locking type of temp table
The problem is that INSERT INTO .. SELECT FROM .. and CREATE
TABLE .. SELECT FROM a temporary table could inadvertently
overwrite the locking type of the temporary table. The lock
type of temporary tables should be a write lock by default.
The solution is to reset the lock type of temporary tables
back to its default value after they are used in a statement.
after few delete statements
Problem: changing a file size might require that it must be
unmapped beforehand.
Fix: unmap the file before changing its size.
The patch for WL 1563 added a new duplicate key error message so that the
key name could be provided instead of the key number. But the error code
for the new message was used even though that did not need to change.
This could cause unnecessary problems for applications that used the old
ER_DUP_ENTRY error code to detect duplicate key errors.
The problem in this bug is when we create temporary tables. When
temporary tables are created for unions, there is some
inferrence being carried out regarding the type of the column.
Whenever this column type is inferred to be REAL (i.e. FLOAT or
DOUBLE), MySQL will always try to maintain exact precision, and
if that is not possible (there are hardware limits, since FLOAT
and DOUBLE are stored as approximate values) will switch to
using approximate values. The problem here is that at this point
the information about number of significant digits is not
available. Furthermore, the number of significant digits should
be increased for the AVG function, however, this was not properly
handled. There are 4 parts to the problem:
#1: DOUBLE and FLOAT fields don't display their proper display
lengths in max_display_length(). This is hard-coded as 53 for
DOUBLE and 24 for FLOAT. Now changed to instead return the
field_length.
#2: Type holders for temporary tables do not preserve the
max_length of the Item's from which they are created, and is
instead reverted to the 53 and 24 from above. This causes
*all* fields to get non-fixed significant digits.
#3: AVG function does not update max_length (display length)
when updating number of decimals.
#4: The function that switches to non-fixed number of
significant digits should use DBL_DIG + 2 or FLT_DIG + 2 as
cut-off values (Since fixed precision does not use the 'e'
notation)
Of these points, #1 is the controversial one, but this
change is preferred and has been cleared with Monty. The
function causes quite a few unit tests to blow up and they had
to b changed, but each one is annotated and motivated. We
frequently see the magical 53 and 24 give way to more relevant
numbers.
The problem was that during DROP TEMPORARY TABLE we tried to acquire
the name lock, though temporary tables belongs to one connection, and
no race is possible.
The solution is to not use table name locking while executing
DROP TEMPORARY TABLE.
The table opening process now works the following way:
- Create common TABLE_SHARE object
- Read the .frm file and unpack it into the TABLE_SHARE object
- Create a TABLE object based on the information in the TABLE_SHARE
object and open a handler to the table object
Other noteworthy changes:
- In TABLE_SHARE the most common strings are now LEX_STRING's
- Better error message when table is not found
- Variable table_cache is now renamed 'table_open_cache'
- New variable 'table_definition_cache' that is the number of table defintions that will be cached
- strxnmov() calls are now fixed to avoid overflows
- strxnmov() will now always add one end \0 to result
- engine objects are now created with a TABLE_SHARE object instead of a TABLE object.
- After creating a field object one must call field->init(table) before using it
- For a busy system this change will give you:
- Less memory usage for table object
- Faster opening of tables (if it's has been in use or is in table definition cache)
- Allow you to cache many table definitions objects
- Faster drop of table
Fixed problems in test suite where some test failed
Fixed access to not initialized memory in federated
Fixed access to not initialized memory when using BIT fields in internal temporary tables
Added protocol::flush() for easier embedded-server code
Increase block allocation variables a bit as they where a bit too small for MySQL 4.1
Added option --silent to client_test
Added bug fix from 3.23 for AIX 4.3.3 and gcc 3.x
Small change in EXCHANGE output
Propagate open-files-limit from mysqld_safe -> mysqld
Fixed speed bug in GROUP BY
Added quotes around database name in CREATE DATABASE db_name (for binary log)
