- More function renames, added comments

- Better comments

sql/sql_select.cc:
  MWL#17: Table elimination
  - Fix buildbot failure: do set correct value to nested_join::n_tables

Fixes after post-review fixes:
- Don't search for tables in JOIN_TAB array. it's not initialized yet.
  use select_lex->leaf_tables instead.

- Post-postreview changes fix: Do set NESTED_JOIN::n_tables to number of 
  tables left after elimination.

- When making inferences "field is bound" -> "key is bound", do check 
  that the field is part of the key

- Continue addressing review feedback: remove "unusable KEYUSEs" 
  extension as it is no longer needed.

sql/item.h:
  MWL#17: Table elimination
  - Code cleanup
sql/opt_table_elimination.cc:
  MWL#17: Table elimination
  - Code cleanup

Address review feedback: 
- Change from Wave-based approach (a-la const table detection) to 
  building and walking functional dependency graph.
- Change from piggy-backing on ref-access code and KEYUSE structures
  to using our own expression analyzer.


sql/item.cc:
  MWL#17: Table elimination
  - Move from C-ish Field_processor_info to C++ ish and generic Field_enumerator
sql/item.h:
  MWL#17: Table elimination
  - Move from C-ish Field_processor_info to C++ ish and generic Field_enumerator
sql/sql_bitmap.h:
  MWL#17: Table elimination
  - Backport of Table_map_iterator from 6.0

- When collecting Item_subselect::refers_to, put references to the correct
  subselect entry.

- More comments
- Renove old code

- Last fixes

sql/item.cc:
  MWL#17: Table elimination
  - Don't make multiple calls of ::walk(check_column_usage_processor),
    call once and cache the value
sql/item.h:
  MWL#17: Table elimination
  - s/KEYUSE::usable/KEYUSE::type/, more comments
sql/opt_table_elimination.cc:
  MWL#17: Table elimination
  - Don't make multiple calls of ::walk(check_column_usage_processor),
    call once and cache the value
sql/sql_select.cc:
  MWL#17: Table elimination
  - s/KEYUSE::usable/KEYUSE::type/, more comments
sql/sql_select.h:
  MWL#17: Table elimination
  - s/KEYUSE::usable/KEYUSE::type/, more comments
sql/table.h:
  MWL#17: Table elimination
  - Better comments

mysql-test/r/table_elim.result:
  MWL#17: Table elimination
  - More tests
mysql-test/t/table_elim.test:
  MWL#17: Table elimination
  - More tests
sql/opt_table_elimination.cc:
  MWL#17: Table elimination
  - Code cleanup
sql/sql_select.cc:
  MWL#17: Table elimination
  - Code cleanup
sql/sql_select.h:
  MWL#17: Table elimination
  - Code cleanup
sql/table.h:
  MWL#17: Table elimination
  - Code cleanup

- Better comments, variable/function renames 

- Moved table elimination code to sql/opt_table_elimination.cc
- Added comments 

.bzrignore:
  MWL#17: Table elimination
  - Moved table elimination code to sql/opt_table_elimination.cc
libmysqld/Makefile.am:
  MWL#17: Table elimination
  - Moved table elimination code to sql/opt_table_elimination.cc
sql/CMakeLists.txt:
  MWL#17: Table elimination
  - Moved table elimination code to sql/opt_table_elimination.cc
sql/Makefile.am:
  MWL#17: Table elimination
  - Moved table elimination code to sql/opt_table_elimination.cc

- fix a typo bug in has_eqref_access_candidate()
- Adjust test to remove race condition

mysql-test/r/mysql-bug41486.result:
  Adjust test to remove race condition
mysql-test/t/mysql-bug41486.test:
  Adjust test to remove race condition
sql/item.cc:
  MWL#17: Table elimination:
    fix a typo bug in has_eqref_access_candidate()

- More testcases
- Let add_ft_key() set keyuse->usable

mysql-test/r/table_elim.result:
  MWL#17: Table elimination
  - More testcases
mysql-test/t/table_elim.test:
  MWL#17: Table elimination
  - More testcases
sql/sql_select.cc:
  MWL#17: Table elimination
  - Let add_ft_key() set keyuse->usable

- Make elimination check to be able detect cases like  t.primary_key_col1=othertbl.col AND t.primary_key_col2=func(t.primary_key_col1).
  These are needed to handle e.g. the case of func() being a correlated subquery that selects the latest value.
- If we've removed a condition with subquery predicate, EXPLAIN [EXTENDED] won't show the subquery anymore

sql/item.cc:
  MWL#17: Table elimination
  - Add tem_field::check_column_usage_processor(). it allows to check which key parts a condition depends on.
sql/item.h:
  MWL#17: Table elimination
  - Add tem_field::check_column_usage_processor(). it allows to check which key parts a condition depends on.
sql/item_subselect.cc:
  MWL#17: Table elimination
  - Item_subselect got 'eliminated' attribute. It is used only to determine if the subselect should be printed by EXPLAIN.
  - Item_subselect got List<Item> refers_to - a list of item in the current select that are referred to from within the subselect.
  - Added Item_*::check_column_usage_processor(). it allows to check which key parts a condition depends on.
  - Added a comment about possible problem in Item_subselect::walk
sql/item_subselect.h:
  MWL#17: Table elimination
  - Item_subselect got 'eliminated' attribute. It is used only to determine if the subselect should be printed by EXPLAIN.
  - Item_subselect got List<Item> refers_to - a list of item in the current select that are referred to from within the subselect.
  - Added Item_*::check_column_usage_processor(). it allows to check which key parts a condition depends on.
sql/item_sum.cc:
  MWL#17: Table elimination
sql/sql_lex.cc:
  MWL#17: Table elimination
sql/sql_lex.h:
  MWL#17: Table elimination
sql/sql_select.h:
  MWL#17: Table elimination

* Fix test results to account for changes in previous cset

* Change valgrind suppression to work on valgrind 3.3.0

- Move eliminate_tables() to before constant table detection. 
- First code for benchmark

sql-bench/test-table-elimination.sh:
  MWL#17: Table elimination
  - sql-bench "Benchmark", incomplete
sql/sql_select.cc:
  MWL#17: Table elimination
  - Move eliminate_tables() to before constant table detection, this will allow
    to spare const table reads (at a cost of not being able to take advantage of 
    tables that are constant because they have no records, but this case is of 
    lesser importance)

- Fix print_join() to work both for EXPLAIN EXTENDED (after table elimination) and for 
  CREATE VIEW (after join->prepare() but without any optimization).

mysql-test/r/union.result:
  MWL#17: Table elimination
  - Adjust test results

- Fix the previous cset: take into account that select_lex may be printed when 
 1. There is no select_lex->join at all (in that case, assume that no tables were eliminated)
 2. select_lex->join exists but there was no JOIN::optimize() call yet. handle this by initializing join->eliminated really early. 

- Do not show eliminated tables in the output of EXPLAIN EXTENDED

- Make elimination work with aggregate functions. The problem was that aggregate functions 
  reported all table bits in used_tables(), and that prevented table elimination. Fixed by 
  making aggregate functions return more correct value from used_tables(). 

mysql-test/r/ps_11bugs.result:
  MWL#17: Table elimination
  - Update test results. The difference is because of Item_ref change: outer references to constants
    are now recognized as constants, too.
mysql-test/r/subselect.result:
  - Update test results. The difference is because of Item_ref change: outer references to constants
    are now recognized as constants, too.
mysql-test/r/table_elim.result:
  MWL#17: Table elimination
  - Check that elimination works in presense of aggreagate functions
mysql-test/t/table_elim.test:
  MWL#17: Table elimination
  - Check that elimination works in presense of aggreagate functions
sql/item.h:
  MWL#17: Table elimination
  - Add Item_ref::const_item() which calls (*ref)->const_item(). Before this diff Item_ref used the 
    default implementation of const_item(){ return used_tables()==0; }. This is no longer true, as 
    COUNT(*) now has used_tables()==0 but const_item()==FALSE.
sql/item_sum.cc:
  MWL#17: Table elimination
  - Make Item_sum() and it descendants not to return all bits in used_tables(). This is needed 
    because otherwise table elimination can't work in presense of aggregate functions
  - COUNT(*) now has used_tables()==0 and const_item()==FALSE. Had to change 
    Item_ref::const_item() to account for this.
sql/item_sum.h:
  MWL#17: Table elimination
  - Add comments

  handle overlapping.

include/m_string.h:
  Fix valgrind failure: provide an implementation of strmov_overlapp() that really can handle overlapping.

- Fix trivial valgrind warning

- First code. Elimination works for simple cases, passes the testsuite.
- Known issues:
  = No elimination is done for aggregate functions.
  = EXPLAIN EXTENDED shows eliminated tables (I think it better not)
  = No benchmark yet
  = The code needs some polishing.

mysql-test/r/table_elim.result:
  MWL#17: Table elimination
  - Testcases
mysql-test/t/table_elim.test:
  MWL#17: Table elimination
  - Testcases
sql/sql_select.cc:
  MWL#17: Table elimination
sql/sql_select.h:
  MWL#17: Table elimination
  - Added JOIN_TAB::eliminated (is JOIN_TAB the best place to store this flag?)
sql/table.h:
  MWL#17: Table elimination
  - ADded NESTED_JOIN::n_tables. We need to have the number of real tables remaining in an outer join nest.

mysql-test/suite/maria/r/maria3.result:
  Merged fix from bug #39200.
mysql-test/suite/maria/t/maria3.test:
  Merged maria3.test
sql/sql_table.cc:
  Bug fix for 39200

 - Version number.
 - Valgrind false alarms in libz.
 - New variant of suppression for Valgrind warning in dlclose().
 - Fix double free() in plugin init error case.

configure.in:
  Fix version number. We should reset the maria variant back to `1' when the MySQL version
  number increases.
include/my_sys.h:
  Fix false alarms in Valgrind for zlib.
  
  Apply same fix as for archive storage handler also to the cases of compression in the
  client protocol, and to the compression SQL function.
mysql-test/valgrind.supp:
  A new variant of the dlclose() suppression is needed now.
mysys/my_compress.c:
  Fix false alarms in Valgrind for zlib.
  
  Apply same fix as for archive storage handler also to the cases of compression in the
  client protocol, and to the compression SQL function.
sql/handler.cc:
  Fix a double free() in error case for plugin initialisation.
sql/item_strfunc.cc:
  Fix false alarms in Valgrind for zlib.
  
  Apply same fix as for archive storage handler also to the cases of compression in the
  client protocol, and to the compression SQL function.

support-files/build-tags:
  Merge.

mysql-test/r/information_schema.result:
  Fixed a result file.
mysql-test/r/innodb-autoinc.result:
  Fixed a result file.
mysql-test/t/connect.test:
  Fixed a problem with merge, needed to close
  connections and use the default