Bug#14521864: MYSQL 5.1 TO 5.5 BUGS PARTITIONING

Due to an internal change in the server code in between 5.1 and 5.5
(wl#2649) the hash function used in KEY partitioning changed
for numeric and date/time columns (from binary hash calculation
to character based hash calculation).

Also enum/set changed from latin1 ci based hash calculation to
binary hash between 5.1 and 5.5. (bug#11759782).

These changes makes KEY [sub]partitioned tables on any of
the affected column types incompatible with 5.5 and above,
since the calculation of partition id differs.

Also since InnoDB asserts that a deleted row was previously
read (positioned), the server asserts on delete of a row that
is in the wrong partition.

The solution for this situation is:

1) The partitioning engine will check that delete/update will go to the
partition the row was read from and give an error otherwise, consisting
of the rows partitioning fields. This will avoid asserts in InnoDB and
also alert the user that there is a misplaced row. A detailed error
message will be given, including an entry to the error log consisting
of both table name, partition and row content (PK if exists, otherwise
all partitioning columns).


2) A new optional syntax for KEY () partitioning in 5.5 is allowed:
[SUB]PARTITION BY KEY [ALGORITHM = N] (list_of_cols)
Where N = 1 uses the same hashing as 5.1 (Numeric/date/time fields uses
binary hashing, ENUM/SET uses charset hashing) N = 2 uses the same
hashing as 5.5 (Numeric/date/time fields uses charset hashing,
ENUM/SET uses binary hashing). If not set on CREATE/ALTER it will
default to 2.

This new syntax should probably be ignored by NDB.


3) Since there is a demand for avoiding scanning through the full
table, during upgrade the ALTER TABLE t PARTITION BY ... command is
considered a no-op (only .frm change) if everything except ALGORITHM
is the same and ALGORITHM was not set before, which allows manually
upgrading such table by something like:
ALTER TABLE t PARTITION BY KEY ALGORITHM = 1 () or
ALTER TABLE t PARTITION BY KEY ALGORITHM = 2 ()


4) Enhanced partitioning with CHECK/REPAIR to also check for/repair
misplaced rows. (Also works for ALTER TABLE t CHECK/REPAIR PARTITION)

CHECK FOR UPGRADE:
If the .frm version is < 5.5.3
and uses KEY [sub]partitioning
and an affected column type
then it will fail with an message:
KEY () partitioning changed, please run:
ALTER TABLE `test`.`t1`  PARTITION BY KEY ALGORITHM = 1 (a)
PARTITIONS 12
(i.e. current partitioning clause, with the addition of
ALGORITHM = 1)

CHECK without FOR UPGRADE:
if MEDIUM (default) or EXTENDED options are given:
Scan all rows and verify that it is in the correct partition.
Fail for the first misplaced row.

REPAIR:
if default or EXTENDED (i.e. not QUICK/USE_FRM):
Scan all rows and every misplaced row is moved into its correct
partitions.


5) Updated mysqlcheck (called by mysql_upgrade) to handle the
new output from CHECK FOR UPGRADE, to run the ALTER statement
instead of running REPAIR.

This will allow mysql_upgrade (or CHECK TABLE t FOR UPGRADE) to upgrade
a KEY [sub]partitioned table that has any affected field type
and a .frm version < 5.5.3 to ALGORITHM = 1 without rebuild.


Also notice that if the .frm has a version of >= 5.5.3 and ALGORITHM
is not set, it is not possible to know if it consists of rows from
5.1 or 5.5! In these cases I suggest that the user does:
(optional)
LOCK TABLE t WRITE;
SHOW CREATE TABLE t;
(verify that it has no ALGORITHM = N, and to be safe, I would suggest
backing up the .frm file, to be used if one need to change to another
ALGORITHM = N, without needing to rebuild/repair)
ALTER TABLE t <old partitioning clause, but with ALGORITHM = N>;
which should set the ALGORITHM to N (if the table has rows from
5.1 I would suggest N = 1, otherwise N = 2)
CHECK TABLE t;
(here one could use the backed up .frm instead and change to a new N
and run CHECK again and see if it passes)
and if there are misplaced rows:
REPAIR TABLE t;
(optional)
UNLOCK TABLES;

1 files changed, 70 insertions, 42 deletions

diff --git a/sql/key.cc b/sql/key.cc
index 9d0f86f2565..f13377146c8 100644
--- a/sql/key.cc
+++ b/sql/key.cc
@@ -1,4 +1,4 @@
-/* Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved.
+/* Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -312,6 +312,70 @@ bool key_cmp_if_same(TABLE *table,const uchar *key,uint idx,uint key_length)
   return 0;
 }
 
+
+/**
+  Unpack a field and append it.
+
+  @param[inout] to           String to append the field contents to.
+  @param        field        Field to unpack.
+  @param        rec          Record which contains the field data.
+  @param        max_length   Maximum length of field to unpack
+                             or 0 for unlimited.
+  @param        prefix_key   The field is used as a prefix key.
+*/
+
+void field_unpack(String *to, Field *field, const uchar *rec, uint max_length,
+                  bool prefix_key)
+{
+  String tmp;
+  DBUG_ENTER("field_unpack");
+  if (!max_length)
+    max_length= field->pack_length();
+  if (field)
+  {
+    if (field->is_null())
+    {
+      to->append(STRING_WITH_LEN("NULL"));
+      DBUG_VOID_RETURN;
+    }
+    CHARSET_INFO *cs= field->charset();
+    field->val_str(&tmp);
+    /*
+      For BINARY(N) strip trailing zeroes to make
+      the error message nice-looking
+    */
+    if (field->binary() &&  field->type() == MYSQL_TYPE_STRING && tmp.length())
+    {
+      const char *tmp_end= tmp.ptr() + tmp.length();
+      while (tmp_end > tmp.ptr() && !*--tmp_end) ;
+      tmp.length(tmp_end - tmp.ptr() + 1);
+    }
+    if (cs->mbmaxlen > 1 && prefix_key)
+    {
+      /*
+        Prefix key, multi-byte charset.
+        For the columns of type CHAR(N), the above val_str()
+        call will return exactly "key_part->length" bytes,
+        which can break a multi-byte characters in the middle.
+        Align, returning not more than "char_length" characters.
+      */
+      uint charpos, char_length= max_length / cs->mbmaxlen;
+      if ((charpos= my_charpos(cs, tmp.ptr(),
+                               tmp.ptr() + tmp.length(),
+                               char_length)) < tmp.length())
+        tmp.length(charpos);
+    }
+    if (max_length < field->pack_length())
+      tmp.length(min(tmp.length(),max_length));
+    ErrConvString err(&tmp);
+    to->append(err.ptr());
+  }
+  else
+    to->append(STRING_WITH_LEN("???"));
+  DBUG_VOID_RETURN;
+}
+
+
 /*
   unpack key-fields from record to some buffer.
 
@@ -329,8 +393,6 @@ bool key_cmp_if_same(TABLE *table,const uchar *key,uint idx,uint key_length)
 void key_unpack(String *to,TABLE *table,uint idx)
 {
   KEY_PART_INFO *key_part,*key_part_end;
-  Field *field;
-  String tmp;
   my_bitmap_map *old_map= dbug_tmp_use_all_columns(table, table->read_set);
   DBUG_ENTER("key_unpack");
 
@@ -346,47 +408,13 @@ void key_unpack(String *to,TABLE *table,uint idx)
     {
       if (table->record[0][key_part->null_offset] & key_part->null_bit)
       {
-	to->append(STRING_WITH_LEN("NULL"));
-	continue;
+        to->append(STRING_WITH_LEN("NULL"));
+        continue;
       }
     }
-    if ((field=key_part->field))
-    {
-      CHARSET_INFO *cs= field->charset();
-      field->val_str(&tmp);
-      /*
-        For BINARY(N) strip trailing zeroes to make
-        the error message nice-looking
-      */
-      if (field->binary() &&  field->type() == MYSQL_TYPE_STRING && tmp.length())
-      {
-        const char *tmp_end= tmp.ptr() + tmp.length();
-        while (tmp_end > tmp.ptr() && !*--tmp_end) ;
-        tmp.length(tmp_end - tmp.ptr() + 1);
-      }
-      if (cs->mbmaxlen > 1 && (key_part->key_part_flag & HA_PART_KEY_SEG))
-      {
-        /* 
-          Prefix key, multi-byte charset. 
-          For the columns of type CHAR(N), the above val_str() 
-          call will return exactly "key_part->length" bytes, 
-          which can break a multi-byte characters in the middle. 
-          Align, returning not more than "char_length" characters. 
-        */
-        uint charpos, char_length= key_part->length / cs->mbmaxlen;
-        if ((charpos= my_charpos(cs, tmp.ptr(),
-                                 tmp.ptr() + tmp.length(),
-                                 char_length)) < tmp.length())
-          tmp.length(charpos);
-      }
-      if (key_part->length < field->pack_length())
-	tmp.length(min(tmp.length(),key_part->length));
-      ErrConvString err(&tmp);
-      to->append(err.ptr());
-    }
-    else
-      to->append(STRING_WITH_LEN("???"));
-  }
+    field_unpack(to, key_part->field, table->record[0], key_part->length,
+                 test(key_part->key_part_flag & HA_PART_KEY_SEG));
+ }
   dbug_tmp_restore_column_map(table->read_set, old_map);
   DBUG_VOID_RETURN;
 }