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🦸‍♂️ Repeating stages

info

Extra activity, do it if you have extra time or are following at home, won't be covered during the hands-on Lab

From the Aggregation Pipelines manual.

All stages except the $out, $merge, $geoNear, $changeStream, and $changeStreamSplitLargeEvent stages can appear multiple times in a pipeline.

So we can repeat most stages, and do something like this to get all books from 1985 with more than 100 pages (although it can make sense or not)

[
    {
        $match: { pages: {$gte: 100} }
    },
    {
        $match: { year: 1985 }
    }
]

💻 Add several $limit stages at the end of the above aggregation, limiting to 1 book and see what happens

Answer
[
    {$match: {pages: {$gte: 100}}}, 
    {$match: {year: 2011}},
    {$limit: 1},
    {$limit: 1},
]