Depends on #6495.

Add in-memory payload index for geo points using mmap as storage.

Loading the in-memory full text payload index from mmap is 24x faster than from RocksDB, as shown in this simple benchmark:

• bfb --geo-payloads -n 2000000 -d1 --indexing-threshold 100:
  • Old RocksDB based index: 11.78s, 11.86s, 11.57s, 11.66s = avg 11.72s
  • New mmap based index: 0.489s, 0.476s, 0.476s, 0.477s = avg 0.480ms (24x faster)

Tasks

• Add test
• Do load benchmark
• Drop mmap caches after load
• Merge Add in-memory payload index on mmap storage (full text) #6495
• Rebase on dev
• Undraft

All Submissions:

• Contributions should target the dev branch. Did you create your branch from dev?
• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

New Feature Submissions:

1. Does your submission pass tests?
2. Have you formatted your code locally using cargo +nightly fmt --all command prior to submission?
3. Have you checked your code using cargo clippy --all --all-features command?

Changes to Core Features:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your core changes, as applicable?
• Have you successfully ran tests with your changes locally?