operations)
Before this change, the boolean predicates:
- X IS TRUE,
- X IS NOT TRUE,
- X IS FALSE,
- X IS NOT FALSE
were implemented by expanding the Item tree in the parser, by using a
construct like:
Item_func_if(Item_func_ifnull(X, <value>), <value>, <value>)
Each <value> was a constant integer, either 0 or 1.
A bug in the implementation of the function IF(a, b, c), in
Item_func_if::fix_length_and_dec(), would cause the following :
When the arguments b and c are both unsigned, the result type of the
function was signed, instead of unsigned.
When the result of the if function is signed, space for the sign could be
counted twice (in the max() expression for a signed argument, and in the
total), causing the member max_length to be too high.
An effect of this is that the final type of IF(x, int(1), int(1)) would be
int(2) instead of int(1).
With this fix, the problems found in Item_func_if::fix_length_and_dec()
have been fixed.
While it's semantically correct to represent 'X IS TRUE' with
Item_func_if(Item_func_ifnull(X, <value>), <value>, <value>),
there are however more problems with this construct.
a)
Building the parse tree involves :
- creating 5 Item instances (3 ints, 1 ifnull, 1 if),
- creating each Item calls my_pthread_getspecific_ptr() once in the operator
new(size), and a second time in the Item::Item() constructor, resulting
in a total of 10 calls to get the current thread.
Evaluating the expression involves evaluating up to 4 nodes at runtime.
This representation could be greatly simplified and improved.
b)
Transforming the parse tree internally with if(ifnull(...)) is fine as long
as this transformation is internal to the server implementation.
With views however, the result of the parse tree is later exposed by the
::print() functions, and stored as part of the view definition.
Doing this has long term consequences:
1)
The original semantic 'X IS TRUE' is lost, and replaced by the
if(ifnull(...)) expression. As a result, SHOW CREATE VIEW does not restore
the original code.
2)
Should a future version of MySQL implement the SQL BOOLEAN data type for
example, views created today using 'X IS NULL' can be exported using
mysqldump, and imported again. Such views would be converted correctly and
automatically to use a BOOLEAN column in the future version.
With 'X IS TRUE' and the current implementations, views using these
"boolean" predicates would not be converted during the export/import, and
would use integer columns instead.
The difference traces back to how SHOW CREATE VIEW preserves 'X IS NULL' but
does not preserve the 'X IS TRUE' semantic.
With this fix, internal representation of 'X IS TRUE' booleans predicates
has changed, so that:
- dedicated Item classes are created for each predicate,
- only 1 Item is created to represent 1 predicate
- my_pthread_getspecific_ptr() is invoked 1 time instead of 10
- SHOW CREATE VIEW preserves the original semantic, and prints 'X IS TRUE'.
Note that, because of the fix in Item_func_if, views created before this fix
will:
- correctly use a int(1) type instead of int(2) for boolean predicates,
- incorrectly print the if(ifnull(...), ...) expression in SHOW CREATE VIEW,
since the original semantic (X IS TRUE) has been lost.
- except for the syntax used in SHOW CREATE VIEW, these views will operate
properly, no action is needed.
Views created after this fix will operate correctly, and will preserve the
original code semantic in SHOW CREATE VIEW.
Objects of the class Item_equal contain an auxiliary member
eval_item of the type cmp_item that is used only for direct
evaluation of multiple equalities. Currently a multiple equality
is evaluated directly only in the cases when the equality holds
at most for one row in the result set.
The compare collation of eval_item was determined incorectly.
It could lead to returning incorrect results for some queries.
with a column of the DATETIME type could return a wrong
result set if the WHERE clause included a BETWEEN condition
on the column.
Fixed the method Item_func_between::fix_length_and_dec
where the aggregation type for BETWEEN predicates calculated
incorrectly if the first argument was a view column of the
DATETIME type.
Depending on the queries we use different data processing methods
and can lose some data in case of double (and decimal in 4.1) fields.
The fix consists of two parts:
1. double comparison changed, now double a is equal to double b
if (a-b) is less than 5*0.1^(1 + max(a->decimals, b->decimals)).
For example, if a->decimals==1, b->decimals==2, a==b if (a-b)<0.005
2. if we use a temporary table, store double values there as is
to avoid any data conversion (rounding).
Removed a lot of compiler warnings
Removed not used variables, functions and labels
Initialize some variables that could be used unitialized (fatal bugs)
%ll -> %l
The bug report has demonstrated the following two problems.
1. If an ORDER/GROUP BY list includes a constant expression being
optimized away and, at the same time, containing single-row
subselects that return more that one row, no error is reported.
Strictly speaking the standard allows to ignore error in this case.
Yet, now a corresponding fatal error is reported in this case.
2. If a query requires sorting by expressions containing single-row
subselects that, however, return more than one row, then the execution
of the query may cause a server crash.
To fix this some code has been added that blocks execution of a subselect
item in case of a fatal error in the method Item_subselect::exec.
We use INT_RESULT type if all arguments are of type INT for 'if', 'case',
'coalesce' functions regardless of arguments' unsigned flag, so sometimes we can
exceed the INT bounds.
when they contain the '!' operator.
Added an implementation for the method Item_func_not::print.
The method encloses any NOT expression into extra parentheses to avoid
incorrect stored representations of views that use the '!' operators.
Without this change when a view was created that contained
the expression !0*5 its stored representation contained not this
expression but rather the expression not(0)*5 .
The operator '!' is of a higher precedence than '*', while NOT is
of a lower precedence than '*'. That's why the expression !0*5
is interpreted as not(0)*5, while the expression not(0)*5 is interpreted
as not((0)*5) unless sql_mode is set to HIGH_NOT_PRECEDENCE.
Now we translate !0*5 into (not(0))*5.
- Make the code produce correct result: use an array of triggers to turn on/off equalities for each
compared column. Also turn on/off optimizations based on those equalities.
- Make EXPLAIN output show "Full scan on NULL key" for tables for which we switch between
ref/unique_subquery/index_subquery and ALL access.
- index_subquery engine now has HAVING clause when it is needed, and it is
displayed in EXPLAIN EXTENDED
- Fix incorrect presense of "Using index" for index/unique-based subqueries (BUG#22930)
// bk trigger note: this commit refers to BUG#24127
Corrected spelling in copyright text
Makefile.am:
Don't update the files from BitKeeper
Many files:
Removed "MySQL Finland AB & TCX DataKonsult AB" from copyright header
Adjusted year(s) in copyright header
Many files:
Added GPL copyright text
Removed files:
Docs/Support/colspec-fix.pl
Docs/Support/docbook-fixup.pl
Docs/Support/docbook-prefix.pl
Docs/Support/docbook-split
Docs/Support/make-docbook
Docs/Support/make-makefile
Docs/Support/test-make-manual
Docs/Support/test-make-manual-de
Docs/Support/xwf
During optimization we replace NULL with 0 for not null
date{time} fields, so uset MODE_NO_ZERO_DATE flag for a while
as we don't want to give extra warnings.
- Removed not used variables and functions
- Added #ifdef around code that is not used
- Renamed variables and functions to avoid conflicts
- Removed some not used arguments
Fixed some class/struct warnings in ndb
Added define IS_LONGDATA() to simplify code in libmysql.c
I did run gcov on the changes and added 'purecov' comments on almost all lines that was not just variable name changes
Blocked evaluation of constant objects of the classes
Item_func_is_null and Item_is_not_null_test at the
prepare phase in the cases when the objects used subqueries.
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.
Added missing DBUG_RETURN statements (in mysqldump.c)
Added missing enums
Fixed a lot of wrong DBUG_PRINT() statements, some of which could cause crashes
Removed usage of %lld and %p in printf strings as these are not portable or produces different results on different systems.
(Mostly in DBUG_PRINT() and unused arguments)
Fixed bug in query cache when used with traceing (--with-debug)
Fixed memory leak in mysqldump
Removed warnings from mysqltest scripts (replaced -- with #)
