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Bug #31890 Partitions: ORDER BY DESC in InnoDB not working.

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It's not InnoDB specific bug.
Error is in QUEUE code, about the way we handle queue->max_at_top.
It's either '0' or '-2' and we do '^' operation to get the proper
direction. Though queue->compare() function can return '-2' as
a result of comparison sometimes. So we'll get
queue->compare() ^ queue->max_at_top == 0 (when max_at_top is -2)
and _downheap() function code will go wrong way here:
...
    if (next_index < elements &&
        (queue->compare(queue->first_cmp_arg,
                        queue->root[next_index]+offset_to_key,
                        queue->root[next_index+1]+offset_to_key) ^
         queue->max_at_top) > 0)
      next_index++;
...

Fixed by changing max_at_top to be either 1 or -1, doing
'* max_at_top' to get proper direction.


include/queues.h:
  Bug #31890 Partitions: ORDER BY DESC in InnoDB not working
  
  max_at_top policy changed
mysql-test/r/partition.result:
  Bug #31890 Partitions: ORDER BY DESC in InnoDB not working
  
  test result
mysql-test/t/partition.test:
  Bug #31890 Partitions: ORDER BY DESC in InnoDB not working
  
  test case
mysys/queues.c:
  Bug #31890 Partitions: ORDER BY DESC in InnoDB not working.
  
  queue->max_at_top policy changed - now it can either be '1' or '-1'.
  We multiply comparison result on max_at_top to get the proper
  direction.
This commit is contained in:
unknown
2007-11-14 22:20:31 +04:00
parent d68b313dbc
commit c33c92d0f2
4 changed files with 80 additions and 24 deletions
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6
include/queues.h
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@@ -31,8 +31,8 @@ typedef struct st_queue {
void *first_cmp_arg;
uint elements;
uint max_elements;
uint offset_to_key; /* compare is done on element+offset */
int max_at_top; /* Set if queue_top gives max */
uint offset_to_key; /* compare is done on element+offset */
int max_at_top; /* Normally 1, set to -1 if queue_top gives max */
int (*compare)(void *, uchar *,uchar *);
uint auto_extent;
} QUEUE;
@@ -43,7 +43,7 @@ typedef struct st_queue {
#define queue_replaced(queue) _downheap(queue,1)
#define queue_set_cmp_arg(queue, set_arg) (queue)->first_cmp_arg= set_arg
#define queue_set_max_at_top(queue, set_arg) \
(queue)->max_at_top= set_arg ? (-1 ^ 1) : 0
(queue)->max_at_top= set_arg ? -1 : 1
typedef int (*queue_compare)(void *,uchar *, uchar *);
int init_queue(QUEUE *queue,uint max_elements,uint offset_to_key,