What is regex in hive?

The Hadoop Hive regular expression functions identify precise patterns of characters in the given string and are useful for extracting string from the data and validation of the existing data, for example, validate date, range checks, checks for characters, and extract specific characters from the data.

RLIKE (Right-Like) is a special function in Hive where if any substring of A matches with B then it evaluates to true. It also obeys Java regular expression pattern.

Also Know, what is Collect_list in hive? collect_set(col) Returns a set of objects(array) with duplicate elements eliminated. collect_list(col) Returns a list of objects(array) with duplicates. (As of Hive 0.13.

Secondly, what are the functions in hive?

Some of the built-in functions are:

  • Mathematical/Numerical Functions.
  • Collection Functions.
  • String Functions.
  • Date Function. It is necessary to have data format in hive to prevent Null error in the output.
  • Conditional Functions.
  • Regular UDF.
  • User-Defined Aggregate Function.
  • User-Defined Table Generating Functions.

How does limit work in hive?

LIMIT Clause The first argument specifies the offset of the first row to return (as of Hive 2.0. 0) and the second specifies the maximum number of rows to return.

How do I use regular expressions?

How to write Regular Expressions? Repeaters : * , + and { } : The asterisk symbol ( * ): The Plus symbol ( + ): The curly braces {…}: Wildcard – ( . ) Optional character – ( ? ) The caret ( ^ ) symbol: Setting position for match :tells the computer that the match must start at the beginning of the string or line. The dollar ( $ ) symbol.

What is Rlike?

In MySQL, the RLIKE operator is used to determine whether or not a string matches a regular expression. It’s a synonym for REGEXP_LIKE() . If the string matches the regular expression provided, the result is 1 , otherwise it’s 0 .

What is the difference between like and Rlike operators in hive?

LIKE is an operator similar to LIKE in SQL. We use LIKE to search for string with similar text. RLIKE (Right-Like) is a special function in Hive where if any substring of A matches with B then it evaluates to true. It also obeys Java regular expression pattern.

What is explode in hive?

Explodes an array to multiple rows. Returns a row-set with a single column (col), one row for each element from the array. explode(MAP m)

In what language is hive written?

Java

What is coalesce in hive?

If you have a field that is full of NULLs, you can use another field to put values in for those NULLs that you think provide a good approximate value of what should be there. I want an example! COALESCE allows you to use other data from other fields as a proxy.

Is numeric function in hive?

The Hive CAST function converts the value of an expression or column to any other type. You can use this function in the WHERE clause with NULL statements to filter out non-numeric values. Cast given value to double, non-null value will be the numeric value.

What is Regexp_extract?

REGEXP_EXTRACT. A string function used in search operations for sophisticated pattern matching including repetition and alternation. the string to search for strings matching the regular expression.

What is UDAF in hive?

User-Defined Aggregation Functions (UDAFs) are an exceptional way to integrate advanced data-processing into Hive. Aggregate functions perform a calculation on a set of values and return a single value. An aggregate function is more difficult to write than a regular UDF.

What is a table generating function on hive?

A user-defined table generating function (UDTF) has the ability to output any number of fields and any number of rows for each row of input. Writing one is very similar to writing a generic user-defined function.

What is the use of UDF?

In the simplest terms, a user-defined function (UDF) in SQL Server is a programming construct that accepts parameters, does work that typically makes use of the accepted parameters, and returns a type of result.

What is map in hive?

Map – a complex data type in Hive which can store Key-Value pairs. Values from a map can be accessed using the keys.

What is lateral view in hive?

Lateral view is used in conjunction with user-defined table generating functions such as explode() . A lateral view first applies the UDTF to each row of base table and then joins resulting output rows to the input rows to form a virtual table having the supplied table alias. Version. Prior to Hive 0.6.

How do you pivot in hive?

Apache Hive does not have direct standard UDF for transposing rows into columns. Transpose & Pivot in Hive Query can be achieved using multi-stage process. You can use collect_list() or collect_set() function and merge the multiple rows into columns and then get the result.