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(Batch) Import items


This page shows how to efficiently add data objects and cross-references to Weaviate. We will collectively refer to these as "items".

We suggest you use batch imports unless you have a specific reason not to. A batch import drastically improves import speed by processing multiple items per request, and clients can parallelize requests.


To import items in batches using a Weaviate client,

  1. Initialize a batcher,
  2. For each source data row:
    • Build an item (object or cross-reference) for Weaviate,
    • Specify the class to add to, and
    • Add it to the batcher.
  3. Ensure that the batches are flushed (some clients require manual flushing).

Depending on the client, additional settings or auto-flushing of batches may be available.

Basic batch import exampleโ€‹

The following example will add objects to YourClassName class using a batch import.

class_name = "YourClassName"  # Replace with your class name
data_objs = [
{"title": f"Object {i+1}"} for i in range(5)
with client.batch() as batch:
for data_obj in data_objs:
Where is the class definition?

In this example, if the class YourClassName does not already exist, it will be created by Weaviate with its auto-schema feature.

Optional object parametersโ€‹

The following apply to objects only (not to cross-references).


You can optionally specify an ID in UUID format. Otherwise, Weaviate will generate a random UUID.

from weaviate.util import generate_uuid5

class_name = "YourClassName" # Replace with your class name
data_objs = [
{"title": f"Object {i+1}"} for i in range(5) # Replace with your actual objects
with client.batch() as batch:
for data_obj in data_objs:
uuid=generate_uuid5(data_obj) # Optional: Specify an object ID


You can optionally specify a vector to represent each object. Otherwise, Weaviate will follow the relevant vectorizer setting.

class_name = "YourClassName"  # Replace with your class name
data_objs = [
{"title": f"Object {i+1}"} for i in range(5) # Replace with your actual objects
vectors = [
[0.25 + i/100] * 10 for i in range(5) # Replace with your actual vectors
with client.batch() as batch:
for i, data_obj in enumerate(data_objs):
vector=vectors[i] # Optional: Specify an object vector

Batch parameters - Python clientโ€‹

Performance parametersโ€‹

The following parameters will have the greatest impact on the batch import speed:

  • batch_size (int) - the number of items to batch before flushing
  • num_workers (int) - the number of parallel workers to use for the batch
  • dynamic (bool) - whether to dynamically adjust the batch_size based on the number of items in the batch

We recommend starting with batch sizes of 100-300 typically, and the number of workers at 1-4. The dynamic parameter is useful if you are not sure what the optimal batch size is.

Unless batch_size is set to None, the batch will be flushed when the number of items in the batch reaches batch_size.

Using these parameters, you can set dynamic or automatic batching:

with client.batch(
batch_size=100, # Specify the batch size
num_workers=2, # Parallelize the process
# dynamic=False # By default
) as batch:
# Add objects to batch

Error handling parametersโ€‹

The following parameters will most impact error handling:

  • timeout_retries (int) & connection_error_retries (int) - Batch-level numbers of retries
  • weaviate_error_retries (int) - Object-level number of retries for an error originating from Weaviate (for example inference / transformer timeouts)
  • callback - Call a function at the end of batching - for example to inspect the response
    • The default is weaviate.util.check_batch_result

For a complete list of batch parameters and details about the types of batching, see the Python client batching section.

How to set batch parametersโ€‹

We recommend setting batch parameters via the client.batch() context manager, which will also automatically flush the batch when exiting.

The below example specifies a batch size of 200 and parallelizes the import process with 2 threads:

with client.batch(
batch_size=200, # Specify the batch size for auto batching
num_workers=2, # Maximum number of parallel threads used during import
) as batch:

Batch parameters - other clientsโ€‹

At this point in time, the other clients do not support batch parameters, and manual flushing is required.

Managing potential duplicationโ€‹

In a Weaviate collection, each object has a unique ID, in UUID format. If not supplied at object creation time, Weaviate will generate a UUID.

Weaviate does not check if you are uploading items with the same properties as ones that exist already. So, to avoid duplication, we recommend using a deterministic ID generation method, such as the generate_uuid5 function in the Python client, or the generateUuid5 function in the TypeScript client.

Duplicate IDs possible across classes

Classes generally act like namespaces, so it is possible to have duplicate IDs across classes.

Tip: Stream data from large filesโ€‹

A good practice for importing large datasets is to stream the input file rather than risking running out of memory by loading it all at once. For Python, this can be achieved with libraries like ijson for JSON files and pandas for CSV files. For Node, a streams-based solution is presented below.

import weaviate
import ijson

# Settings for displaying the import progress
counter = 0
interval = 20 # print progress every this many records; should be bigger than the batch_size

def add_object(obj) -> None:
global counter
properties = {
'question': obj['Question'],
'answer': obj['Answer'],

# Add the object to the batch
# If you Bring Your Own Vectors, add the `vector` parameter here
# vector=obj.vector

# Calculate and display progress
counter += 1
if counter % interval == 0:
print(f'Imported {counter} articles...')

# Configure the batch import
print('JSON streaming, to avoid running out of memory on large files...')
with open('jeopardy_1k.json', 'rb') as f:
objects = ijson.items(f, 'item')
for o in objects:

# Flush any remaining objects in the batch
print(f'Finished importing {counter} articles.')

More Resourcesโ€‹

If you can't find the answer to your question here, please look at the:

  1. Frequently Asked Questions. Or,
  2. Knowledge base of old issues. Or,
  3. For questions: Stackoverflow. Or,
  4. For more involved discussion: Weaviate Community Forum. Or,
  5. We also have a Slack channel.