Method get_slice_memory_size

arrow-data/src/data.rs:510–561

Returns the total number of the bytes of memory occupied by the buffers by this slice of [`ArrayData`] (See also diagram on [`ArrayData`]). This is approximately the number of bytes if a new [`ArrayData`] was formed by creating new [`Buffer`]s with exactly the data needed. For example, a [`DataType::Int64`] with `100` elements, [`Self::get_slice_memory_size`] would return `100 * 8 = 800`. If the

(&self)

    /// first `20` elements, then [`Self::get_slice_memory_size`] on the
    /// sliced [`ArrayData`] would return `20 * 8 = 160`.
    pub fn get_slice_memory_size(&self) -> Result<usize, ArrowError> {
        let mut result: usize = 0;
        let layout = layout(&self.data_type);

        for spec in layout.buffers.iter() {
            match spec {
                BufferSpec::FixedWidth { byte_width, .. } => {
                    let buffer_size = self.len.checked_mul(*byte_width).ok_or_else(|| {
                        ArrowError::ComputeError(
                            "Integer overflow computing buffer size".to_string(),
                        )
                    })?;
                    result += buffer_size;
                }
                BufferSpec::VariableWidth => {
                    let buffer_len = match self.data_type {
                        DataType::Utf8 | DataType::Binary => {
                            let offsets = self.typed_offsets::<i32>()?;
                            (offsets[self.len] - offsets[0]) as usize
                        }
                        DataType::LargeUtf8 | DataType::LargeBinary => {
                            let offsets = self.typed_offsets::<i64>()?;
                            (offsets[self.len] - offsets[0]) as usize
                        }
                        _ => {
                            return Err(ArrowError::NotYetImplemented(format!(
                                "Invalid data type for VariableWidth buffer. Expected Utf8, LargeUtf8, Binary or LargeBinary. Got {}",
                                self.data_type
                            )));
                        }
                    };
                    result += buffer_len;
                }
                BufferSpec::BitMap => {
                    let buffer_size = bit_util::ceil(self.len, 8);
                    result += buffer_size;
                }
                BufferSpec::AlwaysNull => {
                    // Nothing to do
                }
            }
        }

        if self.nulls().is_some() {
            result += bit_util::ceil(self.len, 8);
        }

        for child in &self.child_data {
            result += child.get_slice_memory_size()?;
        }
        Ok(result)
    }

    /// Returns the total number of bytes of memory occupied
    /// physically by this [`ArrayData`] and all its [`Buffer`]s and