Cursors

Many operations provided by aioarangodb (e.g. executing AQL queries) return result cursors to batch the network communication between ArangoDB server and aioarangodb client. Each HTTP request from a cursor fetches the next batch of results (usually documents). Depending on the query, the total number of items in the result set may or may not be known in advance.

Example:

from aioarangodb import ArangoClient

# Initialize the ArangoDB client.
client = ArangoClient()

# Connect to "test" database as root user.
db = await client.db('test', username='root', password='passwd')

# Set up some test data to query against.
await db.collection('students').insert_many([
    {'_key': 'Abby', 'age': 22},
    {'_key': 'John', 'age': 18},
    {'_key': 'Mary', 'age': 21},
    {'_key': 'Suzy', 'age': 23},
    {'_key': 'Dave', 'age': 20}
])

# Execute an AQL query which returns a cursor object.
cursor = await db.aql.execute(
    'FOR doc IN students FILTER doc.age > @val RETURN doc',
    bind_vars={'val': 17},
    batch_size=2,
    count=True
)

# Get the cursor ID.
cursor.id

# Get the items in the current batch.
await cursor.batch()

# Check if the current batch is empty.
await cursor.empty()

# Get the total count of the result set.
await cursor.count()

# Flag indicating if there are more to be fetched from server.
await cursor.has_more()

# Flag indicating if the results are cached.
await cursor.cached()

# Get the cursor statistics.
await cursor.statistics()

# Get the performance profile.
await cursor.profile()

# Get any warnings produced from the query.
await cursor.warnings()

# Return the next item from the cursor. If current batch is depleted, the
# next batch if fetched from the server automatically.
await cursor.next()

# Return the next item from the cursor. If current batch is depleted, an
# exception is thrown. You need to fetch the next batch manually.
cursor.pop()

# Fetch the next batch and add them to the cursor object.
await cursor.fetch()

# Delete the cursor from the server.
await cursor.close()

See Cursor for API specification.

If the fetched result batch is depleted while you are iterating over a cursor (or while calling the method arango.cursor.Cursor.next()), aioarangodb automatically sends an HTTP request to the server to fetch the next batch (just-in-time style). To control exactly when the fetches occur, you can use methods arango.cursor.Cursor.fetch() and arango.cursor.Cursor.pop() instead.

Example:

from aioarangodb import ArangoClient

# Initialize the ArangoDB client.
client = ArangoClient()

# Connect to "test" database as root user.
db = client.db('test', username='root', password='passwd')

# Set up some test data to query against.
db.collection('students').insert_many([
    {'_key': 'Abby', 'age': 22},
    {'_key': 'John', 'age': 18},
    {'_key': 'Mary', 'age': 21}
])

# If you iterate over the cursor or call cursor.next(), batches are
# fetched automatically from the server just-in-time style.
cursor = db.aql.execute('FOR doc IN students RETURN doc', batch_size=1)
result = [doc for doc in cursor]

# Alternatively, you can manually fetch and pop for finer control.
cursor = db.aql.execute('FOR doc IN students RETURN doc', batch_size=1)
while cursor.has_more(): # Fetch until nothing is left on the server.
    cursor.fetch()
while not cursor.empty(): # Pop until nothing is left on the cursor.
    cursor.pop()