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Bug#37830 : ORDER BY ASC/DESC - no difference

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Range scan in descending order for c <= <col> <= c type of
ranges was ignoring the DESC flag.
However some engines like InnoDB have the primary key parts 
as a suffix for every secondary key.
When such primary key suffix is used for ordering ignoring 
the DESC is not valid.
But we generally would like to do this because it's faster.
      
Fixed by performing only reverse scan if the primary key is used.
Removed some dead code in the process.
This commit is contained in:
Georgi Kodinov
2008-07-16 12:31:50 +03:00
parent 52f510ef22
commit 59ab9a0872
5 changed files with 83 additions and 79 deletions
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4
sql/opt_range.h
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@ -667,12 +667,10 @@ public:
int get_type() { return QS_TYPE_RANGE_DESC; }
private:
bool range_reads_after_key(QUICK_RANGE *range);
#ifdef NOT_USED
bool test_if_null_range(QUICK_RANGE *range, uint used_key_parts);
#endif
int reset(void) { rev_it.rewind(); return QUICK_RANGE_SELECT::reset(); }
List<QUICK_RANGE> rev_ranges;
List_iterator<QUICK_RANGE> rev_it;
uint used_key_parts;
};