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MDEV-5606: range optimizer: "x < y" is sargable, while "y > x" is not

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Port to mariadb-1.0 the following fix from mysql-5.6:

  Revision ID: jorgen.loland@oracle.com-20120314131055-ml54x9deueqfsff4
  BUG#13701206: WHERE A>=B DOES NOT GIVE SAME EXECUTION PLAN
                AS WHERE B<=A (RANGE OPTIMIZER)
 
that fix didn't have a public testcase, so I created one.
This commit is contained in:
Sergey Petrunya
2014-02-04 13:27:10 +04:00
parent 4d5f5f4cdf
commit 75a3527777
4 changed files with 112 additions and 11 deletions
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40
sql/opt_range.cc
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@ -7684,7 +7684,8 @@ static SEL_TREE *get_func_mm_tree(RANGE_OPT_PARAM *param, Item_func *cond_func,
param PARAM from SQL_SELECT::test_quick_select
cond_func item for the predicate
field_item field in the predicate
value constant in the predicate
value constant in the predicate (or a field already read from
a table in the case of dynamic range access)
(for BETWEEN it contains the number of the field argument,
for IN it's always 0)
inv TRUE <> NOT cond_func is considered
@ -7953,24 +7954,41 @@ static SEL_TREE *get_mm_tree(RANGE_OPT_PARAM *param,COND *cond)
DBUG_RETURN(ftree);
}
default:
DBUG_ASSERT (!ftree);
if (cond_func->arguments()[0]->real_item()->type() == Item::FIELD_ITEM)
{
field_item= (Item_field*) (cond_func->arguments()[0]->real_item());
value= cond_func->arg_count > 1 ? cond_func->arguments()[1] : 0;
value= cond_func->arg_count > 1 ? cond_func->arguments()[1] : NULL;
if (value && value->is_expensive())
DBUG_RETURN(0);
ftree= get_full_func_mm_tree(param, cond_func, field_item, value, inv);
}
else if (cond_func->have_rev_func() &&
cond_func->arguments()[1]->real_item()->type() ==
Item::FIELD_ITEM)
/*
Even if get_full_func_mm_tree() was executed above and did not
return a range predicate it may still be possible to create one
by reversing the order of the operands. Note that this only
applies to predicates where both operands are fields. Example: A
query of the form
WHERE t1.a OP t2.b
In this case, arguments()[0] == t1.a and arguments()[1] == t2.b.
When creating range predicates for t2, get_full_func_mm_tree()
above will return NULL because 'field' belongs to t1 and only
predicates that applies to t2 are of interest. In this case a
call to get_full_func_mm_tree() with reversed operands (see
below) may succeed.
*/
if (!ftree && cond_func->have_rev_func() &&
cond_func->arguments()[1]->real_item()->type() == Item::FIELD_ITEM)
{
field_item= (Item_field*) (cond_func->arguments()[1]->real_item());
value= cond_func->arguments()[0];
if (value && value->is_expensive())
DBUG_RETURN(0);
ftree= get_full_func_mm_tree(param, cond_func, field_item, value, inv);
}
else
DBUG_RETURN(0);
if (value && value->is_expensive())
DBUG_RETURN(0);
ftree= get_full_func_mm_tree(param, cond_func, field_item, value, inv);
}
DBUG_RETURN(ftree);