Speeding up MongoBD query { $ne: [] }
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I'm currently doing a MongoDB aggregation but then have a query looking for all documents where a certain field, whose value is an array, is empty.
obs = db.collection.count({'things.titles': {'$ne': }})
To ensure this query uses an index, do I just need to do something like this?:
db.collection.ensureIndex({'things.titles': 1})
I understand this creates a multikey index, but it still takes a very long time (more than an hour) on a collection sized at 4739208 documents.
mongodb
asked Apr 19 '16 at 16:04
dalanmillerdalanmiller
1164
bumped to the homepage by Community♦ 11 mins ago
This question has answers that may be good or bad; the system has marked it active so that they can be reviewed.
add a comment |
I'm currently doing a MongoDB aggregation but then have a query looking for all documents where a certain field, whose value is an array, is empty.
obs = db.collection.count({'things.titles': {'$ne': }})
To ensure this query uses an index, do I just need to do something like this?:
db.collection.ensureIndex({'things.titles': 1})
I understand this creates a multikey index, but it still takes a very long time (more than an hour) on a collection sized at 4739208 documents.
mongodb
asked Apr 19 '16 at 16:04
dalanmillerdalanmiller
1164
bumped to the homepage by Community♦ 11 mins ago
This question has answers that may be good or bad; the system has marked it active so that they can be reviewed.
How long is it taking for db.collection.count({'things.titles': }). Also read docs.mongodb.org/manual/core/query-optimization/…
– titogeo
Apr 20 '16 at 12:04
Oddly, a brief few seconds @titogeo.
– dalanmiller
Apr 20 '16 at 14:51
In my tests using size is faster by 3 times than using ne - db.collection.count({'things.titles': { $size : 0}}); Is (db.collection.count() (minus) db.collection.count({'things.titles': { $size : 0}})) faster than using ne. My data size is small.
– titogeo
Apr 21 '16 at 5:17
add a comment |
I'm currently doing a MongoDB aggregation but then have a query looking for all documents where a certain field, whose value is an array, is empty.
obs = db.collection.count({'things.titles': {'$ne': }})
To ensure this query uses an index, do I just need to do something like this?:
db.collection.ensureIndex({'things.titles': 1})
I understand this creates a multikey index, but it still takes a very long time (more than an hour) on a collection sized at 4739208 documents.
mongodb
asked Apr 19 '16 at 16:04
dalanmillerdalanmiller
1164
I'm currently doing a MongoDB aggregation but then have a query looking for all documents where a certain field, whose value is an array, is empty.
obs = db.collection.count({'things.titles': {'$ne': }})
To ensure this query uses an index, do I just need to do something like this?:
db.collection.ensureIndex({'things.titles': 1})
I understand this creates a multikey index, but it still takes a very long time (more than an hour) on a collection sized at 4739208 documents.
mongodb
mongodb
asked Apr 19 '16 at 16:04
dalanmillerdalanmiller
1164
asked Apr 19 '16 at 16:04
dalanmillerdalanmiller
1164
asked Apr 19 '16 at 16:04
dalanmillerdalanmiller
1164
asked Apr 19 '16 at 16:04
dalanmillerdalanmiller
1164
asked Apr 19 '16 at 16:04
dalanmillerdalanmiller
1164
1164
bumped to the homepage by Community♦ 11 mins ago
This question has answers that may be good or bad; the system has marked it active so that they can be reviewed.
bumped to the homepage by Community♦ 11 mins ago
This question has answers that may be good or bad; the system has marked it active so that they can be reviewed.
How long is it taking for db.collection.count({'things.titles': }). Also read docs.mongodb.org/manual/core/query-optimization/…
– titogeo
Apr 20 '16 at 12:04
Oddly, a brief few seconds @titogeo.
– dalanmiller
Apr 20 '16 at 14:51
In my tests using size is faster by 3 times than using ne - db.collection.count({'things.titles': { $size : 0}}); Is (db.collection.count() (minus) db.collection.count({'things.titles': { $size : 0}})) faster than using ne. My data size is small.
– titogeo
Apr 21 '16 at 5:17
add a comment |
How long is it taking for db.collection.count({'things.titles': }). Also read docs.mongodb.org/manual/core/query-optimization/…
– titogeo
Apr 20 '16 at 12:04
Oddly, a brief few seconds @titogeo.
– dalanmiller
Apr 20 '16 at 14:51
In my tests using size is faster by 3 times than using ne - db.collection.count({'things.titles': { $size : 0}}); Is (db.collection.count() (minus) db.collection.count({'things.titles': { $size : 0}})) faster than using ne. My data size is small.
– titogeo
Apr 21 '16 at 5:17
How long is it taking for db.collection.count({'things.titles': }). Also read docs.mongodb.org/manual/core/query-optimization/…
– titogeo
Apr 20 '16 at 12:04
How long is it taking for db.collection.count({'things.titles': }). Also read docs.mongodb.org/manual/core/query-optimization/…
– titogeo
Apr 20 '16 at 12:04
Oddly, a brief few seconds @titogeo.
– dalanmiller
Apr 20 '16 at 14:51
Oddly, a brief few seconds @titogeo.
– dalanmiller
Apr 20 '16 at 14:51
In my tests using size is faster by 3 times than using ne - db.collection.count({'things.titles': { $size : 0}}); Is (db.collection.count() (minus) db.collection.count({'things.titles': { $size : 0}})) faster than using ne. My data size is small.
– titogeo
Apr 21 '16 at 5:17
In my tests using size is faster by 3 times than using ne - db.collection.count({'things.titles': { $size : 0}}); Is (db.collection.count() (minus) db.collection.count({'things.titles': { $size : 0}})) faster than using ne. My data size is small.
– titogeo
Apr 21 '16 at 5:17
add a comment |
1 Answer
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Your question specifies:
... a query looking for all documents where a certain field, whose value is an array, is empty.
Your query is count all documents where the array is not empty, is this intended?
Depending upon the cardinality of the values of this field, this could be causing these values to be expensive.
To query for empty arrays, the operation would be:
db.collection.explain().count( 'things.titles' : [ ] } )
Note that there are edge cases to this query. For example, the following would be returned:
{ "_id" : ..., "things.titles" : [ [ ] ] }
The index usage of the count operation can be determined using the collection.explain() function.
For example:
db.collection.explain().count({'things.titles': {'$ne': }})
The output will provide information showing the index bounds being used (if they exist).
answered Oct 22 '16 at 0:14
Adam HarrisonAdam Harrison
24815
add a comment |
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Your question specifies:
... a query looking for all documents where a certain field, whose value is an array, is empty.
Your query is count all documents where the array is not empty, is this intended?
Depending upon the cardinality of the values of this field, this could be causing these values to be expensive.
To query for empty arrays, the operation would be:
db.collection.explain().count( 'things.titles' : [ ] } )
Note that there are edge cases to this query. For example, the following would be returned:
{ "_id" : ..., "things.titles" : [ [ ] ] }
The index usage of the count operation can be determined using the collection.explain() function.
For example:
db.collection.explain().count({'things.titles': {'$ne': }})
The output will provide information showing the index bounds being used (if they exist).
answered Oct 22 '16 at 0:14
Adam HarrisonAdam Harrison
24815
add a comment |
Your question specifies:
... a query looking for all documents where a certain field, whose value is an array, is empty.
Your query is count all documents where the array is not empty, is this intended?
Depending upon the cardinality of the values of this field, this could be causing these values to be expensive.
To query for empty arrays, the operation would be:
db.collection.explain().count( 'things.titles' : [ ] } )
Note that there are edge cases to this query. For example, the following would be returned:
{ "_id" : ..., "things.titles" : [ [ ] ] }
The index usage of the count operation can be determined using the collection.explain() function.
For example:
db.collection.explain().count({'things.titles': {'$ne': }})
The output will provide information showing the index bounds being used (if they exist).
answered Oct 22 '16 at 0:14
Adam HarrisonAdam Harrison
24815
add a comment |
Your question specifies:
... a query looking for all documents where a certain field, whose value is an array, is empty.
Your query is count all documents where the array is not empty, is this intended?
Depending upon the cardinality of the values of this field, this could be causing these values to be expensive.
To query for empty arrays, the operation would be:
db.collection.explain().count( 'things.titles' : [ ] } )
Note that there are edge cases to this query. For example, the following would be returned:
{ "_id" : ..., "things.titles" : [ [ ] ] }
The index usage of the count operation can be determined using the collection.explain() function.
For example:
db.collection.explain().count({'things.titles': {'$ne': }})
The output will provide information showing the index bounds being used (if they exist).
answered Oct 22 '16 at 0:14
Adam HarrisonAdam Harrison
24815
Your question specifies:
... a query looking for all documents where a certain field, whose value is an array, is empty.
Your query is count all documents where the array is not empty, is this intended?
Depending upon the cardinality of the values of this field, this could be causing these values to be expensive.
To query for empty arrays, the operation would be:
db.collection.explain().count( 'things.titles' : [ ] } )
Note that there are edge cases to this query. For example, the following would be returned:
{ "_id" : ..., "things.titles" : [ [ ] ] }
The index usage of the count operation can be determined using the collection.explain() function.
For example:
db.collection.explain().count({'things.titles': {'$ne': }})
The output will provide information showing the index bounds being used (if they exist).
answered Oct 22 '16 at 0:14
Adam HarrisonAdam Harrison
24815
answered Oct 22 '16 at 0:14
Adam HarrisonAdam Harrison
24815
answered Oct 22 '16 at 0:14
Adam HarrisonAdam Harrison
24815
answered Oct 22 '16 at 0:14
Adam HarrisonAdam Harrison
24815
24815
add a comment |
add a comment |
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How long is it taking for db.collection.count({'things.titles': }). Also read docs.mongodb.org/manual/core/query-optimization/…
– titogeo
Apr 20 '16 at 12:04
Oddly, a brief few seconds @titogeo.
– dalanmiller
Apr 20 '16 at 14:51
In my tests using size is faster by 3 times than using ne - db.collection.count({'things.titles': { $size : 0}}); Is (db.collection.count() (minus) db.collection.count({'things.titles': { $size : 0}})) faster than using ne. My data size is small.
– titogeo
Apr 21 '16 at 5:17