(perf): OwnedValue with buffer to reduce allocations in VDBE

[krishvishal]

Closes: #1236

WIP: more to come.

[jussisaurio]

for these kind of things I tend to prefer

let Some(text) = value.as_text() else {
  value.convert_to_integer();
  return;
}

keeps the nesting in check

[jussisaurio]

Vec::extend_from_slice already does reserve(bytes.len()) internally for T: Copy:

https://github.com/rust-lang/rust/blob/612796c42077605fdd3c6f7dda05745d8f4dc4d8/library/alloc/src/vec/spec_extend.rs#L49-L57

https://github.com/rust-lang/rust/blob/master/library/alloc/src/vec/mod.rs#L2590-L2596

[ihorandrianov]

Storing integers on the heap looks problematic, is limbo becoming javascript? 😅
Should we think about something like

enum OwnedValue {
  BigData(Vec<u8>)
  SmallData([u8; 24]) // or any convenient size so we could fit small strings and integers there,
  Null
  }

[pereman2]

Storing integers on the heap looks problematic, is limbo becoming javascript? 😅 Should we think about something like

enum OwnedValue {
  BigData(Vec<u8>)
  SmallData([u8; 24]) // or any convenient size so we could fit small strings and integers there,
  Null
  }

The idea is to reuse the memory of an OwnedValue for any type. If you replace a Text with an Integer it will drop the memory previously allocated for a string and we don't want that. Now thinking about it, we should probably not heap allocate on int, float and null and have separate values for those like in an enum but keep the buffer alive in case we replace that register and those text and blob values would reference the internal buffer.

[penberg]

This pull request has been marked as stale due to inactivity. It will be closed in 7 days if no further activity occurs.

[penberg]

This pull request has been closed due to inactivity. Please feel free to reopen it if you have further updates.