BUG#18198: Partition function handling

Review fixes

mysql-test/r/partition_range.result

 drop table if exists t1;
+create table t1 (a varchar(10) charset latin1 collate latin1_bin, b int)
+partition by range (length(a) * b)
+(partition p0 values less than (2), partition p1 values less than (10));
+insert into t1 values ('a ', 2),('a',3);
+drop table t1;
+create table t1 (a varchar(10) charset latin1 collate latin1_bin, b int)
+partition by range (b* length(a) * b)
+(partition p0 values less than (2), partition p1 values less than (10));
+insert into t1 values ('a ', 2),('a',3);
+drop table t1;
+create table t1 (a varchar(10) charset latin1 collate latin1_bin,
+b varchar(10) charset latin1 collate latin1_bin)
+partition by range (length(b) * length(a))
+(partition p0 values less than (2), partition p1 values less than (10));
+insert into t1 values ('a ', 'b  '),('a','b');
+drop table t1;
+create table t1 (a varchar(10) charset latin1 collate latin1_bin,
+b varchar(10) charset latin1 collate latin1_bin)
+partition by range (length(a) * length(b))
+(partition p0 values less than (2), partition p1 values less than (10));
+insert into t1 values ('a ', 'b  '),('a','b');
+drop table t1;
+create table t1 (a varchar(10) charset latin1 collate latin1_bin,
+b varchar(10) charset latin1 collate latin1_bin, c int)
+partition by range (length(a) * c)
+(partition p0 values less than (2), partition p1 values less than (10));
+insert into t1 values ('a ', 'b  ', 2),('a','b', 3);
+drop table t1;
+create table t1 (a varchar(10) charset latin1 collate latin1_bin,
+b varchar(10) charset latin1 collate latin1_bin, c int)
+partition by range (c * length(a))
+(partition p0 values less than (2), partition p1 values less than (10));
+insert into t1 values ('a ', 'b  ', 2),('a','b', 3);
+drop table t1;
 create table t1 (a int unsigned)
 partition by range (a)
 (partition pnull values less than (0),

mysql-test/t/partition_hash.test

@@ -9,6 +9,18 @@
 drop table if exists t1;
 --enable_warnings
 
+#
+# BUG 18198: Partition functions handling
+#
+create table t1 (a varchar(10) charset latin1 collate latin1_bin)
+partition by hash(length(a))
+partitions 10;
+insert into t1 values (''),(' '),('a'),('a '),('a  ');
+explain partitions select * from t1 where a='a ';
+explain partitions select * from t1 where a='a';
+explain partitions select * from t1 where a='a ' OR a='a';
+drop table t1;
+
 #
 # More partition pruning tests, especially on interval walking
 #

mysql-test/t/partition_range.test

@@ -9,6 +9,49 @@
 drop table if exists t1;
 --enable_warnings
 
+#
+# BUG 18198: Various tests for partition functions
+#
+create table t1 (a varchar(10) charset latin1 collate latin1_bin, b int)
+partition by range (length(a) * b)
+(partition p0 values less than (2), partition p1 values less than (10));
+insert into t1 values ('a ', 2),('a',3);
+drop table t1;
+
+create table t1 (a varchar(10) charset latin1 collate latin1_bin, b int)
+partition by range (b* length(a) * b)
+(partition p0 values less than (2), partition p1 values less than (10));
+insert into t1 values ('a ', 2),('a',3);
+drop table t1;
+
+create table t1 (a varchar(10) charset latin1 collate latin1_bin,
+                 b varchar(10) charset latin1 collate latin1_bin)
+partition by range (length(b) * length(a))
+(partition p0 values less than (2), partition p1 values less than (10));
+insert into t1 values ('a ', 'b  '),('a','b');
+drop table t1;
+
+create table t1 (a varchar(10) charset latin1 collate latin1_bin,
+                 b varchar(10) charset latin1 collate latin1_bin)
+partition by range (length(a) * length(b))
+(partition p0 values less than (2), partition p1 values less than (10));
+insert into t1 values ('a ', 'b  '),('a','b');
+drop table t1;
+
+create table t1 (a varchar(10) charset latin1 collate latin1_bin,
+                 b varchar(10) charset latin1 collate latin1_bin, c int)
+partition by range (length(a) * c)
+(partition p0 values less than (2), partition p1 values less than (10));
+insert into t1 values ('a ', 'b  ', 2),('a','b', 3);
+drop table t1;
+
+create table t1 (a varchar(10) charset latin1 collate latin1_bin,
+                 b varchar(10) charset latin1 collate latin1_bin, c int)
+partition by range (c * length(a))
+(partition p0 values less than (2), partition p1 values less than (10));
+insert into t1 values ('a ', 'b  ', 2),('a','b', 3);
+drop table t1;
+
 #
 # More checks for partition pruning
 #

sql/item.h

@@ -831,12 +831,20 @@ class Item {
     Check if a partition function is allowed
     SYNOPSIS
       check_partition_func_processor()
-      int_arg                        Return argument
+      int_arg                        Ignored
     RETURN VALUE
-      0
+      TRUE                           Partition function not accepted
+      FALSE                          Partition function accepted
+
     DESCRIPTION
     check_partition_func_processor is used to check if a partition function
-    uses an allowed function. The default is that an item is not allowed
+    uses an allowed function. An allowed function will always ensure that
+    X=Y guarantees that also part_function(X)=part_function(Y) where X is
+    a set of partition fields and so is Y. The problems comes mainly from
+    character sets where two equal strings can be quite unequal. E.g. the
+    german character for double s is equal to 2 s.
+
+    The default is that an item is not allowed
     in a partition function. However all mathematical functions, string
     manipulation functions, date functions are allowed. Allowed functions
     can never depend on server version, they cannot depend on anything

sql/partition_info.cc

@@ -838,11 +838,12 @@ bool partition_info::check_partition_info(THD *thd, handlerton **eng_type,
 
 /*
   Print error for no partition found
+
   SYNOPSIS
     print_no_partition_found()
     table                        Table object
+
   RETURN VALUES
-    NONE
 */
 
 void partition_info::print_no_partition_found(TABLE *table)
@@ -863,10 +864,11 @@ void partition_info::print_no_partition_found(TABLE *table)
   Set up buffers and arrays for fields requiring preparation
   SYNOPSIS
     set_up_charset_field_preps()
-    part_info                        Partition info object
+
   RETURN VALUES
     TRUE                             Memory Allocation error
     FALSE                            Success
+
   DESCRIPTION
     Set up arrays and buffers for fields that require special care for
     calculation of partition id. This is used for string fields with
@@ -1025,5 +1027,4 @@ bool partition_info::set_up_charset_field_preps()
   mem_alloc_error(size);
   DBUG_RETURN(TRUE);
 }
-#endif
-                                                                                                                                              /* WITH_PARTITION_STORAGE_ENGINE */
+#endif /* WITH_PARTITION_STORAGE_ENGINE */

sql/sql_partition.cc

@@ -1437,9 +1437,11 @@ static uint32 get_part_id_from_linear_hash(longlong hash_value, uint mask,
 /*
   Check if a particular field is in need of character set
   handling for partition functions.
+
   SYNOPSIS
     field_is_partition_charset()
     field                         The field to check
+
   RETURN VALUES
     FALSE                        Not in need of character set handling
     TRUE                         In need of character set handling
@@ -1461,8 +1463,9 @@ bool field_is_partition_charset(Field *field)
 
 
 /*
-  Check that partition function do not contain any forbidden
+  Check that partition function doesn't contain any forbidden
   character sets and collations.
+
   SYNOPSIS
     check_part_func_fields()
     ptr                                 Array of Field pointers
@@ -1471,6 +1474,7 @@ bool field_is_partition_charset(Field *field)
   RETURN VALUES
     FALSE                               Success
     TRUE                                Error
+
   DESCRIPTION
     We will check in this routine that the fields of the partition functions
     do not contain unallowed parts. It can also be used to check if there
@@ -2390,9 +2394,13 @@ static uint32 get_part_id_linear_key(partition_info *part_info,
 
 /*
   Copy to field buffers and set up field pointers
+
   SYNOPSIS
     copy_to_part_field_buffers()
     ptr                          Array of fields to copy
+    field_bufs                   Array of field buffers to copy to
+    restore_ptr                  Array of pointers to restore to
+
   RETURN VALUES
     NONE
   DESCRIPTION
@@ -2451,8 +2459,9 @@ static void copy_to_part_field_buffers(Field **ptr,
   SYNOPSIS
     restore_part_field_pointers()
     ptr                            Array of fields to restore
+    restore_ptr                    Array of field pointers to restore to
+
   RETURN VALUES
-    NONE
 */
 
 static void restore_part_field_pointers(Field **ptr, char **restore_ptr)