AggregationCursor

Cursor defaults are access(1), batchSize(100), grant(null), maxTimeMs(2000), skipAcl(false).

access(level)
batchSize(sz)
close()
forEach(fn)
grant(level = null)
group(object)
hasNext()
isClosed()
limit(count)
map(fn)
match(object)
maxTimeMS(ms)
next()
passthru()
pathPrefix(path = null)
project(object)
reduce(memo, fn)
skip(count)
skipAcl(bool = true)
sort(object)
stream(fnEach, fnMap)
toArray()
toList()
unwind(prop)

Exhausting a db.AggregationCursor

const cursor = org.objects.account
  .aggregate()
  .skipAcl()
  .grant(consts.accessLevels.read)
  .sort({
    'name.first': 1
  })
  .project({
    _id: 1,
    'name.first': 1
  })
  .limit(50);

const first_names = []; 
for (let account of cursor) {
  first_names.push( account.name.first );
}
return first_names;

// OR return cursor.map(v => v.name.first)

Reading accounts using db.AggregationCursor and streaming

const cursor = org.objects.account
  .aggregate()
  .skipAcl() 
  .grant(consts.accessLevels.read)
  .sort({
    'name.first': 1
  })
  .project({
    _id: 1,
    first_name: 'name.first'
  })
  .limit(50)
  .stream(); // stream json directly to the response object.

AggregationCursor.access(level)

Sets the minimum context access level the caller needs to return results. To return only results to which the caller has update access, for example, call cursor.access(consts.accessLevels.update).

Arguments

• level (Number)

Returns

this

AggregationCursor.batchSize(sz)

Sets the internal cursor batch size for fetching results. Normally, the default is optimal but in cases where a large number of very small documents is being fetched, a larger batch size may be slightly more performant.

Arguments

• sz (Number) The internal cursor batch size (between 1 and 1000).

Returns

this

AggregationCursor.close()

Releases the cursor resources. It's not necessary to close cursors as this is done automatically when a script ends or is exhausted, but in some cases a script may need to free up a cursor mid-stream in order to open up another one.

Returns

this

AggregationCursor.forEach(fn)

Executes the cursor, calling fn with each document.

Arguments

• fn (Function) a function to call for each element in the form of (document) => {}.

Returns

undefined

AggregationCursor.grant(level = null)

Sets the property grant level for the operation.

Arguments

• level (Number)

Returns

this

AggregationCursor.group(object)

Adds a $group stage to the aggregation.

Arguments

• object (Object)

Returns

this

AggregationCursor.hasNext()

Executes the cursor, returning true if next() can be safely called to fetch the next result.

Returns

bool

AggregationCursor.isClosed()

Returns true if a cursor has been opened and has been subsequently closed or exhausted.

Returns

Boolean

AggregationCursor.limit(count)

Adds a $limit stage to the aggregation. By default, the script toList() limit is 10, though cursors have no default limit.

Arguments

• count (Number)

Returns

this

AggregationCursor.map(fn)

Exhausts the cursor, calling fn with each document, and returning an array of results. Because map() iterates through the cursor, the caller should set a sane limit().

Arguments

• fn (Function) a function to call for each result in the form of (document) => { return document; }.

Returns

Object[]

AggregationCursor.match(object)

Adds a $match stage to the aggregation.

Arguments

• object (Object)

Returns

this

AggregationCursor.maxTimeMs(ms)

Set the maximum time a query is allowed to run.

Arguments

• ms (Number) A number between 10 and 10000.

Returns

this

AggregationCursor.next()

Returns the next result. Throws a RangeError is there are no more results. Use while ( cursor.hasNext() ) { cursor.next() } or for result of cursor loops to iterate cursors.

Returns

Object

AggregationCursor.passthru()

Opens a cursor (without fetching any results) which can be returned from a route script and streamed directly through the api. When returned, the script is detached and the cursor remains open until it's exhausted, incurring no further script ops or serialization costs. This is ideal for returning query results that do not require any post-query in-script processing.
- Without passthru: return org.objects.c_example.aggregate().toList() (script->api->script->api->response)
- With passthru: return org.objects.c_example.aggregate().limit(10).passthru() (script->api->response)

Returns

Object

AggregationCursor.pathPrefix(path = null)

Sets the pipeline prefix for retrieving a nested List property. All cursor options are passed through the path down to the list (including grant and skipAcl). Compatible with next(), toArray(), and with passthru() (to retrieve a streamable cursor). For example, org.objects.c_grandparent.aggregate().pathPrefix( '5a2c44bc8664e438e45387d5.c_parents.5a2c44f88664e438e45387d6.c_children' ).match( {c_prop: value} ) passes the match() option down through 2 list properties to the c_parents.c_children.

Arguments

• path (String) Path to a list property.

Returns

Object

AggregationCursor.project(object)

Adds a $project stage to the aggregation.

Arguments

• object (Object)

Returns

this

AggregationCursor.reduce(fn, memo)

Exhausts the cursor, calling fn with memo for each document, and returning memo. Because reduce() iterates through the cursor, the caller should set a sane limit().

Arguments

• fn (Function) a function to call for each result in the form of (memo, document) => { return memo; }.
• memo (Object) an initial value for fn.

Returns

Object

AggregationCursor.skip(count)

Skips count number of results. Please not that large offsets can be expensive and slow down your query. It's more efficient to use range queries.

Arguments

• count (Number) The number of results to skip.

Returns

this

AggregationCursor.skipAcl(bool = true)

Skips initial lookup access control checks. Use in conjunction with grant() to set property level access.

Arguments

• bool (Boolean)

Returns

this

AggregationCursor.sort(object)

Adds a $sort stage to the aggregation.

Arguments

• object (Object)

Returns

this

AggregationCursor.stream(fnEach, fnMap)

Exhausts the cursor, setting the content type to application/json and writing directly to the Response as a list object. Values returned from the script after stream is called are ignored.

Arguments

• fnEach (Function) optional function - (result, total) => { return false; } - called after each item is written. Returning false ends the stream early.
• fnMap (Function) optional function - (result) => { return result; } - called to transform each result before output, the result of which is JSON.stringify()'d.

Returns

undefined

AggregationCursor.toArray()

Exhausts the cursor and returns an array of results (not a list! see toList() ). Because toArray() iterates through the cursor, the caller should set a sane limit().

Returns

Object[]

AggregationCursor.toList()

Returns a list object based on limit() (or the default limit of 10).

Returns

List ({object: 'list', data: [...], hasMore: true})

AggregationCursor.unwind(prop)

Adds an $unwind stage to the aggregation.

Arguments

• prop (String) the property to unwind.

Returns

this