MongoDB date comparison
datetime, mongodb
Solution
It seems to be related to the date conversion.
What version of MongoDB are you using? In the online shell of MongoDB I get the following:
> new Date("Jul 21, 1983")
"Thu Jul 21 1983 00:00:00 GMT+0200 (CEST)"
> new Date("Aug 7, 1999")
"Sat Aug 07 1999 00:00:00 GMT+0200 (CEST)"
> new Date("Aug 30, 2000")
"Wed Aug 30 2000 00:00:00 GMT+0200 (CEST)"
> new Date("Aug 30, 1999")
"Mon Aug 30 1999 00:00:00 GMT+0200 (CEST)"
However, if I try in MongoDB 2.2.2
> new Date("Jul 21, 1983")
ISODate("1983-07-20T22:00:00Z")
> new Date("Aug 7, 1999")
ISODate("1999-08-06T22:00:00Z")
> new Date("Aug 30, 2000")
ISODate("2000-08-29T22:00:00Z")
> new Date("Aug 30, 1999")
ISODate("1999-08-29T22:00:00Z")
In your case, It seems that MongoDB is indexing the string version and then performing a basic string comparison which would explain the results your are getting.
Problem
How MongoDB performs date comparison? I tried a few test on the MongoDB shell: ``` > db.test.insert( { "dates" : [ new Date("Jul 21, 1983"), new Date("Aug 7, 1999") ] } ) "ok" > db.test.find() [ { "_id" : { "$oid" : "5201e8b7cc93742c160bb9d8" }, "dates" : [ "Thu Jul 21 1983 00:00:00 GMT+0200 (CEST)", "Sat Aug 07 1999 00:00:00 GMT+0200 (CEST)" ] } ] ``` Now I'll try to get all objects with a date in `dates` greater than Aug 30, 2000. ``` > db.test.find( { "dates" : { $gt : new Date("Aug 30, 2000") } } ) [ ] ``` As expected, the document doesn't match. Using "Aug 30, 1999", instead... ``` > db.test.find( { dates : { $gt : new Date("Aug 30, 1999") } } ) [ { "_id" : { "$oid" : "5201e8b7cc93742c160bb9d8" }, "dates" : [ "Thu Jul 21 1983 00:00:00 GMT+0200 (CEST)", "Sat Aug 07 1999 00:00:00 GMT+0200 (CEST)" ] } ] ``` The document matches! What am I missing?