3.4 Case Folding

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Key names and value names are case-insensitive but case-preserving. loregd implements this by storing both forms: the name as written, and a folded form alongside it in a _folded column.

The folded form is computed once, when the name is written, and it is the folded column that appears in every WHERE clause and every primary key. Lookups are therefore plain binary comparisons:

SELECT * FROM path_entries
WHERE parent_guid = ? AND child_name_folded = ?

This is why no custom SQLite collation is registered anywhere in loregd — the case-insensitivity has already happened by the time SQLite sees the query. The canonical name is what comes back in responses, so callers see the case they originally supplied while storage compares the folded form.

Hive names are folded too, though not stored: routing a request to a hive and rejecting duplicate hive declarations (§2.1) both compare folded names.

Layer names are not folded. They are compared as binary, so layer names are case-sensitive.

3.4.1 How the folded form is computed #

loregd derives the folded form from the Go standard library's unicode.ToLower, with three corrections where lowercasing and simple case folding disagree:

Codepoint	Folds to	Why the correction
U+00B5 MICRO SIGN	U+03BC GREEK SMALL LETTER MU	Lowercasing leaves it unchanged.
U+017F LATIN SMALL LETTER LONG S	U+0073 LATIN SMALL LETTER S	Lowercasing leaves it unchanged.
U+0130 LATIN CAPITAL LETTER I WITH DOT ABOVE	unchanged	Its folding is a two-codepoint sequence, which simple folding does not produce.

The standard library's case tables are Unicode 15.0.0.

Important

Lowercasing is not case folding, and the three corrections above do not close the gap. 219 codepoints fold to something other than their Unicode 16.0 simple case folding, and for 47 of those, case-insensitive matching fails outright: two spellings that name the same key do not reach the same folded form.

Greek final sigma is the most reachable example. ς folds to itself, so a key stored as Σ is not found by a lookup for ς. The Cyrillic historic letters at U+1C80–U+1C88 and the Greek symbol variants ϐ ϑ ϕ ϖ ϰ ϱ ϵ behave the same way. Characters introduced in Unicode 16.0 — the Garay block among them — have no case mappings in the 15.0 tables at all, so their case pairs never match.

The Cherokee blocks fold in the opposite direction to the standard, across 172 codepoints. Matching inside a hive stays self-consistent, but the bytes written to the folded columns are not what another implementation folding the same names would produce.

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