SELECT rows with primary key of multiple columns

How do I select all relevant records according to the provided list of pairs?

table:

CREATE TABLE "users_groups" (
    "user_id" INTEGER NOT NULL,
    "group_id" BIGINT NOT NULL,
    PRIMARY KEY (user_id, group_id),
    "permissions" VARCHAR(255)
);

For example, if I have the following JavaScript array of pairs that I should get from DB

[
  {user_id: 1, group_id: 19},
  {user_id: 1, group_id: 11},
  {user_id: 5, group_id: 19}
]

Here we see that the same user_id can be in multiple groups.

I can pass with for-loop over every array element and create the following query:

SELECT * FROM users_groups
    WHERE (user_id = 1 AND group_id = 19) 
    OR (user_id = 1 AND group_id = 11) 
    OR (user_id = 5 AND group_id = 19);

But is this the best solution? Let say if the array is very long. As I know query length may get ~1GB.

what is the best and quick solution to do this?

Bill Karwin's answer will work for Postgres just as well.

However, I have made the experience that joining against a VALUES clause is very often faster than a large IN list (with hundreds if not thousands of elements):

select ug.*
from user_groups ug
  join ( 
     values (1,19), (1,11), (5,19), ... 
  ) as l(uid, guid) on l.uid = ug.user_id and l.guid = ug.group_id;

This assumes that there are no duplicates in the values provided, otherwise the JOIN would result in duplicated rows, which the IN solution would not do.

You tagged both mysql and postgresql, so I don't know which SQL database you're really using.

MySQL at least supports tuple comparisons:

SELECT * FROM users_groups WHERE (user_id, group_id) IN ((1,19), (1,11), (5,19), ...)

This kind of predicate can be optimized in MySQL 5.7 and later. See https://dev.mysql.com/doc/refman/5.7/en/range-optimization.html#row-constructor-range-optimization

I don't know whether PostgreSQL supports this type of predicate, or if it optimizes it.