SERVER-33005 Fix planner to avoid incorrect OR pushdown through $elemMatch.

The PlanEnumerator now tracks pushdown routes which descend
through an $elemMatch object. These routes are pruned when
subsequently descending through an OR.

(cherry picked from commit 17b4094c4d781ffd486b27869f46eea706e490af)

1 files changed, 41 insertions, 0 deletions

diff --git a/jstests/core/elemmatch_or_pushdown.js b/jstests/core/elemmatch_or_pushdown.js
new file mode 100644
index 00000000000..f1a1dacd7ad
--- /dev/null
+++ b/jstests/core/elemmatch_or_pushdown.js
@@ -0,0 +1,41 @@
+/**
+ * Tests that an $elemMatch-$or query is evaluated correctly. Designed to reproduce SERVER-33005.
+ */
+(function() {
+    "use strict";
+
+    const coll = db.elemmatch_or_pushdown;
+    coll.drop();
+
+    assert.writeOK(coll.insert({_id: 0, a: 1, b: [{c: 4}]}));
+    assert.writeOK(coll.insert({_id: 1, a: 2, b: [{c: 4}]}));
+    assert.writeOK(coll.insert({_id: 2, a: 2, b: [{c: 5}]}));
+    assert.writeOK(coll.insert({_id: 3, a: 1, b: [{c: 5}]}));
+    assert.writeOK(coll.insert({_id: 4, a: 1, b: [{c: 6}]}));
+    assert.writeOK(coll.insert({_id: 5, a: 1, b: [{c: 7}]}));
+    assert.commandWorked(coll.createIndex({a: 1, "b.c": 1}));
+
+    assert.eq(coll.find({a: 1, b: {$elemMatch: {$or: [{c: 4}, {c: 5}]}}}).sort({_id: 1}).toArray(),
+              [{_id: 0, a: 1, b: [{c: 4}]}, {_id: 3, a: 1, b: [{c: 5}]}]);
+    assert.eq(coll.find({a: 1, $or: [{a: 2}, {b: {$elemMatch: {$or: [{c: 4}, {c: 5}]}}}]})
+                  .sort({_id: 1})
+                  .toArray(),
+              [{_id: 0, a: 1, b: [{c: 4}]}, {_id: 3, a: 1, b: [{c: 5}]}]);
+
+    coll.drop();
+    assert.writeOK(coll.insert({_id: 0, a: 5, b: [{c: [{f: 8}], d: 6}]}));
+    assert.writeOK(coll.insert({_id: 1, a: 4, b: [{c: [{f: 8}], d: 6}]}));
+    assert.writeOK(coll.insert({_id: 2, a: 5, b: [{c: [{f: 8}], d: 7}]}));
+    assert.writeOK(coll.insert({_id: 3, a: 4, b: [{c: [{f: 9}], d: 6}]}));
+    assert.writeOK(coll.insert({_id: 4, a: 5, b: [{c: [{f: 8}], e: 7}]}));
+    assert.writeOK(coll.insert({_id: 5, a: 4, b: [{c: [{f: 8}], e: 7}]}));
+    assert.writeOK(coll.insert({_id: 6, a: 5, b: [{c: [{f: 8}], e: 8}]}));
+    assert.writeOK(coll.insert({_id: 7, a: 5, b: [{c: [{f: 9}], e: 7}]}));
+    assert.commandWorked(coll.createIndex({"b.d": 1, "b.c.f": 1}));
+    assert.commandWorked(coll.createIndex({"b.e": 1, "b.c.f": 1}));
+
+    assert.eq(coll.find({a: 5, b: {$elemMatch: {c: {$elemMatch: {f: 8}}, $or: [{d: 6}, {e: 7}]}}})
+                  .sort({_id: 1})
+                  .toArray(),
+              [{_id: 0, a: 5, b: [{c: [{f: 8}], d: 6}]}, {_id: 4, a: 5, b: [{c: [{f: 8}], e: 7}]}]);
+}());