Hi,

I've just tested the CONNECT engine on a "big" table (24GB) on my local server :

CREATE TABLE `url_list_connect` (

  `id` int(10) unsigned NOT NULL,

  `url` varchar(2048) NOT NULL DEFAULT '',

  `date` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,

  `id_license_domain` int(10) unsigned NOT NULL DEFAULT '0',

  `id_license` int(10) unsigned NOT NULL DEFAULT '0',

  `dom` mediumint(8) unsigned NOT NULL DEFAULT '0',

  `loadtime` mediumint(8) unsigned NOT NULL DEFAULT '0',

  `gen` mediumint(8) unsigned NOT NULL DEFAULT '0',

  `script` varchar(2048) NOT NULL DEFAULT '',

  `database_time` mediumint(8) unsigned NOT NULL DEFAULT '0'

) ENGINE=CONNECT DEFAULT CHARSET=latin1 `table_type`=MYSQL `dbname`=test `tabname`=url_list `option_list`='user=root,host=localhost,password=xxxx'

The original table is a tokudb table with a tokudb_cache_size of 12Go
(I can see the same behaviour with an InnoDB table).

Then I've tested the following :
SELECT * FROM url_list_connect LIMIT 10;

This query seems to execute a full scan of the table and load the whole table in memory, before returning the 10 first results.
Hence the mysql server finally crashes because out of memory. (even with a small innodb_buffer_pool_size / tokudb_cache_size / tmp_table_size).
I don't see any variable like in cassandra SE which allows to control the full scan behaviour :

"Full table scans are performed in a memory-efficient way. Cassandra SE performs a full table scan as a series of batches, each of which reads not more than cassandra_rnd_batch_size records."

To reproduce : create a table with a size > the total memory on the server, then select without a WHERE clause.

Thanks and regards,
Jocelyn Fournier