Regex query MongoDB Performance issue

Question

i have Mongodb collection which contains single field , each day i am receiving 31000 documents and in the collection i have almost 6 months data

Here is how my data looks like in database

 {
"_id" : ObjectId("59202aa3f32dfba00d0773c3"),
"Data" : "20-05-2017 18:38:13 SYSTEM_000_00_SAVING ",
"__v" : 0
 }
 {
"_id" : ObjectId("59202aa3f32dfba00d0773c4"),
"Data" : "20-05-2017 18:38:13 SyTime_000_09_00:00 ",
"__v" : 0
}

here is my code for query

 DBObject query = new BasicDBObject();
 Pattern regex = Pattern.compile("20-05-2017"); 
 query.put("Data", regex);

i have created index but its still slow

                   [
                {
                    "v" : 1,
                    "key" : {
                        "_id" : 1
                    },
                    "name" : "_id_",
                    "ns" : "NOB_SRB.fdevices"
                },
                {
                    "v" : 1,
                    "unique" : true,
                    "key" : {
                        "Data" : 1.0
                    },
                    "name" : "Data_1",
                    "ns" : "NOB_SRB.fdevices"
                }
            ]

Here is a good answer with a small benchmark: stackoverflow.com/questions/17942275/… — Andriy Kuba
– Andriy Kuba, Commented Sep 16, 2017 at 6:55

Bohemian · Accepted Answer · 2017-09-16 06:53:49Z

1

Add a start of input anchor ^ to the start of the regex:

Pattern regex = Pattern.compile("^20-05-2017");

Because your regex does not have an anchor, the entire field is searched for the date anywhere in it, which requires every character in the field to be compared.

answered Sep 16, 2017 at 6:53

Bohemian♦

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