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<p class="MsoNormal">Hi All,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Gloat mode engaged….<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I had a table which was very big, it had more than the maximum integer4 (2+billion) rows and had to be partitioned 32 ways just to store the data.<span style="color:#1F497D"> It had become a serious issue within the database and in particular
meant I couldn’t transfer this database to another installation which was becoming a necessary step.</span><o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">It looked like this:<o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">Run_id integer4<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">Pid integer4<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">Gid integer2<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">Status integer1<o:p></o:p></span></p>
<p class="MsoNormal">For any run_id there may be as many as (and typically are as many as) 500,000 rows.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Then I got told, ’What? You’re storing that stuff! We don’t need it.’ … but after examining the code for a while I found that they did need it during a particular operational phase and then not until another process which occurs once every
6months.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">So I couldn’t remove the data. But the good news was that those processes accessed the data by run_id only.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">So I made an archive table which looked like this:<o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">Run_id integer4<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">All_data long varchar<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">Tinsert ingresdate</span><o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">The all_data field was composed of all the old rows pid,gid,status data separated by commas and each of the original rows data separated by colons.<o:p></o:p></p>
<p class="MsoNormal">Eg. 1000780,-1,0:1000800,-1,0:1000889,-1,0:1000959,-1,0…<o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">The all_data would typically be about 65M.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal">So how to extract the data when actually needed it? Enter a table procedure and the similar to regular expression pattern matching.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="color:#1F497D">select first 10 pid, gid, status from all_data(run_id =146)<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">pid gid status<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"> 1000018 -1 0<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#1F497D"> 1000020 -1 0<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#1F497D"> 1000034 -1 0<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#1F497D"> 1000041 -1 0<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#1F497D"> 1000056 -1 0<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#1F497D"> 1000062 -1 0<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#1F497D"> 1000075 -1 0<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#1F497D"> 1000089 -1 0<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#1F497D"> 1000093 -1 0<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New";color:#1F497D"> 1000104 -1 0<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="color:#1F497D">(10 rows in 0.004865 secs)<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(*) from all_data(run_id = 162)<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">col1 <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"> 502713<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="color:#1F497D">(1 row in <span style="background:yellow;mso-highlight:yellow">
20.629744</span> secs)<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">By comparison on the source table such a select would take about 0.5 seconds.<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">The trade off of performance for reliably maintaining the data was worth it.<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">Marty<o:p></o:p></span></p>
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