Merge records belonging to same user - without losing payment or punishment information: http://stackoverflow.com/questions/35673982/using-jsonb-array-elements-with-where-in-condition

merge.sql

DROP TABLE IF EXISTS users;
CREATE TABLE users (
        uid SERIAL PRIMARY KEY,

        paid1_until timestamptz NULL,
        paid2_until timestamptz NULL,

        banned_until timestamptz NULL,
        banned_reason varchar(255) NULL
);

INSERT INTO users (paid1_until, paid2_until, banned_until, banned_reason)
VALUES (NULL, NULL, NULL, NULL),
       (current_timestamp + interval '1 month', NULL, NULL, NULL),
       (current_timestamp + interval '2 month', current_timestamp + interval '4 month', NULL, NULL),
       (NULL, current_timestamp + interval '8 month', NULL, NULL);

SELECT min(uid) as out_uid, 
        current_timestamp + sum(paid1_until - current_timestamp) as new_paid1, 
        current_timestamp + sum(paid2_until - current_timestamp) as new_paid2, 
        max(banned_until) as new_banned 
FROM users;

CREATE OR REPLACE FUNCTION merge_users(
        IN in_users jsonb,
        OUT out_uid integer)
        RETURNS integer AS
$func$
DECLARE
        new_paid1 timestamptz;
        new_paid2 timestamptz;
        new_banned timestamptz;
        new_reason varchar(255);
BEGIN
        SELECT min(uid),
                current_timestamp + sum(paid1_until - current_timestamp),
                current_timestamp + sum(paid2_until - current_timestamp),
                max(banned_until)
        INTO
                out_uid, new_paid1, new_paid2, new_banned
        FROM users 
        WHERE uid IN (SELECT JSONB_ARRAY_ELEMENTS(in_users));

        RAISE NOTICE 'out_uid = %', out_uid;
        RAISE NOTICE 'new_paid1 = %', new_paid1;
        RAISE NOTICE 'new_paid2 = %', new_paid2;
        RAISE NOTICE 'new_banned = %', new_banned;

        IF out_uid IS NOT NULL THEN
                SELECT banned_reason
                INTO new_reason
                FROM users
                WHERE new_banned IS NOT NULL
                AND banned_until = new_banned
                LIMIT 1;

                RAISE NOTICE 'new_reason = %', new_reason;

                DELETE FROM users
                WHERE uid IN (SELECT JSONB_ARRAY_ELEMENTS(in_users))
                AND uid <> out_uid;

                UPDATE users 
                SET paid1_until = new_paid1,
                    paid2_until = new_paid2,
                    banned_until = new_banned,
                    banned_reason = new_reason
                WHERE uid = out_uid;
        END IF; 
END
$func$ LANGUAGE plpgsql;