clears when you reboot.
Distributed mode − Drill saves storage plugin configurations in ZooKeeper.

Workspace

The workspace defines the location of files in subdirectories of a local or distributed file system. One or more workspaces can be defined in a plugin.

Create JSON file

As of now we have queried an already packaged “employee.json” file. Let us create a new JSON file named “student_list.json” as shown in the following program.

{
   "ID" : "001",
   "name" : "Adam",
   "age" : 12,
   "gender" : "male",
   "standard" : "six",
   "mark1" : 70,
   "mark2" : 50,
   "mark3" : 60,
   "addr" : "23 new street",
   "pincode" : 111222
}
{
   "ID" : "002",
   "name" : "Amit",
   "age" : 12,
   "gender" : "male",
   "standard" : "six",
   "mark1" : 40,
   "mark2" : 50,
   "mark3" : 40,
   "addr" : "12 old street",
   "pincode" : 111222
}
{
   "ID" : "003",
   "name" : "Bob",
   "age" : 12,
   "gender" : "male",
   "standard" : "six",
   "mark1" : 60,
   "mark2" : 80,
   "mark3" : 70,
   "addr" : "10 cross street",
   "pincode" : 111222
}
{
   "ID" : "004",
   "name" : "David",
   "age" : 12,
   "gender" : "male",
   "standard" : "six",
   "mark1" : 50,
   "mark2" : 70,
   "mark3" : 70,
   "addr" : "15 express avenue",
   "pincode" : 111222
}
{
   "ID" : "005",
   "name" : "Esha",
   "age" : 12,
   "gender" : "female",
   "standard" : "six",
   "mark1" : 70,
   "mark2" : 60,
   "mark3" : 65,
   "addr" : "20 garden street",
   "pincode" : 111222
}
{
   "ID" : "006",
   "name" : "Ganga",
   "age" : 12,
   "gender" : "female",
   "standard" : "six",
   "mark1" : 100,
   "mark2" : 95,
   "mark3" : 98,
   "addr" : "25 north street",
   "pincode" : 111222
}
{
   "ID" : "007",
   "name" : "Jack",
   "age" : 13,
   "gender" : "male",
   "standard" : "six",
   "mark1" : 55,
   "mark2" : 45,
   "mark3" : 45,
   "addr" : "2 park street",
   "pincode" : 111222
}
{
   "ID" : "008",
   "name" : "Leena",
   "age" : 12,
   "gender" : "female",
   "standard" : "six",
   "mark1" : 90,
   "mark2" : 85,
   "mark3" : 95,
   "addr" : "24 south street",
   "pincode" : 111222
}
{
   "ID" : "009",
   "name" : "Mary",
   "age" : 13,
   "gender" : "female",
   "standard" : "six",
   "mark1" : 75,
   "mark2" : 85,
   "mark3" : 90,
   "addr" : "5 west street",
   "pincode" : 111222
}
{
   "ID" : "010",
   "name" : "Peter",
   "age" : 13,
   "gender" : "female",
   "standard" : "six",
   "mark1" : 80,
   "mark2" : 85,
   "mark3" : 88,
   "addr" : "16 park avenue",
   "pincode" : 111222
}

Now, let us query the file to view its full records.

Query

0: jdbc:drill:zk = local> select * from dfs.`/Users/../workspace/Drill-samples/student_list.json`;

Result

ID   name  age  gender  standard  mark1  mark2  mark3      addr           pincode
001  Adam  12    male     six      70     50     60    23 new street      111222
002  Amit  12    male     six      40     50     40    12 old street      111222
003  Bob   12    male     six      60     80     70    10 cross street    111222
004  David 12    male     six      50     70     70    15 express avenue  111222
005  Esha  12   female    six      70     60     65    20 garden street   111222
006  Ganga 12   female    six      100    95     98    25 north street    111222
007  Jack  13    male     six      55     45     45    2 park street      111222
008  Leena 12   female    six      90     85     95    24 south street    111222
009  Mary  13   female    six      75     85     90    5 west street      111222
010  Peter 13   female    six      80     85     88    16 park avenue     111222

SQL Operators

This section will cover the operations on SQL operators using JSON.

Sr.No	Operator & Description
1	AND The AND operator allows the existence of multiple conditions in an SQL statement's WHERE clause.
2	OR The OR operator is used to combine multiple conditions in an SQL statement's WHERE clause.
3	IN The IN operator is used to compare a value to a list of literal values that have been specified.
4	BETWEEN The BETWEEN operator is used to search for values that are within a set of values, given the minimum value and the maximum value.
5	LIKE The LIKE operator is used to compare a value to similar values using wildcard operators.
6	NOT The NOT operator reverses the meaning of the logical operator with which it is used. Eg: NOT EXISTS, NOT BETWEEN, NOT IN, etc. This is a negate operator.

Aggregate Functions

The aggregate functions produce a single result from a set of input values. The following table lists out the functions in further detail.

Sr.No	Function & Description
1	AVG(expression) Averages a column of all records in a data source.
2	COUNT(*) Returns the number of rows that match the given criteria.
3	COUNT([DISTINCT] expression) Returns the number of distinct values in the column.
4	MAX(expression) Returns the largest value of the selected column.
5	MIN(expression) Returns the smallest value of the selected column.
6	SUM(expression) Return the sum of given column.

Statistical Function

The following program shows the query for this function −

Query

0: jdbc:drill:zk = local> select stddev(mark2) from dfs.`/Users/../workspace/Drill-samples/student_list.json`;

Result

EXPR$0
18.020050561034015

Query

0: jdbc:drill:zk = local> select variance(mark2) from dfs.`/Users/../workspace/Drill-samples/student_list.json`;

Result

EXPR$0
324.7222222222223

Variance of mark2 column result is returned as the output.

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