Cleaner/Faster Partial Reading

[stephenberry]

Breaking Partial Read Changes (Faster/Cleaner)

• The option partial_read_nested has been removed, to simplify partial reading and bring better performance. If the option partial_read is true, then short circuiting will occur after the deepest value is read. This ensures that a true "partial" read occurs and post-read skipping is not necessary.
  • If you only want to read certain fields in a struct and perform this multiple times within a larger object, then use glz::skip or set error_on_unknown_keys = false. Either of these approaches will skip keys you don't care about.
• The local metadata for static constexpr auto partial_read = true; will now be ignored. You must explicitly use glz::opts{.partial_read = true} in the Glaze options for partial reading.
  • The local meta parameter was a poor design choice, because we want to separate serialization logic from options, so that the same glz::meta information can be used with various options. It also complicated the code/API.

Tip

When setting up partial reading, it is best to just include the parts of the deepest structure you care about and the parent structures to that location. This ensures the most efficient traversal to the fields of interest and the least amount of C++ struct writing.

The documentation for partial reading has been updated here: [Partial Read](https://github.com/stephenberry/glaze/blob/main/docs/partial-read.md)