Item_sum_hybrid::fix_fields has a code to fix the data type and its attributes:
Item_sum_hybrid::fix_fields(THD *thd, Item **ref)
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{
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...
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Type_std_attributes::set(args[0]);
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...
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Item *item2= item->real_item();
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if (item2->type() == Item::FIELD_ITEM)
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set_handler_by_field_type(((Item_field*) item2)->field->type());
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else if (item->cmp_type() == TIME_RESULT)
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set_handler_by_field_type(item2->field_type());
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else
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set_handler_by_result_type(item2->result_type(),
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max_length, collation.collation);
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switch (Item_sum_hybrid::result_type()) {
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case INT_RESULT:
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case DECIMAL_RESULT:
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case STRING_RESULT:
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break;
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case REAL_RESULT:
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max_length= float_length(decimals);
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break;
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case ROW_RESULT:
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case TIME_RESULT:
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DBUG_ASSERT(0);
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};
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setup_hybrid(thd, args[0], NULL);
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/* MIN/MAX can return NULL for empty set indepedent of the used column */
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maybe_null= 1;
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result_field=0;
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null_value=1;
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fix_length_and_dec();
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...
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}
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This task will introduce a new virtual method in Type_handler:
bool Item_sum_hybrid_fix_length_and_dec(Item_sum_hybrid *func) const;
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and move pieces of the above fragment to relevant implementations of Type_handler_xxx.
The above fragment in Item_sum_hybrid::fix_fields() will be replaced to a call of the new method:
args[0]->type_handler()->Item_sum_hybrid_fix_length_and_dec(this);
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Bug
Major
MDEV-4912 Data type plugin API version 1
