4.0.0rc1

[arun1729]

Release candidate for v4.0.0

v4.0.0: Spindle binary format, mmap reads, in-memory traversal cache (#89)
Major release that replaces the marshal-based on-disk format with a new
binary format (Spindle) and reworks the storage and traversal hot paths.

On-disk format (BREAKING)

• New length-addressable binary record format with a versioned file header
  and per-record int64 timestamps; replaces the marshal/separator v0/v1 format.
• spindle_pack: custom packer for str/int/float/bool/bytes and float arrays
  (no marshal — portable and safe to load untrusted data).
• Index slots shrunk from 32-byte ASCII to 8-byte int64.
• Legacy v0/v1 files are no longer readable; use the migration utility.

Performance

• Reads served from a read-only mmap fast path; writes go through the fd.
• StoreCache LRU caches decoded records (not raw bytes) with optional
  cross-table shared cache.
• MemoryView: in-memory adjacency cache for traversals with demand paging
  (use_memory_view, on by default).
• v(..., track_paths=False) for faster set-based multi-hop traversal.
• Graph edge keys use a 1-byte direction prefix instead of a string suffix.

Migration

• cog.migrate.migrate(path) converts 3.x databases in place, rewriting graph
  edge keys so migrated graphs stay traversable. Originals kept as .v3_backup.

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This discussion was created from the release 4.0.0rc1.