[dfa1]

ORDER BY … LIMIT on a string column built a Java String per row just to compare it with the worst row kept, and almost every row loses that comparison.

• Byte rejection. A row whose first key is a string is first compared, as bytes, with the worst kept key, using VarBinArray#compareUnsigned.
  • FSST decodes only up to the first differing byte (Decompressor#compareUnsigned).
  • Dictionary and offset arrays compare in place.
  • A row that loses is skipped without building a String.
  • This only applies when the bound is ASCII, where byte order provably equals String.compareTo. A 5M-case fuzz with malformed UTF-8 found no disagreement.
• Backward walk. A chunk whose five evenly spaced sample rows rank in strictly reverse order is walked backward: the best rows come first and the rest are rejected. A sample row the filter rejects is never read, since reading it can fail (a u64 past BIGINT), so such a chunk is walked forward instead.
• Forward walk. It uses RowSelection#nextSelected, so perf(calcite): walk only the rows a dictionary filter selects #580's skipping of rows a dictionary filter rejects is kept.

Benchmark. 100M-row file through the jdbc:vortex: driver, warm JVM, median of 15 runs, against main (9bc12092):

query	main	#575
order by eventIdentifier desc limit 10	5616 ms	1680 ms (3.3×)
order by ISIN limit 10	1273 ms	962 ms (one round)

Review fixes. A subagent review raised these, all addressed:

• The sample no longer reads filtered-out rows.
• The PR is rebased onto perf(reader): filter dictionary columns by their values and codes in bulk #576 and perf(calcite): walk only the rows a dictionary filter selects #580, using nextSelected for the forward walk.
• The interop fixture now spans three Rust chunks, and the test asserts it.
• SortStringKeysTest is new. It covers ties across chunk edges, a chunk under 5 rows, and the filtered-sample regression, which fails without the fix.
• The trailing-escape case now has a test, and the comment about it is corrected.

FSST symbol lengths are deliberately not validated at load: Rust doesn't check them either.

./mvnw verify passes (9239 tests).

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