mongodb find $text search query is changed - mongodb

Question

So I am running into some weird behavior in my mongo environment when using the $text operator. I am getting results back when I am expecting none. I expect the string ABCD to match, but there are no entries that contain ACBDE. a wild card index for text is defined('$**': text)
As you can see in the explain the parsed text query is modifying what I have in $search. Any ideas of what might be going on?
> db.catalogentries.find({$text: {$search: 'abcde'}}).pretty().explain()
{
"queryPlanner" : {
"plannerVersion" : 1,
"namespace" : "test.catalogentries",
"indexFilterSet" : false,
"parsedQuery" : {
"$text" : {
"$search" : "abcde",
"$language" : "english",
"$caseSensitive" : false,
"$diacriticSensitive" : false
}
},
"winningPlan" : {
"stage" : "TEXT",
"indexPrefix" : {
},
"indexName" : "$**_text",
"parsedTextQuery" : {
"terms" : [
"abcd"
],
"negatedTerms" : [ ],
"phrases" : [ ],
"negatedPhrases" : [ ]
},
"inputStage" : {
"stage" : "TEXT_MATCH",
"inputStage" : {
"stage" : "TEXT_OR",
"inputStage" : {
"stage" : "IXSCAN",
"keyPattern" : {
"_fts" : "text",
"_ftsx" : 1
},
"indexName" : "$**_text",
"isMultiKey" : true,
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 1,
"direction" : "backward",
"indexBounds" : {
}
}
}
}
},
"rejectedPlans" : [ ]
},
"serverInfo" : {
"host" : "mongo01",
"port" : 27017,
"version" : "3.2.4",
"gitVersion" : "e2ee9ffcf9f5a94fad76802e28cc978718bb7a30"
},
"ok" : 1
}
It also should be noted that if I search ACBDF, ABCDD, or ABC that I get no results as expected.

Answer 1

If your search term isn't an actual word, then you should add $language: 'none' to your query to disable word stemming that can lead to unexpected results like this.
So change your query to:
db.catalogentries.find({$text: {$search: 'abcde', $language: 'none'}})