[pmoust]

Updates the ravel entry in five steps:

1. pins it to Ravel v0.28.0;
2. runs its object store on s3s-fs instead of RustFS;
3. writes larger single-row-group objects on machines with 30 GB or more;
4. sorts rows by a clustering key, with bloom filters only on text columns;
5. turns on Ravel's decoded column-block cache with an 8 GB cap on machines with 30 GB or more.

queries.sql and template.json are unchanged, and the result stays "tuned": "no". The cache cap is the entry's fixed configuration, set by ./start from the machine's memory like the load tier, not tuned per run. This PR replaces #2822 and #2823, which carried steps 3 and 4 separately.

Why the store changes. Ravel holds no data on local disk; a cold statement is a set of ranged GETs against the store, which reads them from the machine's disk. Both stores are single-node S3 servers over that disk, but they differ in what a ranged read costs. On a single drive RustFS reads the whole 1 MiB erasure block around every ranged GET: about 1.5 MB of disk per 10 KB range, measured on c6a.4xlarge with one request at a time against a quiet box. s3s-fs serves a range with one file read. So on RustFS the cold column measured the store's read amplification more than the database. The README's "The object store" section states this beside the figures.

What ./install does now. It downloads the s3s-fs binary for the host architecture from a release on our fork (NOFireAI/s3s s3s-fs-0.17.0-ravel.1, built from commit 9353c1f1b) and verifies it against that release's SHA256SUMS before moving it into place, the way Ravel's own binaries are installed. When the release is unreachable it builds the same commit with cargo install --locked. The commit is the v0.17.0 release plus two changes offered upstream, s3s-project/s3s#1013 (listings return each object's stored ETag, which Ravel's one-time store qualification requires) and s3s-project/s3s#1014 (the access and secret key are read from the environment, so no key sits in a process argument list). The source-build fallback installs a minimal Rust toolchain when the machine has none (measured at about 3 minutes and 1.1 GB of RSS on c6a.large, 30 s on c8g.4xlarge). RustFS is no longer downloaded. rustfs-start is store-start, the store directory is store/, and the generated credentials file is store/credentials.env, still readable by the current user only.

What ./load does now. On machines whose MemTotal is 30,000,000 kB or more, it writes objects with one row group each: --target-bytes 3700000000, --group-target-blocks 512, a 60 s age trigger, pipeline depth 56 and a 14,000,000,000-byte load budget. On c6a.4xlarge that gives about 222 objects of about 46 MB instead of about 420 of 24 MB. Machines below 30 GB keep the previous geometry. Before the load, on every machine, it sets two tenant settings:

• bloom-scope set --scope text: bloom filters only on text columns (log bodies and severity). hits has none, so no column is covered and each block keeps only the minimum filter. No statement in queries.sql has a predicate a bloom filter would answer.
• clustering-key set --column EventDate --column UserID --bucket-width 1d: rows inside each object sort by counter, day, EventDate, UserID and time. That is the order ClickHouse's own entry gives its table with PRIMARY KEY (CounterID, EventDate, UserID, EventTime, WatchID); the counter is already Ravel's stream, so it is not repeated.

Both are table-level layout settings applied once before the load, like a primary key in a CREATE TABLE.

What ./start does now. Ravel 0.28.0 adds a decoded column-block cache, off by default. It keeps decoded columns between statements, so a repeated statement skips their decode. On machines whose MemTotal is 30,000,000 kB or more, ./start passes --decoded-cache-max-bytes 8000000000; below that the cache stays off. Its entries are charged to the server's memory budget, and memory pressure evicts them before a query is refused. The cache does not change the cold column: the driver restarts the server before every cold try, so the cache starts empty. The 8 GB cap was chosen on c6a.4xlarge from 4, 8 and 12 GB. At 4 GB the cache churned and two statements ran slower than without it, and 8 GB came within 0.2 % of 12 GB's warm-run geomean. RAVEL_DECODED_CACHE_BYTES overrides the cap, and 0 turns the cache off.

Measurement. Every column is the entry run through its own benchmark.sh on a fresh c6a.4xlarge with this repository's Ubuntu 24.04 image, on published release binaries (SHA256SUMS verified by ./install), one box per run. Each column adds one step to the one before it.

figure	v0.26.0, RustFS (results/20261025, current)	v0.26.0, s3s-fs	v0.27.0, s3s-fs	+ 30 GB tier (mean of 4 runs)	+ clustering key and text bloom scope (results/20261026)	v0.28.0 + decoded cache (this PR, results/20261030)
load	866 s	878 s	784 s	898 s	647 s	633 s
data size	10.21 GB	10.21 GB	10.20 GB	10.31 GB	8.33 GB	8.33 GB
cold sum	365.7 s	172.8 s	163.1 s	117.5 s	108.0 s	106.2 s
hot sum (better of runs 2 and 3)	57.2 s	57.0 s	51.6 s	52.3 s	50.2 s	37.9 s
concurrent QPS	0.720	0.733	0.792	0.802	0.830	0.920
concurrent error ratio	0.061	0.041	0.054	0.054	0.053	0.055
statements answered	43 of 43	43 of 43	43 of 43	43 of 43	43 of 43	43 of 43

A second run of the clustering-key column measured 107.6 s cold, 50.4 s hot, QPS 0.843 and an error ratio of 0.070. The concurrent errors are memory refusals under concurrency in every column; the four 30 GB-tier runs alone spread from 0.046 to 0.059.

The store swap moves the cold column; the hot column moves with the release (v0.27.0 pushes LIKE '%literal%' on a typed string column into the scan and keeps GROUP BY keys in their string form until the rows a statement returns) and with the decoded cache. The 30 GB tier and the two settings move cold again and shrink the load and the stored data. The tier makes the load about 110 s longer; the settings then make it about 250 s shorter. v0.28.0 resolves the same server defaults as v0.27.0 on c6a.4xlarge: fetch cache 7.1 GB, per-query SQL pool 16.5 GB, fetch concurrency 32.

Answers are equal across all runs on 41 of the 43 statements. q18 (LIMIT without ORDER BY) and q25 (orders by EventTime but returns only SearchPhrase) return different rows between the tries of any single run, on every version and layout above. The statements that order by time and stop at a limit (q24, q25, q27) did not slow down with the clustering key, though rows inside an object are no longer in time order.

The 30 GB tier and the cache cap apply to every machine whose MemTotal is 30,000,000 kB or more; both were measured only on c6a.4xlarge, and the other sizes are left to the usual re-run of the matrix. The RustFS results stay under their own dates.

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