Sergei Petrunia be00e279c6 MDEV-6480: Remove conditions for which range optimizer returned SEL_ARG::IMPOSSIBLE ...

Let range optimizer remove parts of OR-clauses for which range analysis
produced SEL_TREE(IMPOSSIBLE).
There is no need to remove parts of AND-clauses: either they are inside
of OR (and the whole AND-clause will be removed), or the AND-clause is
at the top level, in which case the whole WHERE (or ON) is always FALSE
and this is a degenerate case which receives special treatment.

The removal process takes care not to produce 1-way ORs (in that case
we substitute the OR for its remaining member).

2014-08-27 18:47:33 +04:00

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