BUG#18198: Fixes to handle VARCHAR strings properly

New methods to handle VARCHAR strings and CHAR's which are not
using a binary collation.
Indentation fixes
Now strings are run through strnxfrm before they are processed
by the partition function
We do not allow collations where strnxfrm expands the string since
we want the resulting string to fit in the same value range as
the original.

mysql-test/r/partition_range.result

@@ -709,3 +709,45 @@ WHERE (a >= '2004-07-01' AND a <= '2004-09-30') OR
 id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	p407,p408,p409,p507,p508,p509	ALL	NULL	NULL	NULL	NULL	18	Using where
 DROP TABLE t1;
+create table t1 (a varchar(20))
+partition by range (crc32(md5(a)))
+(partition p0 values less than (100),
+partition p1 values less than maxvalue);
+insert into t1 values ("12345678901234567890");
+insert into t1 values ("A2345678901234567890");
+insert into t1 values ("B2345678901234567890");
+insert into t1 values ("1234567890123456789");
+insert into t1 values ("1234567890123456");
+select * from t1;
+a
+12345678901234567890
+A2345678901234567890
+B2345678901234567890
+1234567890123456789
+1234567890123456
+explain partitions select * from t1 where a = "12345678901234567890";
+id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	p1	ALL	NULL	NULL	NULL	NULL	5	Using where
+explain partitions select * from t1 where a = "12345678901234567890" OR
+a = "A2345678901234567890" OR
+a = "B2345678901234567890" OR
+a = "C2345678901234567890";
+id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	p1	ALL	NULL	NULL	NULL	NULL	5	Using where
+explain partitions select * from t1 where a = "01234567890123456";
+id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	p1	ALL	NULL	NULL	NULL	NULL	5	Using where
+select * from t1 where a = "01234567890123456";
+a
+select * from t1 where a = "12345678901234567890" OR
+a = "A2345678901234567890" OR
+a = "B2345678901234567890" OR
+a = "C2345678901234567890";
+a
+12345678901234567890
+A2345678901234567890
+B2345678901234567890
+select * from t1 where a = "12345678901234567890";
+a
+12345678901234567890
+drop table t1;

mysql-test/t/partition_range.test

@@ -686,3 +686,33 @@ EXPLAIN PARTITIONS SELECT * from t1
 WHERE (a >= '2004-07-01' AND a <= '2004-09-30') OR
       (a >= '2005-07-01' AND a <= '2005-09-30');
 DROP TABLE t1;
+
+#
+# Bug 18198: Try with a couple of cases using VARCHAR fields in
+#            partition function.
+create table t1 (a varchar(20))
+partition by range (crc32(md5(a)))
+(partition p0 values less than (100),
+ partition p1 values less than maxvalue);
+
+insert into t1 values ("12345678901234567890");
+insert into t1 values ("A2345678901234567890");
+insert into t1 values ("B2345678901234567890");
+insert into t1 values ("1234567890123456789");
+insert into t1 values ("1234567890123456");
+select * from t1;
+explain partitions select * from t1 where a = "12345678901234567890";
+explain partitions select * from t1 where a = "12345678901234567890" OR
+                                          a = "A2345678901234567890" OR
+                                          a = "B2345678901234567890" OR
+                                          a = "C2345678901234567890";
+explain partitions select * from t1 where a = "01234567890123456";
+select * from t1 where a = "01234567890123456";
+select * from t1 where a = "12345678901234567890" OR
+                       a = "A2345678901234567890" OR
+                       a = "B2345678901234567890" OR
+                       a = "C2345678901234567890";
+select * from t1 where a = "12345678901234567890";
+
+
+drop table t1;

sql/partition_info.h

@@ -61,6 +61,16 @@ class partition_info : public Sql_alloc
   */
   get_subpart_id_func get_subpartition_id;
 
+  /*
+    When we have various string fields we might need some preparation
+    before and clean-up after calling the get_part_id_func's. We need
+    one such method for get_partition_id and one for
+    get_part_partition_id and one for get_subpartition_id.
+  */
+  get_part_id_func get_partition_id_charset;
+  get_part_id_func get_part_partition_id_charset;
+  get_subpart_id_func get_subpartition_id_charset;
+
   /* NULL-terminated array of fields used in partitioned expression */
   Field **part_field_array;
   /* NULL-terminated array of fields used in subpartitioned expression */
@@ -72,6 +82,16 @@ class partition_info : public Sql_alloc
   */
   Field **full_part_field_array;
 
+  /*
+    When we have a field that requires transformation before calling the
+    partition functions we must allocate field buffers for the field of
+    the fields in the partition function.
+  */
+  char **part_field_buffers;
+  char **subpart_field_buffers;
+  char **restore_part_field_ptrs;
+  char **restore_subpart_field_ptrs;
+
   Item *part_expr;
   Item *subpart_expr;
 
@@ -188,6 +208,8 @@ class partition_info : public Sql_alloc
   bool is_auto_partitioned;
   bool from_openfrm;
   bool has_null_value;
+  bool includes_charset_field_part;
+  bool includes_charset_field_subpart;
 
 
   partition_info()
@@ -195,6 +217,8 @@ class partition_info : public Sql_alloc
     get_subpartition_id(NULL),
     part_field_array(NULL), subpart_field_array(NULL),
     full_part_field_array(NULL),
+    part_field_buffers(NULL), subpart_field_buffers(NULL),
+    restore_part_field_ptrs(NULL), restore_subpart_field_ptrs(NULL),
     part_expr(NULL), subpart_expr(NULL), item_free_list(NULL),
     first_log_entry(NULL), exec_log_entry(NULL), frm_log_entry(NULL),
     list_array(NULL),
@@ -217,7 +241,8 @@ class partition_info : public Sql_alloc
     list_of_part_fields(FALSE), list_of_subpart_fields(FALSE),
     linear_hash_ind(FALSE), fixed(FALSE),
     is_auto_partitioned(FALSE), from_openfrm(FALSE),
-    has_null_value(FALSE)
+    has_null_value(FALSE), includes_charset_field_part(FALSE),
+    includes_charset_field_subpart(FALSE)
   {
     all_fields_in_PF.clear_all();
     all_fields_in_PPF.clear_all();