When values of different types are compared they're converted to a type that
allows correct comparison. This conversion is done for each comparison and
takes some time. When a constant is being compared it's possible to cache the
value after conversion to speedup comparison. In some cases (large dataset,
complex WHERE condition with many type conversions) query might be executed
7% faster.

A test case isn't provided because all changes are internal and isn't visible
outside.

The behavior of the Item_cache is changed to cache values on the first request
of cached value rather than at the moment of storing item to be cached.
A flag named value_cached is added to the Item_cache class. It's set to TRUE
when cache holds the value of the last stored item.
Function named cache_value() is added to the Item_cache class and derived classes.
This function actually caches the value of the saved item.
Item_cache_xxx::store functions now only store item to be cached and set
value_cached flag to FALSE.
Item_cache_xxx::val_xxx functions are changed to call cache_value function
prior to returning cached value if value_cached is FALSE.
The Arg_comparator::set_cmp_func function now calls cache_converted_constant
to cache constants if they need a type conversion.
The Item_cache::get_cache function is overloaded to allow setting of the
cache type.
The cache_converted_constant function is added to the Arg_comparator class.
It checks whether a value can and should be cached and if so caches it.

  UPDATE + VIEW + SP + MERGE + ALTER

When cleaning up the stored procedure's internal 
structures the flag to ignore the errors for 
INSERT/UPDATE IGNORE was not cleaned up.
As a result error ignoring was on during name 
resolution. And this is an abnormal situation : the
SELECT_LEX flag can be on only during query execution.

Fixed by correctly cleaning up the SELECT_LEX flag 
when reusing the SELECT_LEX in a second execution.

SP variables

A function call may end without throwing an error or without setting 
the return value. This can happen when e.g. an error occurs while 
calculating the return value.

Fixed by setting the value to NULL when error occurs during evaluation
of an expression.

fail.

This assertion would occur if UPDATE was used to update multiple
tables containing an AUTO_INCREMENT column and if the inserted
row had a user-supplied value for that column. The assertion 
could then be triggered by the next statement.

The problem was only noticeable on debug builds of the server.

The cause of the problem was that the code for multi update did
not properly reset the TABLE->auto_increment_if_null flag after update.
The flag is used to indicate that a non-null value of an auto_increment field
has been provided by the user or retrieved from a current record.
Open_tables() contains an assertion that tests this flag, and this
was triggered in this case by ALTER TABLE.

This patch fixes the problem by resetting the auto_increment_if_null
field to FALSE once a row has been updated.

This bug is similar to Bug#47274, but for multi update rather
than INSERT DELAYED.

Test case added to update.test.

Problem: involving a spatial index for "non-spatial" queries
(that don't containt MBRXXX() functions) may lead to failed assert.

Fix: don't use spatial indexes in such cases.

Added parentheses around assignment used as truth value for suppressing warnings.

(automerge)

The label "end" was causing compiler warnings as it was no longer used.
To fix the problem we removed it.

line 138 when forcing a spatial index

Problem: "Spatial indexes can be involved in the search 
for queries that use a function such as MBRContains() 
or MBRWithin() in the WHERE clause".
Using spatial indexes for JOINs with =, <=> etc.
predicates is incorrect.

Fix: disable spatial indexes for such queries.

      
If the first argument to GeomFromWKB function is a geometry
field then the function just returns its value.
However in doing so it's not preserving first argument's 
null_value flag and this causes unexpected null value to
be returned to the calling function.
      
Fixed by updating the null_value of the GeomFromWKB function
in such cases (and all other cases that return a NULL e.g.
because of not enough memory for the return buffer).

file
      
Issuing 'FLUSH LOGS' does not close and reopen indexfile.
Instead a SEEK_SET is performed.
      
This patch makes index file to be closed and reopened whenever a
rotation happens (FLUSH LOGS is issued or binary log exceeds 
maximum configured size).

- Initialized caseinfo only if it is NULL

                     grants are reapplied.


After renaming a user and trying to re-apply grants results in additional
grants.

This is because we use username as part of the key for GRANT_TABLE structure.
When the user is renamed, we only change the username stored and the hash key
still contains the old user name and this results in the extra privileges

Fixed by rebuilding the hash key and updating the column_priv_hash structure
when the user is renamed

There are some problems about help text:
- It is stated that "auto" is the default twice. It need be stated only once.
- It is stated that --base64-output is short for --base64-output=always. But that sounds
like the default is "always", not "auto".

Make the help text clear as following:
Determine when the output statements should be base64-encoded BINLOG 
statements: 'never' disables it and works only for binlogs without 
row-based events; 'auto' prints base64 only when necessary (i.e., 
for row-based events and format description events); 'always' prints 
base64 whenever possible. 'always' is for debugging only and should 
not be used in a production system. If this argument is not given, 
the default is 'auto'; if it is given with no argument, 'always' is used.

If a thread is killed in the server, we throw "shutdown" only if one is actually in
progress; otherwise, we throw "query interrupted".

Control-C in the mysql command-line client is "incremental" now.
First Control-C sends KILL QUERY (when connected to 5.0+ server, otherwise, see next)
Next  Control-C sends KILL CONNECTION
Next  Control-C aborts client.

As the first two steps only pertain to an existing query,
Control-C will abort the client right away if no query is running.

client will give more detailed/consistent feedback on Control-C now.

Knowledge of no SSL support is not used
Skip tests the same way e.g. innodb tests are
Does not refer to have_ssl_communication.inc, 
     will add this when merging to 6.0-codebase

Problem: the "caseinfo" member of CHARSET_INFO structure was not
initialized for user-defined Unicode collations, which made the
server crash.
Fix: initializing caseinfo properly.

Adding tests for the bug.