On Tue, Jun 8, 2021 at 10:47 PM Levi Morrison <levi.morri...@datadoghq.com> wrote: > > On Tue, Jun 8, 2021 at 6:22 PM tyson andre <tysonandre...@hotmail.com> wrote: > > > > Hi internals, > > > > > I've created a new RFC https://wiki.php.net/rfc/cachediterable adding > > > CachedIterable, > > > which eagerly evaluates any iterable and contains an immutable copy of > > > the keys and values of the iterable it was constructed from > > > > > > This has the proposed signature: > > > > > > ``` > > > final class CachedIterable implements IteratorAggregate, Countable, > > > JsonSerializable > > > { > > > public function __construct(iterable $iterator) {} > > > public function getIterator(): InternalIterator {} > > > public function count(): int {} > > > // [[$key1, $value1], [$key2, $value2]] > > > public static function fromPairs(array $pairs): CachedIterable {} > > > // [[$key1, $value1], [$key2, $value2]] > > > public function toPairs(): array{} > > > public function __serialize(): array {} // [$k1, $v1, $k2, $v2,...] > > > public function __unserialize(array $data): void {} > > > > > > // useful for converting iterables back to arrays for further > > > processing > > > public function keys(): array {} // [$k1, $k2, ...] > > > public function values(): array {} // [$v1, $v2, ...] > > > // useful to efficiently get offsets at the middle/end of a long > > > iterable > > > public function keyAt(int $offset): mixed {} > > > public function valueAt(int $offset): mixed {} > > > > > > // '[["key1","value1"],["key2","value2"]]' instead of '{...}' > > > public function jsonSerialize(): array {} > > > // dynamic properties are forbidden > > > } > > > ``` > > > > > > Currently, PHP does not provide a built-in way to store the state of an > > > arbitrary iterable for reuse later > > > (when the iterable has arbitrary keys, or when keys might be repeated). > > > It would be useful to do so for many use cases, such as: > > > > > > 1. Creating a rewindable copy of a non-rewindable Traversable > > > 2. Generating an IteratorAggregate from a class still implementing > > > Iterator > > > 3. In the future, providing internal or userland helpers such as > > > iterable_flip(iterable $input), iterable_take(iterable $input, int > > > $limit), > > > iterable_chunk(iterable $input, int $chunk_size), iterable_reverse(), > > > etc (these are not part of the RFC) > > > 4. Providing memory-efficient random access to both keys and values of > > > arbitrary key-value sequences > > > > > > Having this implemented as an internal class would also allow it to be > > > much more efficient than a userland solution > > > (in terms of time to create, time to iterate over the result, and total > > > memory usage). See https://wiki.php.net/rfc/cachediterable#benchmarks > > > > > > After some consideration, this is being created as a standalone RFC, and > > > going in the global namespace: > > > > > > - Based on early feedback on > > > https://wiki.php.net/rfc/any_all_on_iterable#straw_poll (on the namespace > > > preferred in previous polls) > > > It seems like it's way too early for me to be proposing namespaces in > > > any RFCs for PHP adding to modules that already exist, when there is no > > > consensus. > > > > > > An earlier attempt by others on creating a policy for namespaces in > > > general(https://wiki.php.net/rfc/php_namespace_policy#vote) also did not > > > pass. > > > > > > Having even 40% of voters opposed to introducing a given namespace (in > > > pre-existing modules) > > > makes it an impractical choice when RFCs require a 2/3 majority to pass. > > > - While some may argue that a different namespace might pass, > > > https://wiki.php.net/rfc/any_all_on_iterable_straw_poll_namespace#vote > > > had a sharp dropoff in feedback after the 3rd form. > > > I don't know how to interpret that - e.g. are unranked namespaces > > > preferred even less than the options that were ranked or just not seen as > > > affecting the final result. > > > > A heads up - I will probably start voting on > > https://wiki.php.net/rfc/cachediterable this weekend after > > https://wiki.php.net/rfc/cachediterable_straw_poll is finished. > > > > Any other feedback on CachedIterable? > > > > Thanks, > > Tyson > > > > -- > > PHP Internals - PHP Runtime Development Mailing List > > To unsubscribe, visit: https://www.php.net/unsub.php > > > > Based on a recent comment you made on GitHub, it seems like > `CachedIterable` eagerly creates the datastore instead of doing so > on-demand. Is this correct?
Sorry, yes, that's correct and pointed out in the RFC. I think that's a significant implementation flaw. I don't see why we'd balloon memory usage unnecessarily by being eager -- if an operation needs to fetch more data then it can go ahead and do so. -- PHP Internals - PHP Runtime Development Mailing List To unsubscribe, visit: https://www.php.net/unsub.php
