Hi,
I'm trying to write a code in python which executes an expression on
filtered data. So I create a filter and later projector for some expression
but don't get how to combine those two in python:
```python
import pyarrow as pa
import pyarrow.gandiva as gandiva
table = pa.Table.from_arrays([pa.array([1., 31., 46., 3., 57., 44., 22.]),
pa.array([5., 45., 36., 73.,
83., 23., 76.])],
['a', 'b'])
builder = gandiva.TreeExprBuilder()
node_a = builder.make_field(table.schema.field("a"))
node_b = builder.make_field(table.schema.field("b"))
fifty = builder.make_literal(50.0, pa.float64())
eleven = builder.make_literal(11.0, pa.float64())
cond_1 = builder.make_function("less_than", [node_a, fifty], pa.bool_())
cond_2 = builder.make_function("greater_than", [node_a, node_b],
pa.bool_())
cond_3 = builder.make_function("less_than", [node_b, eleven], pa.bool_())
cond = builder.make_or([builder.make_and([cond_1, cond_2]), cond_3])
condition = builder.make_condition(cond)
filter = gandiva.make_filter(table.schema, condition)
# filterResult has type SelectionVector
filterResult = filter.evaluate(table.to_batches()[0],
pa.default_memory_pool())
print(result)
sum = builder.make_function("add", [node_a, node_b], pa.float64())
field_result = pa.field("c", pa.float64())
expr = builder.make_expression(sum, field_result)
projector = gandiva.make_projector(
table.schema, [expr], pa.default_memory_pool())
### Here there is a problem that I don't know how to use filterResult with
projector
r, = projector.evaluate(table.to_batches()[0], result)
```
In C++, I see that it is possible to pass SelectionVector as second
argument to projector::Evaluate:
https://github.com/apache/arrow/blob/c5fa23ea0e15abe47b35524fa6a79c7b8c160fa0/cpp/src/gandiva/tests/filter_project_test.cc#L270
Meanwhile, it looks like it is impossible in `gandiva.pyx`:
https://github.com/apache/arrow/blob/a4eb08d54ee0d4c0d0202fa0a2dfa8af7aad7a05/python/pyarrow/gandiva.pyx#L154
--
Best regards,
Kirill Lykov
