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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
commit a3beaaa3af
9 changed files with 147 additions and 33 deletions
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14
mysql-test/t/select.test
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@ -1527,10 +1527,24 @@ select t2.fld1,t22.fld1 from t2,t2 t22 where t2.fld1 >= 250501 and t2.fld1 <= 25
#
# Test of left join.
#
insert into t2 (fld1, companynr) values (999999,99);
select t2.companynr,companyname from t2 left join t4 using (companynr) where t4.companynr is null;
select count(*) from t2 left join t4 using (companynr) where t4.companynr is not null;
explain select t2.companynr,companyname from t2 left join t4 using (companynr) where t4.companynr is null;
explain select t2.companynr,companyname from t4 left join t2 using (companynr) where t2.companynr is null;
delete from t2 where fld1=999999;
#
# Test left join optimization
explain select t2.companynr,companyname from t4 left join t2 using (companynr) where t2.companynr > 0;
explain select t2.companynr,companyname from t4 left join t2 using (companynr) where t2.companynr > 0 or t2.companynr < 0;
explain select t2.companynr,companyname from t4 left join t2 using (companynr) where t2.companynr > 0 and t4.companynr > 0;
# Following can't be optimized
explain select t2.companynr,companyname from t4 left join t2 using (companynr) where t2.companynr > 0 or t2.companynr is null;
explain select t2.companynr,companyname from t4 left join t2 using (companynr) where t2.companynr > 0 or t2.companynr < 0 or t4.companynr > 0;
explain select t2.companynr,companyname from t4 left join t2 using (companynr) where ifnull(t2.companynr,1)>0;
#
# Joins with forms.