$pull vs. $pullAll

[Daniel W]

I'm using pymongo, and I'm confused why this had the desired effect:

db.POV3.update({'_id':foo['_id']}, {'$pull': {'vhst': {u's': u'NY',
u'vtd': u'', u'd': datetime.datetime(2002, 1, 1, 0, 0), u't':
u'PRIM'}}})

...but this did not: ($pullAll instead of $pull, with the value to be
pulled put into an array)

db.POV3.update({'_id':foo['_id']}, {'$pullAll': {'vhst': [{u's':
u'NY', u'vtd': u'', u'd': datetime.datetime(2002, 1, 1, 0, 0), u't':
u'PRIM'}]}})

The relevant part of the document in mongo was:

"vhst" : [
{
"d" : ISODate("2002-01-01T00:00:00Z"),
"s" : "NY",
"t" : "GEN",
"vtd" : "X"
},
{
"d" : ISODate("2002-01-01T00:00:00Z"),
"s" : "NY",
"t" : "PRIM",
"vtd" : ""
},
{
"s" : "NY",
"vtd" : "X",
"d" : ISODate("2002-01-01T00:00:00Z"),
"t" : "PRIM"
}
],


thanks!

[Tyler Brock]

You put brackets around the value for key "vhst" in the first example
and not in the second.

-Tyler

[Daniel W]

I think you mean brackets on the second example, not the first....

and I did that because:

{ $pull : { field : _value } }

vs.

{ $pullAll : { field : value_array } }

for pullAll, I'm providing an array of values, hence the []

[Tyler Brock]

Order within the document matters, try this one:

db.POV3.update({
'_id': foo['_id']
},
{
'$pullAll': {
'vhst': [{

'd': new Date(Date.UTC(2002, 0, 1)),
's': 'NY',

't': 'PRIM',
'vtd': '',

}]
}
})

I was able to see this query remove my test document (which looks like
yours) on my system.

-Tyler

[Daniel W]

so order within the document matters for $pullAll but not for $pull?
Is there a reason for that?

[Scott Hernandez]

Yes, $pull creates a query spec to match array elements, and $pullAll
takes a list of actual array elements (where order matters) to return,
not a query.

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[Tyler Brock]

Nice Scott,

I thought this stack overflow description was rather good as well:
http://stackoverflow.com/questions/8598685/mongodb-pull-all-element-from-the-array

-Tyler

[Daniel W]

Ah OK. Makes sense. Thanks guys

On Jan 5, 3:11 pm, Tyler Brock <ty...@10gen.com> wrote:
> Nice Scott,
>

> I thought this stack overflow description was rather good as well:http://stackoverflow.com/questions/8598685/mongodb-pull-all-element-f...