Reduce queries on datagrids by pre-populating a cache of fetched objects.
Review Request #3218 — Created July 15, 2012 and submitted
Reduce queries on datagrids by pre-populating a cache of fetched objects. Many columns on the datagrid render related objects, such as a user. We had a cache in place that would prevent duplicate lookups of objects with the same ID, but we'd still do one query per unique ID. Now we allow columns to collect the data before rendering, based on the objects being displayed. By default, this will loop through the objects, build a list of all IDs that will be displayed, and then populate the existing cache with those fetched objects. This reduces the query count to at max one per column for all cases using ForeignKeys. ManyToManyFields is another matter entirely, and will take more specialized work.
Tested this with all the datagrids on my copy of Review Board. Everything worked great. I verified through the list of SQL queries that we only had one per column that used a ForeignKey. ManyToManyFields still caused many more queries. Unit tests also passed.
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So, this will always return on the first obj in object_list, if the column isn't a pk column, and never ...