https://sourceforge.net/p/whitebear/allura-wiki/Query_factory/Recent changes to Query_factoryenTue, 27 May 2014 18:00:05 -0000https://sourceforge.net/p/whitebear/allura-wiki/Query_factory/<div class="markdown_content"><pre>--- v1 +++ v2 @@ -8,3 +8,7 @@ * [Cost_calculation] * [Query_execution] + +## See also + +[Set_engine] </pre> </div>silex6Tue, 27 May 2014 18:00:05 -0000https://sourceforge.net160fc3d95d4eaf64c2ed25ffb6e3da8ced41e7a5https://sourceforge.net/p/whitebear/allura-wiki/Query_factory/<div class="markdown_content"><p><strong>Query factory</strong> goal is to build a tree of filters that should allow calculating results of a given SQL query. As there are always several possible trees for the same result, the query factory should first start a cost calculation in order to estimate number of I/O calls to calculate query according to the chosen tree and then move filters to a different position and start calculation again on the updated tree. </p> <p>The query factory should then repeat updating the filter tree, moving filters to a different position, and run cost calculation again according to the new tree, using the lowest found cost as <em>budget</em> limit, in order to find tree construct that will give the fastest query. Typical move operation include: move filter trees before or after join operation, change sequence order of the join operations, change sequence order of a <em>chain</em> of filters or replace <em>select</em> by <em>filtering</em> filter. </p> <p>Once cost has been estimated, and fastest way to calculate results has been determinate, the query factory should then start actual execution of the request, collect and broadcast results. </p> <h2 id="topics">Topics</h2> <ul> <li><a class="alink" href="/p/whitebear/allura-wiki/Cost_calculation/">[Cost_calculation]</a> </li> <li><a class="alink" href="/p/whitebear/allura-wiki/Query_execution/">[Query_execution]</a> </li> </ul></div>silex6Tue, 27 May 2014 18:00:05 -0000https://sourceforge.net745563c230d196d843ccdf76e6b9356c0ea6c54a