1 files changed, 49 insertions, 0 deletions
diff --git a/jstests/indexn.js b/jstests/indexn.js
new file mode 100644
index 00000000000..9abb001eed9
--- /dev/null
+++ b/jstests/indexn.js
@@ -0,0 +1,49 @@
+// Test "impossible match" queries, or queries that will always have
+// an empty result set.
+
+t = db.jstests_indexn;
+t.drop();
+
+function checkImpossibleMatch( explain ) {
+    printjson(explain);
+    assert.eq( 0, explain.n );
+}
+
+t.save( {a:1,b:[1,2]} );
+
+t.ensureIndex( {a:1} );
+t.ensureIndex( {b:1} );
+
+// {a:1} is a single key index, so no matches are possible for this query
+assert.eq( 0, t.count( {a:{$gt:5,$lt:0}} ) );
+checkImpossibleMatch( t.find( {a:{$gt:5,$lt:0}} ).explain() );
+
+assert.eq( 0, t.count( {a:{$gt:5,$lt:0},b:2} ) );
+checkImpossibleMatch( t.find( {a:{$gt:5,$lt:0},b:2} ).explain() );
+
+assert.eq( 0, t.count( {a:{$gt:5,$lt:0},b:{$gt:0,$lt:5}} ) );
+checkImpossibleMatch( t.find( {a:{$gt:5,$lt:0},b:{$gt:0,$lt:5}} ).explain() );
+
+// One clause of an $or is an "impossible match"
+printjson( t.find( {$or:[{a:{$gt:5,$lt:0}},{a:1}]} ).explain() )
+assert.eq( 1, t.count( {$or:[{a:{$gt:5,$lt:0}},{a:1}]} ) );
+checkImpossibleMatch( t.find( {$or:[{a:{$gt:5,$lt:0}},{a:1}]} ).explain().clauses[ 0 ] );
+
+// One clause of an $or is an "impossible match"; original order of the $or
+// does not matter.
+printjson( t.find( {$or:[{a:1},{a:{$gt:5,$lt:0}}]} ).explain() )
+assert.eq( 1, t.count( {$or:[{a:1},{a:{$gt:5,$lt:0}}]} ) );
+checkImpossibleMatch( t.find( {$or:[{a:1},{a:{$gt:5,$lt:0}}]} ).explain().clauses[ 0 ] );
+
+t.save( {a:2} );
+
+// Descriptive test: query system sees this query as an $or where
+// one clause of the $or is an $and. The $and bounds get intersected
+// forming a clause with empty index bounds. The union of the $or bounds
+// produces the two point intervals [1, 1] and [2, 2].
+assert.eq( 2, t.count( {$or:[{a:1},{a:{$gt:5,$lt:0}},{a:2}]} ) );
+explain = t.find( {$or:[{a:1},{a:{$gt:5,$lt:0}},{a:2}]} ).explain();
+printjson( explain )
+assert.eq( 2, explain.clauses.length );
+checkImpossibleMatch( explain.clauses[ 0 ] );
+assert.eq( [[1, 1], [2,2]], explain.clauses[ 1 ].indexBounds.a );