Details
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Improvement
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Status: Closed
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Major
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Resolution: Done
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None
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The current implementation of filtering excluded paths and custom regex is using a condition like
{ _id: { $nin: [ /^[0-9]{1,3}:\/content\/dam\/.*$/ ]}Mongo cannot evaluate this condition without retrieving the full document, because a value of _null would also match this condition and the index does not contain null values. Therefore, when the index contains excluded paths, the download will be much slower because Mongo has to retrieve every single document to evaluate the condition.
As a workaround, we can transform the regex on an equivalent one that matches the complement of the original regex using negative lookahead. This allows rewriting the filter condition using only positive conditions, which can be evaluated using only the index.
The current implementation of filtering excluded paths and custom regex is using a condition like { _id: { $nin: [ /^[0-9]{1,3}:\/content\/dam\/.*$/ ]} Mongo cannot evaluate this condition without retrieving the full document, because a value of _null would also match this condition and the index does not contain null values. Therefore, when the index contains excluded paths, the download will be much slower because Mongo has to retrieve every single document to evaluate the condition. As a workaround, we can transform the regex on an equivalent one that matches the complement of the original regex using negative lookahead . This allows rewriting the filter condition using only positive conditions, which can be evaluated using only the index.
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