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Mongo Notes
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| // MONGO COMMAND LINE | |
| // start mongod | |
| ulimit -n 2048 && mongod | |
| // open command line interface (mongo shell) | |
| mongo | |
| // CREATING DOCUMENTS | |
| // see what DBs are available | |
| show dbs | |
| // select a DB to use, even if it does not exist | |
| use dbName | |
| // see what collections are available within selected DB | |
| show collections | |
| // as with the DB, a new collection is created just by referring to it | |
| db.collectionName.insertOne({"key1":"value1", "key2":"value2"}) | |
| db.collectionName.insertMany([{}, {}, {}]) | |
| db.collectionName.insertMany([{}, {}, {}], {ordered:false}) | |
| // DELETING DOCUMENTS | |
| // remove all records | |
| db.collectionName.remove({}) | |
| // remove a specific (set of) record(s) | |
| db.collectionName.remove({"key":"value"}) | |
| // remove all records and delete collection from collections list | |
| db.collectionName.drop() | |
| // READING DOCUMENTS | |
| // find the first record in the collection | |
| db.collectionName.findOne() | |
| // first argument to find is called the "query document", which can have one or more fields (selectors) to restrict the result set | |
| db.collectionName.find({"key":"value1", "key.nested":"value2"}) | |
| db.collectionName.find({}).count() | |
| db.collectionName.find({}).pretty() | |
| // document queries can also search for an array of results, in this case an exact match of two values | |
| // order matters, will only find documents with value1 & value2 && in that order, this happens because search values are enclosed in an array | |
| db.collectionName.find({"key":["value1", "value2"]}) | |
| // when searching array, find a value at a specific spot (element) in the array (in this case, the first element in the array) | |
| db.collectionName.find({"key.0":"value1"}) | |
| // CURSORS | |
| var c = db.collectionName.find({"key":"value"}) | |
| c.hasNext() // boolean stating whether or not there are more documents in the cursor | |
| c.next() // displays the next document in the cursor | |
| c.objsLeftInBatch() // show how many objects are left in batch | |
| var doc = function() {return c.hasNext() ? c.next() : null;} // nice doc() function to display next document in batch | |
| // PROJECTION | |
| db.collectionName.find({"key":"value"},{"key2":1}) // projection to limit data sent back for query results (in this case, only key2 is returned) | |
| db.collectionName.find({"key":"value"},{"key2":1, "_id":0}) // and leave out the _id | |
| //COMPARISON OPERATORS | |
| db.collectionName.find({"key":{$gt:100}}) // find key value > 100 | |
| // other operators: $eq, $lt, $gte, $lte, $ne, $in, $nin | |
| // ranges can also be specified | |
| db.collectionName.find({"key":{$gt:100, $lt:150}}) // find key value > 100 and < 150 | |
| // or different field search values | |
| db.collectionName.find({"key1":{$gte:30}, "key2":{$gte:80}}) | |
| // the $ne comparison operator returns all documents with fields != to the value specified && without that field at all | |
| db.collectionName.find({"key":{$ne:"something"}}) | |
| // the $in comparison operator returns all documents with fields == to one of the values specified in the array of values | |
| db.collectionName.find({"key":{$in:["caseA", "caseB", "caseC"]}}) | |
| db.movieDetails.updateMany({"imdb.votes":{$lt:10000}, $and: [ {"year":{$gte:2010}}, {"year":{$lte:2013}}], "tomato.consensus":null}, {$unset: {"tomato.consensus":""}}) | |
| db.students.ensureIndex({'teachers':1}) | |
| db.students.find({teachers:{$all:[0,1]}}).explain() | |
| db.students.createIndex({student_id:1}) | |
| // user true flag to get more details on the query, like number of documents examined | |
| db.students.explain(true).find({student_id:5}) | |
| //compound | |
| db.students.createIndex({student_id:1, class_id:-1}) | |
| db.students.getIndexes() | |
| db.students.dropIndex({student_id:1, class_id:-1}) | |
| // create index with a key and sub-key (dot notation) | |
| db.people.createIndex({"work_history.company":-1}); | |
| // remove one occurrence of an item | |
| db.stuff.remove({thing: 'apple'}, {justOne: true}); | |
| // create a unique index | |
| db.stuff.createIndex({thing:1}, {unique:true}); | |
| // create a sparse index on a unique but optional key | |
| db.stuff.createIndex({optionalThing:1}, {unique:true, sparse:true}); | |
| // create an index in the background (so queries can still be run against the collection) | |
| db.stuff.createIndex({thing:1}, {background:true}); | |
| // get stats on a collection, including index stats (size, etc.) | |
| db.stuff.stats(); | |
| db.stuff.totalIndexSize(); // shortcut just for index size |
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