NumPy Batch Write Guide

Overview

batch_write_numpy() writes multiple records to Aerospike directly from a numpy structured array. Each row becomes a separate write operation, with dtype fields mapped to Aerospike bins.

• Direct array-to-record mapping — no intermediate Python dicts or loops
• Key field extraction — a designated dtype field (default _key) is used as the record's user key
• Automatic bin mapping — all non-underscore-prefixed fields become bins
• Batch execution — all rows are written in a single batch call

When to use

Use batch_write_numpy() when your data is already in numpy arrays (e.g., ML feature stores, sensor data pipelines, scientific datasets). For regular Python dicts, use put() or standard batch operations instead.

Installation

pip install "aerospike-py[numpy]"

Quick Start

Sync Client

import numpy as np
import aerospike_py as aerospike

client = aerospike.client({
    "hosts": [("127.0.0.1", 3000)],
}).connect()

# 1. Define dtype with key field and bin fields
dtype = np.dtype([
    ("_key", "i4"),     # record key (int32)
    ("score", "f8"),    # bin: float64
    ("count", "i4"),    # bin: int32
])

# 2. Create structured array
data = np.array([
    (1, 0.95, 10),
    (2, 0.87, 20),
    (3, 0.72, 15),
], dtype=dtype)

# 3. Batch write
results = client.batch_write_numpy(data, "test", "demo", dtype)

# 4. Check results
for record in results:
    key, meta, bins = record
    print(f"Key: {key}, Gen: {meta['gen']}")

Async Client

import asyncio
import numpy as np
import aerospike_py as aerospike
from aerospike_py import AsyncClient

async def main():
    client = AsyncClient({
        "hosts": [("127.0.0.1", 3000)],
    })
    await client.connect()

    # 1. Define dtype with key field and bin fields
    dtype = np.dtype([
        ("_key", "i4"),
        ("score", "f8"),
        ("count", "i4"),
    ])

    # 2. Create structured array
    data = np.array([
        (1, 0.95, 10),
        (2, 0.87, 20),
        (3, 0.72, 15),
    ], dtype=dtype)

    # 3. Batch write
    results = await client.batch_write_numpy(data, "test", "demo", dtype)

    # 4. Check results
    for record in results:
        key, meta, bins = record
        print(f"Key: {key}, Gen: {meta['gen']}")

    await client.close()

asyncio.run(main())

How It Works

numpy structured array             Aerospike
┌──────┬───────┬───────┐
│ _key │ score │ count │
├──────┼───────┼───────┤          ┌──────────────────────┐
│  1   │ 0.95  │  10   │  ──────▶ │ key=1 {score, count} │
│  2   │ 0.87  │  20   │  ──────▶ │ key=2 {score, count} │
│  3   │ 0.72  │  15   │  ──────▶ │ key=3 {score, count} │
└──────┴───────┴───────┘          └──────────────────────┘
        ▲                                  ▲
   key_field="_key"               bins = non-underscore fields

1. The key_field (default "_key") column is extracted as the user key for each record
2. All fields not prefixed with _ become Aerospike bins
3. Fields prefixed with _ (other than the key field) are ignored

Key Field

By default, the dtype field named "_key" is used as the record key. You can specify a different field with key_field:

Sync Client

dtype = np.dtype([
    ("user_id", "i8"),    # use this as the record key
    ("score", "f8"),
])

data = np.array([(100, 1.5), (101, 2.5)], dtype=dtype)

# Use "user_id" as key instead of "_key"
results = client.batch_write_numpy(
    data, "test", "demo", dtype, key_field="user_id"
)

Async Client

dtype = np.dtype([
    ("user_id", "i8"),
    ("score", "f8"),
])

data = np.array([(100, 1.5), (101, 2.5)], dtype=dtype)

results = await client.batch_write_numpy(
    data, "test", "demo", dtype, key_field="user_id"
)

노트

When using a custom key_field, the field name should not start with _ if you want it to also be stored as a bin. If the field starts with _, it is used only as the key and not written as a bin.

Supported dtype Kinds

The same dtype kinds supported by batch_read() with _dtype are supported for writes:

numpy Kind	Code	Example	Aerospike Value
Signed int	i	"i1", "i2", "i4", "i8"	Int(i64)
Unsigned int	u	"u1", "u2", "u4", "u8"	Int(i64)
Float	f	"f4", "f8"	Float(f64)
Fixed bytes	S	"S8", "S16"	Blob(bytes) or String
Void bytes	V	"V4", "V16"	Blob(bytes)
Sub-array	—	("f4", (128,))	Blob(bytes)

Unsupported dtypes

Unicode strings (U) and Python objects (O) are not supported. Use S (fixed bytes) for string data.

Examples

Sensor Data Ingestion

Sync Client

import numpy as np
import aerospike_py as aerospike

client = aerospike.client({"hosts": [("127.0.0.1", 3000)]}).connect()

dtype = np.dtype([
    ("_key", "i4"),
    ("temperature", "f8"),
    ("humidity", "f4"),
    ("pressure", "f4"),
    ("status", "u1"),
])

# Generate 1000 sensor readings
n = 1000
data = np.zeros(n, dtype=dtype)
data["_key"] = np.arange(n)
data["temperature"] = np.random.normal(25.0, 5.0, n)
data["humidity"] = np.random.uniform(30.0, 90.0, n).astype(np.float32)
data["pressure"] = np.random.normal(1013.25, 10.0, n).astype(np.float32)
data["status"] = 1

results = client.batch_write_numpy(data, "test", "sensors", dtype)
print(f"Wrote {len(results)} records")

Async Client

import asyncio
import numpy as np
import aerospike_py as aerospike
from aerospike_py import AsyncClient

async def main():
    client = AsyncClient({"hosts": [("127.0.0.1", 3000)]})
    await client.connect()

    dtype = np.dtype([
        ("_key", "i4"),
        ("temperature", "f8"),
        ("humidity", "f4"),
        ("pressure", "f4"),
        ("status", "u1"),
    ])

    n = 1000
    data = np.zeros(n, dtype=dtype)
    data["_key"] = np.arange(n)
    data["temperature"] = np.random.normal(25.0, 5.0, n)
    data["humidity"] = np.random.uniform(30.0, 90.0, n).astype(np.float32)
    data["pressure"] = np.random.normal(1013.25, 10.0, n).astype(np.float32)
    data["status"] = 1

    results = await client.batch_write_numpy(data, "test", "sensors", dtype)
    print(f"Wrote {len(results)} records")

    await client.close()

asyncio.run(main())

Vector Embeddings

Store ML embeddings as byte blobs:

import numpy as np
import aerospike_py as aerospike

client = aerospike.client({"hosts": [("127.0.0.1", 3000)]}).connect()

dim = 128
dtype = np.dtype([
    ("_key", "i4"),
    ("embedding", "V" + str(dim * 4)),  # 128 * 4 bytes = 512-byte blob
    ("label", "i4"),
])

n = 100
embeddings = np.random.randn(n, dim).astype(np.float32)

data = np.zeros(n, dtype=dtype)
data["_key"] = np.arange(n)
for i in range(n):
    data["embedding"][i] = embeddings[i].tobytes()
data["label"] = np.random.randint(0, 10, n)

results = client.batch_write_numpy(data, "test", "vectors", dtype)

Write and Read Roundtrip

Combine batch_write_numpy() and batch_read() with _dtype for a full numpy roundtrip:

Sync Client

import numpy as np
import aerospike_py as aerospike

client = aerospike.client({"hosts": [("127.0.0.1", 3000)]}).connect()

# Define dtype
dtype = np.dtype([
    ("_key", "i4"),
    ("x", "f8"),
    ("y", "f8"),
    ("category", "i4"),
])

# Write
data = np.array([
    (1, 1.0, 2.0, 0),
    (2, 3.0, 4.0, 1),
    (3, 5.0, 6.0, 0),
], dtype=dtype)
client.batch_write_numpy(data, "test", "points", dtype)

# Read back with _dtype
read_dtype = np.dtype([("x", "f8"), ("y", "f8"), ("category", "i4")])
keys = [("test", "points", i) for i in range(1, 4)]
batch = client.batch_read(keys, _dtype=read_dtype, policy={"key": aerospike.POLICY_KEY_SEND})

# Vectorized analysis
print(batch.batch_records["x"].mean())       # 3.0
print(batch.batch_records["category"].sum())  # 1

Async Client

import asyncio
import numpy as np
import aerospike_py as aerospike
from aerospike_py import AsyncClient

async def main():
    client = AsyncClient({"hosts": [("127.0.0.1", 3000)]})
    await client.connect()

    dtype = np.dtype([
        ("_key", "i4"),
        ("x", "f8"),
        ("y", "f8"),
        ("category", "i4"),
    ])

    data = np.array([
        (1, 1.0, 2.0, 0),
        (2, 3.0, 4.0, 1),
        (3, 5.0, 6.0, 0),
    ], dtype=dtype)
    await client.batch_write_numpy(data, "test", "points", dtype)

    read_dtype = np.dtype([("x", "f8"), ("y", "f8"), ("category", "i4")])
    keys = [("test", "points", i) for i in range(1, 4)]
    batch = await client.batch_read(keys, _dtype=read_dtype, policy={"key": aerospike.POLICY_KEY_SEND})

    print(batch.batch_records["x"].mean())
    print(batch.batch_records["category"].sum())

    await client.close()

asyncio.run(main())

Pandas DataFrame to Aerospike

Write a pandas DataFrame to Aerospike via numpy:

import numpy as np
import pandas as pd
import aerospike_py as aerospike

client = aerospike.client({"hosts": [("127.0.0.1", 3000)]}).connect()

# DataFrame
df = pd.DataFrame({
    "user_id": [1, 2, 3],
    "score": [0.95, 0.87, 0.72],
    "level": [10, 20, 15],
})

# Convert to structured array
dtype = np.dtype([
    ("_key", "i4"),
    ("score", "f8"),
    ("level", "i4"),
])

data = np.zeros(len(df), dtype=dtype)
data["_key"] = df["user_id"].values
data["score"] = df["score"].values
data["level"] = df["level"].values

results = client.batch_write_numpy(data, "test", "users", dtype)

Error Handling

from aerospike_py.exception import AerospikeError

try:
    results = client.batch_write_numpy(data, "test", "demo", dtype)
    for record in results:
        key, meta, bins = record
        if meta is None:
            print(f"Write failed for key {key}")
except AerospikeError as e:
    print(f"Batch write error: {e}")

Best Practices

• Match dtype to your data — use the smallest sufficient dtype ("f4" vs "f8", "i2" vs "i8") to reduce memory and network transfer
• Batch size — keep arrays at 100-5,000 rows per call for optimal performance
• Key field convention — use "_key" as the default key field to keep the convention consistent
• Underscore prefix — fields starting with _ are excluded from bins, use this for metadata fields
• Roundtrip with batch_read — use the same dtype fields (minus _key) with batch_read(_dtype=...) for efficient read-back
• Large datasets — split large arrays into chunks and write in batches:

chunk_size = 1000
for i in range(0, len(data), chunk_size):
    chunk = data[i:i + chunk_size]
    client.batch_write_numpy(chunk, "test", "demo", dtype)

API Reference

# Sync
results: list[Record] = client.batch_write_numpy(
    data: np.ndarray,
    namespace: str,
    set_name: str,
    _dtype: np.dtype,
    key_field: str = "_key",
    policy: dict | None = None,
)

# Async
results: list[Record] = await client.batch_write_numpy(
    data: np.ndarray,
    namespace: str,
    set_name: str,
    _dtype: np.dtype,
    key_field: str = "_key",
    policy: dict | None = None,
)

Parameter	Type	Default	Description
data	np.ndarray	required	Structured numpy array with record data
namespace	str	required	Target Aerospike namespace
set_name	str	required	Target set name
_dtype	np.dtype	required	Structured dtype describing the array layout
key_field	str	"_key"	Name of the dtype field to use as the record user key
policy	dict | None	None	Optional BatchPolicy overrides

Returns: list[Record] — a list of Record NamedTuples (key, meta, bins) with write results.

See also: NumPy Batch Read Guide for reading records back into numpy arrays.