As favouriteFoods is a simple array of strings, you can just query that field directly: PersonModel.find({ favouriteFoods: “sushi” }, …); // favouriteFoods contains “sushi” But I’d also recommend making the string array explicit in your schema: person = { name : String, favouriteFoods : [String] } The relevant documentation can be found here: https://docs.mongodb.com/manual/tutorial/query-arrays/
If I understand your question, you need to sort in ascending order. Assuming you have some id or date field called “x” you would do … .sort() db.foo.find().sort({x:1}); The 1 will sort ascending (oldest to newest) and -1 will sort descending (newest to oldest.) If you use the auto created _id field it has a … Read more
Of C, A & P (Consistency, Availability & Partition tolerance) which 2 are more important to you? Quick reference, the Visual Guide To NoSQL Systems MongodB : Consistency and Partition Tolerance CouchDB : Availability and Partition Tolerance A blog post, Cassandra vs MongoDB vs CouchDB vs Redis vs Riak vs HBase vs Membase vs Neo4j … Read more
If you also have documents that don’t have the key, you can use: ME.find({ pictures: { $exists: true, $not: {$size: 0} } }) MongoDB doesn’t use indexes if $size is involved, so here is a better solution: ME.find({ pictures: { $exists: true, $ne: [] } }) If your property can have invalid values (like null … Read more
Lots of reads in every query, fewer regular writes Both databases perform well on reads where the hot data set fits in memory. Both also emphasize join-less data models (and encourage denormalization instead), and both provide indexes on documents or rows, although MongoDB’s indexes are currently more flexible. Cassandra’s storage engine provides constant-time writes no … Read more
You can do… JavaScript (shell): db.getCollectionNames() Node.js: db.listCollections() Non-JavaScript (shell only): show collections The reason I call that non-JavaScript is because: $ mongo prodmongo/app –eval “show collections” MongoDB shell version: 3.2.10 connecting to: prodmongo/app 2016-10-26T19:34:34.886-0400 E QUERY [thread1] SyntaxError: missing ; before statement @(shell eval):1:5 $ mongo prodmongo/app –eval “db.getCollectionNames()” MongoDB shell version: 3.2.10 connecting … Read more
There’s a more efficient way to do this in MongoDB 2.2+ now that you can use numeric array indexes (0 based) in query object keys. // Find all docs that have at least two name array elements. db.accommodations.find({‘name.1’: {$exists: true}}) You can support this query with an index that uses a partial filter expression (requires … Read more
Like this: mongo <dbname> –eval “db.dropDatabase()” More info on scripting the shell from the command line here: https://docs.mongodb.com/manual/tutorial/write-scripts-for-the-mongo-shell/#scripting
I routinely use tens of gigabytes of data in just this fashion e.g. I have tables on disk that I read via queries, create data and append back. It’s worth reading the docs and late in this thread for several suggestions for how to store your data. Details which will affect how you store your … Read more
That would have to be: db.users.find({“name”: /.*m.*/}) Or, similar: db.users.find({“name”: /m/}) You’re looking for something that contains “m” somewhere (SQL’s ‘%‘ operator is equivalent to regular expressions’ ‘.*‘), not something that has “m” anchored to the beginning of the string. Note: MongoDB uses regular expressions which are more powerful than “LIKE” in SQL. With regular … Read more