文档中的Mongodb Indexing array字段

Question

I am newbie, trying to index a contents collections. My query looks like

db.contents.find({title:{$regex: /arnab/i}, tags:{$regex: /Times/i}})

below is my index query

db.contents.createIndex({title: 1, tags:1})

tags is any array. Will this query work. Is there any better way to index title, and array tags.

Thanks in advance

Answer 1

Array fields can be indexed just like normal fields. On indexing, MongoDB creates multi-indexes for arrays fields automatically.

db.contents.find({title:{$regex: /arnab/i}, tags:{$regex: /Times/i}}) is a case insensitive contains search using regular expressions.

From the official docs:

For case insensitive regular expression queries, these queries generally cannot use indexes effectively.

So, the index you have created can not be utilised well with this query.

Regex based searches use indexes better when the search is case sensitive. Eg db.contents.find({title:{$regex: /arnab/}, tags:{$regex: /Times/}}) .

And even better when the search is starts with (Prefix Regex) instead of contains . Eg db.contents.find({title:{$regex: /^arnab/}, tags:{$regex: /^Times/}}) .