mariadb/mysql-test/t/func_if.test
unknown a475ed7c6b Bug#24532 (The return data type of IS TRUE is different from similar
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.


mysql-test/r/func_if.result:
  IF(x, unsigned, unsigned) should be unsigned.
mysql-test/r/view.result:
  Preserve the semantic of 'X IS [NOT] (TRUE|FALSE)' boolean predicates.
mysql-test/t/func_if.test:
  IF(x, unsigned, unsigned) should be unsigned.
mysql-test/t/view.test:
  Preserve the semantic of 'X IS [NOT] (TRUE|FALSE)' boolean predicates.
sql/item_cmpfunc.cc:
  Preserve the semantic of 'X IS [NOT] (TRUE|FALSE)' boolean predicates.
  IF(x, unsigned, unsigned) should be unsigned.
sql/item_cmpfunc.h:
  Preserve the semantic of 'X IS [NOT] (TRUE|FALSE)' boolean predicates.
sql/sql_yacc.yy:
  Preserve the semantic of 'X IS [NOT] (TRUE|FALSE)' boolean predicates.
2007-02-12 13:59:29 -07:00

110 lines
2.8 KiB
Text

#
# Init section
#
--disable_warnings
drop table if exists t1;
--enable_warnings
#
# Simple IF tests
#
select IF(0,"ERROR","this"),IF(1,"is","ERROR"),IF(NULL,"ERROR","a"),IF(1,2,3)|0,IF(1,2.0,3.0)+0 ;
#
# Test of IF and case-sensitiveness
#
CREATE TABLE t1 (st varchar(255) NOT NULL, u int(11) NOT NULL) ENGINE=MyISAM;
INSERT INTO t1 VALUES ('a',1),('A',1),('aa',1),('AA',1),('a',1),('aaa',0),('BBB',0);
select if(1,st,st) s from t1 order by s;
select if(u=1,st,st) s from t1 order by s;
select if(u=1,binary st,st) s from t1 order by s;
select if(u=1,st,binary st) s from t1 where st like "%a%" order by s;
explain extended select if(u=1,st,binary st) s from t1 where st like "%a%" order by s;
#
# NULLIF test
#
select nullif(u, 1) from t1;
explain extended select nullif(u, 1) from t1;
drop table t1;
select nullif(1,'test');
#
# Bug 2629
#
select NULLIF(NULL,NULL), NULLIF(NULL,1), NULLIF(NULL,1.0), NULLIF(NULL,"test");
select NULLIF(1,NULL), NULLIF(1.0, NULL), NULLIF("test", NULL);
#
# Problem with IF()
#
create table t1 (num double(12,2));
insert into t1 values (144.54);
select sum(if(num is null,0.00,num)) from t1;
drop table t1;
create table t1 (x int, y int);
insert into t1 values (0,6),(10,16),(20,26),(30,10),(40,46),(50,56);
select min(if(y -x > 5,y,NULL)), max(if(y - x > 5,y,NULL)) from t1;
drop table t1;
#
# BUG#3987
#
create table t1 (a int);
insert t1 values (1),(2);
select if(1>2,a,avg(a)) from t1;
drop table t1;
#
# Bug #5595 NULLIF() IS NULL returns false if NULLIF() returns NULL
#
SELECT NULLIF(5,5) IS NULL, NULLIF(5,5) IS NOT NULL;
#
# Bug #9669 Ordering on IF function with FROM_UNIXTIME function fails
#
CREATE TABLE `t1` (
`id` int(11) NOT NULL ,
`date` int(10) default NULL,
`text` varchar(32) NOT NULL
);
INSERT INTO t1 VALUES (1,1110000000,'Day 1'),(2,1111000000,'Day 2'),(3,1112000000,'Day 3');
SELECT id, IF(date IS NULL, '-', FROM_UNIXTIME(date, '%d-%m-%Y')) AS date_ord, text FROM t1 ORDER BY date_ord ASC;
SELECT id, IF(date IS NULL, '-', FROM_UNIXTIME(date, '%d-%m-%Y')) AS date_ord, text FROM t1 ORDER BY date_ord DESC;
DROP TABLE t1;
#
# Test for bug #11142: evaluation of NULLIF when the first argument is NULL
#
CREATE TABLE t1 (a CHAR(10));
INSERT INTO t1 VALUES ('aaa'), (NULL), (''), ('bbb');
SELECT a, NULLIF(a,'') FROM t1;
SELECT a, NULLIF(a,'') FROM t1 WHERE NULLIF(a,'') IS NULL;
DROP TABLE t1;
# End of 4.1 tests
#
# Bug #16272 IF function with decimal args can produce wrong result
#
create table t1 (f1 int, f2 int);
insert into t1 values(1,1),(0,0);
select f1, f2, if(f1, 40.0, 5.00) from t1 group by f1 order by f2;
drop table t1;
#
# Bug#24532 (The return data type of IS TRUE is different from similar
# operations)
#
# IF(x, unsigned, unsigned) should be unsigned.
#
select if(0, 18446744073709551610, 18446744073709551610);