lemmy/migrations/2020-01-29-030825_create_user_mention_materialized_view/up.sql

CREATE VIEW user_mention_mview AS
with all_comment AS (
    SELECT
        ca.*
    FROM
        comment_aggregates_mview ca
)
SELECT
    ac.id,
    um.id AS user_mention_id,
    ac.creator_id,
    ac.post_id,
    ac.parent_id,
    ac.content,
    ac.removed,
    um.read,
    ac.published,
    ac.updated,
    ac.deleted,
    ac.community_id,
    ac.banned,
    ac.banned_from_community,
    ac.creator_name,
    ac.creator_avatar,
    ac.score,
    ac.upvotes,
    ac.downvotes,
    u.id AS user_id,
    coalesce(cl.score, 0) AS my_vote,
    (
        SELECT
            cs.id::bool
        FROM
            comment_saved cs
        WHERE
            u.id = cs.user_id
            AND cs.comment_id = ac.id) AS saved,
    um.recipient_id
FROM
    user_ u
    CROSS JOIN all_comment ac
    LEFT JOIN comment_like cl ON u.id = cl.user_id
        AND ac.id = cl.comment_id
    LEFT JOIN user_mention um ON um.comment_id = ac.id
UNION ALL
SELECT
    ac.id,
    um.id AS user_mention_id,
    ac.creator_id,
    ac.post_id,
    ac.parent_id,
    ac.content,
    ac.removed,
    um.read,
    ac.published,
    ac.updated,
    ac.deleted,
    ac.community_id,
    ac.banned,
    ac.banned_from_community,
    ac.creator_name,
    ac.creator_avatar,
    ac.score,
    ac.upvotes,
    ac.downvotes,
    NULL AS user_id,
    NULL AS my_vote,
    NULL AS saved,
    um.recipient_id
FROM
    all_comment ac
    LEFT JOIN user_mention um ON um.comment_id = ac.id;