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Trivial optimziations for group_concat

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- Remove some if
- Reorder code
- More code comments
This commit is contained in:
Monty
2026-09-03 16:16:02 +03:00
parent 5fbba64d3b
commit dc6a897961
1 changed files with 14 additions and 8 deletions
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22
sql/item_sum.cc
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@@ -3877,13 +3877,11 @@ int dump_leaf_key(void* key_arg, element_count count __attribute__((unused)),
uint max_length= table->in_use->gconcat_max_len();
String tmp((char *)table->record[1], table->s->reclength,
default_charset_info);
String tmp2;
uchar *key= (uchar *) key_arg;
String *result= &item->result;
Item **arg= item->args, **arg_end= item->args + item->arg_count_field;
uint old_length= result->length();
ulonglong *offset_limit= &item->copy_offset_limit;
ulonglong *row_limit = &item->copy_row_limit;
if (item->limit_clause && !(*row_limit))
{
@@ -3891,16 +3889,15 @@ int dump_leaf_key(void* key_arg, element_count count __attribute__((unused)),
item->walk_stopped= true;
return 1;
}
tmp.length(0);
if (item->limit_clause && (*offset_limit))
if (item->copy_offset_limit)
{
item->copy_offset_limit--;
item->row_count++;
(*offset_limit)--;
return 0;
}
tmp.length(0);
if (!item->result_finalized)
item->result_finalized= true;
else
@@ -4148,6 +4145,10 @@ Item *Item_func_group_concat::copy_or_same(THD* thd)
}
/*
Clear is called for the first element in a new group
*/
void Item_func_group_concat::clear()
{
result.length(0);
@@ -4156,8 +4157,10 @@ void Item_func_group_concat::clear()
warning_for_row= FALSE;
result_cut= FALSE;
result_finalized= false;
copy_offset_limit= 0;
if (offset_limit)
copy_offset_limit= offset_limit->val_int();
/* copy_row_limit does not have to be zeroed if row_limit is not set */
if (row_limit)
copy_row_limit= row_limit->val_int();
if (tree)
@@ -4747,9 +4750,12 @@ String* Item_func_group_concat::val_str(String* str)
result_cut= TRUE;
}
else if (row_limit && copy_row_limit == (ulonglong)row_limit->val_int())
{
/* No rows copied; Empty result */
return &result;
}
else
DBUG_ASSERT(false); // Can't happen
DBUG_ASSERT(false); // Can't happen. If it happens, no wrong result
/*
dump_leaf_key() sets this when it writes a row, but a group can end
without one: an OFFSET can eat every row, and a walk that failed