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DOCS-14111 localField foreignField with lookup #5000

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Feb 25, 2021
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DOCS-14111 localField foreignField with lookup #5000

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12 changes: 4 additions & 8 deletions source/includes/fact-let-variable-access-note.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -12,14 +12,10 @@
:query:`$expr` allows the use of aggregation expressions
inside of the :pipeline:`$match` syntax.

Without the use of the :query:`$expr` operator, :pipeline:`$match`
can refer to fields in a document but cannot access variables
defined by a :pipeline:`$lookup` :ref:`let <lookup-join-let>`
clause.

The :query:`$expr` operator only uses indexes on the ``from``
collection for equality matches. Non-equality match queries, such
as range queries, cannot use indexes on the ``from`` collection.
The :query:`$expr` operator only uses indexes on the joined
``from`` collection for equality matches. Non-equality match
queries, such as range queries, cannot use indexes on the joined
``from`` collection.

- Other (non-:pipeline:`$match`) stages in the :ref:`pipeline
<lookup-join-pipeline>` do not
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