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Fix for BUG#13455: Make "ref" optimizer able to make this inference:

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"t.key BETWEEN c1 AND c2" and c1 = c2 -> can access table t using "t.key = c1".
This commit is contained in:
sergefp@mysql.com
2005-09-30 01:34:19 +04:00
parent acdc193a45
commit 71d8990f8e
6 changed files with 88 additions and 20 deletions
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23
sql/sql_select.cc
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@ -2409,6 +2409,7 @@ add_key_field(KEY_FIELD **key_fields,uint and_level, Item_func *cond,
!field->table->maybe_null || field->null_ptr)
return; // Not a key. Skip it
exists_optimize= KEY_OPTIMIZE_EXISTS;
DBUG_ASSERT(num_values == 1);
}
else
{
@ -2460,7 +2461,26 @@ add_key_field(KEY_FIELD **key_fields,uint and_level, Item_func *cond,
eq_func is NEVER true when num_values > 1
*/
if (!eq_func)
return;
{
/*
Additional optimization: if we're processing
"t.key BETWEEN c1 AND c1" then proceed as if we were processing
"t.key = c1".
TODO: This is a very limited fix. A more generic fix is possible.
There are 2 options:
A) Make equality propagation code be able to handle BETWEEN
(including cases like t1.key BETWEEN t2.key AND t3.key)
B) Make range optimizer to infer additional "t.key = c" equalities
and use them in equality propagation process (see details in
OptimizerKBAndTodo)
*/
if ((cond->functype() == Item_func::BETWEEN) &&
value[0]->eq(value[1], field->binary()))
eq_func= TRUE;
else
return;
}
if (field->result_type() == STRING_RESULT)
{
if ((*value)->result_type() != STRING_RESULT)
@ -2487,7 +2507,6 @@ add_key_field(KEY_FIELD **key_fields,uint and_level, Item_func *cond,
}
}
}
DBUG_ASSERT(num_values == 1);
/*
For the moment eq_func is always true. This slot is reserved for future
extensions where we want to remembers other things than just eq comparisons