Fieldseal

G8 — §7: The blind index's *stored* representation is undefined

Labels: §7 · spec-gap · blocks-vectors Blocks: storage assertions in blind-index/ vectors; adapter DDL in docs/12/13 (both carry an interim recommendation flagged as pending this issue). Status: RESOLVED in spec 2026-08-09, adopted as proposed — new docs/02 §7.11 (raw ⌈b/8⌉ bytes in a binary column as the MUST, declared-per-column lowercase hex as the MAY, exact byte/string equality under a binary collation), §7.2 and §7.8 cross-reference it, §12 gains the stored-form obligation; marker sweep in docs/08 §4.4/§9, docs/09 §3.3, docs/12, docs/13, docs/issues/G03. Numbered §7.11 rather than inserted mid-section because §7.9/§7.10 are referenced by G12, G13, docs/12 and docs/13 — renumbering would have broken live cross-references to settle a cosmetic ordering question. Close tracker issue #8 when this lands.

Gap

§7 fully defines how the index value is computed but never what is written to the database. Raw bytes vs hex vs base64, column type, and width are unstated. The central claim requires two implementations sharing one database to produce byte-identical stored values — a Python-written index a Node process cannot match on is a silent, total failure of L2 interop that no envelope vector would catch.

Proposed direction (starting point, not a decision)

  • Stored form = the raw truncated bytes, length exactly ceil(b/8) (G3’s output), in a binary column (BYTEA/VARBINARY(ceil(b/8))/BLOB).
  • For text-only storage paths, a per-column declared alternative: lowercase hex, no prefix. The choice is part of the index declaration and immutable after first write (§7.8 applies).
  • Equality semantics: exact byte (or exact string, for hex) match — never a collation-sensitive comparison. Adapters MUST create the column with a binary/C-collation to prevent case-insensitive collations from matching differently than the core would.

This mirrors §3.3’s rule for envelopes (binary MUST, base64 MAY with documented overhead) so the two storage stories are symmetric.

Justification

Same interoperability argument as §3.3, applied to the index column; the collation point is standard SQL behavior (a case-insensitive collation over hex text would equate AB and ab — two values the core treats as distinct). No cryptographic content.

What it breaks

Every stored index value’s byte layout — frozen per column after first write (§7.8). Nothing exists yet.

Vector obligations

  • blind-index/ vectors gain a stored field: exact bytes (and the hex alternative) an implementation must write, alongside the computed value.
  • One cross-suite assertion: cross/ scenarios that query by index must match on the stored form.

Review flag

None.

View source: docs/issues/G08-blind-index-stored-representation.md