smc> This happens in the case when mysql does not have to create temporrary
smc> tables in order to obtain result set, but is reading from the live
smc> table itself.
smc> Changing a table during such reading operation would break things.
smc> Please, do note that since 3.23.9 INSERT ANB SELECT can run in
smc> parallel, providing a table does not have deleted rows.
Wouldn't it be an improvement to store the query result in memory
before sending it if the query comes from a distant client ? This
would allow to release the table more quickly ...
Local delivery is quick if the client is connected through unix
socket, but if the client is distant then the "Sending data" delay
depends on communication speed (network bandwidth ...)
Or at least it would be great to have the possibility to choose by
query if the result has to be send back directly from the table or
from a memory buffer/temporary table.