sql: check plans can be run twice in presence of AFTER triggers

When running checks in parallel together, the current logic runs all checks from the main plan (which is used as a queue for any new checks produced by cascades and triggers). This is problematic, because once the post-query loop reaches a second iteration, the checks run in the previous iteration will run again. https://github.com/cockroachdb/cockroach/blob/2ebec1c6f4a99d516e83d0f323c3a5ab96991676/pkg/sql/distsql_running.go#L2215 We need to only run the checks from checksIdx on. Here is a logic test that will produce an unexpectedly found 2 active spans error:

statement ok
CREATE TABLE parent (k INT PRIMARY KEY);

statement ok
CREATE TABLE child (k INT PRIMARY KEY, v INT UNIQUE NOT NULL REFERENCES parent(k) ON UPDATE CASCADE ON DELETE CASCADE);
CREATE TABLE child2 (k INT PRIMARY KEY, v INT UNIQUE NOT NULL REFERENCES parent(k) ON UPDATE CASCADE ON DELETE CASCADE);

statement ok
CREATE TABLE grandchild (
  k INT PRIMARY KEY,
  v INT REFERENCES child(v) ON UPDATE CASCADE ON DELETE CASCADE,
  v2 INT REFERENCES child2(v) ON UPDATE CASCADE ON DELETE CASCADE
);

statement ok
INSERT INTO parent VALUES (1), (2), (3);
INSERT INTO child VALUES (1, 1), (2, 2), (3, 3);
INSERT INTO child2 VALUES (1, 1), (2, 2), (3, 3);
INSERT INTO grandchild VALUES (1, 1, 1), (2, 2, 2), (3, 2, 2), (4, 3, 3);

statement ok
CREATE FUNCTION g() RETURNS TRIGGER LANGUAGE PLpgSQL AS $$
  BEGIN
    RAISE NOTICE '% % ON %: % -> %', TG_WHEN, TG_OP, TG_TABLE_NAME, OLD, NEW;
    RETURN COALESCE(NEW, OLD);
  END
$$;

statement ok
CREATE TRIGGER bar AFTER INSERT OR UPDATE OR DELETE ON child FOR EACH ROW EXECUTE FUNCTION g();

statement ok
UPDATE parent SET k = k + 10 WHERE k < 3;

Note that this test has the same pattern as in #133784 - it just has a different trigger.

Jira issue: CRDB-43756

cockroachdb / cockroach

sql: check plans can be run twice in presence of AFTER triggers #133792