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# Licensed to the Apache Software Foundation (ASF) under one
# or more contributor license agreements.  See the NOTICE file
# distributed with this work for additional information
# regarding copyright ownership.  The ASF licenses this file
# to you under the Apache License, Version 2.0 (the
# "License"); you may not use this file except in compliance
# with the License.  You may obtain a copy of the License at
# http://www.apache.org/licenses/LICENSE-2.0
# Unless required by applicable law or agreed to in writing,
# software distributed under the License is distributed on an
# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
# KIND, either express or implied.  See the License for the
# specific language governing permissions and limitations
# under the License.
import datafusion
import pyarrow as pa
import pyarrow.compute
from datafusion import Accumulator, col, udaf
class MyAccumulator(Accumulator):
    Interface of a user-defined accumulation.
    def __init__(self) -> None:
        self._sum = pa.scalar(0.0)
    def update(self, values: pa.Array) -> None:
        # not nice since pyarrow scalars can't be summed yet. This breaks on `None`
        self._sum = pa.scalar(self._sum.as_py() + pa.compute.sum(values).as_py())
    def merge(self, states: pa.Array) -> None:
        # not nice since pyarrow scalars can't be summed yet. This breaks on `None`
        self._sum = pa.scalar(self._sum.as_py() + pa.compute.sum(states).as_py())
    def state(self) -> pa.Array:
        return pa.array([self._sum.as_py()])
    def evaluate(self) -> pa.Scalar:
        return self._sum
# create a context
ctx = datafusion.SessionContext()
# create a RecordBatch and a new DataFrame from it
batch = pa.RecordBatch.from_arrays(
    [pa.array([1, 2, 3]), pa.array([4, 5, 6])],
    names=["a", "b"],
df = ctx.create_dataframe([[batch]])
my_udaf = udaf(
    MyAccumulator,
    pa.float64(),
    pa.float64(),
    [pa.float64()],
    "stable",
df = df.aggregate([], [my_udaf(col("a"))])
result = df.collect()[0]
assert result.column(0) == pa.array([6.0])

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