maria-developers team mailing list archive
-
maria-developers team
-
Mailing list archive
-
Message #09240
MDEV-9181 (NULLIF(count(table.col)), 0) gives wrong result on 10.1.x
Hi,
Please review a new version of a patch for MDEV-9181.
Thanks.
diff --git a/mysql-test/r/null.result b/mysql-test/r/null.result
index b4cebac..af24ad4 100644
--- a/mysql-test/r/null.result
+++ b/mysql-test/r/null.result
@@ -1465,5 +1465,65 @@ Warnings:
Note 1003 select `test`.`t1`.`a` AS `a` from `test`.`t1` where ((`test`.`t1`.`a` = 2020) and ((case when 2020 = 2010 then NULL else `test`.`t1`.`a` end) = concat('2020',rand())))
DROP TABLE t1;
#
+# MDEV-9181 (NULLIF(count(table.col)), 0) gives wrong result on 10.1.x
+#
+CREATE TABLE t1 (c1 varchar(50) DEFAULT NULL);
+INSERT INTO t1 (c1) VALUES ('hello'), ('hello\r\n'), ('hello'),('hello');
+SELECT NULLIF(COUNT(c1),0) FROM t1;
+NULLIF(COUNT(c1),0)
+4
+SELECT CASE WHEN COUNT(c1)=0 THEN NULL ELSE COUNT(c1) END FROM t1;
+CASE WHEN COUNT(c1)=0 THEN NULL ELSE COUNT(c1) END
+4
+SELECT NULLIF(COUNT(c1)+0,0) AS c1,NULLIF(CAST(COUNT(c1) AS SIGNED),0) AS c2,NULLIF(CONCAT(COUNT(c1)),0) AS c3 FROM t1;
+c1 c2 c3
+4 4 4
+SELECT NULLIF(COUNT(DISTINCT c1),0) FROM t1;
+NULLIF(COUNT(DISTINCT c1),0)
+2
+SELECT CASE WHEN COUNT(DISTINCT c1)=0 THEN NULL ELSE COUNT(DISTINCT c1) END FROM t1;
+CASE WHEN COUNT(DISTINCT c1)=0 THEN NULL ELSE COUNT(DISTINCT c1) END
+2
+DROP TABLE t1;
+CREATE TABLE t1 (
+id INT NOT NULL,
+c1 INT DEFAULT NULL
+);
+INSERT INTO t1 VALUES (1,1),(1,2),(2,3),(2,4);
+SELECT NULLIF(COUNT(c1),0) AS c1,NULLIF(COUNT(c1)+0,0) AS c1_wrapped,CASE WHEN COUNT(c1) IS NULL THEN 0 ELSE COUNT(c1) END AS c1_case FROM t1 GROUP BY id;
+c1 c1_wrapped c1_case
+2 2 2
+2 2 2
+DROP TABLE t1;
+CREATE TABLE t1 (a INT);
+INSERT INTO t1 VALUES (1),(2),(3);
+SET @a=0;
+SELECT NULLIF(LAST_VALUE(@a:=@a+1,a),0) FROM t1;
+NULLIF(LAST_VALUE(@a:=@a+1,a),0)
+1
+2
+3
+SELECT @a;
+@a
+6
+SET @a=0;
+SELECT NULLIF(AVG(a),0), NULLIF(AVG(LAST_VALUE(@a:=@a+1,a)),0) FROM t1;
+NULLIF(AVG(a),0) NULLIF(AVG(LAST_VALUE(@a:=@a+1,a)),0)
+2.0000 2.0000
+SELECT @a;
+@a
+3
+EXPLAIN EXTENDED SELECT NULLIF(a,0) FROM t1;
+id select_type table type possible_keys key key_len ref rows filtered Extra
+1 SIMPLE t1 ALL NULL NULL NULL NULL 3 100.00
+Warnings:
+Note 1003 select nullif(`test`.`t1`.`a`,0) AS `NULLIF(a,0)` from `test`.`t1`
+EXPLAIN EXTENDED SELECT NULLIF(AVG(a),0) FROM t1;
+id select_type table type possible_keys key key_len ref rows filtered Extra
+1 SIMPLE t1 ALL NULL NULL NULL NULL 3 100.00
+Warnings:
+Note 1003 select nullif(<cache>(avg(`test`.`t1`.`a`)),0) AS `NULLIF(AVG(a),0)` from `test`.`t1`
+DROP TABLE t1;
+#
# End of 10.1 tests
#
diff --git a/mysql-test/t/null.test b/mysql-test/t/null.test
index 5347a96..b60f11a 100644
--- a/mysql-test/t/null.test
+++ b/mysql-test/t/null.test
@@ -909,6 +909,45 @@ EXPLAIN EXTENDED
SELECT * FROM t1 WHERE a=2020 AND NULLIF(a,2010)=CONCAT('2020',RAND());
DROP TABLE t1;
+--echo #
+--echo # MDEV-9181 (NULLIF(count(table.col)), 0) gives wrong result on 10.1.x
+--echo #
+CREATE TABLE t1 (c1 varchar(50) DEFAULT NULL);
+INSERT INTO t1 (c1) VALUES ('hello'), ('hello\r\n'), ('hello'),('hello');
+SELECT NULLIF(COUNT(c1),0) FROM t1;
+SELECT CASE WHEN COUNT(c1)=0 THEN NULL ELSE COUNT(c1) END FROM t1;
+SELECT NULLIF(COUNT(c1)+0,0) AS c1,NULLIF(CAST(COUNT(c1) AS SIGNED),0) AS c2,NULLIF(CONCAT(COUNT(c1)),0) AS c3 FROM t1;
+SELECT NULLIF(COUNT(DISTINCT c1),0) FROM t1;
+SELECT CASE WHEN COUNT(DISTINCT c1)=0 THEN NULL ELSE COUNT(DISTINCT c1) END FROM t1;
+DROP TABLE t1;
+
+CREATE TABLE t1 (
+ id INT NOT NULL,
+ c1 INT DEFAULT NULL
+);
+INSERT INTO t1 VALUES (1,1),(1,2),(2,3),(2,4);
+SELECT NULLIF(COUNT(c1),0) AS c1,NULLIF(COUNT(c1)+0,0) AS c1_wrapped,CASE WHEN COUNT(c1) IS NULL THEN 0 ELSE COUNT(c1) END AS c1_case FROM t1 GROUP BY id;
+DROP TABLE t1;
+
+# Testing with side effects
+
+CREATE TABLE t1 (a INT);
+INSERT INTO t1 VALUES (1),(2),(3);
+SET @a=0;
+SELECT NULLIF(LAST_VALUE(@a:=@a+1,a),0) FROM t1;
+SELECT @a;
+SET @a=0;
+SELECT NULLIF(AVG(a),0), NULLIF(AVG(LAST_VALUE(@a:=@a+1,a)),0) FROM t1;
+SELECT @a;
+
+# There should not be cache in here:
+
+EXPLAIN EXTENDED SELECT NULLIF(a,0) FROM t1;
+
+# But there should be a cache in here:
+EXPLAIN EXTENDED SELECT NULLIF(AVG(a),0) FROM t1;
+
+DROP TABLE t1;
--echo #
--echo # End of 10.1 tests
diff --git a/sql/item.h b/sql/item.h
index d5b6463..9c57628 100644
--- a/sql/item.h
+++ b/sql/item.h
@@ -3629,6 +3629,11 @@ class Used_tables_and_const_cache
used_tables_cache|= item->used_tables();
const_item_cache&= item->const_item();
}
+ void used_tables_and_const_cache_update_and_join(Item *item)
+ {
+ item->update_used_tables();
+ used_tables_and_const_cache_join(item);
+ }
/*
Call update_used_tables() for all "argc" items in the array "argv"
and join with the current cache.
@@ -3638,10 +3643,7 @@ class Used_tables_and_const_cache
void used_tables_and_const_cache_update_and_join(uint argc, Item **argv)
{
for (uint i=0 ; i < argc ; i++)
- {
- argv[i]->update_used_tables();
- used_tables_and_const_cache_join(argv[i]);
- }
+ used_tables_and_const_cache_update_and_join(argv[i]);
}
/*
Call update_used_tables() for all items in the list
@@ -3654,10 +3656,7 @@ class Used_tables_and_const_cache
List_iterator_fast<Item> li(list);
Item *item;
while ((item=li++))
- {
- item->update_used_tables();
- used_tables_and_const_cache_join(item);
- }
+ used_tables_and_const_cache_update_and_join(item);
}
};
@@ -5073,6 +5072,12 @@ class Item_cache: public Item_basic_constant
return (this->*processor)(arg);
}
virtual Item *safe_charset_converter(THD *thd, CHARSET_INFO *tocs);
+ void split_sum_func2_example(THD *thd, Item **ref_pointer_array,
+ List<Item> &fields, uint flags)
+ {
+ example->split_sum_func2(thd, ref_pointer_array, fields, &example, flags);
+ }
+ Item *get_example() const { return example; }
};
@@ -5177,6 +5182,30 @@ class Item_cache_str: public Item_cache
bool cache_value();
};
+
+class Item_cache_str_for_nullif: public Item_cache_str
+{
+public:
+ Item_cache_str_for_nullif(THD *thd, const Item *item)
+ :Item_cache_str(thd, item)
+ { }
+ Item *safe_charset_converter(THD *thd, CHARSET_INFO *tocs)
+ {
+ /**
+ Item_cache_str::safe_charset_converter() returns a new Item_cache
+ with Item_func_conv_charset installed on "example". The original
+ Item_cache is not referenced (neither directly nor recursively)
+ from the result of Item_cache_str::safe_charset_converter().
+
+ For NULLIF() purposes we need a different behavior:
+ we need a new instance of Item_func_conv_charset,
+ with the original Item_cache referenced in args[0]. See MDEV-9181.
+ */
+ return Item::safe_charset_converter(thd, tocs);
+ }
+};
+
+
class Item_cache_row: public Item_cache
{
Item_cache **values;
diff --git a/sql/item_cmpfunc.cc b/sql/item_cmpfunc.cc
index 87be0f9..6ad118a 100644
--- a/sql/item_cmpfunc.cc
+++ b/sql/item_cmpfunc.cc
@@ -2531,12 +2531,137 @@ bool Item_func_if::date_op(MYSQL_TIME *ltime, uint fuzzydate)
}
+void Item_func_nullif::split_sum_func(THD *thd, Item **ref_pointer_array,
+ List<Item> &fields, uint flags)
+{
+ if (m_cache)
+ {
+ flags|= SPLIT_SUM_SKIP_REGISTERED; // See Item_func::split_sum_func
+ m_cache->split_sum_func2_example(thd, ref_pointer_array, fields, flags);
+ args[1]->split_sum_func2(thd, ref_pointer_array, fields, &args[1], flags);
+ }
+ else
+ {
+ Item_func::split_sum_func(thd, ref_pointer_array, fields, flags);
+ }
+}
+
+
+void Item_func_nullif::update_used_tables()
+{
+ if (m_cache)
+ {
+ used_tables_and_const_cache_init();
+ used_tables_and_const_cache_update_and_join(m_cache->get_example());
+ used_tables_and_const_cache_update_and_join(arg_count, args);
+ }
+ else
+ {
+ Item_func::update_used_tables();
+ }
+}
+
+
+
void
Item_func_nullif::fix_length_and_dec()
{
if (!args[2]) // Only false if EOM
return;
+ DBUG_ASSERT(args[0] == args[2]);
+ THD *thd= current_thd;
+ if (args[0]->type() == SUM_FUNC_ITEM)
+ {
+ /*
+ NULLIF(l_expr, r_expr)
+
+ is calculated in the way to return a result equal to:
+
+ CASE WHEN l_expr = r_expr THEN NULL ELSE r_expr END.
+
+ There's nothing special with r_expr, because it's referenced
+ only by args[1] and nothing else.
+
+ l_expr needs a special treatment, as it's referenced by both
+ args[0] and args[2] initially.
+
+ args[0] and args[2] can be replaced:
+
+ - to Item_func_conv_charset by character set aggregation routines
+ - to a constant Item by equal field propagation routines
+ (in case of Item_field)
+
+ For aggregate functions we have to wrap the original args[0]/args[2]
+ into Item_cache (see MDEV-9181). In this case the Item_cache
+ instance becomes the subject to character set conversion instead of
+ the original args[0]/args[2], while the original args[0]/args[2] get
+ hidden inside the cache.
+
+ Some examples of what NULLIF can end up with after argument
+ substitution (we don't mention args[1] here for simplicity):
+
+ 1. l_expr is not an aggragate function:
+
+ a. No conversion happened.
+ args[0] and args[2] were not replaced to something else
+ (i.e. neither by character set conversion, nor by propagation):
+
+ args[0] \
+ l_expr
+ args[2] /
+
+ b. Conversion of args[0] happened.
+ args[0] was replaced, e.g. to Item_func_conv_charset:
+
+ args[0] > Item_func_conv_charset \
+ l_expr
+ args[2] >------------------------/
+
+ c. Conversion of args[2] happened:
+
+ args[0] >------------------------\
+ l_expr
+ args[2] > Item_func_conv_charset /
+
+ d. Conversion of both args[0] and args[2] happened
+ (e.g. by equal field propagation).
+
+ args[0] > Item_int
+ args[2] > Item_int
+
+ 2. In case if l_expr is an aggregate function:
+
+ a. No conversion happened:
+
+ args[0] \
+ Item_cache > l_expr
+ args[2] /
+
+ b. Conversion of args[0] happened:
+
+ args[0] > Item_func_conv_charset \
+ Item_cache > l_expr
+ args[2] >------------------------/
+
+ c. Conversion of args[2] happened:
+
+ args[0] >------------------------\
+ Item_cache > l_expr
+ args[2] > Item_func_conv_charset /
+
+ d. Conversion of both args[0] and args[2] happened.
+ (e.g. by equal expression propagation)
+ TODO: check and add an example.
+ */
+ m_cache= args[0]->cmp_type() == STRING_RESULT ?
+ new (thd->mem_root) Item_cache_str_for_nullif(thd, args[0]) :
+ Item_cache::get_cache(thd, args[0]);
+ m_cache->setup(current_thd, args[0]);
+ m_cache->store(args[0]);
+ m_cache->set_used_tables(args[0]->used_tables());
+ args[0]= args[2]= m_cache;
+ }
set_handler_by_field_type(args[2]->field_type());
collation.set(args[2]->collation);
decimals= args[2]->decimals;
@@ -2611,6 +2736,13 @@ void Item_func_nullif::print(String *str, enum_query_type query_type)
}
+int Item_func_nullif::compare()
+{
+ if (m_cache)
+ m_cache->cache_value();
+ return cmp.compare();
+}
+
/**
@note
Note that we have to evaluate the first argument twice as the compare
@@ -2626,7 +2758,7 @@ Item_func_nullif::real_op()
{
DBUG_ASSERT(fixed == 1);
double value;
- if (!cmp.compare())
+ if (!compare())
{
null_value=1;
return 0.0;
@@ -2641,7 +2773,7 @@ Item_func_nullif::int_op()
{
DBUG_ASSERT(fixed == 1);
longlong value;
- if (!cmp.compare())
+ if (!compare())
{
null_value=1;
return 0;
@@ -2656,7 +2788,7 @@ Item_func_nullif::str_op(String *str)
{
DBUG_ASSERT(fixed == 1);
String *res;
- if (!cmp.compare())
+ if (!compare())
{
null_value=1;
return 0;
@@ -2672,7 +2804,7 @@ Item_func_nullif::decimal_op(my_decimal * decimal_value)
{
DBUG_ASSERT(fixed == 1);
my_decimal *res;
- if (!cmp.compare())
+ if (!compare())
{
null_value=1;
return 0;
@@ -2687,7 +2819,7 @@ bool
Item_func_nullif::date_op(MYSQL_TIME *ltime, uint fuzzydate)
{
DBUG_ASSERT(fixed == 1);
- if (!cmp.compare())
+ if (!compare())
return (null_value= true);
return (null_value= args[2]->get_date(ltime, fuzzydate));
}
@@ -2696,7 +2828,7 @@ Item_func_nullif::date_op(MYSQL_TIME *ltime, uint fuzzydate)
bool
Item_func_nullif::is_null()
{
- return (null_value= (!cmp.compare() ? 1 : args[2]->null_value));
+ return (null_value= (!compare() ? 1 : args[2]->null_value));
}
diff --git a/sql/item_cmpfunc.h b/sql/item_cmpfunc.h
index b7c51cd..16f8a24 100644
--- a/sql/item_cmpfunc.h
+++ b/sql/item_cmpfunc.h
@@ -995,10 +995,13 @@ class Item_func_nullif :public Item_func_hybrid_field_type
- Item_field::propagate_equal_fields(ANY_SUBST) for the left "a"
- Item_field::propagate_equal_fields(IDENTITY_SUBST) for the right "a"
*/
+ Item_cache *m_cache;
+ int compare();
public:
// Put "a" to args[0] for comparison and to args[2] for the returned value.
Item_func_nullif(THD *thd, Item *a, Item *b):
- Item_func_hybrid_field_type(thd, a, b, a)
+ Item_func_hybrid_field_type(thd, a, b, a),
+ m_cache(NULL)
{}
bool date_op(MYSQL_TIME *ltime, uint fuzzydate);
double real_op();
@@ -1009,6 +1012,9 @@ class Item_func_nullif :public Item_func_hybrid_field_type
uint decimal_precision() const { return args[2]->decimal_precision(); }
const char *func_name() const { return "nullif"; }
void print(String *str, enum_query_type query_type);
+ void split_sum_func(THD *thd, Item **ref_pointer_array, List<Item> &fields,
+ uint flags);
+ void update_used_tables();
table_map not_null_tables() const { return 0; }
bool is_null();
Item* propagate_equal_fields(THD *thd, const Context &ctx, COND_EQUAL *cond)
