Add a new payload index variant that functions as RAM wrapper around mmap based payload indices. The RAM wrapper functions as immutable payload storage having everything in-memory, but uses the mmap payload index as backing storage.

Pulling everything into RAM is more efficient as there is less indirection. Sharing the mmap storage for this allows to quickly switch between an in-memory and on-disk index type.

In terms of implementation, the new index types are cloned from the immutable RocksDB variant. It's internals have been adjusted to switch from RocksDB backing storage to mmaps.

Index performance during search was measured before. This repurposes the immutable index, and so performance will be the same.

Load time on startup using the new index does change. Here's a basic benchmark measuring load time:

• bfb --int-payloads 100 -n 5000000 -d1 --indexing-threshold 100:
  • Old RocksDB based index:
    • num: 3.13s, 3.19s, 3.25s, 3.20s = avg 3.1925s
    • map: 2.22s, 2.27s, 2.35s, 2.26s = avg 2.275s
  • New mmap based index:
    • num: 2.78s, 2.78s, 2.94s, 2.94s = avg 2.86s (10% faster)
    • map: 1.09s, 1.11s, 1.21s, 1.17s = avg 1.145s (50% faster)

Tasks

• Implement RAM wrapper for other payload index types (will be done in separate PR)
• Remove inefficient intermediate structures
• Properly load/implement new structures
• Benchmark

All Submissions:

• Contributions should target the dev branch. Did you create your branch from dev?
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Changes to Core Features:

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