# Time Series Analysis Functions

When analyzing time based data, you will often have to aggregate by time grains. While some time grains will be easy to calculate, others, such as quarter, can be quite difficult. These functions enable a user to quickly and easily aggregate data by various units of time. Usage is as follows:

SELECT <fields>
FROM <data>
GROUP BY nearestDate(<timestamp_column>, <time increment>

So let’s say that a user wanted to count the number of hits on a web server per 15 minute, the query might look like this:

SELECT nearestDate(`eventDate`, 'QUARTER_HOUR' ) AS eventDate,
COUNT(*) AS hitCount
FROM dfs.`log.httpd`
GROUP BY nearestDate(`eventDate`, 'QUARTER_HOUR')

Currently supports the following time units:

• YEAR,
• QUARTER,
• MONTH,
• WEEK_SUNDAY,
• WEEK_MONDAY,
• DAY,
• HOUR,
• HALF_HOUR,
• QUARTER_HOUR,
• MINUTE,
• HALF_MINUTE,
• QUARTER_MINUTE,
• SECOND

There are two versions of the function, one which accepts a date and interval, and the other accepts a string, format string and interval.

### Time Bucket Functions

These functions are useful for doing time series analysis by grouping the data into arbitrary intervals. Examples in addition to those in this section may be found here.

There are two versions of the function:

• time_bucket(<timestamp>, <interval>)
• time_bucket_ns(<timestamp>,<interval>)

Both functions accept a BIGINT timestamp and an interval in milliseconds as arguments. The time_bucket_ns() function accepts timestamps in nanoseconds and time_bucket() accepts timestamps in milliseconds. Both return timestamps in the original format.

### Examples

The query below calculates the average for the cpu metric for every five minute interval.

SELECT time_bucket(time_stamp, 30000) AS five_min, avg(cpu)
FROM metrics
GROUP BY five_min
ORDER BY five_min DESC LIMIT 12;

## User Agent Functions

Drill UDF for parsing User Agent Strings. This function is based on Niels Basjes Java library for parsing user agent strings which is available here.

### Usage

The function parse_user_agent() takes a user agent string as an argument and returns a map of the available fields. Note that not every field will be present in every user agent string.

SELECT parse_user_agent( columns[0] ) as ua
FROM dfs.`/tmp/data/drill-httpd/ua.csv`;

The query above returns:

{
"DeviceClass":"Desktop",
"DeviceName":"Macintosh",
"DeviceBrand":"Apple",
"OperatingSystemClass":"Desktop",
"OperatingSystemName":"Mac OS X",
"OperatingSystemVersion":"10.10.1",
"OperatingSystemNameVersion":"Mac OS X 10.10.1",
"LayoutEngineClass":"Browser",
"LayoutEngineVersion":"39.0",
"LayoutEngineVersionMajor":"39",
"AgentClass":"Browser",
"AgentName":"Chrome",
"AgentVersion":"39.0.2171.99",
"AgentVersionMajor":"39",
"AgentNameVersion":"Chrome 39.0.2171.99",
"AgentNameVersionMajor":"Chrome 39",
"DeviceCpu":"Intel"
}

The function returns a Drill map, so you can access any of the fields using Drill’s table.map.key notation. For example, the query below illustrates how to extract a field from this map and summarize it: