Sort exceeds limit on text search? - mongodb

Question

I have defined an index like this:
db.imageProperties.createIndex(
{
"imageProperties.cameraMaker": "text",
"imageProperties.cameraModel": "text",
"imageProperties.dateTimeOriginal": -1,
},
{ name: "TextIndex" }
)
But, when I try to run a query with a sort like this:
db.imageProperties.find( { $text: { $search: "nikon" } }, {"imagePath" : 1, _id: 0 } ).sort( { "imageProperties.dateTimeOriginal": -1 } )
I get this error:
Error: error: {
"ok" : 0,
"errmsg" : "Executor error during find command :: caused by :: Sort operation used more than the maximum 33554432 bytes of RAM. Add an index, or specify a smaller limit.",
"code" : 96,
"codeName" : "OperationFailed"
It is my understanding from reading the documentation that it would be possible to combine text search with sorting by creating a combined index as I have done.
This is the output from .explain() on the above query:
> db.imageProperties.find( { $text: { $search: "nikon" } }, {"imagePath" : 1, _id: 0 } ).sort( { "imageProperties.dateTimeOriginal": -1 } ).explain()
{
"queryPlanner": {
"plannerVersion": 1,
"namespace": "olavt-images.imageProperties",
"indexFilterSet": false,
"parsedQuery": {
"$text": {
"$search": "nikon",
"$language": "english",
"$caseSensitive": false,
"$diacriticSensitive": false
}
},
"queryHash": "1DCFCE0B",
"planCacheKey": "650B3A8E",
"winningPlan": {
"stage": "PROJECTION_SIMPLE",
"transformBy": {
"imagePath": 1,
"_id": 0
},
"inputStage": {
"stage": "SORT",
"sortPattern": {
"imageProperties.dateTimeOriginal": -1
},
"inputStage": {
"stage": "SORT_KEY_GENERATOR",
"inputStage": {
"stage": "TEXT",
"indexPrefix": {
},
"indexName": "TextIndex",
"parsedTextQuery": {
"terms": [
"nikon"
],
"negatedTerms": [],
"phrases": [],
"negatedPhrases": []
},
"textIndexVersion": 3,
"inputStage": {
"stage": "TEXT_MATCH",
"inputStage": {
"stage": "FETCH",
"inputStage": {
"stage": "OR",
"inputStage": {
"stage": "IXSCAN",
"keyPattern": {
"_fts": "text",
"_ftsx": 1,
"imageProperties.dateTimeOriginal": -1
},
"indexName": "TextIndex",
"isMultiKey": true,
"isUnique": false,
"isSparse": false,
"isPartial": false,
"indexVersion": 2,
"direction": "backward",
"indexBounds": {
}
}
}
}
}
}
}
}
},
"rejectedPlans": []
},
"serverInfo": {
"host": "4794df1ed9c4",
"port": 27017,
"version": "4.2.5",
"gitVersion": "2261279b51ea13df08ae708ff278f0679c59dc32"
},
"ok": 1
}
How can I get the desired behavior?

Answer 1

The error suggests that sorting the result requires more memory than what is configured.
The field imagePath that you want to project is not covered by the TextIndex try adding a new index:
db.imageProperties.createIndex(
{
"imageProperties.cameraMaker": "text",
"imageProperties.cameraModel": "text",
"imageProperties.dateTimeOriginal": -1,
"imagePath": 1
}
)
Then try the following steps:
Check that the indexes are created successfully by running:
db.imageProperties.getIndexes()
Check whether the correct index is being used:
db.imageProperties.find( { $text: { $search: "nikon" } }, {"imagePath" : 1, _id: 0 } )
.sort( { "imageProperties.dateTimeOriginal": -1 } ).explain()
If you only want a limited rows of results, also add the limit
db.imageProperties.find( { $text: { $search: "nikon" } }, {"imagePath" : 1, _id: 0 } )
.sort( { "imageProperties.dateTimeOriginal": -1 } ).limit(100)
You can also allow disk usage by using aggregation framework with allowDiskUse
db.imageProperties.aggregate([{
$match: { $text: { $search: "nikon" } }
}, {
$sort: { "imageProperties.dateTimeOriginal": -1 }
} , {
$project: { imagePath: 1 }
}], {
allowDiskUse: true
})