rocksdb/unreleased_history
Levi Tamasi ecc084d301 Support the on-demand loading of blobs during iteration (#13069)
Summary:
Pull Request resolved: https://github.com/facebook/rocksdb/pull/13069

Currently, when using range scans with BlobDB, the iterator logic eagerly loads values from blob files when landing on a new entry. This can be wasteful in use cases where the values associated with some keys in the range are not used by the application. The patch introduces a new read option `allow_unprepared_value`; when specified, this option results in the above eager loading getting bypassed. Values needed by the application can be then loaded on an on-demand basis by calling the new iterator API `PrepareValue`. Note that currently, only regular single-CF iterators are supported; multi-CF iterators and transactions will be extended in later PRs.

Reviewed By: jowlyzhang

Differential Revision: D64360723

fbshipit-source-id: ee55502fa15dcb307a984922b9afc9d9da15d6e1
2024-10-16 12:34:57 -07:00
..
behavior_changes Preserve Options File (#13074) 2024-10-16 09:22:51 -07:00
bug_fixes Re-implement GetApproximateMemTableStats for skip lists (#13047) 2024-10-02 14:25:50 -07:00
new_features Support the on-demand loading of blobs during iteration (#13069) 2024-10-16 12:34:57 -07:00
performance_improvements Update history and version for 9.5.fb release (#12880) 2024-07-22 13:15:09 -07:00
public_api_changes Update main branch for 9.6 release (#12945) 2024-08-19 17:36:23 -07:00
add.sh Some fixes to unreleased_history/ (#11504) 2023-06-02 15:55:02 -07:00
README.txt Trigger compaction to the next level if the data age exceeds periodic_compaction_seconds (#12175) 2023-12-28 12:50:08 -08:00
release.sh Update for 8.5.fb branch cut (#11642) 2023-08-02 12:34:11 -07:00

Adding release notes
--------------------

When adding release notes for the next release, add a file to one of these
directories:

unreleased_history/new_features
unreleased_history/behavior_changes
unreleased_history/public_api_changes
unreleased_history/bug_fixes

with a unique name that makes sense for your change, preferably using the .md
extension for syntax highlighting.

There is a script to help, as in

$ unreleased_history/add.sh unreleased_history/bug_fixes/crash_in_feature.md

or simply

$ unreleased_history/add.sh

will take you through some prompts.

The file should usually contain one line of markdown, and "* " is not
required, as it will automatically be inserted later if not included at the
start of the first line in the file. Extra newlines or missing trailing
newlines will also be corrected.

The only times release notes should be added directly to HISTORY are if
* A release is being amended or corrected after it is already "cut" but not
tagged, which should be rare.
* A single commit contains a noteworthy change and a patch release version bump


Ordering of entries
-------------------

Within each group, entries will be included using ls sort order, so important
entries could start their file name with a small three digit number like
100pretty_important.md.

The ordering of groups such as new_features vs. public_api_changes is
hard-coded in unreleased_history/release.sh


Updating HISTORY.md with release notes
--------------------------------------

The script unreleased_history/release.sh does this. Run the script before
updating version.h to the next development release, so that the script will pick
up the version being released. You might want to start with

$ DRY_RUN=1 unreleased_history/release.sh | less

to check for problems and preview the output. Then run

$ unreleased_history/release.sh

which will git rm some files and modify HISTORY.md. You still need to commit the
changes, or revert with the command reported in the output.


Why not update HISTORY.md directly?
-----------------------------------

First, it was common to hit unnecessary merge conflicts when adding entries to
HISTORY.md, which slowed development. Second, when a PR was opened before a
release cut and landed after the release cut, it was easy to add the HISTORY
entry to the wrong version's history. This new setup completely fixes both of
those issues, with perhaps slightly more initial work to create each entry.
There is also now an extra step in using `git blame` to map a release note
to its source code implementation, but that is a relatively rare operation.