hi,<div>   my query schema  is SSBM.My database size is 65G.There are five tables :</div><div><br></div><div>     lineorder      600038145     rows</div><div>     part             1400000 </div><div>     date            2556</div>
<div>     supplier       1000000</div><div>     customer     3000000</div><div>and  my host have  enough memory space up to  500G</div><div>when  i  run query </div><div><br></div><div>select sum(lo_extendedprice*lo_discount) as revenue</div>
<div>from voc.lineorder, voc.dates</div><div>where lo_orderdate = d_datekey</div><div>and d_weeknuminyear = 6</div><div>and d_year = 1994</div><div>and lo_discount between 5 and 7</div><div>and lo_quantity between 26 and 35;</div>
<div><br>the result is below </div><div><br></div><div><div>| revenue       |</div><div>+===============+</div><div>| 2605756481323 |</div><div>+---------------+</div><div>1 tuple (6.2s)</div></div><div><br></div><div>but  if  i  delete the condition  of  &quot; lo_discount between 5 and 7&quot;</div>
<div><br></div><div>the  run  result  is  more  faster than  the  original one.</div><div><br></div><div>query </div><div>  </div><div>select sum(lo_extendedprice*lo_discount) as revenue</div><div>from voc.lineorder, voc.dates</div>
<div>where lo_orderdate = d_datekey</div><div>and d_weeknuminyear = 6</div><div>and d_year = 1994</div><div>and lo_quantity between 26 and 35;   </div><div><br></div><div><div>+---------------+</div><div>| revenue       |</div>
<div>+===============+</div><div>| 7990711777299 |</div><div>+---------------+</div><div>1 tuple (410.451ms)</div></div><div><br></div><div>at the  same  time  ,if i  delete  the  condition of  &quot;lo_quantity between 26 and 35&quot;</div>
<div>the run result is more faster  than  the original one  too.</div><div><br></div><div>query </div><div><br></div><div><div>select sum(lo_extendedprice*lo_discount) as revenue</div><div>from voc.lineorder, voc.dates</div>
<div>where lo_orderdate = d_datekey</div><div>and d_weeknuminyear = 6</div><div>and d_year = 1994</div><div>and lo_quantity between 26 and 35;</div></div><div><br></div><div><div>+---------------+</div><div>| revenue       |</div>
<div>+===============+</div><div>| 7990711777299 |</div><div>+---------------+</div><div>1 tuple (463.617ms)</div></div><div><br></div><div>i am  confused  and  if the semijoin costs  a lot of  execution time ? Thank you for your help.</div>
<div><br></div><div>best reguards,</div><div><br></div><div>guangliang peng</div>