lemmy/replaceable_schema.sql

-- This sets up the `r` schema, which contains things that can be safely dropped and replaced instead of being
-- changed using migrations.
--
-- Statements in this file may not create or modify things outside of the `r` schema (indicated by the `r.` prefix),
-- except for these things, which are associated with something other than a schema (usually a table):
--   * A trigger if the function name after `EXECUTE FUNCTION` is in `r` (dropping `r` drops the trigger)
--
-- The default schema is not temporarily set to `r` because it would not affect some things (such as triggers) which
-- makes it hard to tell if the rule above is being followed.
--
-- If you add something here that depends on something (such as a table) created in a new migration, then down.sql must use
-- `CASCADE` when dropping it. This doesn't need to be fixed in old migrations because the "replaceable-schema" migration
-- runs `DROP SCHEMA IF EXISTS r CASCADE` in down.sql.

BEGIN;

DROP SCHEMA IF EXISTS r CASCADE;

CREATE SCHEMA r;

-- Rank calculations

CREATE OR REPLACE FUNCTION r.controversy_rank (upvotes numeric, downvotes numeric)
    RETURNS float
    AS $$
BEGIN
    IF downvotes <= 0 OR upvotes <= 0 THEN
        RETURN 0;
    ELSE
        RETURN (upvotes + downvotes) * CASE WHEN upvotes > downvotes THEN
            downvotes::float / upvotes::float
        ELSE
            upvotes::float / downvotes::float
        END;
    END IF;
END;
$$
LANGUAGE plpgsql
IMMUTABLE;

-- Selects both old and new rows in a trigger and allows using `sum(count_diff)` to get the number to add to a count
CREATE FUNCTION r.combine_transition_tables ()
    RETURNS SETOF record
    LANGUAGE sql
    AS $$
    SELECT
        -1 AS count_diff,
        *
    FROM
        old_table
    UNION ALL
    SELECT
        1 AS count_diff,
        *
    FROM
        new_table;
$$;

-- These triggers resolve an item's reports when the item is marked as removed.

CREATE PROCEDURE r.resolve_reports_when_target_removed (target_name text)
    LANGUAGE plpgsql
    AS $a$
BEGIN
    EXECUTE format($b$
        CREATE FUNCTION r.resolve_reports_when_%1$s_removed ()
            RETURNS trigger
            LANGUAGE plpgsql
            AS $$
        BEGIN
            UPDATE
                %1$s_report AS report
            SET
                resolved = TRUE,
                resolver_id = mod_person_id,
                updated = now()
            FROM
                new_removal
            WHERE
                report.%1$s_id = new_removal.%1$a_id AND new_removal.removed;

            RETURN NULL;
        END
        $$;

        CREATE TRIGGER resolve_reports
            AFTER INSERT ON mod_remove_%1$s
            REFERENCING NEW TABLE AS new_removal
            FOR EACH STATEMENT
            EXECUTE FUNCTION r.resolve_reports_when_%1$s_removed ();
        $b$,
        target_name);
END
$a$;

CALL r.resolve_reports_when_target_removed ('comment');

CALL r.resolve_reports_when_target_removed ('post');

-- These triggers create and update rows in each aggregates table to match its associated table's rows.
-- Deleting rows and updating IDs are already handled by `CASCADE` in foreign key constraints.

CALL r.upsert_aggregates ('comment', 'published', NULL);

CALL r.upsert_aggregates ('community', 'published', NULL);

CALL r.upsert_aggregates ('person', NULL, NULL);

CALL r.upsert_aggregates (
    'post',
    'published, newest_comment_time, newest_comment_time_necro, community_id, creator_id, instance_id, featured_community, featured_local',
    'published AS newest_comment_time, published AS newest_comment_time_necro, (SELECT community.instance_id FROM community WHERE community.id = community_id LIMIT 1) AS instance_id'
);

CREATE FUNCTION r.comment_aggregates_from_comment ()
    RETURNS trigger
    LANGUAGE plpgsql
    AS $$
BEGIN
    INSERT INTO comment_aggregates (comment_id, published)
    SELECT
        id,
        published
    FROM
        new_comment;

    RETURN NULL;
END
$$;

CREATE TRIGGER aggregates
    AFTER INSERT ON comment
    REFERENCING NEW TABLE AS new_comment
    FOR EACH STATEMENT
    EXECUTE FUNCTION r.comment_aggregates_from_comment ();

CREATE FUNCTION r.community_aggregates_from_community ()
    RETURNS trigger
    LANGUAGE plpgsql
    AS $$
BEGIN
    INSERT INTO community_aggregates (community_id, published)
    SELECT
        community_id,
        published
    FROM
        new_community;

    RETURN NULL;
END
$$;

CREATE TRIGGER aggregates
    AFTER INSERT ON community
    REFERENCING NEW TABLE AS new_community
    FOR EACH STATEMENT
    EXECUTE FUNCTION r.community_aggregates_from_community ();

CREATE FUNCTION r.person_aggregates_from_person ()
    RETURNS trigger
    LANGUAGE plpgsql
    AS $$
BEGIN
    INSERT INTO person_aggregates (person_id)
    SELECT
        id,
    FROM
        new_person;

    RETURN NULL;
END
$$;

CREATE TRIGGER aggregates
    AFTER INSERT ON person
    REFERENCING NEW TABLE AS new_person
    FOR EACH STATEMENT
    EXECUTE FUNCTION r.person_aggregates_from_person ();

CREATE FUNCTION r.post_aggregates_from_post ()
    RETURNS trigger
    LANGUAGE plpgsql
    AS $$
BEGIN
    INSERT INTO post_aggregates (post_id, published, newest_comment_time, newest_comment_time_necro, community_id, creator_id, instance_id, featured_community, featured_local)
    SELECT
        id,
        published,
        published,
        published,
        community_id,
        creator_id,
        (SELECT community.instance_id FROM community WHERE community.id = community_id LIMIT 1),
        featured_community,
        featured_local
    FROM
        new_post
    ON CONFLICT DO UPDATE SET
        featured_community = excluded.featured_community,
        featured_local = excluded.featured_local;

    RETURN NULL;
END
$$;

CREATE TRIGGER aggregates
    AFTER INSERT OR UPDATE OF featured_community, featured_local ON post
    REFERENCING NEW TABLE AS new_post
    FOR EACH STATEMENT
    EXECUTE FUNCTION r.post_aggregates_from_post ();

CREATE FUNCTION r.site_aggregates_from_site ()
    RETURNS trigger
    LANGUAGE plpgsql
    AS $$
BEGIN
    -- we only ever want to have a single value in site_aggregate because the site_aggregate triggers update all rows in that table.
    -- a cleaner check would be to insert it for the local_site but that would break assumptions at least in the tests
    IF NOT EXISTS (
    SELECT
        1
    FROM
        site_aggregates) THEN
        INSERT INTO
            site_aggregates (site_id)
        VALUES
            (NEW.id);

    RETURN NULL;
END
$$;

CREATE TRIGGER aggregates
    AFTER INSERT ON site
    FOR EACH ROW
    EXECUTE FUNCTION r.site_aggregates_from_site ();

-- These triggers update aggregates in response to votes.

CREATE PROCEDURE r.aggregates_from_like (target_name text, creator_id_getter text)
    LANGUAGE plpgsql
    AS $a$
BEGIN
    EXECUTE format($b$
        CREATE FUNCTION r.%1$s_aggregates_from_like ()
            RETURNS trigger
            LANGUAGE plpgsql
            AS $$
        BEGIN
            WITH
                -- Update aggregates for target
                target_diff (creator_id, score) AS (
                    UPDATE
                        %1$s_aggregates AS target_aggregates
                    SET
                        score = score + diff.upvotes - diff.downvotes,
                        upvotes = upvotes + diff.upvotes,
                        downvotes = downvotes + diff.downvotes,
                        controversy_rank = controversy_rank (
                            (upvotes + diff.upvotes)::numeric,
                            (downvotes + diff.downvotes)::numeric
                        )
                    FROM (
                        SELECT
                            target_id,
                            sum(count_diff) FILTER (WHERE score = 1) AS upvotes,
                            sum(count_diff) FILTER (WHERE score <> 1) AS downvotes
                        FROM
                            r.combine_transition_tables ()
                        GROUP BY
                            target_id
                    ) AS diff
                    WHERE
                        target_aggregates.comment_id = diff.target_id
                    RETURNING
                        %2$s,
                        diff.upvotes - diff.downvotes
                )
            -- Update aggregates for target's creator
            UPDATE
                person_aggregates
            SET
                %1$s_score = %1$s_score + diff.score;
            FROM (
                SELECT
                    creator_id,
                    sum(score)
                FROM
                    target_diff
                GROUP BY
                    creator_id
            ) AS diff
            WHERE
                person_aggregates.person_id = diff.creator_id;

            RETURN NULL;
        END
        $$;

        CREATE TRIGGER aggregates
            AFTER INSERT OR DELETE OR UPDATE OF score ON %1$s_like
            REFERENCING OLD TABLE AS old_table NEW TABLE AS new_table
            FOR EACH STATEMENT
            EXECUTE FUNCTION r.%1$s_aggregates_from_like;
        $b$,
        target_name,
        creator_id_getter);
END
$a$;

CALL r.aggregates_from_like ('comment', '(SELECT creator_id FROM comment WHERE comment.id = target_aggregates.comment_id LIMIT 1)');

CALL r.aggregates_from_like ('post', 'target_aggregates.creator_id');

COMMIT;