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MongoDB::Collection(3pm)       User Contributed Perl Documentation       MongoDB::Collection(3pm)

NAME
       MongoDB::Collection - A MongoDB Collection

VERSION
       version v2.2.2

SYNOPSIS
           # get a Collection via the Database object
           $coll = $db->get_collection("people");

           # insert a document
           $coll->insert_one( { name => "John Doe", age => 42 } );

           # insert one or more documents
           $coll->insert_many( \@documents );

           # delete a document
           $coll->delete_one( { name => "John Doe" } );

           # update a document
           $coll->update_one( { name => "John Doe" }, { '$inc' => { age => 1 } } );

           # find a single document
           $doc = $coll->find_one( { name => "John Doe" } )

           # Get a MongoDB::Cursor for a query
           $cursor = $coll->find( { age => 42 } );

           # Cursor iteration
           while ( my $doc = $cursor->next ) {
               ...
           }

DESCRIPTION
       This class models a MongoDB collection and provides an API for interacting with it.

       Generally, you never construct one of these directly with "new".  Instead, you call
       "get_collection" on a MongoDB::Database object.

USAGE
   Error handling
       Unless otherwise explicitly documented, all methods throw exceptions if an error occurs.
       The error types are documented in MongoDB::Error.

       To catch and handle errors, the Try::Tiny and Safe::Isa modules are recommended:

           use Try::Tiny;
           use Safe::Isa; # provides $_isa

           try {
               $coll->insert_one( $doc )
           }
           catch {
               if ( $_->$_isa("MongoDB::DuplicateKeyError" ) {
                   ...
               }
               else {
                   ...
               }
           };

       To retry failures automatically, consider using Try::Tiny::Retry.

   Transactions
       To conduct operations in a transactions, get a MongoDB::ClientSession from "start_session"
       in MongoDB::MongoClient.  Start the transaction on the session using "start_transaction"
       and pass the session as an option to all operations.  Then call "commit_transaction" or
       "abort_transaction" on the session.  See the MongoDB::ClientSession for options and usage
       details.

       For detailed instructions on using transactions with MongoDB, see the MongoDB manual page:
       Transactions <https://docs.mongodb.com/master/core/transactions>.

   Terminology
       Document

       A collection of key-value pairs.  A Perl hash is a document.  Array references with an
       even number of elements and Tie::IxHash objects may also be used as documents.

       Ordered document

       Many MongoDB::Collection method parameters or options require an ordered document: an
       ordered list of key/value pairs.  Perl's hashes are not ordered and since Perl v5.18 are
       guaranteed to have random order.  Therefore, when an ordered document is called for, you
       may use an array reference of pairs or a Tie::IxHash object.  You may use a hash reference
       if there is only one key/value pair.

       Filter expression

       A filter expression provides the query criteria
       <http://docs.mongodb.org/manual/tutorial/query-documents/> to select a document for
       deletion.  It must be an "Ordered document".

ATTRIBUTES
   database
       The MongoDB::Database representing the database that contains the collection.

   name
       The name of the collection.

   read_preference
       A MongoDB::ReadPreference object.  It may be initialized with a string corresponding to
       one of the valid read preference modes or a hash reference that will be coerced into a new
       MongoDB::ReadPreference object.  By default it will be inherited from a MongoDB::Database
       object.

   write_concern
       A MongoDB::WriteConcern object.  It may be initialized with a hash reference that will be
       coerced into a new MongoDB::WriteConcern object.  By default it will be inherited from a
       MongoDB::Database object.

   read_concern
       A MongoDB::ReadConcern object.  May be initialized with a hash reference or a string that
       will be coerced into the level of read concern.

       By default it will be inherited from a MongoDB::Database object.

   max_time_ms
       Specifies the default maximum amount of time in milliseconds that the server should use
       for working on a query.

       Note: this will only be used for server versions 2.6 or greater, as that was when the
       $maxTimeMS meta-operator was introduced.

   bson_codec
       An object that provides the "encode_one" and "decode_one" methods, such as from BSON.  It
       may be initialized with a hash reference that will be coerced into a new BSON object.  By
       default it will be inherited from a MongoDB::Database object.

METHODS
   client
           $client = $coll->client;

       Returns the MongoDB::MongoClient object associated with this object.

   full_name
           $full_name = $coll->full_name;

       Returns the full name of the collection, including the namespace of the database it's in
       prefixed with a dot character.  E.g. collection "foo" in database "test" would result in a
       "full_name" of "test.foo".

   indexes
           $indexes = $collection->indexes;

           $collection->indexes->create_one( [ x => 1 ], { unique => 1 } );
           $collection->indexes->drop_all;

       Returns a MongoDB::IndexView object for managing the indexes associated with the
       collection.

   clone
           $coll2 = $coll1->clone( write_concern => { w => 2 } );

       Constructs a copy of the original collection, but allows changing attributes in the copy.

   with_codec
           $coll2 = $coll1->with_codec( $new_codec );
           $coll2 = $coll1->with_codec( prefer_numeric => 1 );

       Constructs a copy of the original collection, but clones the "bson_codec".  If given an
       object that does "encode_one" and "decode_one", it is equivalent to:

           $coll2 = $coll1->clone( bson_codec => $new_codec );

       If given a hash reference or a list of key/value pairs, it is equivalent to:

           $coll2 = $coll1->clone(
               bson_codec => $coll1->bson_codec->clone( @list )
           );

   insert_one
           $res = $coll->insert_one( $document );
           $res = $coll->insert_one( $document, $options );
           $id = $res->inserted_id;

       Inserts a single document into the database and returns a MongoDB::InsertOneResult or
       MongoDB::UnacknowledgedResult object.

       If no "_id" field is present, one will be added when a document is serialized for the
       database without modifying the original document.  The generated "_id" may be retrieved
       from the result object.

       An optional hash reference of options may be given.

       Valid options include:

       o   "bypassDocumentValidation" - skips document validation, if enabled; this is ignored
           for MongoDB servers older than version 3.2.

       o   "session" - the session to use for these operations. If not supplied, will use an
           implicit session. For more information see MongoDB::ClientSession

   insert_many
           $res = $coll->insert_many( [ @documents ] );
           $res = $coll->insert_many( [ @documents ], { ordered => 0 } );

       Inserts each of the documents in an array reference into the database and returns a
       MongoDB::InsertManyResult or MongoDB::UnacknowledgedResult.  This is syntactic sugar for
       doing a MongoDB::BulkWrite operation.

       If no "_id" field is present, one will be added when a document is serialized for the
       database without modifying the original document.  The generated "_id" may be retrieved
       from the result object.

       An optional hash reference of options may be provided.

       Valid options include:

       o   "bypassDocumentValidation" - skips document validation, if enabled; this is ignored
           for MongoDB servers older than version 3.2.

       o   "session" - the session to use for these operations. If not supplied, will use an
           implicit session. For more information see MongoDB::ClientSession

       o   "ordered" - when true, the server will halt insertions after the first error (if any).
           When false, all documents will be processed and any error will only be thrown after
           all insertions are attempted.  The default is true.

       On MongoDB servers before version 2.6, "insert_many" bulk operations are emulated with
       individual inserts to capture error information.  On 2.6 or later, this method will be
       significantly faster than individual "insert_one" calls.

   delete_one
           $res = $coll->delete_one( $filter );
           $res = $coll->delete_one( { _id => $id } );
           $res = $coll->delete_one( $filter, { collation => { locale => "en_US" } } );

       Deletes a single document that matches a filter expression and returns a
       MongoDB::DeleteResult or MongoDB::UnacknowledgedResult object.

       A hash reference of options may be provided.

       Valid options include:

       o   "collation" - a document defining the collation for this operation. See docs for the
           format of the collation document here:
           <https://docs.mongodb.com/master/reference/collation/>.

       o   "session" - the session to use for these operations. If not supplied, will use an
           implicit session. For more information see MongoDB::ClientSession

   delete_many
           $res = $coll->delete_many( $filter );
           $res = $coll->delete_many( { name => "Larry" } );
           $res = $coll->delete_many( $filter, { collation => { locale => "en_US" } } );

       Deletes all documents that match a filter expression and returns a MongoDB::DeleteResult
       or MongoDB::UnacknowledgedResult object.

       Valid options include:

       o   "collation" - a document defining the collation for this operation. See docs for the
           format of the collation document here:
           <https://docs.mongodb.com/master/reference/collation/>.

       o   "session" - the session to use for these operations. If not supplied, will use an
           implicit session. For more information see MongoDB::ClientSession

   replace_one
           $res = $coll->replace_one( $filter, $replacement );
           $res = $coll->replace_one( $filter, $replacement, { upsert => 1 } );

       Replaces one document that matches a filter expression and returns a MongoDB::UpdateResult
       or MongoDB::UnacknowledgedResult object.

       The replacement document must not have any field-update operators in it (e.g.  $set).

       A hash reference of options may be provided.

       Valid options include:

       o   "bypassDocumentValidation" - skips document validation, if enabled; this is ignored
           for MongoDB servers older than version 3.2.

       o   "collation" - a document defining the collation for this operation. See docs for the
           format of the collation document here:
           <https://docs.mongodb.com/master/reference/collation/>.

       o   "session" - the session to use for these operations. If not supplied, will use an
           implicit session. For more information see MongoDB::ClientSession

       o   "upsert" - defaults to false; if true, a new document will be added if one is not
           found

   update_one
           $res = $coll->update_one( $filter, $update );
           $res = $coll->update_one( $filter, $update, { upsert => 1 } );

       Updates one document that matches a filter expression and returns a MongoDB::UpdateResult
       or MongoDB::UnacknowledgedResult object.

       The update document must have only field-update operators in it (e.g.  $set).

       A hash reference of options may be provided.

       Valid options include:

       o   "arrayFilters" - An array of filter documents that determines which array elements to
           modify for an update operation on an array field. Only available for MongoDB servers
           of version 3.6+.

       o   "bypassDocumentValidation" - skips document validation, if enabled; this is ignored
           for MongoDB servers older than version 3.2.

       o   "collation" - a document defining the collation for this operation. See docs for the
           format of the collation document here:
           <https://docs.mongodb.com/master/reference/collation/>.

       o   "session" - the session to use for these operations. If not supplied, will use an
           implicit session. For more information see MongoDB::ClientSession

       o   "upsert" - defaults to false; if true, a new document will be added if one is not
           found by taking the filter expression and applying the update document operations to
           it prior to insertion.

   update_many
           $res = $coll->update_many( $filter, $update );
           $res = $coll->update_many( $filter, $update, { upsert => 1 } );

       Updates one or more documents that match a filter expression and returns a
       MongoDB::UpdateResult or MongoDB::UnacknowledgedResult object.

       The update document must have only field-update operators in it (e.g.  $set).

       A hash reference of options may be provided.

       Valid options include:

       o   "arrayFilters" - An array of filter documents that determines which array elements to
           modify for an update operation on an array field. Only available for MongoDB servers
           of version 3.6+.

       o   "bypassDocumentValidation" - skips document validation, if enabled; this is ignored
           for MongoDB servers older than version 3.2.

       o   "collation" - a document defining the collation for this operation. See docs for the
           format of the collation document here:
           <https://docs.mongodb.com/master/reference/collation/>.

       o   "session" - the session to use for these operations. If not supplied, will use an
           implicit session. For more information see MongoDB::ClientSession

       o   "upsert" - defaults to false; if true, a new document will be added if one is not
           found by taking the filter expression and applying the update document operations to
           it prior to insertion.

   find
           $cursor = $coll->find( $filter );
           $cursor = $coll->find( $filter, $options );

           $cursor = $coll->find({ i => { '$gt' => 42 } }, {limit => 20});

       Executes a query with a filter expression and returns a lazy "MongoDB::Cursor" object.
       (The query is not immediately issued to the server; see below for details.)

       The query can be customized using MongoDB::Cursor methods, or with an optional hash
       reference of options.

       Valid options include:

       o   "allowPartialResults" - get partial results from a mongos if some shards are down
           (instead of throwing an error).

       o   "batchSize" - the number of documents to return per batch.

       o   "collation" - a document defining the collation for this operation. See docs for the
           format of the collation document here:
           <https://docs.mongodb.com/master/reference/collation/>.

       o   "comment" - attaches a comment to the query.

       o   "cursorType" - indicates the type of cursor to use. It must be one of three string
           values: 'non_tailable' (the default), 'tailable', and 'tailable_await'.

       o   "hint" - specify an index to use
           <http://docs.mongodb.org/manual/reference/command/count/#specify-the-index-to-use>;
           must be a string, array reference, hash reference or Tie::IxHash object.

       o   "limit" - the maximum number of documents to return.

       o   "max" - specify the exclusive upper bound for a specific index.

       o   "maxAwaitTimeMS" - the maximum amount of time for the server to wait on new documents
           to satisfy a tailable cursor query. This only applies to a "cursorType" of
           'tailable_await'; the option is otherwise ignored. (Note, this will be ignored for
           servers before version 3.2.)

       o   "maxScan" - (DEPRECATED) maximum number of documents or index keys to scan.

       o   "maxTimeMS" - the maximum amount of time to allow the query to run. (Note, this will
           be ignored for servers before version 2.6.)

       o   "min" - specify the inclusive lower bound for a specific index.

       o   "modifiers" - (DEPRECATED) a hash reference of dollar-prefixed query modifiers
           <http://docs.mongodb.org/manual/reference/operator/query-modifier/> modifying the
           output or behavior of a query. Top-level options will always take precedence over
           corresponding modifiers.  Supported modifiers include $comment, $hint, $maxScan,
           $maxTimeMS, $max, $min, $orderby, $returnKey, $showDiskLoc, and $snapshot.  Some
           options may not be supported by newer server versions.

       o   "noCursorTimeout" - if true, prevents the server from timing out a cursor after a
           period of inactivity.

       o   "projection" - a hash reference defining fields to return. See "limit fields to return
           <http://docs.mongodb.org/manual/tutorial/project-fields-from-query-results/>" in the
           MongoDB documentation for details.

       o   "session" - the session to use for these operations. If not supplied, will use an
           implicit session. For more information see MongoDB::ClientSession

       o   "returnKey" - Only return the index field or fields for the results of the query
           <https://docs.mongodb.com/manual/reference/operator/meta/returnKey/>.

       o   "showRecordId" - modifies the output of a query by adding a field $recordId
           <https://docs.mongodb.com/manual/reference/method/cursor.showRecordId/> that uniquely
           identifies a document in a collection.

       o   "skip" - the number of documents to skip before returning.

       o   "sort" - an ordered document defining the order in which to return matching documents.
           See the $orderby documentation
           <https://docs.mongodb.com/manual/reference/operator/meta/orderby/> for examples.

       For more information, see the Read Operations Overview
       <http://docs.mongodb.org/manual/core/read-operations-introduction/> in the MongoDB
       documentation.

       Note, a MongoDB::Cursor object holds the query and does not issue the query to the server
       until the result method is called on it or until an iterator method like next is called.
       Performance will be better directly on a MongoDB::QueryResult object:

           my $query_result = $coll->find( $filter )->result;

           while ( my $next = $query_result->next ) {
               ...
           }

   find_one
           $doc = $collection->find_one( $filter, $projection );
           $doc = $collection->find_one( $filter, $projection, $options );

       Executes a query with a filter expression and returns a single document.

       If a projection argument is provided, it must be a hash reference specifying fields to
       return.  See Limit fields to return <http://docs.mongodb.org/manual/tutorial/project-
       fields-from-query-results/> in the MongoDB documentation for details.

       If only a filter is provided or if the projection document is an empty hash reference, all
       fields will be returned.

           my $doc = $collection->find_one( $filter );
           my $doc = $collection->find_one( $filter, {}, $options );

       A hash reference of options may be provided as a third argument. Valid keys include:

       o   "collation" - a document defining the collation for this operation. See docs for the
           format of the collation document here:
           <https://docs.mongodb.com/master/reference/collation/>.

       o   "maxTimeMS" - the maximum amount of time in milliseconds to allow the command to run.
           (Note, this will be ignored for servers before version 2.6.)

       o   "session" - the session to use for these operations. If not supplied, will use an
           implicit session. For more information see MongoDB::ClientSession

       o   "sort" - an ordered document defining the order in which to return matching documents.
           If $orderby also exists in the modifiers document, the sort field overwrites $orderby.
           See docs for $orderby
           <http://docs.mongodb.org/manual/reference/operator/meta/orderby/>.

       See also core documentation on querying: <http://docs.mongodb.org/manual/core/read/>.

   find_id
           $doc = $collection->find_id( $id );
           $doc = $collection->find_id( $id, $projection );
           $doc = $collection->find_id( $id, $projection, $options );

       Executes a query with a filter expression of "{ _id => $id }" and returns a single
       document.

       See the find_one documentation for details on the $projection and $options parameters.

       See also core documentation on querying: <http://docs.mongodb.org/manual/core/read/>.

   find_one_and_delete
           $doc = $coll->find_one_and_delete( $filter );
           $doc = $coll->find_one_and_delete( $filter, $options );

       Given a filter expression, this deletes a document from the database and returns it as it
       appeared before it was deleted.

       A hash reference of options may be provided. Valid keys include:

       o   "collation" - a document defining the collation for this operation. See docs for the
           format of the collation document here:
           <https://docs.mongodb.com/master/reference/collation/>.

       o   "maxTimeMS" - the maximum amount of time in milliseconds to allow the command to run.
           (Note, this will be ignored for servers before version 2.6.)

       o   "projection" - a hash reference defining fields to return. See "limit fields to return
           <http://docs.mongodb.org/manual/tutorial/project-fields-from-query-results/>" in the
           MongoDB documentation for details.

       o   "session" - the session to use for these operations. If not supplied, will use an
           implicit session. For more information see MongoDB::ClientSession

       o   "sort" - an ordered document defining the order in which to return matching documents.
           See docs for $orderby
           <http://docs.mongodb.org/manual/reference/operator/meta/orderby/>.

   find_one_and_replace
           $doc = $coll->find_one_and_replace( $filter, $replacement );
           $doc = $coll->find_one_and_replace( $filter, $replacement, $options );

       Given a filter expression and a replacement document, this replaces a document from the
       database and returns it as it was either right before or right after the replacement.  The
       default is 'before'.

       The replacement document must not have any field-update operators in it (e.g.  $set).

       A hash reference of options may be provided. Valid keys include:

       o   "bypassDocumentValidation" - skips document validation, if enabled; this is ignored
           for MongoDB servers older than version 3.2.

       o   "collation" - a document defining the collation for this operation. See docs for the
           format of the collation document here:
           <https://docs.mongodb.com/master/reference/collation/>.

       o   "maxTimeMS" - the maximum amount of time in milliseconds to allow the command to run.

       o   "projection" - a hash reference defining fields to return. See "limit fields to return
           <http://docs.mongodb.org/manual/tutorial/project-fields-from-query-results/>" in the
           MongoDB documentation for details.

       o   "returnDocument" - either the string 'before' or 'after', to indicate whether the
           returned document should be the one before or after replacement. The default is
           'before'.

       o   "session" - the session to use for these operations. If not supplied, will use an
           implicit session. For more information see MongoDB::ClientSession

       o   "sort" - an ordered document defining the order in which to return matching documents.
           See docs for $orderby
           <http://docs.mongodb.org/manual/reference/operator/meta/orderby/>.

       o   "upsert" - defaults to false; if true, a new document will be added if one is not
           found

   find_one_and_update
           $doc = $coll->find_one_and_update( $filter, $update );
           $doc = $coll->find_one_and_update( $filter, $update, $options );

       Given a filter expression and a document of update operators, this updates a single
       document and returns it as it was either right before or right after the update.  The
       default is 'before'.

       The update document must contain only field-update operators (e.g. $set).

       A hash reference of options may be provided. Valid keys include:

       o   "arrayFilters" - An array of filter documents that determines which array elements to
           modify for an update operation on an array field. Only available for MongoDB servers
           of version 3.6+.

       o   "bypassDocumentValidation" - skips document validation, if enabled; this is ignored
           for MongoDB servers older than version 3.2.

       o   "collation" - a document defining the collation for this operation. See docs for the
           format of the collation document here:
           <https://docs.mongodb.com/master/reference/collation/>.

       o   "maxTimeMS" - the maximum amount of time in milliseconds to allow the command to run.
           (Note, this will be ignored for servers before version 2.6.)

       o   "projection" - a hash reference defining fields to return. See "limit fields to return
           <http://docs.mongodb.org/manual/tutorial/project-fields-from-query-results/>" in the
           MongoDB documentation for details.

       o   "returnDocument" - either the string 'before' or 'after', to indicate whether the
           returned document should be the one before or after replacement. The default is
           'before'.

       o   "session" - the session to use for these operations. If not supplied, will use an
           implicit session. For more information see MongoDB::ClientSession

       o   "sort" - an ordered document defining the order in which to return matching documents.
           See docs for $orderby
           <http://docs.mongodb.org/manual/reference/operator/meta/orderby/>.

       o   "upsert" - defaults to false; if true, a new document will be added if one is not
           found

   watch
       Watches for changes on this collection-

       Perform an aggregation with an implicit initial $changeStream stage and returns a
       MongoDB::ChangeStream result which can be used to iterate over the changes in the
       collection. This functionality is available since MongoDB 3.6.

           my $stream = $collection->watch();
           my $stream = $collection->watch( \@pipeline );
           my $stream = $collection->watch( \@pipeline, \%options );

           while (1) {

               # This inner loop will only run until no more changes are
               # available.
               while (my $change = $stream->next) {
                   # process $change
               }
           }

       The returned stream will not block forever waiting for changes. If you want to respond to
       changes over a longer time use "maxAwaitTimeMS" and regularly call "next" in a loop.

       Note: Using this helper method is preferred to manually aggregating with a $changeStream
       stage, since it will automatically resume when the connection was terminated.

       The optional first argument must be an array-ref of aggregation pipeline
       <http://docs.mongodb.org/manual/core/aggregation-pipeline/> documents. Each pipeline
       document must be a hash reference. Not all pipeline stages are supported after
       $changeStream.

       The optional second argument is a hash reference with options:

       o   "fullDocument" - The fullDocument to pass as an option to the $changeStream stage.
           Allowed values: "default", "updateLookup". Defaults to "default".  When set to
           "updateLookup", the change notification for partial updates will include both a delta
           describing the changes to the document, as well as a copy of the entire document that
           was changed from some time after the change occurred.

       o   "resumeAfter" - The logical starting point for this change stream. This value can be
           obtained from the "_id" field of a document returned by "next" in
           MongoDB::ChangeStream. Cannot be specified together with "startAtOperationTime"

       o   "maxAwaitTimeMS" - The maximum number of milliseconds for the server to wait before
           responding.

       o   "startAtOperationTime" - A BSON::Timestamp specifying at what point in time changes
           will start being watched. Cannot be specified together with "resumeAfter". Plain
           values will be coerced to BSON::Timestamp objects.

       o   "session" - the session to use for these operations. If not supplied, will use an
           implicit session. For more information see MongoDB::ClientSession

       See "aggregate" for more available options.

       See the manual section on Change Streams <https://docs.mongodb.com/manual/changeStreams/>
       for general usage information on change streams.

       See the Change Streams specification
       <https://github.com/mongodb/specifications/blob/master/source/change-streams.rst> for
       details on change streams.

   aggregate
           @pipeline = (
               { '$group' => { _id => '$state,' totalPop => { '$sum' => '$pop' } } },
               { '$match' => { totalPop => { '$gte' => 10 * 1000 * 1000 } } }
           );

           $result = $collection->aggregate( \@pipeline );
           $result = $collection->aggregate( \@pipeline, $options );

       Runs a query using the MongoDB 2.2+ aggregation framework and returns a
       MongoDB::QueryResult object.

       The first argument must be an array-ref of aggregation pipeline
       <http://docs.mongodb.org/manual/core/aggregation-pipeline/> documents.  Each pipeline
       document must be a hash reference.

       Note: Some pipeline documents have ordered arguments, such as $sort.  Be sure to provide
       these argument using Tie::IxHash.  E.g.:

           { '$sort' => Tie::IxHash->new( age => -1, posts => 1 ) }

       A hash reference of options may be provided. Valid keys include:

       o   "allowDiskUse" - if, true enables writing to temporary files.

       o   "batchSize" - the number of documents to return per batch.

       o   "bypassDocumentValidation" - skips document validation, if enabled. (Note, this will
           be ignored for servers before version 3.2.)

       o   "collation" - a document defining the collation for this operation. See docs for the
           format of the collation document here:
           <https://docs.mongodb.com/master/reference/collation/>.

       o   "explain" - if true, return a single document with execution information.

       o   "maxTimeMS" - the maximum amount of time in milliseconds to allow the command to run.
           (Note, this will be ignored for servers before version 2.6.)

       o   "hint" - An index to use for this aggregation. (Only compatible with servers above
           version 3.6.) For more information, see the other aggregate options here:
           <https://docs.mongodb.com/manual/reference/command/aggregate/index.html>

       o   "session" - the session to use for these operations. If not supplied, will use an
           implicit session. For more information see MongoDB::ClientSession

       Note MongoDB 2.6+ added the '$out' pipeline operator.  If this operator is used to write
       aggregation results directly to a collection, an empty result will be returned. Create a
       new collection> object to query the generated result collection.  When $out is used, the
       command is treated as a write operation and read preference is ignored.

       See Aggregation <http://docs.mongodb.org/manual/aggregation/> in the MongoDB manual for
       more information on how to construct aggregation queries.

       Note The use of aggregation cursors is automatic based on your server version.  However,
       if migrating a sharded cluster from MongoDB 2.4 to 2.6 or later, you must upgrade your
       mongod servers first before your mongos routers or aggregation queries will fail.  As a
       workaround, you may pass "cursor => undef" as an option.

   count_documents
           $count = $coll->count_documents( $filter );
           $count = $coll->count_documents( $filter, $options );

       Returns a count of documents matching a filter expression.  To return a count of all
       documents, use an empty hash reference as the filter.

       NOTE: this may result in a scan of all documents in the collection.  For a fast count of
       the total documents in a collection see "estimated_document_count" instead.

       A hash reference of options may be provided. Valid keys include:

       o   "collation" - a document defining the collation for this operation. See docs for the
           format of the collation document here:
           <https://docs.mongodb.com/master/reference/collation/>.

       o   "hint" - specify an index to use; must be a string, array reference, hash reference or
           Tie::IxHash object. (Requires server version 3.6 or later.)

       o   "limit" - the maximum number of documents to count.

       o   "maxTimeMS" - the maximum amount of time in milliseconds to allow the command to run.
           (Note, this will be ignored for servers before version 2.6.)

       o   "skip" - the number of documents to skip before counting documents.

       o   "session" - the session to use for these operations. If not supplied, will use an
           implicit session. For more information see MongoDB::ClientSession

       NOTE: When upgrading from the deprecated "count" method, some legacy operators are not
       supported and must be replaced:

           +-------------+--------------------------------+
           | Legacy      | Modern Replacement             |
           +=============+================================+
           | $where      | $expr (Requires MongoDB 3.6+)  |
           +-------------+--------------------------------+
           | $near       | $geoWithin with $center        |
           +-------------+--------------------------------+
           | $nearSphere | $geoWithin with $centerSphere  |
           +-------------+--------------------------------+

   estimated_document_count
           $count = $coll->estimated_document_count();
           $count = $coll->estimated_document_count($options);

       Returns an estimated count of documents based on collection metadata.

       NOTE: this method does not support sessions or transactions.

       A hash reference of options may be provided. Valid keys include:

       o   "maxTimeMS" - the maximum amount of time in milliseconds to allow the command to run.
           (Note, this will be ignored for servers before version 2.6.)

   distinct
           $result = $coll->distinct( $fieldname );
           $result = $coll->distinct( $fieldname, $filter );
           $result = $coll->distinct( $fieldname, $filter, $options );

       Returns a MongoDB::QueryResult object that will provide distinct values for a specified
       field name.

       The query may be limited by an optional filter expression.

       A hash reference of options may be provided. Valid keys include:

       o   "collation" - a document defining the collation for this operation. See docs for the
           format of the collation document here:
           <https://docs.mongodb.com/master/reference/collation/>.

       o   "maxTimeMS" - the maximum amount of time in milliseconds to allow the command to run.
           (Note, this will be ignored for servers before version 2.6.)

       o   "session" - the session to use for these operations. If not supplied, will use an
           implicit session. For more information see MongoDB::ClientSession

       See documentation for the distinct command
       <http://docs.mongodb.org/manual/reference/command/distinct/> for details.

   rename
           $newcollection = $collection->rename("mynewcollection");

       Renames the collection.  If a collection already exists with the new collection name, this
       method will throw an exception.

       A hashref of options may be provided.

       Valid options include:

       o   "session" - the session to use for these operations. If not supplied, will use an
           implicit session. For more information see MongoDB::ClientSession

       It returns a new MongoDB::Collection object corresponding to the renamed collection.

   drop
           $collection->drop;

       Deletes a collection as well as all of its indexes.

   ordered_bulk
           $bulk = $coll->ordered_bulk;
           $bulk->insert_one( $doc1 );
           $bulk->insert_one( $doc2 );
           ...
           $result = $bulk->execute;

       Returns a MongoDB::BulkWrite object to group write operations into fewer network round-
       trips.  This method creates an ordered operation, where operations halt after the first
       error. See MongoDB::BulkWrite for more details.

       The method "initialize_ordered_bulk_op" may be used as an alias.

       A hash reference of options may be provided.

       Valid options include:

       o   "bypassDocumentValidation" - skips document validation, if enabled; this is ignored
           for MongoDB servers older than version 3.2.

   unordered_bulk
       This method works just like "ordered_bulk" except that the order that operations are sent
       to the database is not guaranteed and errors do not halt processing.  See
       MongoDB::BulkWrite for more details.

       The method "initialize_unordered_bulk_op" may be used as an alias.

       A hash reference of options may be provided.

       Valid options include:

       o   "bypassDocumentValidation" - skips document validation, if enabled; this is ignored
           for MongoDB servers older than version 3.2.

   bulk_write
           $res = $coll->bulk_write( [ @requests ], $options )

       This method provides syntactic sugar to construct and execute a bulk operation directly,
       without using "initialize_ordered_bulk" or "initialize_unordered_bulk" to generate a
       MongoDB::BulkWrite object and then calling methods on it.  It returns a
       MongoDB::BulkWriteResponse object just like the MongoDB::BulkWrite execute method.

       The first argument must be an array reference of requests.  Requests consist of pairs of a
       MongoDB::Collection write method name (e.g. "insert_one", "delete_many") and an array
       reference of arguments to the corresponding method name.  They may be given as pairs, or
       as hash or array references:

           # pairs -- most efficient
           @requests = (
               insert_one  => [ { x => 1 } ],
               replace_one => [ { x => 1 }, { x => 4 } ],
               delete_one  => [ { x => 4 } ],
               update_many => [ { x => { '$gt' => 5 } }, { '$inc' => { x => 1 } } ],
           );

           # hash references
           @requests = (
               { insert_one  => [ { x => 1 } ] },
               { replace_one => [ { x => 1 }, { x => 4 } ] },
               { delete_one  => [ { x => 4 } ] },
               { update_many => [ { x => { '$gt' => 5 } }, { '$inc' => { x => 1 } } ] },
           );

           # array references
           @requests = (
               [ insert_one  => [ { x => 1 } ] ],
               [ replace_one => [ { x => 1 }, { x => 4 } ] ],
               [ delete_one  => [ { x => 4 } ] ],
               [ update_many => [ { x => { '$gt' => 5 } }, { '$inc' => { x => 1 } } ] ],
           );

       Valid method names include "insert_one", "insert_many", "delete_one", "delete_many"
       "replace_one", "update_one", "update_many".

       An optional hash reference of options may be provided.

       Valid options include:

       o   "bypassDocumentValidation" - skips document validation, if enabled; this is ignored
           for MongoDB servers older than version 3.2.

       o   "ordered" - when true, the bulk operation is executed like "initialize_ordered_bulk".
           When false, the bulk operation is executed like "initialize_unordered_bulk".  The
           default is true.

       o   "session" - the session to use for these operations. If not supplied, will use an
           implicit session. For more information see MongoDB::ClientSession

       See MongoDB::BulkWrite for more details on bulk writes.  Be advised that the legacy Bulk
       API method names differ slightly from MongoDB::Collection method names.

AUTHORS
       o   David Golden <david AT mongodb.com>

       o   Rassi <rassi AT mongodb.com>

       o   Mike Friedman <friedo AT friedo.com>

       o   Kristina Chodorow <k.chodorow AT gmail.com>

       o   Florian Ragwitz <rafl AT debian.org>

COPYRIGHT AND LICENSE
       This software is Copyright (c) 2020 by MongoDB, Inc.

       This is free software, licensed under:

         The Apache License, Version 2.0, January 2004

perl v5.30.3                                2020-08-15                   MongoDB::Collection(3pm)

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