casting - MongoDb - Change type from Int to Double -

we have collection looks this:

{     "_id" : "10571:6",     "v" : 261355,     "ts" : 4.88387e+008 } 

now, of "v" ints, doubles. want change them doubles.

i've tried few things nothing works (v int32 record, want change double):

db.getcollection('vehiclelastvalues') .find (      {_id : "10572:6"} ) .foreach ( function (x) {     temp = x.v * 1.0;     db.getcollection('vehiclelastvalues').save(x); }} 

things i've tried:

x.v = x.v * 1.1 / 1.1; x.v = parsefloat (new string(x.v)); 

but can't saved double...

by default "numbers" stored "double" in mongodb unless cast overwise.

take following samples:

db.sample.insert({ "a": 1 }) db.sample.insert({ "a": numberlong(1) }) db.sample.insert({ "a": numberint(1) }) db.sample.insert({ "a": 1.223 }) 

this yields collection this:

{ "_id" : objectid("559bb1b4a23c8a3da73e0f76"), "a" : 1 } { "_id" : objectid("559bb1bba23c8a3da73e0f77"), "a" : numberlong(1) } { "_id" : objectid("559bb29aa23c8a3da73e0f79"), "a" : 1 } { "_id" : objectid("559bb30fa23c8a3da73e0f7a"), "a" : 1.223 } 

despite different constructor functions note how several of data points there same. mongodb shell doesn't distinquish between them, there way can tell.

there of course $type query operator, allows selection of bson types.

so testing type 1 - "double":

> db.sample.find({ "a": { "$type": 1 } }) { "_id" : objectid("559bb1b4a23c8a3da73e0f76"), "a" : 1 } { "_id" : objectid("559bb30fa23c8a3da73e0f7a"), "a" : 1.223 } 

you see both first insert , last selected, of course not other two.

so test bson type 16 - 32-bit integer

> db.sample.find({ "a": { "$type": 16 } }) { "_id" : objectid("559bb29aa23c8a3da73e0f79"), "a" : 1 } 

that "third" insertion used numberint() function in shell. function , other serialization driver can set specific bson type.

and bson type 18 - 64-bit integer

> db.sample.find({ "a": { "$type": 18 } }) { "_id" : objectid("559bb1bba23c8a3da73e0f77"), "a" : numberlong(1) } 

the "second" insertion contructed via numberlong().

if wanted "weed out" things "not double" do:

db.sample.find({ "$or": [{ "a": { "$type": 16 } },{ "a": { "$type": 18 } }]}) 

which other valid numeric types other "double" itself.

so "convert" these in collection, can "bulk" process this:

var bulk = db.sample.initializeunorderedbulkop(),     count = 0; db.sample.find({      "$or": [         { "a": { "$type": 16 } },         { "a": { "$type": 18 } }     ] }).foreach(function(doc) {     bulk.find({ "_id": doc._id })         .updateone({              "$set": { "b": doc.a.valueof() } ,             "$unset": { "a": 1 }          });     bulk.find({ "_id": doc._id })         .updateone({ "$rename": { "b": "a" } });     count++;     if ( count % 1000 == 0 ) {         bulk.execute()         bulk = db.sample.initializeunorderedbulkop();     } }) if ( count % 1000 != 0 ) bulk.execute(); 

what performed in 3 steps "in bulk":

1. re-cast value new field "double"
2. remove old field unwanted type
3. rename new field old field name

this necessary since bson type information "sticky" field element once created. in order "re-cast" need remove old data includes original field assignment.

so should explain how "detect" , "re-cast" unwanted types in documents.