"Frank Millman" <frank@chagford.com> writes: > Pavel Stehule wrote: >> 2017-09-12 8:45 GMT+02:00 Frank Millman <frank@chagford.com>: >>> I am experimenting with optimising a SQL statement. One version uses 4 LEFT JOIN’s and a 5-way CASE statement in the body. The second moves the filtering into the JOIN section, and I end up with 16 LEFT JOIN’s and no CASE statements.
>> you can experimentally try increase FROM_COLLAPSE_LIMIT to some higher number 14 maybe 16
> I tried increasing FROM_COLLAPSE_LIMIT, but it made no difference.
For this you need to increase join_collapse_limit, not from_collapse_limit. (Usually, though, there's little reason not to keep them the same.)