Re: Setting group_concat_max_len

[Rick James]

Please provide
SHOW VARIABLES LIKE '%buffer%'; -- I want to see your cache settings
SHOW TABLE STATUS LIKE 'tbl' \G -- How big? What Engine?
SELECT SUM(LENGTH(xml_piece)) FROM tbl WHERE ...; -- how long does it take to touch the data?
SELECT LENGTH(GROUP_CONCAT(xml_piece)) FROM tbl WHERE ...; -- versus how long the GROUP_CONCAT takes.

I ran an experiment and found GROUP_CONCAT took less than twice as long as it took to fetch the data.