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// Test use of covered indexes when there are multiple candidate indexes.
t = db.jstests_coveredIndex5;
t.drop();
t.ensureIndex( { a:1, b:1 } );
t.ensureIndex( { a:1, c:1 } );
function checkFields( query, projection ) {
t.ensureIndex( { z:1 } ); // clear query patterns
t.dropIndex( { z:1 } );
results = t.find( query, projection ).toArray();
expectedFields = [];
for ( k in projection ) {
if ( k != '_id' ) {
expectedFields.push( k );
}
}
vals = [];
for ( i in results ) {
r = results[ i ];
printjson(r);
assert.eq( 0, r.a );
assert.eq( expectedFields, Object.keySet( r ) );
for ( k in projection ) {
if ( k != '_id' && k != 'a' ) {
vals.push( r[ k ] );
}
}
}
if ( vals.length != 0 ) {
vals.sort();
assert.eq( [ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 ], vals );
}
}
function checkCursorCovered( cursor, covered, count, query, projection ) {
checkFields( query, projection );
explain = t.find( query, projection ).explain( true );
if (covered) {
assert.eq( cursor, explain.cursor );
}
assert.eq( covered, explain.indexOnly );
assert.eq( count, explain.n );
}
for( i = 0; i < 10; ++i ) {
t.save( { a:0, b:i, c:9-i } );
}
checkCursorCovered( 'BtreeCursor a_1_b_1', true, 10, { a:0 }, { _id:0, a:1 } );
checkCursorCovered( 'BtreeCursor a_1_b_1', false, 10, { a:0, d:null }, { _id:0, a:1 } );
checkCursorCovered( 'BtreeCursor a_1_b_1', false, 10, { a:0, d:null }, { _id:0, a:1, b:1 } );
// Covered index on a,c not preferentially selected.
checkCursorCovered( 'BtreeCursor a_1_b_1', false, 10, { a:0, d:null }, { _id:0, a:1, c:1 } );
t.save( { a:0, c:[ 1, 2 ] } );
t.save( { a:1 } );
checkCursorCovered( 'BtreeCursor a_1_b_1', false, 11, { a:0, d:null }, { _id:0, a:1 } );
t.save( { a:0, b:[ 1, 2 ] } );
t.save( { a:1 } );
checkCursorCovered( 'BtreeCursor a_1_b_1', false, 12, { a:0, d:null }, { _id:0, a:1 } );
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