database/mariadb
1
0
Fork 0
mirror of https://github.com/MariaDB/server.git synced 2025-07-30 16:24:05 +03:00
Code Activity

Fix sorting of NULL values (Should always be first)

Browse Source 
Fix problem with HAVING and MAX() IS NOT NULL


Docs/manual.texi:
  Changelog & NULL usage with ORDER BY
client/mysqldump.c:
  Cleanup disable keys
mysql-test/r/distinct.result:
  Fix results after ORDER BY with NULL fix
mysql-test/r/group_by.result:
  Fix results after ORDER BY with NULL fix
mysql-test/r/having.result:
  Testcase for bug with HAVING
mysql-test/t/distinct.test:
  Test for DISTINCT + ORDER BY DESC bug
mysql-test/t/having.test:
  Test of HAVING and MAX IS NOT NULL
sql/filesort.cc:
  Fix sorting of NULL values (Should always be first)
sql/item.h:
  Fix problem with HAVING and MAX() IS NOT NULL
sql/item_sum.h:
  Fix problem with HAVING and MAX() IS NOT NULL
sql/opt_range.cc:
  Fix problem with HAVING and MAX() IS NOT NULL
sql/opt_range.h:
  Fix sorting of NULL values
sql/sql_select.cc:
  Fix sorting of ORDER BY ... DESC on NULL values.
This commit is contained in:
unknown
2002-03-02 09:51:24 +02:00
parent ae670b7666
commit ad4fcb8a01
13 changed files with 144 additions and 36 deletions
Download Patch File Download Diff File Expand all files Collapse all files

36
Docs/manual.texi
View File

@ -8146,6 +8146,9 @@ version 4.0;
@itemize @bullet
@item
Use @code{ORDER BY column DESC} now always sorts @code{NULL} values
first; In 3.23 this was not always consistent.
@item
@code{SHOW INDEX} has 2 columns more (@code{Null} and @code{Index_type})
than it had in 3.23.
@item
@ -12661,9 +12664,15 @@ mysql> SELECT 1 IS NULL, 1 IS NOT NULL;
+-----------+---------------+
@end example
Note that two @code{NULL} are compared as equal is when you do an
@code{GROUP BY}.
In MySQL, 0 or @code{NULL} means false and anything else means true.
The default truth value from a boolean operation is 1.
When doing an @code{ORDER BY}, @code{NULL} values are always sorted first,
even if you are using @code{DESC}.
This special treatment of @code{NULL} is why, in the previous section, it
was necessary to determine which animals are no longer alive using
@code{death IS NOT NULL} instead of @code{death <> NULL}.
@ -13191,7 +13200,7 @@ mysql> DESCRIBE pet;
@end example
@code{Field} indicates the column name, @code{Type} is the data type for
the column, @code{Null} indicates whether or not the column can contain
the column, @code{NULL} indicates whether or not the column can contain
@code{NULL} values, @code{Key} indicates whether or not the column is
indexed, and @code{Default} specifies the column's default value.
@ -16481,8 +16490,10 @@ password will be set to the password specified by the @code{IDENTIFIED BY}
clause, if one is given. If the user already had a password, it is replaced
by the new one.
Optional @code{PASSWORD} changes behaviour of @code{IDENTIFIED BY} from
accepting plain password to accept encrypted password as argument.
If you don't want to send the password in clear text you can use the
@code{PASSWORD} option followed by a scrambled password from SQL
function @code{PASSWORD()} or the C API function
@code{make_scrambled_password(char *to, const char *password)}.
@strong{Warning:} If you create a new user but do not specify an
@code{IDENTIFIED BY} clause, the user has no password. This is insecure.
@ -25531,7 +25542,13 @@ You have different @code{ORDER BY} and @code{GROUP BY} expressions.
@item
The used table index is an index type that doesn't store rows in order.
(Like index in @code{HEAP} tables).
(Like the @code{HASH} index in @code{HEAP} tables).
@item
The index colum may contain @code{NULL} values and one is using
@code{ORDER BY ... DESC}. This is because in SQL @code{NULL} values is
always sorted before normal values, independent of you are using
@code{DESC} or not.
@end itemize
@ -26466,6 +26483,9 @@ probably much faster, as this will require us to do much fewer seeks.)
Note that if such a query uses @code{LIMIT} to only retrieve
part of the rows, MySQL will use an index anyway, as it can
much more quickly find the few rows to return in the result.
@item
If the index range may contain @code{NULL} values and you are using
@code{ORDER BY ... DESC}
@end itemize
@node Indexes, Multiple-column indexes, MySQL indexes, Optimising Database Structure
@ -29975,7 +29995,7 @@ mysql> select 2 > 2;
@cindex @code{NULL}, testing for null
@findex <=> (Equal to)
@item <=>
Null safe equal:
NULL safe equal:
@example
mysql> select 1 <=> 1, NULL <=> NULL, 1 <=> NULL;
-> 1 1 0
@ -48618,6 +48638,12 @@ Our TODO section contains what we plan to have in 4.0. @xref{TODO MySQL 4.0}.
@itemize @bullet
@item
Use @code{ORDER BY column DESC} now sorts @code{NULL} values first.
@item
Fixed bug in @code{SELECT DISTINCT ... ORDER BY DESC} optimization.
@item
Fixed bug in @code{... HAVING 'GROUP_FUNCTION'(xxx) IS [NOT] NULL}.
@item
Allow numeric user id to @code{mysqld --user=#}.
@item
Fixed a bug where @code{SQL_CALC_ROWS} returned a wrong value when used

15
client/mysqldump.c
View File

@ -35,7 +35,7 @@
** and adapted to mysqldump 05/11/01 by Jani Tolonen
*/
#define DUMP_VERSION "8.22"
#define DUMP_VERSION "8.23"
#include <my_global.h>
#include <my_sys.h>
@ -897,8 +897,6 @@ static uint getTableStructure(char *table, char* db)
fputs(";\n", sql_file);
}
}
if (opt_disable_keys)
fprintf(sql_file,"\n/*!40000 ALTER TABLE %s DISABLE KEYS */;\n",table_name);
if (cFlag)
{
strpos=strmov(strpos,") VALUES ");
@ -1023,7 +1021,7 @@ static void dumpTable(uint numFields, char *table)
strxmov(strend(query), " WHERE ",where,NullS);
}
if (!opt_xml)
fputs("\n\n", md_result_file);
fputs("\n", md_result_file);
if (mysql_query(sock, query))
{
DBerror(sock, "when retrieving data from server");
@ -1048,6 +1046,9 @@ static void dumpTable(uint numFields, char *table)
return;
}
if (opt_disable_keys)
fprintf(md_result_file,"/*!40000 ALTER TABLE %s DISABLE KEYS */;\n",
quote_name(table, table_buff));
if (opt_lock)
fprintf(md_result_file,"LOCK TABLES %s WRITE;\n",
quote_name(table,table_buff));
@ -1207,11 +1208,11 @@ static void dumpTable(uint numFields, char *table)
safe_exit(EX_CONSCHECK);
return;
}
if (opt_disable_keys)
fprintf(md_result_file,"\n/*!40000 ALTER TABLE %s ENABLE KEYS */;\n",
quote_name(table,table_buff));
if (opt_lock)
fputs("UNLOCK TABLES;\n", md_result_file);
if (opt_disable_keys)
fprintf(md_result_file,"/*!40000 ALTER TABLE %s ENABLE KEYS */;\n",
quote_name(table,table_buff));
if (opt_autocommit)
fprintf(md_result_file, "commit;\n");
mysql_free_result(res);

15
mysql-test/r/distinct.result
View File

@ -77,6 +77,7 @@ NULL NULL
10 VMT
select id+0 as a,max(id),concat(facility) as b from t1 group by a order by b desc,a;
a max(id) b
NULL NULL NULL
10 10 VMT
9 9 SRV
8 8 RV
@ -89,7 +90,6 @@ a max(id) b
1 1 /L
-1 -1
0 0
NULL NULL NULL
select id >= 0 and id <= 5 as grp,count(*) from t1 group by grp;
grp count(*)
0 7
@ -336,3 +336,16 @@ a c
4 NULL
3 NULL
drop table t1;
create table t1 (a char(1), key(a)) type=myisam;
insert into t1 values('1'),('1');
select * from t1 where a >= '1';
a
1
1
select distinct a from t1 order by a desc;
a
1
select distinct a from t1 where a >= '1' order by a desc;
a
1
drop table t1;

4
mysql-test/r/group_by.result
View File

@ -226,7 +226,7 @@ key (score)
INSERT INTO t1 VALUES (1,1,1),(2,2,2),(2,1,1),(3,3,3),(4,3,3),(5,3,3);
explain select userid,count(*) from t1 group by userid desc;
table type possible_keys key key_len ref rows Extra
t1 ALL NULL NULL NULL NULL 6 Using temporary
t1 ALL NULL NULL NULL NULL 6 Using temporary; Using filesort
select userid,count(*) from t1 group by userid desc;
userid count(*)
3 3
@ -244,6 +244,8 @@ spid count(*)
2 2
select spid,count(*) from t1 where spid between 1 and 2 group by spid desc;
spid count(*)
2 2
1 1
explain select sql_big_result spid,sum(userid) from t1 group by spid desc;
table type possible_keys key key_len ref rows Extra
t1 ALL NULL NULL NULL NULL 6 Using filesort

19
mysql-test/r/having.result
View File

@ -44,3 +44,22 @@ AND start <= 999660;
id start end chr_strand
133197 813898 813898 -1.0000
drop table t1,t2;
CREATE TABLE t1 (Fld1 int(11) default NULL,Fld2 int(11) default NULL);
INSERT INTO t1 VALUES (1,10),(1,20),(2,NULL),(2,NULL),(3,50);
select Fld1, max(Fld2) as q from t1 group by Fld1 having q is not null;
Fld1 q
1 20
3 50
select Fld1, max(Fld2) from t1 group by Fld1 having max(Fld2) is not null;
Fld1 max(Fld2)
1 20
3 50
select Fld1, max(Fld2) from t1 group by Fld1 having avg(Fld2) is not null;
Fld1 max(Fld2)
1 20
3 50
select Fld1, max(Fld2) from t1 group by Fld1 having std(Fld2) is not null;
Fld1 max(Fld2)
1 20
3 50
drop table t1;

11
mysql-test/t/distinct.test
View File

@ -207,3 +207,14 @@ insert into t1 (a) values (1),(2),(3),(4),(1),(2),(3),(4);
select distinct a from t1 group by b,a having a > 2 order by a desc;
select distinct a,c from t1 group by b,c,a having a > 2 order by a desc;
drop table t1;
#
# Test problem with DISTINCT and ORDER BY DESC
#
create table t1 (a char(1), key(a)) type=myisam;
insert into t1 values('1'),('1');
select * from t1 where a >= '1';
select distinct a from t1 order by a desc;
select distinct a from t1 where a >= '1' order by a desc;
drop table t1;

12
mysql-test/t/having.test
View File

@ -48,3 +48,15 @@ GROUP BY e.id
HAVING chr_strand= -1 and end >= 0
AND start <= 999660;
drop table t1,t2;
#
# Test problem with having and MAX() IS NOT NULL
#
CREATE TABLE t1 (Fld1 int(11) default NULL,Fld2 int(11) default NULL);
INSERT INTO t1 VALUES (1,10),(1,20),(2,NULL),(2,NULL),(3,50);
select Fld1, max(Fld2) as q from t1 group by Fld1 having q is not null;
select Fld1, max(Fld2) from t1 group by Fld1 having max(Fld2) is not null;
select Fld1, max(Fld2) from t1 group by Fld1 having avg(Fld2) is not null;
select Fld1, max(Fld2) from t1 group by Fld1 having std(Fld2) is not null;
drop table t1;

3
sql/filesort.cc
View File

@ -452,9 +452,6 @@ static void make_sortkey(register SORTPARAM *param,
{
if (field->is_null())
{
if (sort_field->reverse)
bfill(to,sort_field->length+1,(char) 255);
else
bzero((char*) to,sort_field->length+1);
to+= sort_field->length+1;
continue;

5
sql/item.h
View File

@ -343,6 +343,11 @@ public:
null_value=(*ref)->null_value;
return tmp;
}
bool is_null()
{
(void) (*ref)->val_int_result();
return (*ref)->null_value;
}
bool get_date(TIME *ltime,bool fuzzydate)
{
return (null_value=(*ref)->get_date(ltime,fuzzydate));

3
sql/item_sum.h
View File

@ -64,6 +64,7 @@ public:
{ return new Item_field(field);}
table_map used_tables() const { return ~(table_map) 0; } /* Not used */
bool const_item() const { return 0; }
bool is_null() { return null_value; }
void update_used_tables() { }
void make_field(Send_field *field);
void print(String *str);
@ -202,6 +203,7 @@ public:
enum Type type() const { return FIELD_AVG_ITEM; }
double val();
longlong val_int() { return (longlong) val(); }
bool is_null() { (void) val_int(); return null_value; }
String *val_str(String*);
void make_field(Send_field *field);
void fix_length_and_dec() {}
@ -239,6 +241,7 @@ public:
double val();
longlong val_int() { return (longlong) val(); }
String *val_str(String*);
bool is_null() { (void) val_int(); return null_value; }
void make_field(Send_field *field);
void fix_length_and_dec() {}
};

15
sql/opt_range.cc
View File

@ -2523,13 +2523,13 @@ int QUICK_SELECT::cmp_next(QUICK_RANGE *range)
/*
* This is a hack: we inherit from QUICK_SELECT so that we can use the
* get_next() interface, but we have to hold a pointer to the original
* QUICK_SELECT because its data are used all over the place. What
* should be done is to factor out the data that is needed into a base
* class (QUICK_SELECT), and then have two subclasses (_ASC and _DESC)
* which handle the ranges and implement the get_next() function. But
* for now, this seems to work right at least.
This is a hack: we inherit from QUICK_SELECT so that we can use the
get_next() interface, but we have to hold a pointer to the original
QUICK_SELECT because its data are used all over the place. What
should be done is to factor out the data that is needed into a base
class (QUICK_SELECT), and then have two subclasses (_ASC and _DESC)
which handle the ranges and implement the get_next() function. But
for now, this seems to work right at least.
*/
QUICK_SELECT_DESC::QUICK_SELECT_DESC(QUICK_SELECT *q, uint used_key_parts)
@ -2538,6 +2538,7 @@ QUICK_SELECT_DESC::QUICK_SELECT_DESC(QUICK_SELECT *q, uint used_key_parts)
bool not_read_after_key = file->option_flag() & HA_NOT_READ_AFTER_KEY;
QUICK_RANGE *r;
it.rewind();
for (r = it++; r; r = it++)
{
rev_ranges.push_front(r);

3
sql/opt_range.h
View File

@ -77,6 +77,7 @@ public:
void reset(void) { next=0; it.rewind(); }
int init() { return error=file->index_init(index); }
virtual int get_next();
virtual bool reverse_sorted() { return 0; }
int cmp_next(QUICK_RANGE *range);
bool unique_key_range();
};
@ -87,6 +88,7 @@ class QUICK_SELECT_DESC: public QUICK_SELECT
public:
QUICK_SELECT_DESC(QUICK_SELECT *q, uint used_key_parts);
int get_next();
bool reverse_sorted() { return 1; }
private:
int cmp_prev(QUICK_RANGE *range);
bool range_reads_after_key(QUICK_RANGE *range);
@ -96,6 +98,7 @@ private:
List_iterator<QUICK_RANGE> rev_it;
};
class SQL_SELECT :public Sql_alloc {
public:
QUICK_SELECT *quick; // If quick-select used

23
sql/sql_select.cc
View File

@ -594,8 +594,7 @@ mysql_select(THD *thd,TABLE_LIST *tables,List<Item> &fields,COND *conds,
HA_POS_ERROR : thd->select_limit,0))))
order=0;
select_describe(&join,need_tmp,
(order != 0 &&
(!need_tmp || order != group || simple_group)),
order != 0 && !skip_sort_order,
select_distinct);
error=0;
goto err;
@ -5431,7 +5430,16 @@ static uint find_shortest_key(TABLE *table, key_map usable_keys)
}
/* Return 1 if we don't have to do file sorting */
/*
Test if we can skip the ORDER BY by using an index.
If we can use an index, the JOIN_TAB / tab->select struct
is changed to use the index.
Return:
0 We have to use filesort to do the sorting
1 We can use an index.
*/
static bool
test_if_skip_sort_order(JOIN_TAB *tab,ORDER *order,ha_rows select_limit,
@ -5476,6 +5484,12 @@ test_if_skip_sort_order(JOIN_TAB *tab,ORDER *order,ha_rows select_limit,
if (order_direction == -1) // If ORDER BY ... DESC
{
if (select && select->quick)
{
/*
Don't reverse the sort order, if it's already done.
(In some cases test_if_order_by_key() can be called multiple times
*/
if (!select->quick->reverse_sorted())
{
// ORDER BY range_key DESC
QUICK_SELECT_DESC *tmp=new QUICK_SELECT_DESC(select->quick,
@ -5486,6 +5500,7 @@ test_if_skip_sort_order(JOIN_TAB *tab,ORDER *order,ha_rows select_limit,
DBUG_RETURN(0); // Reverse sort not supported
}
select->quick=tmp;
}
DBUG_RETURN(1);
}
if (tab->ref.key_parts < used_key_parts)
@ -7028,7 +7043,7 @@ static void select_describe(JOIN *join, bool need_tmp_table, bool need_order,
net_store_null(packet);
net_store_null(packet);
}
sprintf(buff,"%.0f",join->best_positions[i].records_read);
sprintf(buff,"%.0f",(double) join->best_positions[i].records_read);
net_store_data(packet,buff);
my_bool key_read=table->key_read;
if (tab->type == JT_NEXT &&