The bug could cause wrong results for queries over Maria tables when
index condition pushdown was used.

The set of Ordered keys of a rowid merge engine is dense. Thus when
we decide not to create a key for a column that has only NULLs, this
column shouldn't be counted.

Notice that the caller has already precomputed the correct total
number of keys that should be created.

Post-review fix - avoid re-evaluation of the having clause
when it evaluates to true.

sql/sql_expression_cache.cc:
  Type of the variable fixed.
sql/sql_expression_cache.h:
  Type of the variable fixed.

The cause for this bug is that MariaDB 5.3 still processes derived tables
(subqueries in the FROM clause) by fully executing them during the parse
phase. This will be remedied by MWL#106 once merged into the main 5.3.

The assert statement is triggered when MATERIALIZATION is ON for EXPLAIN
EXTENDED for derived tables with an IN subquery as follows:
- mysql_parse calls JOIN::exec for the derived table as if it is regular
  execution (not explain).
- When materialization is ON, this call goes all the way to
  subselect_hash_sj_engine::exec, which creates a partial match engine
  because of NULL presence.
- In order to proceed with normal execution, the hash_sj engine substitutes
  itself with the created partial match engine.
- After the parse phase it turns out that this execution was part of
  EXPLAIN EXTENDED, which in turn calls
  Item_cond::print -> ... -> Item_subselect::print,
  which calls engine->print().
  Since subselect_hash_sj_engine::exec substituted the current
  Item_subselect engine with a  partial match engine, eventually we call
  its ::print() method. However the partial match engines are designed only
  for execution, hence there is no implementation of this print() method.

The fix temporarily removes the assert, until this code is merged with
MWL#106.

The bug was a result of missing logic to handle the case
when there are 'expensive' predicates that are not evaluated
during constant table optimization. Such is the case for
the IN predicate, which is considered expensive if it is
computed via materialization. In general this bug can be
triggered with any expensive predicate instead of IN.

When FALSE constant predicates are not evaluated during constant
optimization, the execution path changes so that instead of
setting JOIN::zero_result_cause after make_join_select, and
exiting JOIN::exec via the call to return_zero_rows(), execution
ends in JOIN::exec in the branch:
if (join->tables == join->const_tables)
{
  ...
  else if (join->send_row_on_empty_set())
     ...
     rc= join->result->send_data(*columns_list);
}
Unlike return_zero_rows(), this branch didn't evaluate the
having clause of the query.

The patch adds a call to evaluate the HAVING clause of a query even
when all tables are constant, because even for an empty result set
some aggregate functions may produce a NULL value.

bugfix: engine defined table options were not showing up in INFORMATION_SCHEMA.TABLES.CREATE_OPTIONS

BUG#26447 prefer a clustered key for an index scan, as secondary index is always slower
  ... which was fixed to cause
BUG#35850 queries take 50% longer
  ... and was reverted

and

BUG#39653 prefer a secondary index for an index scan, as clustered key is always slower
  ... which was fixed to cause
BUG#55656 mysqldump takes six days instead of half an hour
  ... and was amended with a special case workaround


sql/opt_range.cc:
  move get_index_only_read_time() into the handler class
sql/sql_select.cc:
  use cost not an index length when choosing a cheaper index

(Otherwise we get different EXPLAINs for xtradb and innodb plugin).

- Fix a crash in nested semi-join subquery processing

- When building multiple-equalities for HAVING, don't set JOIN::cond_equal, set
  join_having_equal instead. Setting JOIN::cond_equal based on HAVING makes 
  equality propagation data self-inconsistent

and mistakingly pulled in back for maria-5.1.50.

It should be turned on back when the tree for MWL#128 is merged
into the main 5.3 merge.

- post-merge fixes

Fixes for bugs found by running test case for LP#608369 "Page: 1 Found wrong page type 0' on CHECK TABLE EXTENDED"
Fixed overflow when using long --debug=xxxxxx line.
Fixed that "mysqld --disable-debug --debug" works.
Ensure that MariaDB doesn't start if the Aria engine didn't start and we are using Aria for temporary tables.
More DBUG_ASSERT() and more info in debug log.


dbug/dbug.c:
  Fixed crash in mysqld caused by an overflow when using long --debug=xxxxxx line
sql/mysqld.cc:
  Fixed that "mysqld --disable-debug --debug" works.
  Documented myisam-recover=OFF option
storage/maria/ha_maria.cc:
  Ensure that MariaDB doesn't start if the Aria engine didn't start and we are using Aria for temporary tables.
storage/maria/ma_delete.c:
  Added missing write of changed key on node page.
  This could fix LP#608369 "Page: 1 Found wrong page type 0' on CHECK TABLE EXTENDED"
  Changed so that we log page numbers (not positions)
  Added KEY_OP_DEBUG_2 log entry to get more debug information into the log
storage/maria/ma_key_recover.c:
  Changed so that we log page numbers (not positions)
  In case of wrong page information after index_redo, dump pages to debug log
storage/maria/ma_loghandler.h:
  Added KEY_OP_DEBUG_2
storage/maria/ma_search.c:
  Changed so that we log page numbers (not positions)
storage/maria/ma_write.c:
  Changed so that we log page numbers (not positions)

sql/sql_parse.cc:
  Make some not commonly used functions with big local variables to separate functions to make default stack usage smaller.
  Decrease size of db_buff[] (Was bigger than needed)
  Allocate current_global_status_var with malloc().
storage/maria/ha_maria.cc:
  Don't allocate HA_CHECK on stack (it's > 100K)
storage/maria/ma_check.c:
  Removed duplicated code

- Re-commit Monty's merge, partially fixed by Igor and SergeyP, 
  but still broken

- _ma_apply_redo_index: Assertion `page_offset != 0 && page_offset + length <= page_length' failed
Fixes one bug and one log assert when inserting rows:
- _ma_log_split: Assertion `org_length <= info->s->max_index_block_size' failed
- write_block_record:  Assertion '(data_length < MAX_TAIL_SIZE(block_size)' failed
Mark in recovery log where _ma_log_add() calls was done (for better debugging).

storage/maria/ma_bitmap.c:
  Don't write a head part on a tail page. (Caused an assert in write_block_record())
storage/maria/ma_delete.c:
  Mark in recovery log where _ma_log_add() calls was done
storage/maria/ma_key_recover.c:
  Mark in recovery log where _ma_log_add() calls was done
  Fixed not handled logging case for overfull index pages.
storage/maria/ma_key_recover.h:
  Mark in recovery log where _ma_log_add() calls was done
storage/maria/ma_loghandler.h:
  Mark in recovery log where _ma_log_add() calls was done
storage/maria/ma_rt_key.c:
  Mark in recovery log where _ma_log_add() calls was done
storage/maria/ma_write.c:
  Mark in recovery log where _ma_log_add() calls was done.
  Fixed wrong call to _ma_split_page() for overfull pages