MDEV-9408 CREATE TABLE SELECT MAX(int_column) creates different columns for table vs view
There were three almost identical pieces of the code:
- Field *Item_func::tmp_table_field();
- Field *Item_sum::create_tmp_field();
- Field *create_tmp_field_from_item();
with a difference in very small details (hence the bugs):
Only Item_func::tmp_table_field() was correct, the other two were not.
Removing the two incorrect pieces of the redundant code.
Joining these three functions/methods into a single virtual method
Item::create_tmp_field().
Additionally, moving Item::make_string_field() and
Item::tmp_table_field_from_field_type() from the public into the
protected section of the class declaration, as they are now not
needed outside of Item.
find_item_in_list() now recognize view fields like a fields even if they rever to an expression.
The problem of schema name do not taken into account for field with it and
derived table fixed.
Duplicating code removed
THD::>save_prep_leaf_list was set to true by multi-table update
statements with mergeable selects and never reset.
Make every statement reset it at start.
IS REJECTED.
Analysis
========
View creation with named columns over UNION is rejected.
Consider the following view definition:
CREATE VIEW v1 (fld1, fld2) AS SELECT 1 AS a, 2 AS b
UNION ALL SELECT 1 AS a, 1 AS a;
A 'duplicate column' error was reported due to the duplicate
alias name in the secondary SELECT. The VIEW column names
are either explicitly specified or determined from the
first SELECT (which can be auto generated if not specified).
Since a duplicate column name check was performed even
for the secondary SELECTs, an error was reported.
Fix
====
Check for duplicate column names only for the named
columns if specified or only for the first SELECT.
Do not use merge_for_insert for commands which use SELECT because optimizer can't work with such tables.
Fixes which makes multi-delete working with normally merged views.
~40% bugfixed(*) applied
~40$ bugfixed reverted (incorrect or we're not buggy)
~20% bugfixed applied, despite us being not buggy
(*) only changes in the server code, e.g. not cmakefiles
It is triple bug with one test suite:
1. Incorrect outer table detection
2. Incorrect leaf table processing for multi-update (should be full like for usual updates and inserts)
3. ON condition fix_fields() fould be called for all tables of the query.
