Mongo DB

1

Arbiters always have exactly __ vote election. Used to decide primary with even # of secondaries.

no

Can you index compound index for 2 arrays

reporting and backups

Hidden members do not receive reads. Therefore the only traffic they receive is basic replication. This makes them good for ___ and creating ____.

$not

Inverts the effect of a query expression and returns documents that do not match the query expression.

$in

Matches any of the values specified in an array

j: true

MongoDB returns only after the requested number of members, including the primary, have written to the journal.

schemas

Mongoose _____ maps to a MongoDB collection

$slice

Returns a subset of an array.

delayed

This member of a replica set should be hidden, has a priority of 0, and set on a delay. "Rolling backup"

$unset

This operator will delete a particular field.

csv

You can connect to multiple members of the replica set using this list ___.

document databases

excel at storing objects

User.find({name: "deadpool"}, callback)

find "deadpool" in User collection. Mongoose

arbiter

in a replicate set the ___ node does not have a copy of data set and cannot become a primary.

$nin

value not in an array

hidden

A ___ member maintains a copy of the primary's data set but is invisible to client applications. Must be priority 0 members.

true

A copy of the oplog is kept on both the primary and secondary servers. T/F?

read

A priority 0 member maintains a copy of the data set, accepts ___ operations, and votes in elections.

0

A priority __ member is a secondary that cannot become a primary. These members cannot trigger elections.

$

Acts as a placeholder to update the first element that matches the query condition in an update.

$push

Adds an item to an array.

primary

After database operations performed on this replica set member ___ , then record the operations on the primary's oplog.

$concatArrays

Concatenates arrays to return the concatenated array.

db.collection.createIndex({ name: 1})

Create an index on the property name_id, ascending

db.collection.createIndex({age_id: -1, height: 1})

Create an multikey index on the age_id property descending and height ascending.

db.collection.createIndex({"people.name": 1})

Create an multikey index on the people array containing objects for property name

db.collection.createIndex({"student_id: 1"}, {unique: true })

Create an unique index for student_id ascending

$unwind

Deconstructs an array field from the input documents to output a document for each element. Each output document is the input document with the value of the array field replaced by the element. aggregation stage

replica

Delayed members contain copies of a replica set's data set.

$isArray

Determines if the operand is an array. Returns a boolean.

one

How many members do you need to connect to in a replicate set to automatically detect the other members ___?

db.collection.insert

In MongoDB __ __ __ method adds new documents into a collection

db.collection.remove()

In MongoDB __ __ __ method removes documents from a collection

db.collection.find

In MongoDB __ __ __ method retrieves documents from a collection.

$and

Joins query clauses with a logical AND returns all documents that match the conditions of both clauses.

$nor

Joins query clauses with a logical NOR returns all documents that fail to match both clauses.

$or

Joins query clauses with logical OR returns all documents that match the conditions of either clause.

$limit

Limits the number of documents passed to the next stage in the pipeline. aggregation stage

$all

Matches arrays that contain all elements specified in the query.

$exists

Matches document that have specified field.

$each

Modifies the $push and $addToSet operators to append multiple items for array updates.

$slice

Modifies the $push operator to limit the size of updated arrays.

$sort

Modifies the $push operator to reorder documents stored in array.

$position

Modifies the $push operator to specify the position in the array to add elements.

document

MongoDB is a type of NoSQL database that is a _____ database.

object document mapper

Mongoose is an ____ for MongoDB.

sparse indexes,

Only contain entries for documents that have the indexed field, even if the index field contains a null value.

$match

Passes along the documents with only the specified fields to the next stage in the pipeline. The specified fields can be existing fields from the input documents or newly computed fields. aggregation stage

$project

Passes along the documents with only the specified fields to the next stage in the pipeline. The specified fields can be existing fields from the input documents or newly computed fields. aggregation stage

$pop

Removes the first or last item of an array.

db.collection.replaceOne(filter, replacement, options)

Replaces a single document within the collection based on the filter

true

Replication supports mixed-mode storage engines. For examples, a mmapv1 primary and wiredTiger secondary.

w:1

Requests acknowlegement the write operation has propagated to the standalone mongod or the primary in a replica set.

$sum

Returns a sum of numerical values. Ignores non-numeric values. Changed in version 3.2: Available in both $group and $project stages.

$first

Returns a value from the first document for each group. Order is only defined if the documents are in a defined order. Available in $group stage only.

$push

Returns an array of expression values for each group. Available in $group stage only.

$avg

Returns an average of numerical values. Ignores non-numeric values. Changed in version 3.2: Available in both $group and $project stages.

$arrayElemAt

Returns the element at the specified array index.

$max

Returns the highest expression value for each group. Changed in version 3.2: Available in both $group and $project stages.

$size

Returns the number of elements in the array. Accepts a single expression as argument.

$filter

Selects a subset of the array to return an array with only the elements that match the filter condition.

$type

Selects documents if a field is of the specified type.

$elemMatch

Selects documents if element in the array field matches all the specified $elemMatch conditions.

$size

Selects documents if the array field is a specifed size.

$regex

Selects documents where values match a specified regular expression.

beginning

Should $match come at the beginning or end of the aggregation pipeline? This should limit the total # of documents in the aggregation pipeline.

$skip

Skips over the specified number of documents that pass into the stage and passes the remaining documents to the next stage in the pipeline.

$sort

Sorts all input documents and returns them to the pipeline in sorted order.

$pull

The __ operator removes from an existing array all instances of a value or values that match a specified condition.

w

The __ option waits for server to respond to write.

buffer

The node.js driver will ___ during an election for a new primary in a replica set.

asynchronous

The secondary members copy and apply the primary oplog in an _____ process.

primary

This __ node receives all write operations in a replica set.

$set

This operator replaces the value of a field with the specified value. If it does not exist it will add a new field.

db.collection.updateOne(filter, update, options)

Updates a single document within the collection based on the filter.

db.collection.updateMany(filter, update, options)

Updates multiple documents within the collection based on the filter.

rs.slaveOk()

What command do I run to read from a secondary in replica set in mongo shell?

stale asynchronous

When setting for readConcern is anything other than "local" you may receive ___ data. Data in the secondary may not reflect the most recent write due to ____ replication.

{ background: true }

____ operation so that MongoDB database remains available during the index building operation.

key-value databases

applications with data-schemas easily mapped into key-value pairs

User.findOneAndRemove({name:"deadpool"}, callback)

find User named 'deadpool' and remove from the User collection. Mongoose

User.findOneAndUpdate({name: "deadpool"}, {name:"wolverine"}, callback)

find User named 'deadpool' and update name to 'wolverine' in User collection. Mongoose

User.findByIdAndUpdate(1, {name: "hulk"}, callback)

find User with id 1 and update name to 'hulk in User collection. Mongoose

User.find({}, callback)

find all documents in User collection. Mongoose

User.findById(1, callback)

find by document with user_id 1 in User collection. Mongoose

User.findByIdAndRemove(1, callback)

find user_id 1 and remove from User collection. Mongoose

$gte

greater than or equal to specified value

db.movies.insertMany(document, writeConcern, ordered)

insert many documents into the the movies collection

db.movies.insertOne(document, writeConcern)

insert one document into the movies collection

sharding

is a method for storing data across multiple machines.

storage engine

is the component of the database that is responsible for managing how data is stored, both in memory and on disk

$lte

less than or equal to specifed value

$gt

matches value greater than specified value

cursor.explain()/db.collection.explain()

methods provide statistics about the performance of a query.

mongo.connect(database, callback)

mongo method for connecting to db

rs.status()

mongo shell command to retrieve config file?

WiredTiger

mongodb 3.2 default storage engine

b-tree

mongodb indexes use a ___ data structures

$ne

not equal to specified value

mongorestore

program writes data from a binary database dump created by mongodump to a MongoDB instance.

local

readConcern property ___ reads from the primary reflect the latest writes in absence of failover

majority

readConcern property ____ read operations from the primary or the secondaries have "eventual consistency"

"eventual consistency"

readable members are not required to reflect the latest writes at all times?

secondaries

replicate the primary's oplog and apply the operations to their data sets such that the secondaries' data sets reflect the primary's data set.

db.moviesDetails.find({ rated: "PG-13"}).count

retrieve total number of movies rated PG-13 from the moviesDetails collection

mongod --port 27018

run command line for mongo to run on port 27018

collection scan

scan every document in a collection, to select those documents that match the query statement.

indexes

special data structures that store a small portion of the collection's data set in an easy to traverse form. The index stores the value of a specific field or set of fields, ordered by the value of the field.

cursor.sort(sort)

specifies the order in which the query returns matching documents.Must apply sort() to the cursor before retreiving any documents from the database.

oplog

the ___ is a special capped collection that keeps a rolling record of all operations that modify the data stored in your databases

tied

the arbiter could be useful if you have a __ election for primary.

arbiter

this member of the replica set does not have a copy of the data set and cannot become a primary.

local

this readConcern setting is the default. This setting reads fromt the primary reflect the latest writes in absence of a failover

Query#find(criteria callback)

when the query is executed, the result will be an array of documents.