Fixed bug with UPDATE/DELETE on UNIQUE key which could be NULL

Docs/manual.texi

@@ -27391,8 +27391,22 @@ master-slave relationship with @code{log-slave-updates} enabled.
 Note, however, that many queries will not work right in this kind of
 setup unless your client code is written to take care of the potential
 problems that can happen from updates that occur in different sequence
-on different servers. Note that the log format has changed in Version 3.23.26
-so that pre-3.23.26 slaves will not be able to read it.
+on different servers.
+
+This means that you can do a setup like the following:
+
+@example
+A -> B -> C -> A
+@end example
+
+This setup will only works if you only do non conflicting updates
+between the tables.  In other words, if you insert data in A and C, you
+should never insert a row in A that may have a conflicting key with a
+row insert in C.  You should also not update the sam rows on two servers
+if the order in which the updates are applied matters.
+
+Note that the log format has changed in Version 3.23.26 so that
+pre-3.23.26 slaves will not be able to read it.
 @item
 If the query on the slave gets an error, the slave thread will
 terminate, and a message will appear in the @code{.err} file. You should
@@ -28847,9 +28861,11 @@ explicitely lock the table with @code{LOCK TABLES} or execute a command that
 will modify every row in the table, like @code{ALTER TABLE}.
 
 In @strong{MySQL} Version 3.23.7 and above, you can insert rows into
-@code{MyISAM} tables at the same time other threads are reading from
-the table.  Note that currently this only works if there are no holes after
-deleted rows in the table at the time the insert is made.
+@code{MyISAM} tables at the same time other threads are reading from the
+table.  Note that currently this only works if there are no holes after
+deleted rows in the table at the time the insert is made. When all holes
+has been filled with new data, concurrent inserts will automaticly be
+enabled again.
 
 Table locking enables many threads to read from a table at the same
 time, but if a thread wants to write to a table, it must first get
@@ -42743,6 +42759,9 @@ not yet 100% confident in this code.
 @appendixsubsec Changes in release 3.23.37
 @itemize @bullet
 @item
+@code{UPDATE} and @code{DELETE} with @code{WHERE unique_key_part IS NULL}
+didn't update/delete all rows.
+@item
 Disabled @code{INSERT DELAYED} for tables that supports transactions.
 @item
 Fixed bug when using date functions on @code{TEXT}/@code{BLOB} column

mysql-test/r/null_key.result

@@ -92,3 +92,31 @@ NULL	9	0
 NULL	9	0
 a	b	c
 6	6	0
+table	type	possible_keys	key	key_len	ref	rows	Extra
+t1	ref	idx1	idx1	5	const	1	where used
+table	type	possible_keys	key	key_len	ref	rows	Extra
+t1	const	idx1	idx1	5	const	1	
+id
+101
+102
+105
+106
+109
+110
+id
+101
+102
+105
+106
+109
+110
+id	uniq_id
+3	1
+4	2
+7	3
+8	4
+id	uniq_id
+3	1
+4	2
+7	3
+8	4

mysql-test/t/null_key.test

@@ -45,3 +45,49 @@ select * from t1 where (a is null or a = 7) and b=7 and c=0;
 select * from t1 where a is null and b=9 or a is null and b=7 limit 3;
 select * from t1 where b like "6%";
 drop table t1;
+
+
+#
+# The following failed for Matt Loschert
+#
+
+DROP TABLE IF EXISTS t1,t2;
+CREATE TABLE t1 (
+  id int(10) unsigned NOT NULL auto_increment,
+  uniq_id int(10) unsigned default NULL,
+  PRIMARY KEY  (id),
+  UNIQUE KEY idx1 (uniq_id)
+) TYPE=MyISAM;
+
+CREATE TABLE t2 (
+  id int(10) unsigned NOT NULL auto_increment,
+  uniq_id int(10) unsigned default NULL,
+  PRIMARY KEY  (id)
+) TYPE=MyISAM;
+
+INSERT INTO t1 VALUES (1,NULL),(2,NULL),(3,1),(4,2),(5,NULL),(6,NULL),(7,3),(8,4),(9,NULL),(10,NULL);
+INSERT INTO t2 VALUES (1,NULL),(2,NULL),(3,1),(4,2),(5,NULL),(6,NULL),(7,3),(8,4),(9,NULL),(10,NULL);
+
+#
+# Check IS NULL optimization
+#
+explain select id from t1 where uniq_id is null;
+explain select id from t1 where uniq_id =1;
+#
+# Check updates
+#
+UPDATE t1 SET id=id+100 where uniq_id is null;
+UPDATE t2 SET id=id+100 where uniq_id is null;
+select id from t1 where uniq_id is null;
+select id from t2 where uniq_id is null;
+#
+# Delete all records from each table where the uniq_id field is null
+#
+DELETE FROM t1 WHERE uniq_id IS NULL;
+DELETE FROM t2 WHERE uniq_id IS NULL;
+#
+# Select what is left -- notice the difference
+#
+SELECT * FROM t1 ORDER BY uniq_id, id;
+SELECT * FROM t2 ORDER BY uniq_id, id;
+DROP table t1,t2;

mysys/Makefile.am

@@ -49,9 +49,9 @@ EXTRA_DIST =		thr_alarm.c thr_lock.c my_pthread.c my_thr_init.c \
 			thr_mutex.c thr_rwlock.c
 libmysys_a_LIBADD =	@THREAD_LOBJECTS@
 # test_fn removed 980815 since it not upp to date test_dir
-noinst_PROGRAMS =	testhash test_charset @THREAD_LPROGRAMS@
+noinst_PROGRAMS =	test_charset @THREAD_LPROGRAMS@
 # test_dir_DEPENDENCIES=	$(LIBRARIES)
-testhash_DEPENDENCIES=	$(LIBRARIES)
+# testhash_DEPENDENCIES=	$(LIBRARIES)
 test_charset_DEPENDENCIES=	$(LIBRARIES)
 EXTRA_PROGRAMS =	
 DEFS =			-DDEFAULT_BASEDIR=\"$(prefix)\" \
@@ -81,17 +81,17 @@ FLAGS=$(DEFS) $(INCLUDES) $(CPPFLAGS) $(CFLAGS) @NOINST_LDFLAGS@
 #
 
 test_thr_alarm: thr_alarm.c $(LIBRARIES)
-	$(CP) -f $(srcdir)/thr_alarm.c ./test_thr_alarm.c
+	$(CP) $(srcdir)/thr_alarm.c ./test_thr_alarm.c
 	$(LINK) $(FLAGS) -DMAIN  ./test_thr_alarm.c $(LDADD) $(LIBS)
 	$(RM) -f ./test_thr_alarm.*
 
 test_thr_lock: thr_lock.c $(LIBRARIES)
-	$(CP) -f $(srcdir)/thr_lock.c test_thr_lock.c
+	$(CP) $(srcdir)/thr_lock.c test_thr_lock.c
 	$(LINK) $(FLAGS) -DMAIN  ./test_thr_lock.c $(LDADD) $(LIBS)
 	$(RM) -f ./test_thr_lock.*
 
 test_vsnprintf: my_vsnprintf.c $(LIBRARIES)
-	$(CP) -f $(srcdir)/my_vsnprintf.c test_vsnprintf.c
+	$(CP) $(srcdir)/my_vsnprintf.c test_vsnprintf.c
 	$(LINK) $(FLAGS) -DMAIN ./test_vsnprintf.c $(LDADD) $(LIBS)
 	$(RM) -f test_vsnprintf.*
 
@@ -102,7 +102,7 @@ test_charset: test_charset.c $(LIBRARIES)
 	$(LINK) $(FLAGS) -DMAIN $(srcdir)/test_charset.c $(LDADD) $(LIBS)
 
 testhash: testhash.c $(LIBRARIES)
-	$(LINK) $(FLAGS) -DMAIN $(srcdir)/test_dir.c $(LDADD) $(LIBS)
+	$(LINK) $(FLAGS) -DMAIN $(srcdir)/testhash.c $(LDADD) $(LIBS)
 
 # Don't update the files from bitkeeper
 %::SCCS/s.%

sql/field.cc

@@ -3891,7 +3891,7 @@ String *Field_blob::val_str(String *val_buffer __attribute__((unused)),
   char *blob;
   memcpy_fixed(&blob,ptr+packlength,sizeof(char*));
   if (!blob)
-    val_ptr->length(0);
+    val_ptr->set("",0);				// A bit safer than ->length(0)
   else
     val_ptr->set((const char*) blob,get_length(ptr));
   return val_ptr;

sql/opt_range.cc

@@ -321,7 +321,7 @@ static bool get_quick_keys(PARAM *param,QUICK_SELECT *quick,KEY_PART *key,
 static bool eq_tree(SEL_ARG* a,SEL_ARG *b);
 
 static SEL_ARG null_element(SEL_ARG::IMPOSSIBLE);
-
+static bool null_part_in_key(KEY_PART *key_part, const char *key, uint length);
 
 /***************************************************************************
 ** Basic functions for SQL_SELECT and QUICK_SELECT
@@ -2306,7 +2306,15 @@ get_quick_keys(PARAM *param,QUICK_SELECT *quick,KEY_PART *key,
       KEY *table_key=quick->head->key_info+quick->index;
       flag=EQ_RANGE;
       if (table_key->flags & HA_NOSAME && key->part == table_key->key_parts-1)
-	flag|= UNIQUE_RANGE;
+      {
+	if (!(table_key->flags & HA_NULL_PART_KEY) ||
+	    !null_part_in_key(key,
+			      param->min_key,
+			      (uint) (tmp_min_key - param->min_key)))
+	  flag|= UNIQUE_RANGE;
+	else
+	  flag|= NULL_RANGE;
+      }
     }
   }
 
@@ -2339,7 +2347,7 @@ bool QUICK_SELECT::unique_key_range()
   if (ranges.elements == 1)
   {
     QUICK_RANGE *tmp;
-    if ((tmp=ranges.head())->flag & EQ_RANGE)
+    if (((tmp=ranges.head())->flag & (EQ_RANGE | NULL_RANGE)) == EQ_RANGE)
     {
       KEY *key=head->key_info+index;
       return ((key->flags & HA_NOSAME) &&
@@ -2349,6 +2357,24 @@ bool QUICK_SELECT::unique_key_range()
   return 0;
 }
 
+
+/* Returns true if any part of the key is NULL */
+
+static bool null_part_in_key(KEY_PART *key_part, const char *key, uint length)
+{
+  for (const char *end=key+length ; 
+       key < end;
+       key+= key_part++->part_length)
+  {
+    if (key_part->null_bit)
+    {
+      if (*key++)
+	return 1;
+    }
+  }
+  return 0;
+}
+
 /****************************************************************************
 ** Create a QUICK RANGE based on a key
 ****************************************************************************/

sql/opt_range.h

@@ -30,6 +30,7 @@
 #define NEAR_MAX	8
 #define UNIQUE_RANGE	16
 #define EQ_RANGE	32
+#define NULL_RANGE	64
 
 typedef struct st_key_part {
   uint16 key,part,part_length;