This allows to simplify net_real_read() and net_real_write() a bit.
Removed some superfluous #ifdef/ifndef MYSQL_SERVER from net_serv.cc
The code always runs in server, either normal or embedded.
Dead code for switching socket between blocking and non-blocking modes,
is also removed.
Removed pthread_kill() with alarm signal that woke up main thread on
server shutdown. Used shutdown(2) on polling sockets instead, to the same
effect.
Removed yet another superstitious pthread_kill(), that ran on non-Windows
in terminate_slave_thread().
In particular:
* @@debug
deprecated since 5.5.37
* sr_YU locale
deprecated since 10.0.11
* "engine_condition_pushdown" in the @@optimizer_switch
deprecated since 10.1.1
* @@date_format, @@datetime_format, @@time_format, @@max_tmp_tables
deprecated since 10.1.2
* @@wsrep_causal_reads
deprecated since 10.1.3
* "parser" in mroonga table comment
deprecated since 10.2.11
The patch is inspired from MySQL. Instead of using a single String to
hold the current active debug_sync signal, use a Hash_set to store
LEX_STRINGS. This patch ensures that a signal can not be lost, by being
overwritten by another thread via set DEBUG_SYNC = '... SIGNAL ...';
All signals are kepts "alive" until they are consumed by a wait event.
This requires updating test cases that assume the GLOBAL signal is never
consumed.
Follow-up work needed:
Port the additional syntax that allows one to set multiple signals
and also conditionally deactivate signals when waiting.
* rename in_subquery_conversion_threshold to in_predicate_conversion_threshold
* make it debug-only, hide from users
* change from ulong to uint - same type and range on all architectures
