Mongo subset query with indexing.
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I am attempting to optimize the for the following use case. I want to retrieve all documents whose array field is a subset of the querying array.
Ex. subset(['a', 'b', 'c']) => [{arr: ['a', 'b']}, {arr: ['c']}, {arr: ['a', 'b', 'c']}]
So far the query $not:{$elemMatch:{$nin:[arr]}} has allowed me to achieve the expected behavior. This query, however, does not use the index on array field I have selected, resulting in a full collection scan each time. I did some research, and apparently a $elemMatch preceded by a $not results in the index not being used. Is there any other way to reproduce my query such that it uses the index? This query currently takes almost a full second at 1M documents.
database mongodb indexing
asked Nov 16 '18 at 19:52
Kunaal NaikKunaal Naik
1
add a comment |
I am attempting to optimize the for the following use case. I want to retrieve all documents whose array field is a subset of the querying array.
Ex. subset(['a', 'b', 'c']) => [{arr: ['a', 'b']}, {arr: ['c']}, {arr: ['a', 'b', 'c']}]
So far the query $not:{$elemMatch:{$nin:[arr]}} has allowed me to achieve the expected behavior. This query, however, does not use the index on array field I have selected, resulting in a full collection scan each time. I did some research, and apparently a $elemMatch preceded by a $not results in the index not being used. Is there any other way to reproduce my query such that it uses the index? This query currently takes almost a full second at 1M documents.
database mongodb indexing
asked Nov 16 '18 at 19:52
Kunaal NaikKunaal Naik
1
add a comment |
I am attempting to optimize the for the following use case. I want to retrieve all documents whose array field is a subset of the querying array.
Ex. subset(['a', 'b', 'c']) => [{arr: ['a', 'b']}, {arr: ['c']}, {arr: ['a', 'b', 'c']}]
So far the query $not:{$elemMatch:{$nin:[arr]}} has allowed me to achieve the expected behavior. This query, however, does not use the index on array field I have selected, resulting in a full collection scan each time. I did some research, and apparently a $elemMatch preceded by a $not results in the index not being used. Is there any other way to reproduce my query such that it uses the index? This query currently takes almost a full second at 1M documents.
database mongodb indexing
asked Nov 16 '18 at 19:52
Kunaal NaikKunaal Naik
1
I am attempting to optimize the for the following use case. I want to retrieve all documents whose array field is a subset of the querying array.
Ex. subset(['a', 'b', 'c']) => [{arr: ['a', 'b']}, {arr: ['c']}, {arr: ['a', 'b', 'c']}]
So far the query $not:{$elemMatch:{$nin:[arr]}} has allowed me to achieve the expected behavior. This query, however, does not use the index on array field I have selected, resulting in a full collection scan each time. I did some research, and apparently a $elemMatch preceded by a $not results in the index not being used. Is there any other way to reproduce my query such that it uses the index? This query currently takes almost a full second at 1M documents.
database mongodb indexing
database mongodb indexing
asked Nov 16 '18 at 19:52
Kunaal NaikKunaal Naik
1
asked Nov 16 '18 at 19:52
Kunaal NaikKunaal Naik
1
asked Nov 16 '18 at 19:52
Kunaal NaikKunaal Naik
1
asked Nov 16 '18 at 19:52
Kunaal NaikKunaal Naik
1
asked Nov 16 '18 at 19:52
Kunaal NaikKunaal Naik
1
1
add a comment |
add a comment |
1 Answer
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Why is the $not used with $nin? Wouldn't $or [$in with {$exists: false}] suffice?
Could you provide your index and the executionStats of your query?
ex. db..find({}).explain('executionStats')
answered Nov 16 '18 at 20:41
derekjgrovederekjgrove
64
add a comment |
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1 Answer
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1 Answer
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active
oldest
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Why is the $not used with $nin? Wouldn't $or [$in with {$exists: false}] suffice?
Could you provide your index and the executionStats of your query?
ex. db..find({}).explain('executionStats')
answered Nov 16 '18 at 20:41
derekjgrovederekjgrove
64
add a comment |
Why is the $not used with $nin? Wouldn't $or [$in with {$exists: false}] suffice?
Could you provide your index and the executionStats of your query?
ex. db..find({}).explain('executionStats')
answered Nov 16 '18 at 20:41
derekjgrovederekjgrove
64
add a comment |
Why is the $not used with $nin? Wouldn't $or [$in with {$exists: false}] suffice?
Could you provide your index and the executionStats of your query?
ex. db..find({}).explain('executionStats')
answered Nov 16 '18 at 20:41
derekjgrovederekjgrove
64
Why is the $not used with $nin? Wouldn't $or [$in with {$exists: false}] suffice?
Could you provide your index and the executionStats of your query?
ex. db..find({}).explain('executionStats')
answered Nov 16 '18 at 20:41
derekjgrovederekjgrove
64
answered Nov 16 '18 at 20:41
derekjgrovederekjgrove
64
answered Nov 16 '18 at 20:41
derekjgrovederekjgrove
64
answered Nov 16 '18 at 20:41
derekjgrovederekjgrove
64
64
add a comment |
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