There were two problems: RESET QUERY CACHE took a long time to complete
and other threads were blocked during this time.
The patch does three things:
1 fixes a bug with improper use of test-lock-test_again technique.
AKA Double-Checked Locking is applicable here only in few places.
2 Somewhat improves performance of RESET QUERY CACHE.
Do my_hash_reset() instead of deleting elements one by one. Note
however that the slowdown also happens when inserting into sorted
list of free blocks, should be rewritten using balanced tree.
3 Makes RESET QUERY CACHE non-blocking.
The patch adjusts the locking protocol of the query cache in the
following way: it introduces a flag flush_in_progress, which is
set when Query_cache::flush_cache() is in progress. This call
sets the flag on enter, and then releases the lock. Every other
call is able to acquire the lock, but does nothing if
flush_in_progress is set (as if the query cache is disabled).
The only exception is the concurrent calls to
Query_cache::flush_cache(), that are blocked until the flush is
over. When leaving Query_cache::flush_cache(), the lock is
acquired and the flag is reset, and one thread waiting on
Query_cache::flush_cache() (if any) is notified that it may
proceed.
- Added empty constructors and virtual destructors to many classes and structs
- Removed some usage of the offsetof() macro to instead use C++ class pointers
if inner routine has more local variables than outer one, and
one of its last variables was used as argument to NOT operator".
THD::spcont was non-0 when we were parsing stored routine/trigger
definition during execution of another stored routine. This confused
methods of Item_splocal and forced them use wrong runtime context.
Fix ensures that we always have THD::spcont equal to zero during
routine/trigger body parsing. This also allows to avoid problems
with errors which occur during parsing and SQL exception handlers.
enabled query cache for ndb
modified engine interface somewhat
sql/ha_innodb.h
enabled query cache for ndb
modified engine interface somewhat
sql/ha_ndbcluster.cc
enabled query cache for ndb
modified engine interface somewhat
ndb will only allow caching and retrieval if running autocommit
- return false, but do not invalidate
commit count is used as engine data, i.e.
- store commit count before store of cache
- allow retrieval if commit count has not changed on a table
- invalidate if commit count has changed
sql/ha_ndbcluster.h
enabled query cache for ndb
modified engine interface somewhat
sql/handler.cc
enabled query cache for ndb
modified engine interface somewhat
sql/handler.h
enabled query cache for ndb
modified engine interface somewhat
new virtual handler method cached_table_registration called on each table before alowing store in query cache
- return TRUE - ok to cache, FALSE - not allowed to cache, invalidate queries if engine_data below has changed
- sets ulonglong (engine_data) that is stored in query cache for each table
- sets callback to be called for each table before usage of cached query, callback = 0 -> no check later
sql/mysql_priv.h
enabled query cache for ndb
modified engine interface somewhat
callcack prototype for callback to engine before query cache retrieval
sql/sql_cache.cc
enabled query cache for ndb
modified engine interface somewhat
if callback is set on table in cache, do callback to check if allowed to use cache
if not allowed to use cache, check if engine_data has changed, if so, invalidate all queries with that table
+ changes to store and pass callback and engine_data around
sql/sql_cache.h
enabled query cache for ndb
modified engine interface somewhat
changes to store callback and engine_data
sql/table.h
enabled query cache for ndb
modified engine interface somewhat
changes to store callback and engine_data
Made a some new buffers thread specific and changeable.
Resize of key_buffer.
AUTO_COMMIT -> AUTOCOMMIT
Fixed mutex bug in DROP DATABASE
Fixed bug when using auto_increment as second part of a key where first part could include NULL.
Split handler->extra() to extra() and extra_opt() to be able to support thread specific buffers.
Don't write message to error log when slave reconnects becasue of timeout.
Fixed possible update problem when using DELETE/UPDATE on small tables
(In some cases we used index even if table scanning would be better)
A lot of minior code cleanups
Fixes for building MySQL with gcc 3.0
Added SIGNED / UNSIGNED casts
Fixed core dump bug in net_clear() with libmysqld.
Back to using semaphores in query cache.
Added 'Null' and 'Index_type' to SHOW INDEX.
Added new operators to be used with gcc 3.0.x
Update of query cache code.
Added semaphores for Windows (not yet in use)
Added pthread_mutex_trylock for windows.
Changed some sql_alloc() -> thd->alloc()
Removed a lot of compiler warnings on Linux Alpha (64 bit)
Fixed some core dumps on 64 bit systems (wrong type for packet_len)
