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<p class="MsoNormal"><span style="color:#1F497D">Sorry hit the wrong button on that last mail…<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">If I reduce down to a single join condition the tuple estimates become sensible. Note that the right branch shows a consistent set of tuples all the way.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">SELECT count(*)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">FROM comms c<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"> LEFT JOIN researcher r ON c.launch_id = r.researcher_id AND c.launch_type in (0,2)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Executing . . .<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">********************************************************************<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">QUERY PLAN 7,2, no timeout, of simple aggregate
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"> aggregate expression -> count(*)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#1F497D"> right join<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#1F497D"> Hash Join(launch_id)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#1F497D"> Heap<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#1F497D"> Pages 79 Tups 52520<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#1F497D"> D85 C1232<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#1F497D"> / \<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#1F497D"> Proj-rest Proj-rest<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#1F497D"> Sorted(NU) Sorted(NU)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#1F497D"> Pages 25 Tups 6117 Pages 221 Tups 52520<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#1F497D"> D9 C61 D76 C525<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#1F497D">/ /<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#1F497D">researcher_id_idx comms_launch_indx<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#1F497D">I(r) I(c)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#1F497D">B-Tree(NU) B-Tree(NU)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#1F497D">Pages 36 Tups 6117 Pages 305 Tups 52520<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> Martin Bowes [mailto:martin.bowes@ndph.ox.ac.uk]
<br>
<b>Sent:</b> 01 February 2018 14:00<br>
<b>To:</b> Karl and Betty Schendel; info-ingres@lists.planetingres.org<br>
<b>Subject:</b> Re: [Info-ingres] Bad tuple estimate on left join<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoPlainText"><span style="color:black">Hi Karl,<o:p></o:p></span></p>
<p class="MsoPlainText"><span style="color:black"><o:p> </o:p></span></p>
<p class="MsoPlainText"><span style="color:black">The Proj-rest node is indeed handling the WHERE clause.<o:p></o:p></span></p>
<p class="MsoPlainText"><span style="color:black">If I simply count the number of rows in comms that satisfy WHERE c.active=1 AND c.comm_type=2 I get 745 as the QEP showed.<o:p></o:p></span></p>
<p class="MsoPlainText"><span style="color:black"><o:p> </o:p></span></p>
<p class="MsoPlainText"><span style="color:black">Nonetheless I ran the query without the where clause. This changed the plan to a right join and the tuple counts are still weird.<o:p></o:p></span></p>
<p class="MsoPlainText"><span style="color:black">See below.<o:p></o:p></span></p>
<p class="MsoPlainText"><span style="color:black"><o:p> </o:p></span></p>
<p class="MsoPlainText">SELECT count(*)<o:p></o:p></p>
<p class="MsoPlainText">FROM comms c<o:p></o:p></p>
<p class="MsoPlainText"> LEFT JOIN researcher r ON c.launch_id = r.researcher_id AND c.launch_type in (0,2)<o:p></o:p></p>
<p class="MsoPlainText"> LEFT JOIN user_details ud ON ud.user_id = r.user_id<o:p></o:p></p>
<p class="MsoPlainText">Executing . . .<o:p></o:p></p>
<p class="MsoPlainText"><o:p> </o:p></p>
<p class="MsoPlainText"><o:p> </o:p></p>
<p class="MsoPlainText">********************************************************************<o:p></o:p></p>
<p class="MsoPlainText"><o:p> </o:p></p>
<p class="MsoPlainText">QUERY PLAN 2,2, no timeout, of simple aggregate <o:p></o:p></p>
<p class="MsoPlainText"> aggregate expression -> count(*)<o:p></o:p></p>
<p class="MsoPlainText"><o:p> </o:p></p>
<p class="MsoPlainText"><o:p> </o:p></p>
<p class="MsoPlainText"><span style="font-family:"Courier New""> left join<o:p></o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New""> K Join(user_id)<o:p></o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New""> Heap<o:p></o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New""> Pages 2 Tups 786<o:p></o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New""> D161 C1279<o:p></o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New""> / \<o:p></o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New""> right join user_details<o:p></o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New""> Hash Join(researcher_id)(ud)<o:p></o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New""> Sort on(user_id) B-Tree(user_id)<o:p></o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New""> Pages 4 Tups 786 Pages 29 Tups 6200<o:p></o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New""> D109 C1248<o:p></o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New""> / \<o:p></o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New""> Proj-rest Proj-rest<o:p></o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New""> Sorted(NU) Sorted(NU)<o:p></o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New""> Pages 28 Tups 6117 Pages 221 Tups 52520<o:p></o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New""> D33 C61 D76 C525<o:p></o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New"">/ /<o:p></o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New"">researcher comms_launch_indx<o:p></o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New"">(r) I(c)<o:p></o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New"">B-Tree(NU) B-Tree(NU)<o:p></o:p></span></p>
<p class="MsoPlainText"><span style="font-family:"Courier New"">Pages 33 Tups 6117 Pages 305 Tups 52520<o:p></o:p></span></p>
<p class="MsoPlainText"><o:p> </o:p></p>
<p class="MsoPlainText"><o:p> </o:p></p>
<p class="MsoPlainText"><o:p> </o:p></p>
<p class="MsoPlainText"><span style="color:black"><o:p> </o:p></span></p>
<p class="MsoPlainText">I wonder if that Kjoin tuple estimate is including the where clause as well, since the where restriction has to be applied somewhere, and the cost tree (QEP) doesn't normally show a separate proj-rest above joins. (Maybe it should!)
Do you still get 11 if you take the where clause off?<o:p></o:p></p>
<p class="MsoPlainText"><o:p> </o:p></p>
<p class="MsoPlainText">(although in this instance, the where restrictions can apply at the orig level, so maybe they're included at the proj-rest.)<o:p></o:p></p>
<p class="MsoPlainText"><o:p> </o:p></p>
<p class="MsoPlainText">Karl<o:p></o:p></p>
<p class="MsoPlainText"><o:p> </o:p></p>
<p class="MsoPlainText">_______________________________________________<o:p></o:p></p>
<p class="MsoPlainText">Info-ingres mailing list<o:p></o:p></p>
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<p class="MsoPlainText"><a href="http://lists.planetingres.org/mailman/listinfo/info-ingres"><span style="color:windowtext;text-decoration:none">http://lists.planetingres.org/mailman/listinfo/info-ingres</span></a><o:p></o:p></p>
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