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Type:
Bug
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Resolution: Duplicate
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Priority:
Major - P3
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None
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Affects Version/s: None
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Component/s: Index Maintenance, Write Ops
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Query
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Minor Change
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ALL
The DataFileMgr::updateRecord() and getIndexChanges() code finds the index key sets for a document both pre and post update. Values present in one but not both of these key sets are added / removed from the appropriate indexes, while values present in both are untouched in the indexes. The implementation uses key equality rather than bit equivalence to determine if a key exists in both the pre and post update key set. So if a key is changed from one numeric type to another but its new value is equal to its original value, the key will not be updated in the index. As a result a covered index query can return a key with the wrong data type.
Test:
c = db.c;
c.drop();
c.ensureIndex( { a:1 } );
c.save( { a:5 } );
printjson( c.find( { a:5 }, { _id:0, a:1 } ).hint( { a:1 } ).toArray() );
printjson( c.find( { a:5 }, { _id:0, a:1 } ).hint( { $natural:1 } ).toArray() );
c.update( {}, { $set:{ a:NumberLong( 5 ) } } );
// Because NumberLong( 5 ) == 5, the index key is not updated.
printjson( c.find( { a:5 }, { _id:0, a:1 } ).hint( { a:1 } ).toArray() );
printjson( c.find( { a:5 }, { _id:0, a:1 } ).hint( { $natural:1 } ).toArray() );
c.remove();
c.save( { a:5 } );
obj = c.findOne();
obj.a = NumberLong( 5 );
c.update( {}, obj );
// Because NumberLong( 5 ) == 5, the index key is not updated.
printjson( c.find( { a:5 }, { _id:0, a:1 } ).hint( { a:1 } ).toArray() );
printjson( c.find( { a:5 }, { _id:0, a:1 } ).hint( { $natural:1 } ).toArray() );
– Aaron
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run the following script:
t = db.users;
t.drop();
t.insert( { age: 5, name : "xxx" } );
t.insert( { age: 5, name : "yyy" } );
t.insert( { age: 5, name : "zzz" } );
t.ensureIndex( {age: 1} );
rec = t.findOne( {name: "yyy"} );
delete rec.name;
rec.age = NumberLong(5);
t.update( {name: "yyy"}, rec );
t.find( {age:5}, {_id:0, age:1} )
The last output should be:
{ "age" : 5 }
{ "age" : NumberLong(5) }
{ "age" : 5 }
but actually, the output is:
{ "age" : 5 }
{ "age" : 5 }
{ "age" : 5 }
The type info is lost.