Spark SQL provides built-in standard array functions defines in DataFrame API, these come in handy when we need to make operations on array (ArrayType) column. All these accept input as, array column and several other arguments based on the function.
When possible try to leverage standard library as they are little bit more compile-time safety, handles null and perform better when compared to UDF’s. If your application is critical on performance try to avoid using custom UDF at all costs as these are not guarantee on performance.
Spark SQL array functions are grouped as collection functions “collection_funcs” in spark SQL along with several map functions. These array functions come handy when we want to perform some operations and transformations on array columns.
Though I’ve explained here with Scala, a similar methods could be used to work Spark SQL array function with PySpark and if time permits I will cover it in the future. If you are looking for PySpark, I would still recommend reading through this article as it would give you an Idea on Spark array functions and usage.
Spark SQL Array Functions:
| Date Functions Syntax | Date Function Description |
|---|---|
| current_date () : Column | Returns the current date as a date column. |
| date_format(dateExpr: Column, format: String): Column | Converts a date/timestamp/string to a value of string in the format specified by the date format given by the second argument. |
| to_date(e: Column): Column | Converts the column into `DateType` by casting rules to `DateType`. |
| to_date(e: Column, fmt: String): Column | Converts the column into a `DateType` with a specified format |
| add_months(startDate: Column, numMonths: Int): Column | Returns the date that is `numMonths` after `startDate`. |
| date_add(start: Column, days: Int): Column date_sub(start: Column, days: Int): Column | Returns the date that is `days` days after `start` |
| datediff(end: Column, start: Column): Column | Returns the number of days from `start` to `end`. |
| months_between(end: Column, start: Column): Column | Returns number of months between dates `start` and `end`. A whole number is returned if both inputs have the same day of month or both are the last day of their respective months. Otherwise, the difference is calculated assuming 31 days per month. |
| months_between(end: Column, start: Column, roundOff: Boolean): Column | Returns number of months between dates `end` and `start`. If `roundOff` is set to true, the result is rounded off to 8 digits; it is not rounded otherwise. |
| next_day(date: Column, dayOfWeek: String): Column | Returns the first date which is later than the value of the `date` column that is on the specified day of the week. For example, `next_day('2015-07-27', "Sunday")` returns 2015-08-02 because that is the first Sunday after 2015-07-27. |
| trunc(date: Column, format: String): Column | Returns date truncated to the unit specified by the format. For example, `trunc("2018-11-19 12:01:19", "year")` returns 2018-01-01 format: 'year', 'yyyy', 'yy' to truncate by year, 'month', 'mon', 'mm' to truncate by month |
| date_trunc(format: String, timestamp: Column): Column | Returns timestamp truncated to the unit specified by the format. For example, `date_trunc("year", "2018-11-19 12:01:19")` returns 2018-01-01 00:00:00 format: 'year', 'yyyy', 'yy' to truncate by year, 'month', 'mon', 'mm' to truncate by month, 'day', 'dd' to truncate by day, Other options are: 'second', 'minute', 'hour', 'week', 'month', 'quarter' |
| year(e: Column): Column | Extracts the year as an integer from a given date/timestamp/string |
| quarter(e: Column): Column | Extracts the quarter as an integer from a given date/timestamp/string. |
| month(e: Column): Column | Extracts the month as an integer from a given date/timestamp/string |
| dayofweek(e: Column): Column | Extracts the day of the week as an integer from a given date/timestamp/string. Ranges from 1 for a Sunday through to 7 for a Saturday |
| dayofmonth(e: Column): Column | Extracts the day of the month as an integer from a given date/timestamp/string. |
| dayofyear(e: Column): Column | Extracts the day of the year as an integer from a given date/timestamp/string. |
| weekofyear(e: Column): Column | Extracts the week number as an integer from a given date/timestamp/string. A week is considered to start on a Monday and week 1 is the first week with more than 3 days, as defined by ISO 8601 |
| last_day(e: Column): Column | Returns the last day of the month which the given date belongs to. For example, input "2015-07-27" returns "2015-07-31" since July 31 is the last day of the month in July 2015. |
| from_unixtime(ut: Column): Column | Converts the number of seconds from unix epoch (1970-01-01 00:00:00 UTC) to a string representing the timestamp of that moment in the current system time zone in the yyyy-MM-dd HH:mm:ss format. |
| from_unixtime(ut: Column, f: String): Column | Converts the number of seconds from unix epoch (1970-01-01 00:00:00 UTC) to a string representing the timestamp of that moment in the current system time zone in the given format. |
| unix_timestamp(): Column | Returns the current Unix timestamp (in seconds) as a long |
| unix_timestamp(s: Column): Column | Converts time string in format yyyy-MM-dd HH:mm:ss to Unix timestamp (in seconds), using the default timezone and the default locale. |
| unix_timestamp(s: Column, p: String): Column | Converts time string with given pattern to Unix timestamp (in seconds). |
