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MDEV-36092 New-style hint: [NO_]SPLIT_MATERIALIZED

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Support for optimizer hints NO_SPLIT_MATERIALIZED and
SPLIT_MATERIALIZED.  These hints allow fine-grained control
of the "lateral derived" optimization within a query.

Introduces new overload of hint_table_state function which
tells both a hint's value as well as whether it is present.
This is useful to disambiguate cases that the other version
of hint_table_state cannot, such as when a hint is forcing
a behavior in the optimizer that it would not normally do
and the corresponding optimizer switch is enabled.
This commit is contained in:
Dave Gosselin
2025-04-24 15:03:05 -04:00
committed by Dave Gosselin
parent 07d71fdcf8
commit 62a1f0d990
8 changed files with 1467 additions and 26 deletions
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49
sql/opt_hints.cc
View File

@@ -47,6 +47,7 @@ struct st_opt_hint_info opt_hint_info[]=
{{STRING_WITH_LEN("JOIN_FIXED_ORDER")}, false, true, false},
{{STRING_WITH_LEN("DERIVED_CONDITION_PUSHDOWN")}, false, false, false},
{{STRING_WITH_LEN("MERGE")}, false, false, false},
{{STRING_WITH_LEN("SPLIT_MATERIALIZED")}, false, false, false},
{null_clex_str, 0, 0, 0}
};
@@ -608,6 +609,54 @@ static bool get_hint_state(Opt_hints *hint,
}
/*
In addition to indicating the state of a hint, also indicates
if the hint is present or not. Serves to disambiguate cases
that the other version of hint_table_state cannot, such as
when a hint is forcing a behavior in the optimizer that it
would not normally do and the corresponding optimizer switch
is enabled.
@param thd Current thread connection state
@param table_list Table having the hint
@param type_arg The hint kind in question
@return appropriate value from hint_state enumeration
indicating hint enabled/disabled (if present) or
if the hint was not present.
*/
hint_state hint_table_state(const THD *thd,
const TABLE_LIST *table_list,
opt_hints_enum type_arg)
{
if (!table_list->opt_hints_qb)
return hint_state::NOT_PRESENT;
DBUG_ASSERT(!opt_hint_info[type_arg].has_arguments);
Opt_hints *hint= table_list->opt_hints_table;
Opt_hints *parent_hint= table_list->opt_hints_qb;
if (hint && hint->is_specified(type_arg))
{
const bool hint_value= hint->get_switch(type_arg);
return hint_value ? hint_state::ENABLED :
hint_state::DISABLED;
}
if (opt_hint_info[type_arg].check_upper_lvl &&
parent_hint->is_specified(type_arg))
{
const bool hint_value= parent_hint->get_switch(type_arg);
return hint_value ? hint_state::ENABLED :
hint_state::DISABLED;
}
return hint_state::NOT_PRESENT;
}
/*
@brief
Check whether a given optimization is enabled for table.keyno.