Trait datafusion_execution::memory_pool::proxy::VecAllocExt

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pub trait VecAllocExt {
    type T;

    // Required methods
    fn push_accounted(&mut self, x: Self::T, accounting: &mut usize);
    fn allocated_size(&self) -> usize;
}

Expand description

Extension trait for Vec to account for allocations.

Required Associated Types§

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type T

Item type.

Required Methods§

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fn push_accounted(&mut self, x: Self::T, accounting: &mut usize)

Push new element to vector and increase accounting by any newly allocated bytes.

Note that allocation counts capacity, not size

§Example:

// use allocated to incrementally track how much memory is allocated in the vec
let mut allocated = 0;
let mut vec = Vec::new();
// Push data into the vec and the accounting will be updated to reflect
// memory allocation
vec.push_accounted(1, &mut allocated);
assert_eq!(allocated, 16); // space for 4 u32s
vec.push_accounted(1, &mut allocated);
assert_eq!(allocated, 16); // no new allocation needed

// push more data into the vec
for _ in 0..10 { vec.push_accounted(1, &mut allocated); }
assert_eq!(allocated, 64); // underlying vec has space for 10 u32s
assert_eq!(vec.allocated_size(), 64);

§Example with other allocations:

// You can use the same allocated size to track memory allocated by
// another source. For example
let mut allocated = 27;
let mut vec = Vec::new();
vec.push_accounted(1, &mut allocated); // allocates 16 bytes for vec
assert_eq!(allocated, 43); // 16 bytes for vec, 27 bytes for other

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fn allocated_size(&self) -> usize

Return the amount of memory allocated by this Vec to store elements (size_of<T> * capacity).

Note this calculation is not recursive, and does not include any heap allocations contained within the Vec’s elements. Does not include the size of self

§Example:

let mut vec = Vec::new();
// Push data into the vec and the accounting will be updated to reflect
// memory allocation
vec.push(1);
assert_eq!(vec.allocated_size(), 16); // space for 4 u32s
vec.push(1);
assert_eq!(vec.allocated_size(), 16); // no new allocation needed

// push more data into the vec
for _ in 0..10 { vec.push(1); }
assert_eq!(vec.allocated_size(), 64); // space for 64 now