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  1. Core Server
  2. SERVER-67153

Clarify behavior of array traversal in agg expression

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Details

    • Improvement
    • Status: Backlog
    • Major - P3
    • Resolution: Unresolved
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    Description

      Consider the following document:

      {b: {[{c: 2}, {c: 3}]}}
      

      If it is referred from an agg expression such as [\{$project: {a: "$b.c"}}]

      then the result (assigned at field "a") will be (unsurprisingly) [2, 3].

      Now consider this document which adds extra array nesting:

      {b: {[[{c: 2}, {c: 3}]]}}
      

      Currently in classic, the expression returns an empty array [], instead of the more arguably rational result of [[2, 3]]

      This bug is about clarifying this behavior and specifically determining if it makes sense to adopt it going forward, particularly in the context of the new optimizer.

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            backlog-query-optimization Backlog - Query Optimization
            svilen.mihaylov@mongodb.com Svilen Mihaylov
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            Dates

              Created:
              Updated: