// Test "impossible match" queries, or queries that will always have
// an empty result set.

t = db.jstests_indexn;
t.drop();

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}} ) );

assert.eq( 0, t.count( {a:{$gt:5,$lt:0},b:2} ) );

assert.eq( 0, t.count( {a:{$gt:5,$lt:0},b:{$gt:0,$lt:5}} ) );

// 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}]} ) );

// 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}}]} ) );

t.save( {a:2} );
assert.eq( 2, t.count( {$or:[{a:1},{a:{$gt:5,$lt:0}},{a:2}]} ) );
