Each ingest shard owns its own SQLite file. N processes write in
true parallel (no WAL writer-lock contention). Cross-shard reads
attach all shards as UNION ALL views over the standard tables, so
existing query code (`SELECT * FROM documents`) works unchanged.
CLI:
aborist ingest --shards-dir DIR --shard 0/4 # write to DIR/000.db
aborist --shards-dir DIR stats # read across all shards
aborist --shards-dir DIR analyze # ditto
aborist --shards-dir DIR verify -n 20 # Merkle round-trips
# on a sample drawn
# from all shards
Makefile:
SHARDS_DIR=~/.aborist/shards
ingest-cur-attached SHARDS=4 ingest-old-attached SHARDS=4
stats-shards cross-shard stats
Implementation lives in store.connect_query():
- opens a fresh in-memory connection
- ATTACH DATABASE per shard file under aliases sh000, sh001, ...
- CREATE TEMP VIEW <table> AS UNION ALL SELECT * FROM <alias>.<table>
for the eight shardable tables (documents, chunks, merkle_nodes,
edges, derivations, providence_cache, audit_events, falsifications)
- exposes a _shards temp table for tools that want the shard list
Benchmark (20k cur, 4 cores):
Phase 1a serial 55.3 s
Phase 1b shared-WAL 43.1 s
Phase 2 attached-forever 40.1 s (no WAL contention)
The 7% gap vs Phase 1b is bz2-decompression duplication: each shard
decodes the full dump independently. Architectural wins are bigger
than that number — write isolation, per-shard crash recovery,
audit chain stays per-shard checkable, shards can migrate to other
disks, new shards are pure append (never rewrite existing files).
Merge cost remains: zero. `ls $SHARDS_DIR/*.db` is the registry.
Workers each parse the full SQL stream but only emit rows whose index
satisfies (idx % total == rank). N processes cooperate against a
single shared SQLite file; WAL+synchronous=NORMAL handles writer
contention via BEGIN IMMEDIATE serialization.
Implementation chose OS-level processes over in-process mp.Queue: the
gain ceiling is identical (writer is the bottleneck either way) and
the surface area is one new flag plus stride-filter logic instead of
a queue-based pipeline with picklable workers.
Makefile gains:
ingest-cur-parallel SHARDS=4
ingest-old-parallel SHARDS=4
Benchmark on 20k cur articles:
serial 55.3 s 361 docs/s 1.0x CPU usage
4-way parallel 43.1 s 464 docs/s ~3.0x CPU usage 1.28x wall
Both runs landed 19,999 unique documents — correctness verified.
The write-lock is now the bottleneck; further gains require Phase 2
attach-forever sharding (each shard owns its own SQLite file, queries
fan out via ATTACH DATABASE, zero merge cost).
The 2003-05-16 archive ships three files:
20030516_cur_tablesql.bz2 82 MB current snapshot (single revision/page)
old_tablesqlbz2.1 640 MiB \
old_tablesqlbz2.2 252 MiB / split halves of old (full revision
history). Concatenate before bzcat.
Generalize the parser:
WikipediaSqlDump(table='cur'|'old') — shared statement parser, single
column-position contract for the
first 4 fields (id/ns/title/text)
WikipediaCurDump — back-compat wrapper, table='cur'
WikipediaOldDump — new, table='old'; old has no is_redirect, every
revision is real
Old rows surface old_id and old_timestamp via Document.extra so a
downstream pass can sort revisions chronologically before re-ingesting
through the supersedes-edge path.
Makefile gains:
fetch-cur / fetch-old / fetch (both)
ingest-cur / ingest-old / ingest (cur default)
WP_OLD target concatenates the two split parts
CLI ingest --source now accepts wikipedia_cur or wikipedia_old.
Smoke (real dump): 5 revisions of "AtlasShrugged/Companies" yielded
correctly with old_id=2..10, timestamps from January 2002.
