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Change Item_true and Item_false to pointers
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This is a prerequisite for moving them to a readonly segment.
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@montywi @cvicentiu
montywi authored and cvicentiu committed Jul 18, 2021
1 parent b32b1f2 commit d378a46
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Showing 6 changed files with 25 additions and 23 deletions.
6 changes: 3 additions & 3 deletions sql/item.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -55,8 +55,8 @@ const char *item_empty_name="";
const char *item_used_name= "\0";

static int save_field_in_field(Field *, bool *, Field *, bool);
const Item_bool_static Item_false("FALSE", 0);
const Item_bool_static Item_true("TRUE", 1);
Item_bool_static *Item_false;
Item_bool_static *Item_true;

/**
Compare two Items for List<Item>::add_unique()
Expand Down Expand Up @@ -445,7 +445,7 @@ Item::Item(THD *thd):
Item::Item():
name(null_clex_str), orig_name(0), is_expensive_cache(-1)
{
DBUG_ASSERT(my_progname == NULL); // before main()
DBUG_ASSERT(!mysqld_server_started); // Created early
base_flags= item_base_t::FIXED;
with_flags= item_with_t::NONE;
null_value= 0;
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3 changes: 2 additions & 1 deletion sql/item.h
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Expand Up @@ -4424,7 +4424,8 @@ class Item_bool_static :public Item_bool
{ DBUG_ASSERT(0); }
};

extern const Item_bool_static Item_false, Item_true;
/* The following variablese are stored in a read only segment */
extern Item_bool_static *Item_false, *Item_true;

class Item_uint :public Item_int
{
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4 changes: 2 additions & 2 deletions sql/item_xmlfunc.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -1232,13 +1232,13 @@ my_xpath_keyword(MY_XPATH *x,

static Item *create_func_true(MY_XPATH *xpath, Item **args, uint nargs)
{
return (Item*) &Item_true;
return (Item*) Item_true;
}


static Item *create_func_false(MY_XPATH *xpath, Item **args, uint nargs)
{
return (Item*) &Item_false;
return (Item*) Item_false;
}


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3 changes: 3 additions & 0 deletions sql/mysqld.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -5368,6 +5368,9 @@ static int init_server_components()
if (!opt_bootstrap)
servers_init(0);
init_status_vars();
Item_false= new (&startup_root) Item_bool_static("FALSE", 0);
Item_true= new (&startup_root) Item_bool_static("TRUE", 1);

DBUG_RETURN(0);
}

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2 changes: 1 addition & 1 deletion sql/sql_base.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -7427,7 +7427,7 @@ store_top_level_join_columns(THD *thd, TABLE_LIST *table_ref,
/* Add a TRUE condition to outer joins that have no common columns. */
if (table_ref_2->outer_join &&
!table_ref_1->on_expr && !table_ref_2->on_expr)
table_ref_2->on_expr= (Item*) &Item_true;
table_ref_2->on_expr= (Item*) Item_true;

/* Change this table reference to become a leaf for name resolution. */
if (left_neighbor)
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30 changes: 14 additions & 16 deletions sql/sql_select.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -2560,7 +2560,7 @@ int JOIN::optimize_stage2()
if (!conds && outer_join)
{
/* Handle the case where we have an OUTER JOIN without a WHERE */
conds= (Item*) &Item_true;
conds= (Item*) Item_true;
}

if (impossible_where)
Expand Down Expand Up @@ -2730,9 +2730,7 @@ int JOIN::optimize_stage2()

if (conds && const_table_map != found_const_table_map &&
(select_options & SELECT_DESCRIBE))
{
conds= (Item*) &Item_false;
}
conds= (Item*) Item_false;

/* Cache constant expressions in WHERE, HAVING, ON clauses. */
cache_const_exprs();
Expand Down Expand Up @@ -3049,7 +3047,7 @@ int JOIN::optimize_stage2()
having= having->remove_eq_conds(thd, &select_lex->having_value, true);
if (select_lex->having_value == Item::COND_FALSE)
{
having= (Item*) &Item_false;
having= (Item*) Item_false;
zero_result_cause= "Impossible HAVING noticed after reading const tables";
error= 0;
select_lex->mark_const_derived(zero_result_cause);
Expand Down Expand Up @@ -5625,7 +5623,7 @@ make_join_statistics(JOIN *join, List<TABLE_LIST> &tables_list,
if (join->cond_value == Item::COND_FALSE)
{
join->impossible_where= true;
conds= (Item*) &Item_false;
conds= (Item*) Item_false;
}

join->cond_equal= NULL;
Expand Down Expand Up @@ -11872,7 +11870,7 @@ make_join_select(JOIN *join,SQL_SELECT *select,COND *cond)
below to check if we should use 'quick' instead.
*/
DBUG_PRINT("info", ("Item_int"));
tmp= (Item*) &Item_true;
tmp= (Item*) Item_true;
}

}
Expand Down Expand Up @@ -15455,7 +15453,7 @@ COND *Item_cond_and::build_equal_items(THD *thd,
if (!cond_args->elements &&
!cond_equal.current_level.elements &&
!eq_list.elements)
return (Item*) &Item_true;
return (Item*) Item_true;

List_iterator_fast<Item_equal> it(cond_equal.current_level);
while ((item_equal= it++))
Expand Down Expand Up @@ -15562,7 +15560,7 @@ COND *Item_func_eq::build_equal_items(THD *thd,
Item_equal *item_equal;
int n= cond_equal.current_level.elements + eq_list.elements;
if (n == 0)
return (Item*) &Item_true;
return (Item*) Item_true;
else if (n == 1)
{
if ((item_equal= cond_equal.current_level.pop()))
Expand Down Expand Up @@ -15966,7 +15964,7 @@ Item *eliminate_item_equal(THD *thd, COND *cond, COND_EQUAL *upper_levels,
List<Item> eq_list;
Item_func_eq *eq_item= 0;
if (((Item *) item_equal)->const_item() && !item_equal->val_int())
return (Item*) &Item_false;
return (Item*) Item_false;
Item *item_const= item_equal->get_const();
Item_equal_fields_iterator it(*item_equal);
Item *head;
Expand Down Expand Up @@ -16111,7 +16109,7 @@ Item *eliminate_item_equal(THD *thd, COND *cond, COND_EQUAL *upper_levels,
switch (eq_list.elements)
{
case 0:
res= cond ? cond : (Item*) &Item_true;
res= cond ? cond : (Item*) Item_true;
break;
case 1:
if (!cond || cond->is_bool_literal())
Expand Down Expand Up @@ -17949,7 +17947,7 @@ Item_func_isnull::remove_eq_conds(THD *thd, Item::cond_result *cond_value,

*/

Item *item0= (Item*) &Item_false;
Item *item0= (Item*) Item_false;
Item *eq_cond= new(thd->mem_root) Item_func_eq(thd, args[0], item0);
if (!eq_cond)
return this;
Expand Down Expand Up @@ -29630,7 +29628,7 @@ void JOIN::make_notnull_conds_for_range_scans()
Found a IS NULL conjunctive predicate for a null-rejected field
in the WHERE clause
*/
conds= (Item*) &Item_false;
conds= (Item*) Item_false;
cond_equal= 0;
impossible_where= true;
DBUG_VOID_RETURN;
Expand All @@ -29653,7 +29651,7 @@ void JOIN::make_notnull_conds_for_range_scans()
Found a IS NULL conjunctive predicate for a null-rejected field
of the inner table of an outer join with ON expression tbl->on_expr
*/
tbl->on_expr= (Item*) &Item_false;
tbl->on_expr= (Item*) Item_false;
}
}
}
Expand Down Expand Up @@ -29804,7 +29802,7 @@ void build_notnull_conds_for_inner_nest_of_outer_join(JOIN *join,
if (used_tables &&
build_notnull_conds_for_range_scans(join, nest_tbl->on_expr, used_tables))
{
nest_tbl->on_expr= (Item*) &Item_false;
nest_tbl->on_expr= (Item*) Item_false;
}

li.rewind();
Expand All @@ -29818,7 +29816,7 @@ void build_notnull_conds_for_inner_nest_of_outer_join(JOIN *join,
}
else if (build_notnull_conds_for_range_scans(join, tbl->on_expr,
tbl->table->map))
tbl->on_expr= (Item*) &Item_false;
tbl->on_expr= (Item*) Item_false;
}
}
}
Expand Down

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