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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.
//go:build go1.18
package compute_test
import (
"context"
"fmt"
"log"
"github.com/apache/arrow-go/v18/arrow"
"github.com/apache/arrow-go/v18/arrow/array"
"github.com/apache/arrow-go/v18/arrow/compute"
"github.com/apache/arrow-go/v18/arrow/compute/exec"
"github.com/apache/arrow-go/v18/arrow/memory"
)
// This example demonstrates how to register a custom scalar function.
func Example_customFunction() {
pool := memory.NewGoAllocator()
ctx := context.Background()
execCtx := compute.DefaultExecCtx()
ctx = compute.SetExecCtx(ctx, execCtx)
add42 := compute.NewScalarFunction("add_42", compute.Arity{
NArgs: 1,
}, compute.FunctionDoc{
Summary: "Returns the input values plus 42",
ArgNames: []string{"input"},
})
if err := add42.AddNewKernel(
[]exec.InputType{
// We accept a single argument (array) of Int8 type.
{
Kind: exec.InputExact,
Type: arrow.PrimitiveTypes.Int8,
},
},
// We'll return a single Int8 array.
exec.NewOutputType(arrow.PrimitiveTypes.Int8),
func(ctx *exec.KernelCtx, span *exec.ExecSpan, result *exec.ExecResult) error {
// The second buffer contains the values. Both for the input and the output arrays.
for i, x := range span.Values[0].Array.Buffers[1].Buf {
result.Buffers[1].Buf[i] = x + 42
}
return nil
},
nil,
); err != nil {
log.Fatal(err)
}
execCtx.Registry.AddFunction(add42, true)
inputArrayBuilder := array.NewInt8Builder(pool)
for i := 0; i < 16; i++ {
inputArrayBuilder.Append(int8(i))
}
inputArray := inputArrayBuilder.NewArray()
outputArrayDatum, err := compute.CallFunction(
compute.SetExecCtx(context.Background(), execCtx),
"add_42",
nil,
&compute.ArrayDatum{Value: inputArray.Data()},
)
if err != nil {
log.Fatal(err)
}
fmt.Println(array.NewInt8Data(outputArrayDatum.(*compute.ArrayDatum).Value).Int8Values())
// Output:
// [42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57]
}
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