What is right deep verses left deep? Good question. In join trees (not VST) the object on the left is acted upon first then the object on the right. Below are left deep and right deep examples of the same query, showing query text join tree join tree modified to more clearly show actions VST showing the same actions All of this boils down to the point that a right deep HJ can return rows earlier than a left deep HJ. A left deep HJ has to wait for each join to finished completely so that the result set can be hashed before the next…
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photo by David Blackwell. Not sure if you can imagine or have ever experienced a meeting where you bring in your statspack or AWR report, all 30 pages of it, point out some glaring issues that anybody could see and proposed some precise solutions, only to have the management team’s eyes glaze over. Then after you finish your pitch they all start arguing as to what the problem might be despite your clear presentation of the problem and solution. Have you ever had that same meeting with a printout of top activity from Oracle Enterprise Manager, with it’s load graph…
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See Brendan Gregg’s blog on how important and cool heatmaps can be for showing latency information and how average latency hides what is really going on: Now if we want to create heatmap graphics, how can we do it? Two popular web methods for displaying graphics are Highcharts and D3. Two colleges of mine whipped up some quick examples in both Highcharts and D3 to show latency heatmaps and those two examples are shown below. The data in the charts is random just for the purposes of showing examples of these graphics in actions. Highcharts Heatmap see code at http://jsfiddle.net/vladiweb/GNd3G/ D3 Heatmap…