Execute an aggregation on the collection view.

@example Aggregate documents.

  view.aggregate([
    { "$group" => { "_id" => "$city", "tpop" => { "$sum" => "$pop" }}}
  ])

@param [ Array<Hash> ] pipeline The aggregation pipeline. @param [ Hash ] options The aggregation options.

@return [ Aggregation ] The aggregation object.

@since 2.0.0

Allows the query to get partial results if some shards are down.

@example Allow partial results.

  view.allow_partial_results

@return [ View ] The new view.

@since 2.0.0

Tell the query‘s cursor to stay open and wait for data.

@example Await data on the cursor.

  view.await_data

@return [ View ] The new view.

@since 2.0.0

The number of documents returned in each batch of results from MongoDB.

@example Set the batch size.

  view.batch_size(5)

@note Specifying 1 or a negative number is analogous to setting a limit.

@param [ Integer ] batch_size The size of each batch of results.

@return [ Integer, View ] Either the batch_size value or a new View.

@since 2.0.0

Associate a comment with the query.

@example Add a comment.

  view.comment('slow query')

@note Set profilingLevel to 2 and the comment will be logged in the profile

  collection along with the query.

@param [ String ] comment The comment to be associated with the query.

@return [ String, View ] Either the comment or a

  new +View+.

@since 2.0.0

Get a count of matching documents in the collection.

@example Get the number of documents in the collection.

  collection_view.count

@param [ Hash ] opts Options for the operation.

@option opts :skip [ Integer ] The number of documents to skip. @option opts :hint [ Hash ] Override default index selection and force

  MongoDB to use a specific index for the query.

@option opts :limit [ Integer ] Max number of docs to count. @option opts :max_time_ms [ Integer ] The maximum amount of time to allow the

  command to run.

@option opts [ Hash ] :read The read preference options. @option opts [ Hash ] :collation The collation to use. @option opts [ Mongo::Session ] :session The session to use for the operation.

@return [ Integer ] The document count.

@since 2.0.0

@deprecated Use count_documents or estimated_document_count instead. However, note that

  the following operators will need to be substituted when switching to #count_documents:
    * $where should be replaced with $expr (only works on 3.6+)
    * $near should be replaced with $geoWithin with $center
    * $nearSphere should be replaced with $geoWithin with $centerSphere

Get a count of matching documents in the collection.

@example Get the number of documents in the collection.

  collection_view.count

@param [ Hash ] opts Options for the operation.

@option opts :skip [ Integer ] The number of documents to skip. @option opts :hint [ Hash ] Override default index selection and force

  MongoDB to use a specific index for the query. Requires server version 3.6+.

@option opts :limit [ Integer ] Max number of docs to count. @option opts :max_time_ms [ Integer ] The maximum amount of time to allow the

  command to run.

@option opts [ Hash ] :read The read preference options. @option opts [ Hash ] :collation The collation to use.

@return [ Integer ] The document count.

@since 2.6.0

The type of cursor to use. Can be :tailable or :tailable_await.

@example Set the cursor type.

  view.cursor_type(:tailable)

@param [ :tailable, :tailable_await ] type The cursor type.

@return [ :tailable, :tailable_await, View ] Either the cursor type setting or a new View.

@since 2.3.0

Get a list of distinct values for a specific field.

@example Get the distinct values.

  collection_view.distinct('name')

@param [ String, Symbol ] field_name The name of the field. @param [ Hash ] opts Options for the distinct command.

@option opts :max_time_ms [ Integer ] The maximum amount of time to allow the

  command to run.

@option opts [ Hash ] :read The read preference options. @option opts [ Hash ] :collation The collation to use.

@return [ Array<Object> ] The list of distinct values.

@since 2.0.0

Gets an estimate of the count of documents in a collection using collection metadata.

@example Get the number of documents in the collection.

  collection_view.estimated_document_count

@param [ Hash ] opts Options for the operation.

@option opts :max_time_ms [ Integer ] The maximum amount of time to allow the command to

  run.

@option opts [ Hash ] :read The read preference options.

@return [ Integer ] The document count.

@since 2.6.0

The index that MongoDB will be forced to use for the query.

@example Set the index hint.

  view.hint(name: 1)

@param [ Hash ] hint The index to use for the query.

@return [ Hash, View ] Either the hint or a new View.

@since 2.0.0

The max number of docs to return from the query.

@example Set the limit.

  view.limit(5)

@param [ Integer ] limit The number of docs to return.

@return [ Integer, View ] Either the limit or a new View.

@since 2.0.0

Execute a map/reduce operation on the collection view.

@example Execute a map/reduce.

  view.map_reduce(map, reduce)

@param [ String ] map The map js function. @param [ String ] reduce The reduce js function. @param [ Hash ] options The map/reduce options.

@return [ MapReduce ] The map reduce wrapper.

@since 2.0.0

A cumulative time limit in milliseconds for processing get more operations on a cursor.

@example Set the max await time ms value.

  view.max_await_time_ms(500)

@param [ Integer ] max The max time in milliseconds.

@return [ Integer, View ] Either the max await time ms value or a new View.

@since 2.1.0

Set the max number of documents to scan.

@example Set the max scan value.

  view.max_scan(1000)

@param [ Integer ] value The max number to scan.

@return [ Integer, View ] The value or a new View.

@since 2.0.0

@deprecated This option is deprecated as of MongoDB server

  version 4.0.

A cumulative time limit in milliseconds for processing operations on a cursor.

@example Set the max time ms value.

  view.max_time_ms(500)

@param [ Integer ] max The max time in milliseconds.

@return [ Integer, View ] Either the max time ms value or a new View.

@since 2.1.0

Set the maximum value to search.

@example Set the max value.

  view.max_value(_id: 1)

@param [ Hash ] value The max field and value.

@return [ Hash, View ] The value or a new View.

@since 2.1.0

Set the minimum value to search.

@example Set the min value.

  view.min_value(_id: 1)

@param [ Hash ] value The min field and value.

@return [ Hash, View ] The value or a new View.

@since 2.1.0

“meta” operators that let you modify the output or behavior of a query.

@example Set the modifiers document.

  view.modifiers(:$orderby => Mongo::Index::ASCENDING)

@param [ Hash ] doc The modifiers document.

@return [ Hash, View ] Either the modifiers document or a new View.

@since 2.1.0

The server normally times out idle cursors after an inactivity period (10 minutes) to prevent excess memory use. Set this option to prevent that.

@example Set the cursor to not timeout.

  view.no_cursor_timeout

@return [ View ] The new view.

@since 2.0.0

The fields to include or exclude from each doc in the result set.

@example Set the fields to include or exclude.

  view.projection(name: 1)

@note A value of 0 excludes a field from the doc. A value of 1 includes it.

  Values must all be 0 or all be 1, with the exception of the _id value.
  The _id field is included by default. It must be excluded explicitly.

@param [ Hash ] document The field and 1 or 0, to include or exclude it.

@return [ Hash, View ] Either the fields or a new View.

@since 2.0.0

The read preference to use for the query.

@note If none is specified for the query, the read preference of the

  collection will be used.

@param [ Hash ] value The read preference mode to use for the query.

@return [ Symbol, View ] Either the read preference or a

  new +View+.

@since 2.0.0

Set whether to return only the indexed field or fields.

@example Set the return key value.

  view.return_key(true)

@param [ true, false ] value The return key value.

@return [ true, false, View ] The value or a new View.

@since 2.1.0

Set whether the disk location should be shown for each document.

@example Set show disk location option.

  view.show_disk_loc(true)

@param [ true, false ] value The value for the field.

@return [ true, false, View ] Either the value or a new

  +View+.

@since 2.0.0

Alias for show_disk_loc

The number of docs to skip before returning results.

@example Set the number to skip.

  view.skip(10)

@param [ Integer ] number Number of docs to skip.

@return [ Integer, View ] Either the skip value or a

  new +View+.

@since 2.0.0

Set the snapshot value for the view.

@note When set to true, prevents documents from returning more than

  once.

@example Set the snapshot value.

  view.snapshot(true)

@param [ true, false ] value The snapshot value.

@since 2.0.0

@deprecated This option is deprecated as of MongoDB server

  version 4.0.

The key and direction pairs by which the result set will be sorted.

@example Set the sort criteria

  view.sort(name: -1)

@param [ Hash ] spec The attributes and directions to sort by.

@return [ Hash, View ] Either the sort setting or a

  new +View+.

@since 2.0.0