Handle "col<>const" in the same way that MDEV-21958 did for
"col NOT IN(const-list)": do not use the condition for range/index_merge
accesses if there is a unique UNIQUE KEY(col).
The testcase is in main/range.test. The rest of test updates are
due to widespread use of 'pk<>1' in the testsuite. Changed the test
to use different but equivalent forms of the conditions.
WL#2474 "Multi Range Read: Change the default MRR implementation to implement new MRR interface"
WL#2475 "Batched range read functions for MyISAM/InnoDb"
"Index condition pushdown for MyISAM/InnoDB"
Igor's fix from sp1r-igor@olga.mysql.com-20080330055902-07614:
There could be observed the following problems:
1. EXPLAIN did not mention pushdown conditions from on expressions in the
'extra' column. As a result if a query had no where conditions pushed
down to a table, but had on conditions pushed to this table the 'extra'
column in the EXPLAIN for the table missed 'using where'.
2. Conditions for ref access were not eliminated from on expressions
though such conditions were eliminated from the where condition.
