$push accumulator do in MongoDB aggregation?The $push accumulator adds values to an array during aggregation. It collects values from multiple documents into a single array.
$push to collect all values of a field into an array?Use $push inside $group stage like this: { $group: { _id: null, allValues: { $push: "$fieldName" } } }. This gathers all fieldName values into allValues array.
$push add complex objects to arrays?Yes, $push can add any value, including objects, arrays, or computed expressions, to the resulting array.
$push without grouping?$push must be used inside a $group stage. Without grouping, it cannot accumulate values into an array.
$push?You can combine $push with $slice in a $group stage to limit array size, for example: { $group: { _id: null, limitedArray: { $push: "$field" } } }, { $project: { limitedArray: { $slice: ["$limitedArray", 5] } } }.
$push accumulator in MongoDB?$push collects values into an array during aggregation.
$push be used in an aggregation pipeline?$push works only inside $group to accumulate values.
$push add objects to the array it builds?$push can add any value, including objects and arrays.
$push?Use $slice in a following stage to limit array size after $push.
$push outside of a $group stage?$push must be inside $group; otherwise, it causes an error.
$push accumulator works in MongoDB aggregation and give a simple example.$push in an aggregation pipeline.