​
reduce_agg

Reduces all input values into a single value. inputFunction will be invoked for each non-null input value. In addition to taking the input value, inputFunction takes the current state, initially initialState, and returns the new state. combineFunction will be invoked to combine two states into a new state. The final state is returned. Supported Signatures 
function reduce_agg($1, $10, function($10, $1, $10), function($10, $10, $10)) returns $10
🔗 Official Documentation

​
regexp_replace

Removes every instance of the substring matched by the regular expression pattern from string. Examples:
examples.sql
SELECT REGEXP_REPLACE('text foo another text', 'foo', 'bar') -- value 'text bar another text'
Supported Signatures 
function regexp_replace(varchar, joniregexp) returns varchar
function regexp_replace(varchar, joniregexp, varchar) returns varchar
🔗 Official Documentation