In multi-table delete a table for delete can't be used for selecting in
subselects. Appropriate error was raised but wasn't checked which leads to a
crash at the execution phase.
The mysql_execute_command() now checks for errors before executing select
for multi-delete.
argument can lead to a wrong result.
md5() and sha() functions treat their arguments as case sensitive strings.
But when they are compared their arguments were compared as a case
insensitive strings which leads to two functions with different arguments
and thus different results to being identical. This can lead to a wrong
decision made in the range optimizer and thus lead to a wrong result set.
Item_func_md5::fix_length_and_dec() and Item_func_sha::fix_length_and_dec()
functions now set binary collation on their arguments.
The Item_func_concat::val_str() function tries to make as less re-allocations
as possible. This results in appending strings returned by 2nd and next
arguments to the string returned by 1st argument if the buffer for the first
argument has enough free space. A constant subselect is evaluated only once
and its result is stored in an Item_cache_str. In the case when the first
argument of the concat() function is such a subselect Item_cache_str returns
the stored value and Item_func_concat::val_str() append values of other
arguments to it. But for the next row the value in the Item_cache_str isn't
restored because the subselect is a constant one and it isn't evaluated second
time. This results in appending string values of 2nd and next arguments to the
result of the previous Item_func_concat::val_str() call.
The Item_func_concat::val_str() function now checks whether the first argument
is a constant one and if so it doesn't append values of 2nd and next arguments
to the string value returned by it.
A pattern to generate binlog for DROPped temp table in close_temporary_tables
was buggy: could not deal with a grave-accent-in-name table.
The fix exploits `append_identifier()' for quoting and duplicating accents.
Binlog lacks encoding info about DROPped temporary table.
Idea of the fix is to switch temporary to system_charset_info when a temporary table
is DROPped for binlog. Since that is the server, that automatically, but not the client, who generates the query
the binlog should be updated on the server's encoding for the coming DROP.
The `write_binlog_with_system_charset()' is introduced to replace similar problematic places in the code.
A query with a group by and having clauses could return a wrong
result set if the having condition contained a constant conjunct
evaluated to FALSE.
It happened because the pushdown condition for table with
grouping columns lost its constant conjuncts.
Pushdown conditions are always built by the function make_cond_for_table
that ignores constant conjuncts. This is apparently not correct when
constant false conjuncts are present.
The bug was as follows: When merge_key_fields() encounters "t.key=X OR t.key=Y" it will
try to join them into ref_or_null access via "t.key=X OR NULL". In order to make this
inference it checks if Y<=>NULL, ignoring the fact that value of Y may be not yet known.
The fix is that the check if Y<=>NULL is made only if value of Y is known (i.e. it is a
constant).
TODO: When merging to 5.0, replace used_tables() with const_item() everywhere in merge_key_fields().
The reason of the bug is in that `get_var_with_binlog' performs missed
assingment of
the variables as side-effect. Doing that it eventually calls
`free_underlaid_joins' to pass as an argument `thd->lex->select_lex' of the lex
which belongs to the user query, not
to one which is emulated i.e SET @var1:=NULL.
`get_var_with_binlog' is refined to supply a temporary lex to sql_set_variables's stack.
