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bug #27531: 5.1 part of the fix:

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- added join cache indication in EXPLAIN (Extra column).
 - prefer filesort over full scan over 
   index for ORDER BY (because it's faster).
 - when switching from REF to RANGE because
   RANGE uses longer key turn off sort on
   the head table only as the resulting 
   RANGE access is a candidate for join cache
   and we don't want to disable it by sorting
   on the first table only.
This commit is contained in:
gkodinov/kgeorge@magare.gmz
2007-05-04 18:06:06 +03:00
parent 19b9c7a8cd
commit 306371a850
31 changed files with 216 additions and 202 deletions
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6
mysql-test/r/compress.result
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@@ -611,11 +611,11 @@ id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t3 ref period period 4 test.t1.period 4181
explain select * from t3 as t1,t3 where t1.period=t3.period order by t3.period limit 10;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t3 index period period 4 NULL 41810
1 SIMPLE t3 ALL period NULL NULL NULL 41810 Using filesort
1 SIMPLE t1 ref period period 4 test.t3.period 4181
explain select * from t3 as t1,t3 where t1.period=t3.period order by t1.period limit 10;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index period period 4 NULL 41810
1 SIMPLE t1 ALL period NULL NULL NULL 41810 Using filesort
1 SIMPLE t3 ref period period 4 test.t1.period 4181
select period from t1;
period
@@ -1434,7 +1434,7 @@ companynr companynr
41 40
explain select distinct t2.companynr,t4.companynr from t2,t4 where t2.companynr=t4.companynr+1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t4 index NULL PRIMARY 1 NULL 12 Using index; Using temporary
1 SIMPLE t4 index NULL PRIMARY 1 NULL 12 Using index; Using temporary; Using join cache
1 SIMPLE t2 ALL NULL NULL NULL NULL 1199 Using where
select t2.fld1,t2.companynr,fld3,period from t3,t2 where t2.fld1 = 38208 and t2.fld1=t3.t2nr and period = 1008 or t2.fld1 = 38008 and t2.fld1 =t3.t2nr and period = 1008;
fld1 companynr fld3 period