Fix geometry type: perf, nil-limit crash, adapter pollution, and DDL hardening

[waratuman]

Summary

Security & performance review of the PostGIS geometry type and adapter. Four fixes, ranked by impact.

1. Perf — RGeo factory rebuilt on every read

oid/geometry.rb — cast allocated a fresh GEOS factory (and serialize/parsers) for every geometry value loaded from the DB, even though the SRID is fixed per column. The factory, WKB/WKT parsers, and WKB generator are now built once in the initializer. Eager construction (rather than lazy ||= memoization) is also required because ActiveRecord freezes Type instances after initialization — lazy memoization raised FrozenError in Rails 8.1 (verified).

2. Correctness — bare geometry column crashed on read

A column defined as plain geometry (no geometry(Type,srid) modifier) has no limit, so limit[:srid] raised NoMethodError on read. Added a srid helper defaulting to 0 (PostGIS "unknown SRID").

3. Bug — merge! polluted the parent PostgreSQL adapter

NATIVE_DATABASE_TYPES = PostgreSQLAdapter::NATIVE_DATABASE_TYPES.merge!(...) mutated the parent adapter's hash in place, leaking :geometry into the vanilla postgresql adapter (and would raise FrozenError if that constant were frozen). Changed to non-mutating merge.

4. Security (low) — unvalidated interpolation into DDL

type_to_sql interpolated srid straight into the geometry(...) type modifier. Now coerced with to_i, so it can't carry arbitrary SQL text. (type is still interpolated; it's the developer-supplied geometry type name.)

Verification

Exercised end-to-end against a real PostGIS database (all pass):

• srid sanitization: type_to_sql(:geometry, limit: { srid: "4326); DROP TABLE geos;--" }) → geometry(Point,4326)
• typed Point create/reload round-trip
• bare geometry column create/reload (nil-limit path, no crash)
• factory built eagerly on the frozen type instance
• parent PostgreSQLAdapter::NATIVE_DATABASE_TYPES no longer contains :geometry

Note: the rake test task currently fails to load in this environment due to a pre-existing incompatibility between minitest 6 and this ActiveSupport's autorun (minitest/rails_plugin missing) — unrelated to these changes; verification was done via a direct script exercising the same code paths.

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