Postgresql - Dynamically create multi-level ordering with function - sql

Question

I am creating a function which will build and execute a dynamic sql statement. Basically it is building the ORDER BY clause, which will have the ability to ORDER multiple levels deep based on an array of VARCHARs passed in by the user.
For instance a user's input would be an array:
{{orderColumn, orderDirection},{orderColumn, orderDirection},...}
Obviously, I understand where the issue is in the statement, because postgres prints it out rather clearly. The problem is that I can't figure out the correct syntax in this particular case. Perhaps I am doing it incorrectly and there is a much better route for me to take, I am not set on this approach. If I can do this without dynamic sql it would be even better. Help or insight would be appreciated.
For reference I am using PostgreSQL 9.6.9
My code so far...
CREATE OR REPLACE FUNCTION profile.sp_rider_search(
_limit integer,
_offset integer,
_term text,
_orderBy VARCHAR[],
_registration_date timestamp with time zone DEFAULT
to_timestamp((0)::double precision))
RETURNS TABLE(customer_id integer
, first_name character varying
, last_name character varying
, dob date
, cell_phone character varying
, email character varying
, registration_date timestamp with time zone
, full_count integer)
AS $func$
DECLARE
sql TEXT := 'SELECT pp.user_id AS customer_id,
pp.first_name,
pp.last_name,
pp.date_of_birth AS dob,
pp.cell_phone,
aau.email,
pp.created AS registration_date,
count(*) OVER()::integer AS full_count
FROM profile.profile pp
LEFT JOIN authsvc.all_users aau ON aau.id = pp.user_id
WHERE pp.created > $5 AND (
pp.last_name ILIKE % || $3 || %
OR pp.first_name ILIKE % || $3 || %
OR pp.cell_phone ILIKE % || $3 || %
OR CAST(pp.user_id AS TEXT) ILIKE % || $3 || %
OR aau.email ILIKE % || $3 || %
OR CONCAT(pp.first_name,'' '',pp.last_name) ILIKE % || $3 || %
)
ORDER BY';
_item TEXT;
BEGIN
FOREACH _item IN ARRAY $4
LOOP
CASE WHEN _item[2] = 1 THEN
CASE WHEN _item[1] = 'last_name' THEN
sql := sql || ' pp.last_name, ';
WHEN _item[1] = 'first_name' THEN
sql := sql || ' pp.first_name, ';
WHEN _item[1] = 'email' THEN
sql := sql || ' aau.email, ';
WHEN _item[1] = 'phone' THEN
sql := sql || ' pp.cell_phone, ';
WHEN _item[1] = 'customer_id' THEN
sql := sql || ' pp.user_id::TEXT, ';
WHEN _item[1] = 'registration_date' THEN
sql := sql || ' pp.created::TEXT, ';
END
END
CASE WHEN _item[2] = -1 THEN
CASE WHEN _item[1] = 'last_name' THEN
sql := sql || ' pp.last_name DESC, ';
WHEN _item[1] = 'first_name' THEN
sql := sql || ' pp.first_name DESC, ';
WHEN _item[1] = 'email' THEN
sql := sql || ' aau.email DESC, ';
WHEN _item[1] = 'phone' THEN
sql := sql || ' pp.cell_phone DESC, ';
WHEN _item[1] = 'customer_id' THEN
sql := sql || ' pp.user_id::TEXT DESC, ';
WHEN _item[1] = 'registration_date' THEN
sql := sql || ' pp.created::TEXT DESC, ';
END
END
END LOOP;
sql := sql || 'LIMIT $1
OFFSET $2;'
RETURN QUERY EXECUTE sql
USING _limit,
_offset,
_term,
_orderBy,
_registration_date;
END;
$func$ LANGUAGE plpgsql;
On execution of this statement I get the error:
ERROR: syntax error at or near "END"
LINE 57: END
^
SQL state: 42601
Character: 998

Answer 1

I had a few syntax errors in my statement that I finally ironed out, hopefully this will help others. I needed to add in END CASE; for each case statement, I also had to add a semicolon after OFFSET $2; as well as remove a trailing comma from the order by statements.
Final working code -->
CREATE OR REPLACE FUNCTION profile.sp_rider_search(
_limit integer,
_offset integer,
_term text,
_orderBy VARCHAR[],
_registration_date timestamp with time zone DEFAULT
to_timestamp((0)::double precision),
_preferred_column TEXT DEFAULT '')
RETURNS TABLE(customer_id integer
, first_name character varying
, last_name character varying
, dob date
, cell_phone character varying
, email character varying
, registration_date timestamp with time zone
, full_count integer)
AS $func$
DECLARE
sql TEXT := 'SELECT pp.user_id AS customer_id,
pp.first_name,
pp.last_name,
pp.date_of_birth AS dob,
pp.cell_phone,
aau.email,
pp.created AS registration_date,
count(*) OVER()::integer AS full_count
FROM profile.profile pp
LEFT JOIN authsvc.all_users aau ON aau.id = pp.user_id
WHERE pp.created > $5 AND (
pp.last_name ILIKE % || $3 || %
OR pp.first_name ILIKE % || $3 || %
OR pp.cell_phone ILIKE % || $3 || %
OR CAST(pp.user_id AS TEXT) ILIKE % || $3 || %
OR aau.email ILIKE % || $3 || %
OR CONCAT(pp.first_name,'' '',pp.last_name) ILIKE % || $3 || %
)
ORDER BY';
_item TEXT;
BEGIN
FOREACH _item IN ARRAY $4
LOOP
CASE WHEN _item[2] = 1 THEN
CASE WHEN _item[1] = 'last_name' THEN
sql := sql || ' pp.last_name, ';
WHEN _item[1] = 'first_name' THEN
sql := sql || 'pp.first_name, ';
WHEN _item[1] = 'email' THEN
sql := sql || 'aau.email, ';
WHEN _item[1] = 'phone' THEN
sql := sql || 'pp.cell_phone, ';
WHEN _item[1] = 'customer_id' THEN
sql := sql || 'pp.user_id::TEXT, ';
WHEN _item[1] = 'registration_date' THEN
sql := sql || 'pp.created::TEXT, ';
END CASE;
WHEN _item[2] = -1 THEN
CASE WHEN _item[1] = 'last_name' THEN
sql := sql || ' pp.last_name DESC, ';
WHEN _item[1] = 'first_name' THEN
sql := sql || 'pp.first_name DESC, ';
WHEN _item[1] = 'email' THEN
sql := sql || 'aau.email DESC, ';
WHEN _item[1] = 'phone' THEN
sql := sql || 'pp.cell_phone DESC, ';
WHEN _item[1] = 'customer_id' THEN
sql := sql || 'pp.user_id::TEXT DESC, ';
WHEN _item[1] = 'registration_date' THEN
sql := sql || 'pp.created::TEXT DESC, ';
END CASE;
END CASE;
END LOOP;
sql := TRIM(TRAILING ',' FROM sql);
sql := sql || 'LIMIT $1
OFFSET $2;';
RETURN QUERY EXECUTE sql
USING _limit,
_offset,
_term,
_orderBy,
_registration_date;
END;
$func$ LANGUAGE plpgsql;