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Bug #22342: No results returned for query using max and group by

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When using index for group by and range access the server isolates    
 a set of ranges based on the conditions over the key parts of the
 index used. Then it uses only the ranges over the GROUP BY fields to
 jump from one group to another. Since the GROUP BY fields may form a
 prefix over the index, we may use only a prefix of the ranges produced
 by the range optimizer.
 Each range contains a notion on whether it includes its border values.
 The problem is that when using a range prefix, the last range is open
 because it assumes that there is a range on the next keypart. Thus when
 we use a prefix range as it is, it excludes all border values.
 The solution is when ignoring the suffix of the range conditions 
 (to jump over the GROUP BY prefix only) the server must change the 
 remaining intervals so they always contain their borders, e.g. 
 if the whole range was :
 (1,-inf) <= (<group_by_col>,<min_max_arg_col>) < (1, 3) we must make
 (1) <= (<group_by_col>) <= (1) because (a,b) < (c1,c2) means :
 a < c1 OR (a = c1 AND b < c2).
This commit is contained in:
gkodinov/kgeorge@macbook.gmz
2006-10-16 19:30:19 +03:00
parent 2e2c5a20c0
commit 0e954d2c1a
4 changed files with 75 additions and 0 deletions
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37
sql/opt_range.cc
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@ -8374,6 +8374,7 @@ TRP_GROUP_MIN_MAX::make_quick(PARAM *param, bool retrieve_full_rows,
quick->quick_prefix_select= NULL;
quick->update_key_stat();
quick->adjust_prefix_ranges();
DBUG_RETURN(quick);
}
@ -8603,6 +8604,42 @@ bool QUICK_GROUP_MIN_MAX_SELECT::add_range(SEL_ARG *sel_range)
}
/*
Opens the ranges if there are more conditions in quick_prefix_select than
the ones used for jumping through the prefixes.
SYNOPSIS
QUICK_GROUP_MIN_MAX_SELECT::adjust_prefix_ranges()
NOTES
quick_prefix_select is made over the conditions on the whole key.
It defines a number of ranges of length x.
However when jumping through the prefixes we use only the the first
few most significant keyparts in the range key. However if there
are more keyparts to follow the ones we are using we must make the
condition on the key inclusive (because x < "ab" means
x[0] < 'a' OR (x[0] == 'a' AND x[1] < 'b').
To achive the above we must turn off the NEAR_MIN/NEAR_MAX
*/
void QUICK_GROUP_MIN_MAX_SELECT::adjust_prefix_ranges ()
{
if (quick_prefix_select &&
group_prefix_len < quick_prefix_select->max_used_key_length)
{
DYNAMIC_ARRAY *arr;
uint inx;
for (inx= 0, arr= &quick_prefix_select->ranges; inx < arr->elements; inx++)
{
QUICK_RANGE *range;
get_dynamic(arr, (gptr)&range, inx);
range->flag &= ~(NEAR_MIN | NEAR_MAX);
}
}
}
/*
Determine the total number and length of the keys that will be used for
index lookup.