Add incremental delta refresh and fix Decimal/datetime cache binding

CHANGELOG.md

@@ -6,6 +6,27 @@ All notable changes to this project will be documented in this file.
 
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+## [1.3.1] - 2026-06-05
+
+### Fixed
+- **`decimal.Decimal` (and `datetime`) binding error** — `NUMERIC`/`DECIMAL`/`MONEY` columns from SQL Server (pyodbc) arrive as `decimal.Decimal`, which `sqlite3` cannot bind, crashing the cache load with `type 'decimal.Decimal' is not supported`. Values are now coerced to sqlite-bindable types (`Decimal`→`str`, `datetime`/`date`/`time`→ISO, `uuid.UUID`→`str`, `bytearray`→`bytes`) at the cache boundary — on full load, on delta upsert, and for WHERE parameters. Coercion is local (no global `sqlite3.register_adapter`), so the host application's `sqlite3` behaviour is untouched. Cache columns are `TEXT`, so the conversion is lossless and exact (no rounding).
+
+### Added
+- **Incremental (delta) refresh** — `CachingEngine(engine, delta={...})` with `DeltaConfig(change_column, key_columns)`. Delta-tracked tables are kept in sync by pulling only changed rows (`WHERE change_column >= watermark`) and upserting them by key, instead of full reloads.
+  - Data-driven high-watermark = `max(change_column)` cached, persisted in `cache.db`; `>=` overlap + idempotent upsert so no row is missed and boundary rows are harmlessly re-read.
+  - Catch-up on startup (since last shutdown) and a background thread refreshing every `SQLMEM_REFRESH_INTERVAL` seconds (default 300); `engine.refresh()` triggers a pull on demand.
+  - Primary key is auto-discovered from the source DB (`inspect(engine).get_pk_constraint`) when `key_columns` is omitted; required explicitly for views (raises `ValueError`).
+- `DeltaConfig` exported from the public API.
+- `engine.reset()` — wipes the whole cache (RAM + `cache.db`) for a clean rebuild after structural source changes.
+- `SQLMEM_REFRESH_INTERVAL` env var (default `300`).
+
+### Changed
+- `pyproject.toml` — bumped version to `1.3.1`
+- `cache.py` — schema version bumped to `3`; `_sqlmem_tables` gained a `last_synced_at` watermark column. New methods: `execute_in_memory` (lock-serialized read), `get_table_columns`, `create_unique_index`, `get/set_last_synced_at`, `max_value`, `upsert_rows`, `reset`. Existing on-disk caches are discarded and rebuilt on load.
+- `executor.py` — loading a delta-tracked table augments the column set with its key and change columns, creates the unique key index, and records the initial watermark; in-memory reads now go through the cache lock.
+
+---
+
 ## [1.2.0] - 2026-06-04
 
 ### Added