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LEFT JOIN optimization: Change LEFT JOIN to normal join if possible

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mysql-test/r/select.result:
  Added test for LEFT JOIN optimization
mysql-test/t/select.test:
  Added test for LEFT JOIN optimization
sql/item.h:
  LEFT JOIN optimization
sql/item_cmpfunc.cc:
  LEFT JOIN optimization
sql/item_cmpfunc.h:
  LEFT JOIN optimization
sql/item_func.cc:
  LEFT JOIN optimization
sql/item_func.h:
  LEFT JOIN optimization
sql/item_strfunc.cc:
  LEFT JOIN optimization
sql/sql_base.cc:
  Heart of LEFT JOIN optimization
This commit is contained in:
unknown
2003-06-26 05:38:19 +03:00
parent 3d5f6a8867
commit a3beaaa3af
9 changed files with 147 additions and 33 deletions
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34
mysql-test/r/select.result
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@ -2569,16 +2569,46 @@ fld1 fld1
250503 250505
250504 250505
250505 250505
insert into t2 (fld1, companynr) values (999999,99);
select t2.companynr,companyname from t2 left join t4 using (companynr) where t4.companynr is null;
companynr companyname
99 NULL
select count(*) from t2 left join t4 using (companynr) where t4.companynr is not null;
count(*)
1199
explain select t2.companynr,companyname from t2 left join t4 using (companynr) where t4.companynr is null;
table type possible_keys key key_len ref rows Extra
t2 ALL NULL NULL NULL NULL 1199
t2 ALL NULL NULL NULL NULL 1200
t4 eq_ref PRIMARY PRIMARY 1 test.t2.companynr 1 Using where; Not exists
explain select t2.companynr,companyname from t4 left join t2 using (companynr) where t2.companynr is null;
table type possible_keys key key_len ref rows Extra
t4 ALL NULL NULL NULL NULL 12
t2 ALL NULL NULL NULL NULL 1199 Using where; Not exists
t2 ALL NULL NULL NULL NULL 1200 Using where; Not exists
delete from t2 where fld1=999999;
explain select t2.companynr,companyname from t4 left join t2 using (companynr) where t2.companynr > 0;
table type possible_keys key key_len ref rows Extra
t2 ALL NULL NULL NULL NULL 1199 Using where
t4 eq_ref PRIMARY PRIMARY 1 test.t2.companynr 1
explain select t2.companynr,companyname from t4 left join t2 using (companynr) where t2.companynr > 0 or t2.companynr < 0;
table type possible_keys key key_len ref rows Extra
t2 ALL NULL NULL NULL NULL 1199 Using where
t4 eq_ref PRIMARY PRIMARY 1 test.t2.companynr 1
explain select t2.companynr,companyname from t4 left join t2 using (companynr) where t2.companynr > 0 and t4.companynr > 0;
table type possible_keys key key_len ref rows Extra
t2 ALL NULL NULL NULL NULL 1199 Using where
t4 eq_ref PRIMARY PRIMARY 1 test.t2.companynr 1 Using where
explain select t2.companynr,companyname from t4 left join t2 using (companynr) where t2.companynr > 0 or t2.companynr is null;
table type possible_keys key key_len ref rows Extra
t4 ALL NULL NULL NULL NULL 12
t2 ALL NULL NULL NULL NULL 1199 Using where
explain select t2.companynr,companyname from t4 left join t2 using (companynr) where t2.companynr > 0 or t2.companynr < 0 or t4.companynr > 0;
table type possible_keys key key_len ref rows Extra
t4 ALL PRIMARY NULL NULL NULL 12
t2 ALL NULL NULL NULL NULL 1199 Using where
explain select t2.companynr,companyname from t4 left join t2 using (companynr) where ifnull(t2.companynr,1)>0;
table type possible_keys key key_len ref rows Extra
t4 ALL NULL NULL NULL NULL 12
t2 ALL NULL NULL NULL NULL 1199 Using where
select distinct t2.companynr,t4.companynr from t2,t4 where t2.companynr=t4.companynr+1;
companynr companynr
37 36