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MDEV-40180 Cache constant args in JSON_EQUALS and JSON_OVERLAPS #5455

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MDEV-40180 Cache constant args in JSON_EQUALS and JSON_OVERLAPS #5455

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136 changes: 104 additions & 32 deletions sql/item_jsonfunc.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -622,48 +622,107 @@ bool Item_func_json_equals::val_bool()
longlong result= 0;
int arg_num= 0;
String a_tmp, b_tmp;
String *a= nullptr, *b= nullptr;
THD *thd;
json_engine_t je;
bool a_const= args[0]->const_item(), b_const= args[1]->const_item();

if ((null_value= args[0]->null_value || args[1]->null_value))
return 1;

String *a= args[0]->val_json(&a_tmp);
if ((null_value= a == nullptr))
return 1;
String *b= args[1]->val_json(&b_tmp);
if ((null_value= b == nullptr))
return 1;

DYNAMIC_STRING a_res;
if (init_dynamic_string(&a_res, NULL, 0, 0))
{
null_value= 1;
return 1;
}
thd= current_thd;
JSON_DO_PAUSE_EXECUTION(thd, 0.0002);
je.killed_ptr= (uint32_t *) &thd->killed;

DYNAMIC_STRING b_res;
if (init_dynamic_string(&b_res, NULL, 0, 0))
/* Process First Argument */
if (a_const && a_parsed)

@grooverdan grooverdan Jul 31, 2026

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a_parsed is always the same as cached_a.str != nullptr so I think a_parsed can be eliminated.

{
dynstr_free(&a_res);
null_value= 1;
return 1;
if(a_null)

@grooverdan grooverdan Jul 30, 2026

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space after if

goto return_null;
}
else
{
a= args[0]->val_json(&a_tmp);

@grooverdan grooverdan Jul 30, 2026

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note after next rebase the null checking of a needs to be after this. 63d779c by @vuvova corrected my mistake (thank you!), lets not regress it.

if (!a)
goto set_a_null;

if (!cached_a.str)
{
if (init_dynamic_string(&cached_a, NULL, 0, 0))

@grooverdan grooverdan Jul 31, 2026

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As this is going to contain a normalized form of a, use a->length() as the 3rd arg for the initial size.

The failure of this is a memory allocation failure. While it hasn't been done well in other examples in this file yet, the response is:

my_error(ER_OUTOFMEMORY, MYF(0), a->length());
goto return_null

As a pushed error it shouldn't return here

goto set_a_null;
}
else
{
cached_a.length= 0;

@grooverdan grooverdan Jul 31, 2026

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just a comment in code here about resetting string for next value.

}

thd= current_thd;
JSON_DO_PAUSE_EXECUTION(thd, 0.0002);
je.killed_ptr= (uint32_t *) &thd->killed;
if (json_normalize_engine(&je, &cached_a, a->ptr(), a->length(), a->charset()))
{
goto set_a_null;
}

if (json_normalize_engine(&je, &a_res, a->ptr(), a->length(), a->charset()))
goto return_null;
if (a_const)
{
a_null= false;

@grooverdan grooverdan Jul 31, 2026

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I think can set a_null unconditionally. Its only looked at under a_const ==true anyway0.

a_parsed= true;
}
}

arg_num++;
if (json_normalize_engine(&je, &b_res, b->ptr(), b->length(), b->charset()))
goto return_null;

result= strcmp(a_res.str, b_res.str) ? 0 : 1;
/* Process Second Argument */
if (b_const && b_parsed)

@grooverdan grooverdan Jul 31, 2026

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same comments on first arg parsing apply here too.

{
if(b_null)
goto return_null;
}
else
{
b= args[1]->val_json(&b_tmp);
if (!b)
goto set_b_null;

if (!cached_b.str)
{
if (init_dynamic_string(&cached_b, NULL, 0, 0))
goto set_b_null;
}
else
{
cached_b.length= 0;
}

if (json_normalize_engine(&je, &cached_b, b->ptr(), b->length(), b->charset()))
{
goto set_b_null;
}

if (b_const)
{
b_null= false;
b_parsed= true;
}
}

result= strcmp(cached_a.str, cached_b.str) ? 0 : 1;
goto end;

set_a_null:
if (a_const)
{
a_null= true;
a_parsed= true;
}
goto return_null;

set_b_null:
if (b_const)
{
b_null= true;
b_parsed= true;
}

return_null:
null_value= 1;

Expand All @@ -675,8 +734,6 @@ bool Item_func_json_equals::val_bool()
a= b;
report_json_error(a, &je, arg_num);
}
dynstr_free(&b_res);
dynstr_free(&a_res);
return result;
}

Expand Down Expand Up @@ -5046,17 +5103,34 @@ bool Item_func_json_overlaps::val_bool()
json_engine_t je, ve;
int result;
THD *thd;
bool b_const= args[1]->const_item();

if ((null_value= (js == nullptr) || args[0]->null_value))
return 0;

thd= current_thd;
JSON_DO_PAUSE_EXECUTION(thd, 0.0002);

if (!a2_parsed)
if (b_const && a2_parsed)
{
val= args[1]->val_json(&tmp_val);
a2_parsed= a2_constant;
val= (cached_val.is_alloced() || cached_val.length()) ? &cached_val : 0;
}
else
{
String *v= args[1]->val_json(&tmp_val);
if (v)
{
cached_val.copy(v->ptr(), v->length(), v->charset());

@grooverdan grooverdan Jul 31, 2026 •
edited
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still copying here.

if (b_const)
{
   if (cached_val.is_allocated())
      val= &cached_val; /* or something*/
   else
   {
      val= args[1]->val_json(&cached_val);
   }
}
else
{
  something using local val= tmp_str (as local)
}

(incomplete)

val= &cached_val;
}
else
{
cached_val.length(0);
val= 0;
}

if (b_const)
a2_parsed= true;
}

if (val == 0)
Expand Down Expand Up @@ -5092,8 +5166,6 @@ bool Item_func_json_overlaps::val_bool()

bool Item_func_json_overlaps::fix_length_and_dec(THD *thd)
{
a2_constant= args[1]->const_item();
a2_parsed= FALSE;
set_maybe_null();

return Item_bool_func::fix_length_and_dec(thd);
Expand Down
30 changes: 26 additions & 4 deletions sql/item_jsonfunc.h
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Original file line number Diff line number Diff line change
Expand Up @@ -126,9 +126,21 @@ class Item_func_json_valid: public Item_bool_func

class Item_func_json_equals: public Item_bool_func
{
DYNAMIC_STRING cached_a, cached_b;
bool a_parsed, b_parsed;
bool a_null, b_null;
public:
Item_func_json_equals(THD *thd, Item *a, Item *b):
Item_bool_func(thd, a, b) {}
Item_bool_func(thd, a, b), a_parsed(false), b_parsed(false), a_null(false), b_null(false)
{
cached_a.str= 0;
cached_b.str= 0;
}
~Item_func_json_equals() override
{
dynstr_free(&cached_a);
dynstr_free(&cached_b);
}
LEX_CSTRING func_name_cstring() const override
{
static LEX_CSTRING name= {STRING_WITH_LEN("json_equals") };
Expand All @@ -138,6 +150,11 @@ class Item_func_json_equals: public Item_bool_func
Item *shallow_copy(THD *thd) const override
{ return get_item_copy<Item_func_json_equals>(thd, this); }
bool val_bool() override;
void cleanup() override
{
a_parsed= b_parsed= false;
Item_bool_func::cleanup();
}
};


Expand Down Expand Up @@ -848,18 +865,23 @@ extern bool is_json_type(const Item *item);
class Item_func_json_overlaps: public Item_bool_func
{
String tmp_js;
bool a2_constant, a2_parsed;
String tmp_val, *val;
bool a2_parsed;
String tmp_val, cached_val, *val;
public:
Item_func_json_overlaps(THD *thd, Item *a, Item *b):
Item_bool_func(thd, a, b) {}
Item_bool_func(thd, a, b), a2_parsed(false) {}
LEX_CSTRING func_name_cstring() const override
{
static LEX_CSTRING name= {STRING_WITH_LEN("json_overlaps") };
return name;
}
bool fix_length_and_dec(THD *thd) override;
bool val_bool() override;
void cleanup() override
{
a2_parsed= false;
Item_bool_func::cleanup();
}
Item *shallow_copy(THD *thd) const override
{ return get_item_copy<Item_func_json_overlaps>(thd, this); }
};
Expand Down