- better comments
- rename variables to better reflect their meaning

- First part of the fix: enable Early NULLs filtering to work when WHERE clause is present

BUG#628785: multi_range_read.cc:430: int DsMrr_impl::dsmrr_init(): Assertion `do_sort_keys || do_rowid_fetch' failed 
- Make Ds_MrrImpl::check_cpk_scan() follow the execution code' logic: don't
  do MRR scans on clustered PK when mrr_sort_keys=off.

- When find_all_keys() checks which table columns are needed for table scan
  that is done before the sorting, it should also analyze pushed index condition.
  This is achieved by remembering/checking pre-index-pushed condition.

- More test coverage

- Relax overly-strict assert added in previous commit
- Run generic MRR testsuite for Maria engine, too.

- Address review feedback, step 1 

- Make testcase stable 

- don't allocate space for rowid buffer when we don't really need it.
- fix buffer iterator

Incorrect limitation on number of parameters removed.

mysql-test/r/subselect_cache.result:
  Test suite added.
mysql-test/t/subselect_cache.test:
  Test suite added.
sql/sql_class.h:
  Iterator changed.
sql/sql_expression_cache.cc:
  Incorrect limitation removed.
  Removing NULL references from subquery parameter list added.

Removed indirect reference in equalities for cache index lookup.

We should use a direct reference because some optimization of the
query may optimize out a condition predicate and if the outer reference
is the only element of the condition predicate the indirect reference
becomes NULL.

We can resolve correctly the indirect reference in
Expression_cache_tmptable::make_equalities because it is called before
optimization of the cached subquery.


mysql-test/r/subquery_cache.result:
  The test suite for the bug added.
mysql-test/t/subquery_cache.test:
  The test suite for the bug added.
sql/sql_expression_cache.cc:
  Removed indirect reference in equalities for cache index lookup.

Added get_tmp_table_item() to cache wrapper as it has all not simple Items (Item_func, Item_field, Item_subquery).

mysql-test/r/subquery_cache.result:
  Tests for bugs fixed.
mysql-test/t/subquery_cache.test:
  Tests for bugs fixed.
sql/item.cc:
  Added get_tmp_table_item() to cache wrapper as it has all not simple Items (Item_func, Item_field, Item_subquery).
sql/item.h:
  Added get_tmp_table_item() to cache wrapper as it has all not simple Items (Item_func, Item_field, Item_subquery).

check_join_cache_usage() by the change:

Revno: 2793
Revision Id: igor@askmonty.org-20091221022615-kx5ieiu0okmiupuc
Timestamp: Sun 2009-12-20 18:26:15 -0800

Backport into MariaDB-5.2 the following:
WL#2771 "Block Nested Loop Join and Batched Key Access Join"

- Let DS-MRR/CPK take advantage of materialized keys, when possible

- Lots of TODO comments
- add mrr_sort_keys flag to @@optimizer_switch
- [from Igor] SQL layer part passes HA_MRR_MATERIALIZED_KEYS flag
- Don't call rnd_pos() many times in a row if sorted rowid buffer
  has the same rowid value for multiple consequive (rowid, range_id) pairs.

was not cleaned up between PS re-executions. The reason was two-fold:
- a merge with mysql-6.0 missed select_union::cleanup() that should
  have cleaned up the temp table, and
- the subclass of select_union used by materialization didn't call
  the base class cleanup() method.

- Merge with current 5.3

- Let "mysqld  --help --verbose" list all optimizer options
- Make it possible to add new @@optimizer_switch flags w/o causing .result 
  changes all over the testsuite:
  = Remove "select @@optimizer_switch" from tests that do not need all switches
  = Move @@optimizer_switch-specific tests to t/optimizer_switch.test

Updated configure.in to have version 5.3

configure.in:
  Updated to version 5.3.0

Improved speed of thr_alarm from O(N) to O(1). thr_alarm is used to handle timeouts and kill of connections.
Fixed compiler warnings.
queues.h and queues.c are now based on the UNIREG code and thus made BSD.
Fix code to use new queue() interface. This mostly affects how you access elements in the queue.
If USE_NET_CLEAR is not set, don't clear connection from unexpected characters. This should give a speed up when doing a lot of fast queries.
Fixed some code in ma_ft_boolean_search.c that had not made it from myisam/ft_boolean_search.c


include/queues.h:
  Use UNIREG code base (BSD)
  Changed init_queue() to take all initialization arguments.
  New interface to access elements in queue
include/thr_alarm.h:
  Changed to use time_t instead of ulong (portability)
  Added index_in_queue, to be able to remove random element from queue in O(1)
mysys/queues.c:
  Use UNIREG code base (BSD)
  init_queue() and reinit_queue() now takes more initialization arguments. (No need for init_queue_ex() anymore)
  Now one can tell queue_insert() to store in the element a pointer to where element is in queue. This allows one to remove elements from queue in O(1) instead of O(N)
mysys/thr_alarm.c:
  Use new option in queue() to allow fast removal of elements.
  Do less inside LOCK_alarm mutex.
  This should give a major speed up of thr_alarm usage when there is many threads
sql/create_options.cc:
  Fixed wrong printf
sql/event_queue.cc:
  Use new queue interface()
sql/filesort.cc:
  Use new queue interface()
sql/ha_partition.cc:
  Use new queue interface()
sql/ha_partition.h:
  Fixed compiler warning
sql/item_cmpfunc.cc:
  Fixed compiler warning
sql/item_subselect.cc:
  Use new queue interface()
  Removed not used variable
sql/net_serv.cc:
  If USE_NET_CLEAR is not set, don't clear connection from unexpected characters.
  This should give a speed up when doing a lot of fast queries at the disadvantage that if there is a bug in the client protocol the connection will be dropped instead of being unnoticed.
sql/opt_range.cc:
  Use new queue interface()
  Fixed compiler warnings
sql/uniques.cc:
  Use new queue interface()
storage/maria/ma_ft_boolean_search.c:
  Copy code from myisam/ft_boolean_search.c
  Use new queue interface()
storage/maria/ma_ft_nlq_search.c:
  Use new queue interface()
storage/maria/ma_sort.c:
  Use new queue interface()
storage/maria/maria_pack.c:
  Use new queue interface()
  Use queue_fix() instead of own loop to fix queue.
storage/myisam/ft_boolean_search.c:
  Use new queue interface()
storage/myisam/ft_nlq_search.c:
  Use new queue interface()
storage/myisam/mi_test_all.sh:
  Remove temporary file from last run
storage/myisam/myisampack.c:
  Use new queue interface()
  Use queue_fix() instead of own loop to fix queue.
storage/myisam/sort.c:
  Use new queue interface()
storage/myisammrg/myrg_queue.c:
  Use new queue interface()
storage/myisammrg/myrg_rnext.c:
  Use new queue interface()
storage/myisammrg/myrg_rnext_same.c:
  Use new queue interface()
storage/myisammrg/myrg_rprev.c:
  Use new queue interface()