with other alterations causes lost tables
Using RENAME clause combined with other clauses of ALTER TABLE led to
data loss (the data was there but not accessible). This could happen if the
changes do not change the table much. Adding and droppping of fields and
indices was safe. Renaming a column with MODIFY or CHANGE was unsafe operation,
if the actual column didn't change (changing from int to int, which is a noop)
Depending on the storage engine (SE) the behavior is different:
1)MyISAM/MEMORY - the ALTER TABLE statement completes
without any error but next SELECT against the new table fails.
2)InnoDB (and every other transactional table) - The ALTER TABLE statement
fails. There are the the following files in the db dir -
`new_table_name.frm` and a temporary table's frm. If the SE is file
based, then the data and index files will be present but with the old
names. What happens is that for InnoDB the table is not renamed in the
internal DDIC.
Fixed by adding additional call to mysql_rename_table() method, which should
not include FRM file rename, because it has been already done during file
names juggling.
We create Item_cache_* object for each operand for each left operand of
a subquery predicate. We also create Item_func_conv_charset for each string
constant that needs charset conversion. So here we have Item_cache wrapped
into Item_func_conv_charset.
When Item_func_conv_charset wraps an constant Item it gets it's value
in constructor. The problem is that Item_cache is ready to be used only
at execution time, which is too late.
The fix makes Item_cache wrapping constant to get ready at fix_fields() time.
Before this fix, a call to a User Defined Function (UDF) could,
under some circumstances, be interpreted as a call to a Stored function
instead. This occurred if a native function was invoked in the parameters
for the UDF, as in "select my_udf(abs(x))".
The root cause of this defect is the introduction, by the fix for Bug 21809,
of st_select_lex::udf_list, and it's usage in the parser in sql_yacc.yy
in the rule function_call_generic (in 5.1).
While the fix itself for Bug 21809 is correct in 5.0, the code change
merged into the 5.1 release created the issue, because the calls in 5.1 to :
- lex->current_select->udf_list.push_front(udf)
- lex->current_select->udf_list.pop()
are not balanced in case of native functions, causing the udf_list,
which is really a stack, to be out of sync with the internal stack
maintained by the bison parser.
Instead of moving the call to udf_list.pop(), which would have fixed the
symptom, this patch goes further and removes the need for udf_list.
This is motivated by two reasons:
a) Maintaining a stack in the MySQL code in sync with the stack maintained
internally in sql_yacc.cc (not .yy) is extremely dependent of the
implementation of yacc/bison, and extremely difficult to maintain.
It's also totally dependent of the structure of the grammar, and has a risk
to break with regression defects each time the grammar itself is changed.
b) The previous code did report construct like "foo(expr AS name)" as
syntax errors (ER_PARSER_ERROR), which is incorrect, and misleading.
The syntax is perfectly valid, as this expression is valid when "foo" is
a UDF. Whether this syntax is legal or not depends of the semantic of "foo".
With this change:
a) There is only one stack (in bison), and no List<udf_func> to maintain.
b) "foo(expr AS name)", when used incorrectly, is reported as semantic error:
- ER_WRONG_PARAMETERS_TO_NATIVE_FCT (for native functions)
- ER_WRONG_PARAMETERS_TO_STORED_FCT (for stored functions)
This is achieved by the changes implemented in item_create.cc
