BEGINNER HACKERS: array_remove(anyarray, anyarray)

On 12/10/15 6:25 PM, Jim Nasby wrote:
> Recently I had need of removing occurrences of a number of values from
> an array. Obviously I could have nested array_remove() call or wrapped
> the whole thing in a SELECT unnest(), but that seems rather silly and
> inefficient.
>
> Any one have objections to changing array_replace_internal() to make
> search and replace arrays instead of Datums?

Seeing none... let's see if someone wants to tackle this.

The goal is to modify array_replace_internal() (in 
src/backend/utils/adt/arrayfuncs.c) so that two of it's arguments 
(search and replace) can be arrays. I believe the best way to do that 
would be to add bool search_isarray and bool replace_isarray arguments, 
and have array_replace_internal() act accordingly if those are true.

The expected behavior when search_isarray is true would be to search for 
a group of elements that completely match the search array. When 
replace_isarray is true, then any replacements into *array would be the 
elements from replace, growing or shrinking the array as necessary.

The user visible array_remove and array_replace functions will need to 
check the data type of their inputs using get_fn_expr_argtype(). You can 
find examples of that in arrayfuncs.c.

A complete patch will also need regression tests 
(src/test/regress/sql/arrays.sql) and tweaks to the documentation for 
those functions (doc/src/sgml/func.sgml).
-- 
Jim Nasby, Data Architect, Blue Treble Consulting, Austin TX
Experts in Analytics, Data Architecture and PostgreSQL
Data in Trouble? Get it in Treble! http://BlueTreble.com