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).

1 files changed, 3 insertions, 3 deletions

diff --git a/sql/opt_range.h b/sql/opt_range.h
index 1ca245ea420..f602408ea82 100644
--- a/sql/opt_range.h
+++ b/sql/opt_range.h
@@ -994,7 +994,7 @@ class SQL_SELECT :public Sql_alloc {
   {
     key_map tmp;
     tmp.set_all();
-    return test_quick_select(thd, tmp, 0, limit, force_quick_range, FALSE) < 0;
+    return test_quick_select(thd, tmp, 0, limit, force_quick_range, FALSE, FALSE) < 0;
   }
   /* 
     RETURN
@@ -1011,7 +1011,7 @@ class SQL_SELECT :public Sql_alloc {
   }
   int test_quick_select(THD *thd, key_map keys, table_map prev_tables,
 			ha_rows limit, bool force_quick_range, 
-                        bool ordered_output);
+                        bool ordered_output, bool remove_false_parts_of_where);
 };
 
 
@@ -1036,7 +1036,7 @@ SQL_SELECT *make_select(TABLE *head, table_map const_tables,
 			table_map read_tables, COND *conds,
                         bool allow_null_cond,  int *error);
 
-bool calculate_cond_selectivity_for_table(THD *thd, TABLE *table, Item *cond);
+bool calculate_cond_selectivity_for_table(THD *thd, TABLE *table, Item **cond);
 
 #ifdef WITH_PARTITION_STORAGE_ENGINE
 bool prune_partitions(THD *thd, TABLE *table, Item *pprune_cond);