Bulk update with associative array in PostgreSQL - sql

Question

Let's say I have an associative array (defined in another language) like so:
apply = {
'qwer': ['tju', 'snf', 'rjtj', 'sadgg']
'asdf': ['rtj', 'sfm', 'rtjt', 'adjdj']
...
'zxcv': ['qwr', 'trj', '3w4u', '3tt3']
}
And I have a table like so:
CREATE TABLE apples (
id integer,
name varchar(10),
key varchar(10),
value varchar(10)
);
I want to apply an update where if apples.value is in one of the lists of the apply variable, then set the apples.key to the key of the array. If apples.value was tju then set apples.key to qwer.
My current approach looks like this (mixing PostgreSQL with any procedural language):
for key in apply.keys:
UPDATE apples SET key=$key
FROM (SELECT unnest(array($apply[key])) AS value) AS update_table
WHERE value=update_table.value
I want to do this in a single statement.

Answer 1

As proof of concept for the given example, with the string formatted exactly as you display:
Demonstrating a prepared statement, like your client probably uses.
PREPARE my_update AS
UPDATE apples a
SET key = upd.key
FROM (
SELECT trim (split_part(key_val, ': ', 1), ' ''') AS key
, string_to_array(translate(split_part(key_val, ': ', 2), '[]''', ''), ', ') AS val_arr
FROM unnest(string_to_array(trim($1, E'{}\n'), E'\n')) key_val
) upd
WHERE a.value = ANY(upd.val_arr);
EXECUTE in the same session any number of times:
EXECUTE my_update($assoc_arr${
'qwer': ['tju', 'snf', 'rjtj', 'sadgg']
'asdf': ['rtj', 'sfm', 'rtjt', 'adjdj']
'zxcv': ['qwr', 'trj', '3w4u', '3tt3']
}$assoc_arr$);
SQL Fiddle.
Related:
Insert text with single quotes in PostgreSQL
Split given string and prepare case statement
But I would rather process the type in its original language and pass key and val_arr separately.