Prevent queryset caching when exporting #44
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Without this, even moderately large exports (10k rows or more) can quickly exhaust a system's memory.
bmihelac
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Sep 11, 2013
Prevent queryset caching when exporting
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Merged, thanks! |
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By default, Django querysets will cache result rows as they are loaded. This can waste a large amount of memory when iteratively consuming a large queryset, like
Resource.export()does. In my case, trying to export in the order of tens of thousands rows will quickly consume gigabytes of memory, before running into swap, making the export practically unusable.Calling
iterator()on the queryset fixes this behavior, and makes the large exports in question succeed without a problem.The proposed change makes using
iterator()the default behavior ofResource.export(), which should avoid the resource exhaustion problem without changing API behavior (particularly for code that overridesModelResource.get_queryset()orExportMixin.get_export_queryset()), and should not have any adverse effects.(Note: This change does not affect
ModelInstanceLoader.get_queryset(), which does not iterative access.)