Subselect executes twice, at JOIN::optimize stage
and at JOIN::execute stage. At optimize stage
Innodb prebuilt struct which is used for the
retrieval of column values is initialized in.
ha_innobase::index_read(), prebuilt->sql_stat_start is true.
After QUICK_ROR_INTERSECT_SELECT finished his job it
restores read_set/write_set bitmaps with initial values
and deactivates one of the handlers used by
QUICK_ROR_INTERSECT_SELECT in JOIN::cleanup
(it's the case when we reuse original handler as one of
 handlers required by QUICK_ROR_INTERSECT_SELECT object).
On second subselect execution inactive handler is activated
in  QUICK_RANGE_SELECT::reset, file->ha_index_init().
In ha_index_init Innodb prebuilt struct is reinitialized
with inappropriate read_set/write_set bitmaps. Further
reinitialization in ha_innobase::index_read() does not
happen as prebuilt->sql_stat_start is false.
It leads to partial retrieval of required field values
and we get a mix of field values from different records
in the record buffer.
The fix is to reset
read_set/write_set bitmaps as these values
are required for proper intialization of
internal InnoDB struct which is used for
the retrieval of column values
(see build_template(), ha_innodb.cc)

           adding new indexes

A fast alter table requires that the existing (old) table
and indices are unchanged (i.e only new indices can be
added).  To verify this, the layout and flags of the old
table/indices are compared for equality with the new.

The PACK_KEYS option is a no-op in InnoDB, but the flag
exists, and is used in the table compare.  We need to
check this (table) option flag before deciding whether an 
index should be packed or not.  If the table has
explicitly set PACK_KEYS to 0, the created indices should
not be marked as packed/packable. 

compression protocol.

The loss of connection was caused by a malformed packet
sent by the server in case when query cache was in use.
When storing data in the query cache, the query  cache
memory allocation algorithm had a tendency to reduce
the amount of memory block necessary to store a result
set, up to finally storing the entire result set in a single
block. With a significant result set, this memory block
could turn out to be quite large - 30, 40 MB and on.
When such a result set was sent to the client, the entire
memory block was compressed and written to network as a
single network packet. However, the length of the
network packet is limited by 0xFFFFFF (16MB), since
the packet format only allows 3 bytes for packet length.
As a result, a malformed, overly large packet
with truncated length would be sent to the client
and break the client/server protocol.

The solution is, when sending result sets from the query
cache, to ensure that the data is chopped into
network packets of size <= 16MB, so that there
is no corruption of packet length. This solution,
however, has a shortcoming: since the result set
is still stored in the query cache as a single block,
at the time of sending, we've lost boundaries of individual
logical packets (one logical packet = one row of the result
set) and thus can end up sending a truncated logical
packet in a compressed network packet.

As a result, on the client we may require more memory than 
max_allowed_packet to keep, both, the truncated
last logical packet, and the compressed next packet.
This never (or in practice never) happens without compression,
since without compression it's very unlikely that
a) a truncated logical packet would remain on the client
when it's time to read the next packet
b) a subsequent logical packet that is being read would be
so large that size-of-new-packet + size-of-old-packet-tail >
max_allowed_packet.
To remedy this issue, we send data in 1MB sized packets,
that's below the current client default of 16MB for
max_allowed_packet, but large enough to ensure there is no
unnecessary overhead from too many syscalls per result set.

ORDER BY computed col
      
GROUP BY implies ORDER BY in the MySQL dialect of SQL. Therefore, when an
index on the first table in the query is used, and that index satisfies
ordering according to the GROUP BY clause, the query optimizer estimates the
number of tuples that need to be read from this index. If there is a LIMIT
clause, table statistics on tables following this 'sort table' are employed.

There may be a separate ORDER BY clause however, which mandates reading the
whole 'sort table' anyway. But the previous estimate was left untouched.

Fixed by removing the estimate from EXPLAIN output if GROUP BY is used in
conjunction with an ORDER BY clause that mandates using a temporary table.

            Version "5.1.42 SUSE MySQL RPM"

When a query was using a DATE or DATETIME value formatted
using different formatting than "yyyy-mm-dd HH:MM:SS", a
query with a greater-or-equal '>=' condition matched only
greater values in an indexed TIMESTAMP column.

The problem was introduced by the fix for the bug 46362
and partially solved (for DATE and DATETIME columns only)
by the fix for the bug 47925.

The stored_field_cmp_to_item function has been modified
to take into account TIMESTAMP columns like we do for
DATE and DATETIME columns.

The patch caused some test failures when merged to 5.5 because,
unlike 5.1, it utilizes Item_cache_row to actually cache row
values. The problem was that Item_cache_row::bring_value()
essentially did nothing. In particular, it did not update its
null_value, so all Item_cache_row objects were always having
their null_values set to TRUE. This went unnoticed previously,
but now when Arg_comparator::compare_row() actually depends on
the row's null_value to evaluate the comparison, the problem
has surfaced.

Fixed by calling the underlying item's bring_value() and
updating null_value in Item_cache_row::bring_value().

Since the problem also exists in 5.1 code (albeit hidden, since
the relevant code is not used anywhere), the addendum patch is
against 5.1.

            result

Row subqueries producing no rows were not handled as UNKNOWN
values in row comparison expressions.

That was a result of the following two problems:

1. Item_singlerow_subselect did not mark the resulting row
value as NULL/UNKNOWN when no rows were produced.

2. Arg_comparator::compare_row() did not take into account that
a whole argument may be NULL rather than just individual scalar
values.

Before bug#34384 was fixed, the above problems were hidden
because an uninitialized (i.e. without any stored value) cached
object would appear as NULL for scalar values in a row subquery
returning an empty result. After the fix
Arg_comparator::compare_row() would try to evaluate
uninitialized cached objects.

Fixed by removing the aforementioned problems.

Updated according to reviewers comments.

      
The EXISTS transformation has additional switches to catch the known corner
cases that appear when transforming an IN predicate into EXISTS. Guarded
conditions are used which are deactivated when a NULL value is seen in the
outer expression's row. When the inner query block supplies NULL values,
however, they are filtered out because no distinction is made between the
guarded conditions; guarded NOT x IS NULL conditions in the HAVING clause that
filter out NULL values cannot be de-activated in isolation from those that
match values or from the outer expression or NULL's.

The above problem is handled by making the guarded conditions remember whether
they have rejected a NULL value or not, and index access methods are taking
this into account as well. 

The bug consisted of 

1) Not resetting the property for every nested loop iteration on the inner
   query's result.

2) Not propagating the NULL result properly from inner query to IN optimizer.

3) A hack that may or may not have been needed at some point. According to a
   comment it was aimed to fix #2 by returning NULL when FALSE was actually
   the result. This caused failures when #2 was properly fixed. The hack is
   now removed.

The fix resolves all three points.

multi-table UPDATE IGNORE.
The problem was that if there was an active SELECT statement
during trigger execution, an error risen during the execution
may cause a crash. The fix is to temporary reset LEX::current_select
before trigger execution and restore it afterwards. This way
errors risen during the trigger execution are processed as
if there was no active SELECT.

inited==INDEX

When an error occurs while sending the data in a temporary table there was no
cleanup performed. This caused a failed assertion in the case when different
access methods were used for populating the table vs. retrieving the data from
the table if IGNORE was specified and sql_safe_updates = 0. In this case
execution continues, but the handler expects to continue with the access
method used for row retrieval.

Fixed by doing the cleanup even if errors occur.

for a prepared statement.

          case than in corr index".
      
Server was unable to find existing or explicitly created supporting
index for foreign key if corresponding statement clause used field
names in case different than one used in key specification and created
yet another supporting index.
In cases when name of constraint (and thus name of generated index)
was the same as name of existing/explicitly created index this led
to duplicate key name error.
      
The problem was that unlike all other code Key_part_spec::operator==()
compared field names in case sensitive fashion. As result routines
responsible for getting rid of redundant generated supporting indexes
for foreign key were not working properly for versions of field names
using different cases.

(backported from mysql-trunk)

Added --force-restart

Allow --testcase-timeout=<mins> to be set in .opt file for test

Bug#46754: 'rows' field doesn't reflect partition pruning
  
Update of test results after fixing the above bugs.
(fix in separate commit).

Bug#46754: 'rows' field doesn't reflect partition pruning

The EXPLAIN's result in 'rows' field
was evaluated to number of rows when the table was opened
(not from the table cache) and only the partitions left
after pruning was updated with its correct number
of rows.

The evaluation of the 'rows' field was using handler::records()
which is a potentially expensive call, and ignores the partitioning
pruning.

The fix was to use the handlers stats.records after updating it
with ::info(HA_STATUS_VARIABLE) instead.

Added code resulted in strange linking problem for embedded on Windows
Avoided by not doing this for embedded mode
It's irrelevant for embedded server anyway, --protocol will be ignored

Make the my_compiler.h header, like my_attribute.h, part of
the distribution. This is required due to the dependency of
the former on the latter (which can undefine __attribute__).

            "Access compatibility" syntax

The "wild" "DELETE FROM table_name.* ... USING ..." syntax
for multi-table DELETE statements is documented but it was
lost in the fix for the bug 30234.

The table_ident_opt_wild parser rule has been added
to restore the lost syntax.

Check for number of line strings in the incoming polygon data (wkb) and
for number of points in the incoming linestring wkb.

            == MYSQL_TYPE_LONGLONG

A MIN/MAX() function with a subquery as its argument could lead
to a debug assertion on debug builds or wrong data on release
ones.

The problem was a combination of the following factors:

- Item_sum_hybrid::fix_fields() might use the argument
(args[0]) to calculate 'hybrid_field_type' which was later used
to decide how the data should be sent to the client.

- Item_sum::make_field() might use the argument again to
calculate the field's type when sending result set metadata to
the client.

- The argument could be changed in between these two calls via
  Item::set_arg() leading to inconsistent metadata being
  reported.

Here is what was happening for the bug's test case:

1. Item_sum_hybrid::fix_fields() calculates hybrid_field_type
as MYSQL_TYPE_LONGLONG based on args[0] which is an
Item::SUBSELECT_ITEM at that time.

2. A temporary table is created to execute the
query. create_tmp_field_from_item() creates a Field_long object
according to the subselect's max_length.

3. The subselect item in Item_sum_hybrid is replaced by the
Item_field object referencing the newly created Field_long.

4. Item_sum::make_field() rightfully returns the
MYSQL_TYPE_LONG type when calculating the result set metadata.

5. When sending the actual data, Item::send() relies on the
virtual field_type() function which in our case returns
previously calculated hybrid_field_type == MYSQL_TYPE_LONGLONG.

It looks like the only solution is to never refer to the
argument's metadata after the result metadata has been
calculated in fix_fields(), since the argument itself may be
different by then. In this sense, Item_sum::make_field() should
never be used, because it may rely on the argument's metadata
and is only called after fix_fields(). The "default"
implementation in Item::make_field() should be used instead as
it relies only on field_type(), but not on the argument's type.

Fixed by removing Item_sum::make_field() so that the superclass
implementation Item::make_field() is always used.

Free memory allocated by the server for all plugins,
with or without deinit() method.

InnoDB Plugin 1.0.11 has been released with MySQL 5.1.50.