Add initial SQLmem package structure with SQL parser, cache manager, column registry, and tests

tests/test_cache.py

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+import sqlite3
+from pathlib import Path
+
+import pytest
+
+from sqlmem.cache import CacheManager
+
+
+@pytest.fixture
+def cache(tmp_path):
+    c = CacheManager(db_path=tmp_path / "test_cache.db", backup_interval=9999)
+    yield c
+    c.close()
+
+
+@pytest.fixture
+def source_conn():
+    conn = sqlite3.connect(":memory:")
+    conn.execute("CREATE TABLE users (name TEXT, email TEXT, status TEXT)")
+    conn.executemany(
+        "INSERT INTO users VALUES (?, ?, ?)",
+        [("alice", "alice@example.com", "active"), ("bob", "bob@example.com", "inactive")],
+    )
+    conn.commit()
+    yield conn
+    conn.close()
+
+
+def test_table_not_cached_initially(cache):
+    assert cache.is_table_cached("users") is False
+
+
+def test_load_table(cache, source_conn):
+    cache.load_table("users", ["name", "email"], source_conn)
+    assert cache.is_table_cached("users") is True
+
+
+def test_loaded_data_correct(cache, source_conn):
+    cache.load_table("users", ["name", "email"], source_conn)
+    rows = cache.connection.execute("SELECT name, email FROM users").fetchall()
+    assert len(rows) == 2
+    assert ("alice", "alice@example.com") in rows
+
+
+def test_mark_table_refreshed(cache, source_conn):
+    cache.load_table("users", ["name"], source_conn)
+    row = cache.connection.execute(
+        "SELECT row_count FROM _sqlmem_tables WHERE table_name = 'users'"
+    ).fetchone()
+    assert row[0] == 2
+
+
+def test_backup_and_reload(tmp_path, source_conn):
+    db_path = tmp_path / "cache.db"
+    c1 = CacheManager(db_path=db_path, backup_interval=9999)
+    c1.load_table("users", ["name"], source_conn)
+    c1.close()
+
+    c2 = CacheManager(db_path=db_path, backup_interval=9999)
+    assert c2.is_table_cached("users") is True
+    c2.close()

tests/test_parser.py

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+import pytest
+
+from sqlmem.exceptions import ReadOnlyError, UnsupportedQueryError
+from sqlmem.parser import parse
+
+
+def test_simple_select():
+    result = parse("SELECT name, email FROM users WHERE status = 'active'")
+    assert result.table == "users"
+    # WHERE columns are also extracted — needed for in-memory SQLite filtering
+    assert {"name", "email"}.issubset(set(result.columns))
+    assert "status" in result.columns
+
+
+def test_multiple_columns():
+    result = parse("SELECT a, b, c FROM orders")
+    assert result.table == "orders"
+    assert set(result.columns) == {"a", "b", "c"}
+
+
+def test_insert_raises_readonly():
+    with pytest.raises(ReadOnlyError):
+        parse("INSERT INTO users (name) VALUES ('alice')")
+
+
+def test_update_raises_readonly():
+    with pytest.raises(ReadOnlyError):
+        parse("UPDATE users SET name = 'bob' WHERE id = 1")
+
+
+def test_delete_raises_readonly():
+    with pytest.raises(ReadOnlyError):
+        parse("DELETE FROM users WHERE id = 1")
+
+
+def test_wildcard_raises_unsupported():
+    with pytest.raises(UnsupportedQueryError):
+        parse("SELECT * FROM users")
+
+
+def test_join_raises_unsupported():
+    with pytest.raises(UnsupportedQueryError):
+        parse("SELECT a.name, b.title FROM users a JOIN orders b ON a.id = b.user_id")

tests/test_registry.py

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+import sqlite3
+
+import pytest
+
+from sqlmem.registry import ColumnRegistry
+
+
+@pytest.fixture
+def registry():
+    conn = sqlite3.connect(":memory:")
+    return ColumnRegistry(conn)
+
+
+def test_empty_registry(registry):
+    assert registry.get_columns("users") == set()
+
+
+def test_update_and_get(registry):
+    registry.update("users", ["name", "email"])
+    assert registry.get_columns("users") == {"name", "email"}
+
+
+def test_update_accumulates(registry):
+    registry.update("users", ["name", "email"])
+    registry.update("users", ["email", "status"])
+    assert registry.get_columns("users") == {"name", "email", "status"}
+
+
+def test_needs_refetch_missing(registry):
+    registry.update("users", ["name"])
+    missing = registry.needs_refetch("users", ["name", "email"])
+    assert missing == ["email"]
+
+
+def test_needs_refetch_none_missing(registry):
+    registry.update("users", ["name", "email"])
+    missing = registry.needs_refetch("users", ["name"])
+    assert missing == []
+
+
+def test_independent_tables(registry):
+    registry.update("users", ["name"])
+    registry.update("orders", ["total"])
+    assert registry.get_columns("users") == {"name"}
+    assert registry.get_columns("orders") == {"total"}