How to use aggregate $match to match by _id?
If you want to use the aggregation framework and use $match to match elements by _id, you can’t pass them as strings: these options don’t work: I think it’s a bug, since in other queries, strings are implicitly converted to type objectId.
Table of Contents
How does the compare object check for available methods?
One set of objects is the reference and the other set of objects is the difference. Compare-Object checks the methods available to compare an entire object. If it can’t find a suitable method, it calls the ToString() methods of the input objects and compares the results to the string. You can provide one or more properties to use for the comparison.
Why is the side indicator not included in the compare object?
SideIndicator shows which input object the output belongs to. When the PassThru parameter is used, the output displayed in the console might not include the SideIndicator property. The default format view of the Compare-Object object type output does not include the SideIndicator property. For more information, see Example 5 in this article.
Why doesn’t the aggregate match the BSON type?
Any value that is possibly “string” or at least not of the correct BSON type must be manually converted to match. But while using the aggregate function, we have to use the mongoose object to cast the _id as an object, eg. This will work fine.
Why does mongoose’s aggregate $match not match?
The reason is that aggregation pipelines “normally” modify the structure of the document, and therefore Mongoose does not assume that the “schema” is applied to the document at any given pipeline stage. It is arguable that the “first” pipeline stage when it is a $match stage should do this, since the document is in fact not altered.
When to put a $match in an aggregation pipeline?
Put the $match as early as possible in the aggregation pipeline. Because $match limits the total number of documents in the aggregation pipeline, the above $match operations minimize the amount of processing in the pipeline.