Skip relationship query when we know there are none #14480
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A majority of the time, parent_rel_ids is an array. So it is easy enough to get the size. If parent_rel_ids is an empty array, then essentially we're running Relationship.where(:id => []) Which will return no records. Rails agrees as it produces a query with "WHERE 1=0" This skips these queries. The savings is variable. One customer's database returned no savings, the other went from 81 queries to 67 (17%) Tests were in place for parents and no parents
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fixed cop. |
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Checked commit kbrock@ed76942 with ruby 2.2.6, rubocop 0.47.1, and haml-lint 0.20.0 |
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When
parent_rel_idsis an empty array, we perform a no-op query. This PR removes this extra query.numbers
comments* Memory usage does not reflect 1,550,176 freed objects.
* Memory usage does not reflect 1,274,302 freed objects.
analysis
Typically, the widget report
"Host Summary for VMs", shows a number of skipped queries. But results are data dependent, and some data sets show the same query count for the before and after cases.Since only non-result queries are skipped, row counts will be identical and timings will only show modest savings. (runtime variances actually showed this query time as higher)