Map/Reduce Using Stored Javascript By Java Driver

[玉 付]

MongoDB v1.6.2

Given stored map and reduce and finalize functions as follows:
> db.system.js.find({},{_id:1})
{ "_id" : "mm" }
{ "_id" : "rr" }
{ "_id" : "ff" }

But the following command is wrong , because map function will emit
sth
> db.f.mapReduce("mm","rr")
{
"result" : "tmp.mr.mapreduce_1300965424_25",
"timeMillis" : 2,
"counts" : {
"input" : 2,
"emit" : 0,
"output" : 0
},
"ok" : 1,
}

So I change the command, and the result is correct.
> db.f.mapReduce(db.eval("mm"),db.eval("rr"))
{
"result" : "tmp.mr.mapreduce_1300965446_26",
"timeMillis" : 4,
"counts" : {
"input" : 2,
"emit" : 4,
"output" : 1
},
"ok" : 1,
}

Then I write it in java
MapReduceOutput mrout = coll.mapReduce("db.eval('mm')",
"db.eval('rr')", "mrout", null);

Here is the exception:
com.mongodb.CommandResult$CommandFailure: command failed [command
failed [mapreduce] { "assertion" : "map invoke failed: JS Error:
uncaught exception: {\n\t\"assertion\" : \"internal error: locks are
not upgradeable: { \\\"opid\\\" : 85231711, \\\"active\\\" : true, \\
\"waitingForLock\\\" : false, \\\"secs_running\\\" : 0, \\\"op\\\" : \\
\"query\\\", \\\"ns\\\" : \\\"?\\\", \\\"query\\\" : { \\\"$eval\\\" :
\\\"mm\\\" }, \\\"client\\\" : \\\"0.0.0.0:0\\\", \\\"desc\\\" : \\
\"conn\\\" }\",\n\t\"assertionCode\" : 10293,\n\t\"errmsg\" : \"db
assertion failure\",\n\t\"ok\" : 0\n}" , "assertionCode" : 9014 ,
"errmsg" : "db assertion failure" , "ok" : 0.0}

Does it mean we cannot call mapReduce using stored js function?

[Nat]

can you list the actual result of db.system.js.find({},{_id:1})
including the script?

[Scott Hernandez]

For this you should not use db.eval with map/reduce params. Just us
the function names stored in system.js

MapReduceOutput mrout = coll.mapReduce("mm", "rr", "mrout", null);

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[Nat]

I think to use it from java, you need to retrieve the map/reduce
script from db.system.js using find() method manually. From my test,
it looks like 1.6.x doesn't seem to support map reduce stored js
functions.

[axlfu]

@Nat

> db.system.js.find({},{_id:1})
{ "_id" : "mm" }
{ "_id" : "rr" }
{ "_id" : "ff" }
>

You mean we cannot write java code to implement this requirement?
Will mongoDB v1.8.0 and Java Driver 2.5.1 support ?

[Eliot Horowitz]

Its working for a different reason than you think.
db.eval is actually just pulling the source code into shell.

you want
db.f.mapReduce("mm( this )","rr( this )")

or something like that

On Thu, Mar 24, 2011 at 7:26 AM, 玉 付 <freese...@gmail.com> wrote:

[axlfu]

Well , it's map reduce, of course can not pass this to map and reduce
function
And result is also an exception:

com.mongodb.CommandResult$CommandFailure: command failed [command
failed [mapreduce] { "assertion" : "map invoke failed: JS Error:

TypeError: this.scheme has no properties nofile_b:1" ,

"assertionCode" : 9014 , "errmsg" : "db assertion failure" , "ok" :
0.0}

Here is my map function segment:
mm = function (){
this.scheme.forEach(function (z) {if (z.status==0)
...
...

[Eliot Horowitz]

Ah, you need to either not use this and pass a paramter mm = function(
obj ) { ... }
or do mm.apply( this )

2011/3/24 axlfu <freese...@gmail.com>:

[axlfu]

Would u plz give me a complete example?

Honestly, I am totally confused......

Not only map function ,but also reduce and finalize function, how to
do so with java driver 2.5.1 and mongodb 1.8.0?

Thanks very much

On 3月25日, 上午11时07分, Eliot Horowitz <eliothorow...@gmail.com> wrote:
> Ah, you need to either not use this and pass a paramter mm = function(
> obj ) { ... }
> or do mm.apply( this )
>

> 2011/3/24 axlfu <freesearc...@gmail.com>:

[Nat]

It seems to be too complicated for my liking... but if your M/R
functions are m, r respectively:

> db.foo.mapReduce("function() { m.apply(this); }","function(k,vals) { return r(k, vals); }")

[axlfu]

Thanks very much for your patience