From fe13637b2bf0ed26970d1103c6e9254c0887c48a Mon Sep 17 00:00:00 2001
From: Steve Tarzia <steve.tarzia@mongodb.com>
Date: Mon, 7 Mar 2022 23:01:01 +0000
Subject: SERVER-62242 fixed $indexOfArray handling of duplicate vals in const
 arrays

---
 jstests/aggregation/bugs/server62242.js | 32 ++++++++++++++++++++++++++++++++
 src/mongo/db/pipeline/expression.cpp    |  6 +++---
 2 files changed, 35 insertions(+), 3 deletions(-)
 create mode 100644 jstests/aggregation/bugs/server62242.js

diff --git a/jstests/aggregation/bugs/server62242.js b/jstests/aggregation/bugs/server62242.js
new file mode 100644
index 00000000000..273dddbf16d
--- /dev/null
+++ b/jstests/aggregation/bugs/server62242.js
@@ -0,0 +1,32 @@
+// SERVER-62242
+// $indexOfArray does not work with duplicate values in array
+(function() {
+"use strict";
+
+const c = db[jsTest.name()];
+c.drop();
+
+c.save({_id: 0, number: 222});
+
+// before SERVER-62242, this incorrectly returned {_id: 0, number: 222, idx: -1}
+assert.eq(
+    [{_id: 0, number: 222, idx: 2}],
+    c.aggregate([{$addFields: {idx: {$indexOfArray: [[111, 111, 222], "$number"]}}}]).toArray());
+
+// this query was OK
+assert.eq([{_id: 0, number: 222, idx: 2}],
+          c.aggregate([
+               {$addFields: {idx: {$indexOfArray: [[111, 111, 222, 333], "$number"]}}}
+           ]).toArray());
+
+// also test for cases where a range is specified
+assert.eq([{_id: 0, number: 222, idx: -1}],
+          c.aggregate([
+               {$addFields: {idx: {$indexOfArray: [[111, 111, 222, 333], "$number", 0, 1]}}}
+           ]).toArray());
+
+assert.eq([{_id: 0, number: 222, idx: 3}],
+          c.aggregate([
+               {$addFields: {idx: {$indexOfArray: [[111, 111, 222, 222, 333], "$number", 3, 5]}}}
+           ]).toArray());
+})();
diff --git a/src/mongo/db/pipeline/expression.cpp b/src/mongo/db/pipeline/expression.cpp
index a1b99d4d307..0fce881ba18 100644
--- a/src/mongo/db/pipeline/expression.cpp
+++ b/src/mongo/db/pipeline/expression.cpp
@@ -3443,14 +3443,14 @@ public:
     }
 
     virtual Value evaluate(const Document& root, Variables* variables) const {
-
-        auto args = evaluateAndValidateArguments(root, _children, _indexMap.size(), variables);
+        int arraySize = _children[0]->evaluate(root, variables).getArrayLength();
+        auto args = evaluateAndValidateArguments(root, _children, arraySize, variables);
         auto indexVec = _indexMap.find(args.targetOfSearch);
 
         if (indexVec == _indexMap.end())
             return Value(-1);
 
-        // Search through the vector of indecies for first index in our range.
+        // Search through the vector of indexes for first index in our range.
         for (auto index : indexVec->second) {
             if (index >= args.startIndex && index < args.endIndex) {
                 return Value(index);
-- 
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