JSON_ARRAYAGG in MCS works differently than in InnoDB.

DROP DATABASE IF EXISTS json_arrayagg_db;CREATE DATABASE json_arrayagg_db;

USE json_arrayagg_db;CREATE TABLE t1 (a INT, b VARCHAR(80));

INSERT INTO t1 VALUES

       (1, "Hello"),(1, "World"), (2, "This"),(2, "Will"), (2, "Work"),(2, "!"), (3, NULL),

       (1, "Hello"),(1, "World"), (2, "This"),(2, "Will"), (2, "Work"),(2, "!"), (3, NULL);

SELECT JSON_ARRAYAGG(a), JSON_ARRAYAGG(b) FROM t1 GROUP BY a;

DROP TABLE t1;

CREATE TABLE t1 (a INT, b VARCHAR(80))ENGINE=COLUMNSTORE;

INSERT INTO t1 VALUES

       (1, "Hello"),(1, "World"), (2, "This"),(2, "Will"), (2, "Work"),(2, "!"), (3, NULL),

       (1, "Hello"),(1, "World"), (2, "This"),(2, "Will"), (2, "Work"),(2, "!"), (3, NULL);

SELECT JSON_ARRAYAGG(a), JSON_ARRAYAGG(b) FROM t1 GROUP BY a;

void JsonArrayAggOrderBy::processRow(const rowgroup::Row& row)

{

  // check if this is a distinct row

  if (fDistinct && fDistinctMap->find(row.getPointer()) != fDistinctMap->end())

    return;

  // this row is skipped if any concatenated column is null.

  if (concatColIsNull(row))

    return;

...