Hi Alexey, I'm looking at how JSON_ARRAYAGG and JSON_OBJECTAGG work at processing JSON documents. I'm trying these examples, first on MySQL-8: create table t30 (col1 json); insert into t30 values('{"color":"red", "size":1}' ); insert into t30 values('{"color":"blue", "size":2}' ); select JSON_ARRAYAGG(col1) from t30; +-------------------------------------------------------------+ | JSON_ARRAYAGG(col1) | +-------------------------------------------------------------+ | [{"size": 1, "color": "red"}, {"size": 2, "color": "blue"}] | +-------------------------------------------------------------+ Good. create table t31 (name varchar(100), contents json); insert into t31 values('obj1', '{"color":"blue", "size":2}' ); insert into t31 values('obj2', '{"color":"red", "size":1}' ); select JSON_OBJECTAGG(name, contents) from t31; +-----------------------------------------------------------------------------+ | JSON_OBJECTAGG(name, contents) | +-----------------------------------------------------------------------------+ | {"obj1": {"size": 2, "color": "blue"}, "obj2": {"size": 1, "color": "red"}} | +-----------------------------------------------------------------------------+ Good. Now, trying these on MariaDB, I get: MariaDB [test]> select JSON_ARRAYAGG(col1) from t30; +------------------------------------------------------------------------+ | JSON_ARRAYAGG(col1) | +------------------------------------------------------------------------+ | ["{\"color\":\"red\", \"size\":1}","{\"color\":\"blue\", \"size\":2}"] | +------------------------------------------------------------------------+ MariaDB [test]> select JSON_OBJECTAGG(name, contents) from t31; +---------------------------------------------------------------------------------------+ | JSON_OBJECTAGG(name, contents) | +---------------------------------------------------------------------------------------+ | {"obj1":"{\"color\":\"blue\", \"size\":2}", "obj2":"{\"color\":\"red\", \"size\":1}"} | +---------------------------------------------------------------------------------------+ The JSON documents are coverted into strings. I think, the users will prefer MySQL's behavior. But which behaivor is "correct"? (i.e. required by the standard, etc) Is MariaDBs's behaivor a bug? Is this expected? BR Sergei -- Sergei Petrunia, Software Developer MariaDB Corporation | Skype: sergefp | Blog: http://s.petrunia.net/blog