Bug#16274455: CAN NOT ACESS PARTITIONED TABLES WHEN

DOWNGRADED FROM 5.6.11 TO 5.6.10

Problem was new syntax not accepted by previous version.

Fixed by adding version comment of /*!50531 around the
new syntax.

Like this in the .frm file:
'PARTITION BY KEY /*!50611 ALGORITHM = 2 */ () PARTITIONS 3'
and also changing the output from SHOW CREATE TABLE to:
CREATE TABLE t1 (a INT)
/*!50100 PARTITION BY KEY */ /*!50611 ALGORITHM = 1 */ /*!50100 ()
PARTITIONS 3 */

It will always add the ALGORITHM into the .frm for KEY [sub]partitioned
tables, but for SHOW CREATE TABLE it will only add it in case it is the non
default ALGORITHM = 1.

Also notice that for 5.5, it will say /*!50531 instead of /*!50611, which
will make upgrade from 5.5 > 5.5.31 to 5.6 < 5.6.11 fail!
If one downgrades an fixed version to the same major version (5.5 or 5.6) the
bug 14521864 will be visible again, but unless the .frm is updated, it will
work again when upgrading again.

Also fixed so that the .frm does not get updated version
if a single partition check passes.

1 files changed, 59 insertions, 26 deletions

diff --git a/sql/sql_partition.cc b/sql/sql_partition.cc
index a64520a298d..6850f5ada63 100644
--- a/sql/sql_partition.cc
+++ b/sql/sql_partition.cc
@@ -2412,6 +2412,58 @@ end:
   return err;
 }
 
+
+/**
+  Add 'KEY' word, with optional 'ALGORTIHM = N'.
+
+  @param fptr                   File to write to.
+  @param part_info              partition_info holding the used key_algorithm
+  @param current_comment_start  NULL, or comment string encapsulating the
+                                PARTITION BY clause.
+
+  @return Operation status.
+    @retval 0    Success
+    @retval != 0 Failure
+*/
+
+static int add_key_with_algorithm(File fptr, partition_info *part_info,
+                                  const char *current_comment_start)
+{
+  int err= 0;
+  err+= add_part_key_word(fptr, partition_keywords[PKW_KEY].str);
+
+  /*
+    current_comment_start is given when called from SHOW CREATE TABLE,
+    Then only add ALGORITHM = 1, not the default 2 or non-set 0!
+    For .frm current_comment_start is NULL, then add ALGORITHM if != 0.
+  */
+  if (part_info->key_algorithm == partition_info::KEY_ALGORITHM_51 || // SHOW
+      (!current_comment_start &&                                      // .frm
+       (part_info->key_algorithm != partition_info::KEY_ALGORITHM_NONE)))
+  {
+    /* If we already are within a comment, end that comment first. */
+    if (current_comment_start)
+      err+= add_string(fptr, "*/ ");
+    err+= add_string(fptr, "/*!50531 ");
+    err+= add_part_key_word(fptr, partition_keywords[PKW_ALGORITHM].str);
+    err+= add_equal(fptr);
+    err+= add_space(fptr);
+    err+= add_int(fptr, part_info->key_algorithm);
+    err+= add_space(fptr);
+    err+= add_string(fptr, "*/ ");
+    if (current_comment_start)
+    {
+      /* Skip new line. */
+      if (current_comment_start[0] == '\n')
+        current_comment_start++;
+      err+= add_string(fptr, current_comment_start);
+      err+= add_space(fptr);
+    }
+  }
+  return err;
+}
+
+
 /*
   Generate the partition syntax from the partition data structure.
   Useful for support of generating defaults, SHOW CREATE TABLES
@@ -2456,7 +2508,8 @@ char *generate_partition_syntax(partition_info *part_info,
                                 bool use_sql_alloc,
                                 bool show_partition_options,
                                 HA_CREATE_INFO *create_info,
-                                Alter_info *alter_info)
+                                Alter_info *alter_info,
+                                const char *current_comment_start)
 {
   uint i,j, tot_num_parts, num_subparts;
   partition_element *part_elem;
@@ -2490,18 +2543,8 @@ char *generate_partition_syntax(partition_info *part_info,
         err+= add_string(fptr, partition_keywords[PKW_LINEAR].str);
       if (part_info->list_of_part_fields)
       {
-        err+= add_part_key_word(fptr, partition_keywords[PKW_KEY].str);
-        if (part_info->key_algorithm != partition_info::KEY_ALGORITHM_NONE)
-        {
-          /*
-            Can't add a !50530 comment, since we are already within a comment!
-          */
-          err+= add_part_key_word(fptr, partition_keywords[PKW_ALGORITHM].str);
-          err+= add_equal(fptr);
-          err+= add_space(fptr);
-          err+= add_int(fptr, part_info->key_algorithm);
-          err+= add_space(fptr);
-        }
+        err+= add_key_with_algorithm(fptr, part_info,
+                                     current_comment_start);
         err+= add_part_field_list(fptr, part_info->part_field_list);
       }
       else
@@ -2541,19 +2584,9 @@ char *generate_partition_syntax(partition_info *part_info,
       err+= add_string(fptr, partition_keywords[PKW_LINEAR].str);
     if (part_info->list_of_subpart_fields)
     {
-      add_part_key_word(fptr, partition_keywords[PKW_KEY].str);
-      if (part_info->key_algorithm != partition_info::KEY_ALGORITHM_NONE)
-      {
-        /*
-          Can't add a !50530 comment, since we are already within a comment!
-        */
-        err+= add_part_key_word(fptr, partition_keywords[PKW_ALGORITHM].str);
-        err+= add_equal(fptr);
-        err+= add_space(fptr);
-        err+= add_int(fptr, part_info->key_algorithm);
-        err+= add_space(fptr);
-      }
-      add_part_field_list(fptr, part_info->subpart_field_list);
+      err+= add_key_with_algorithm(fptr, part_info,
+                                   current_comment_start);
+      err+= add_part_field_list(fptr, part_info->subpart_field_list);
     }
     else
       err+= add_part_key_word(fptr, partition_keywords[PKW_HASH].str);