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Scott Fries
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#124 Adding support for invalidating cache objects (#125)
Co-authored-by: Scott Fries <Scott@ScottFries.com>
1 parent 5768fb9 commit 7e5e6d1

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Lines changed: 137 additions & 56 deletions

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‎docs/cache.md‎

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@@ -50,6 +50,44 @@ To create a cache with a virtually unlimited size, you can specify a `max_size`
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const auto cached_query = sqlgen::cache<0>(query);
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```
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### Cache Invalidation
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The cache has no mechanism for determining if a cached result is still valid/up-to-date. Because of this, the cache should be explicitly `clear`ed before use any time another query is made that invalidates the cache.
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```cpp
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#include <sqlgen.hpp>
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struct User {
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std::string name;
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int age;
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};
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const auto conn = sqlgen::sqlite::connect();
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const auto user = User{.name = "John", .age = 30};
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sqlgen::write(conn, user);
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const auto user_b = User{.name = "Mary", .age = 25};
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sqlgen::write(conn, user_b);
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const auto query = sqlgen::read<std::vector<User>>;
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const auto cached_query = sqlgen::cache<100>(query);
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const auto users1 = cached_query(conn).value();
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// The cache size will now contain a result consisting of John & Mary
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const auto user_c = User{.name = "Bill", .age = 50};
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sqlgen::write(conn, user_c);
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// Because the query was previously cached, user2 will still only contain John & Mary while Bill will be absent.
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const auto users2 = cached_query(conn).value();
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cached_query.clear(conn);
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// Now, the query will be executed again since it's no longer cached. Afterwards, the cache will again store an up-to-date result and users3 will contain John, Mary, & Bill.
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const auto users3 = cached_query(conn).value();
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```
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### Thread Safety and Concurrency
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The cache is thread-safe and can be accessed from multiple threads concurrently. A `std::shared_mutex` is used to protect the cache from data races.

‎include/sqlgen/cache.hpp‎

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@@ -65,6 +65,11 @@ class CacheImpl {
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});
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}
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static void clear() {
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std::unique_lock write_lock(mtx_);
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cache_.clear();
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}
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static const auto& cache() { return cache_; }
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private:
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_max_size>::cache();
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}
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template <class Connection>
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requires is_connection<Connection>
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static void clear(const Result<Ref<Connection>>&) {
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CacheImpl<QueryT, std::remove_cvref_t<Connection>, _max_size>::clear();
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}
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QueryT query_;
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};
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‎tests/duckdb/test_cache.cpp‎

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@@ -26,20 +26,28 @@ TEST(duckdb, test_cache) {
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const auto cached_query = sqlgen::cache<100>(query);
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const auto user1 = conn.and_then(cache<100>(query)).value();
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EXPECT_EQ(cached_query.cache(conn).size(), 1);
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const auto user2 = cached_query(conn).value();
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const auto user3 = cached_query(conn).value();
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EXPECT_EQ(user1.name, "John");
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EXPECT_EQ(user1.age, 30);
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EXPECT_EQ(user2.name, "John");
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EXPECT_EQ(user2.age, 30);
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EXPECT_EQ(cached_query.cache(conn).size(), 1);
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EXPECT_EQ(user3.name, "John");
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EXPECT_EQ(user3.age, 30);
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auto test_cache_population = [&]() {
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const auto user1 = conn.and_then(cache<100>(query)).value();
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EXPECT_EQ(cached_query.cache(conn).size(), 1);
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const auto user2 = cached_query(conn).value();
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const auto user3 = cached_query(conn).value();
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EXPECT_EQ(user1.name, "John");
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EXPECT_EQ(user1.age, 30);
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EXPECT_EQ(user2.name, "John");
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EXPECT_EQ(user2.age, 30);
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EXPECT_EQ(cached_query.cache(conn).size(), 1);
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EXPECT_EQ(user3.name, "John");
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EXPECT_EQ(user3.age, 30);
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};
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test_cache_population();
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// Test cache invalidation
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cached_query.clear(conn);
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EXPECT_EQ(cached_query.cache(conn).size(), 0);
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test_cache_population();
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}
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} // namespace test_cache

‎tests/mysql/test_cache.cpp‎

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@@ -33,20 +33,28 @@ TEST(mysql, test_cache) {
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const auto cached_query = sqlgen::cache<100>(query);
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const auto user1 = conn.and_then(cache<100>(query)).value();
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EXPECT_EQ(cached_query.cache(conn).size(), 1);
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const auto user2 = cached_query(conn).value();
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const auto user3 = cached_query(conn).value();
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EXPECT_EQ(user1.name, "John");
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EXPECT_EQ(user1.age, 30);
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EXPECT_EQ(user2.name, "John");
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EXPECT_EQ(user2.age, 30);
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EXPECT_EQ(cached_query.cache(conn).size(), 1);
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EXPECT_EQ(user3.name, "John");
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EXPECT_EQ(user3.age, 30);
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auto test_cache_population = [&]() {
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const auto user1 = conn.and_then(cache<100>(query)).value();
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EXPECT_EQ(cached_query.cache(conn).size(), 1);
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const auto user2 = cached_query(conn).value();
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const auto user3 = cached_query(conn).value();
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EXPECT_EQ(user1.name, "John");
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EXPECT_EQ(user1.age, 30);
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EXPECT_EQ(user2.name, "John");
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EXPECT_EQ(user2.age, 30);
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EXPECT_EQ(cached_query.cache(conn).size(), 1);
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EXPECT_EQ(user3.name, "John");
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EXPECT_EQ(user3.age, 30);
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};
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test_cache_population();
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// Test cache invalidation
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cached_query.clear(conn);
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EXPECT_EQ(cached_query.cache(conn).size(), 0);
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test_cache_population();
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}
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} // namespace test_cache

‎tests/postgres/test_cache.cpp‎

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@@ -33,20 +33,28 @@ TEST(postgres, test_cache) {
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const auto cached_query = sqlgen::cache<100>(query);
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const auto user1 = conn.and_then(cache<100>(query)).value();
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EXPECT_EQ(cached_query.cache(conn).size(), 1);
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const auto user2 = cached_query(conn).value();
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const auto user3 = cached_query(conn).value();
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EXPECT_EQ(user1.name, "John");
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EXPECT_EQ(user1.age, 30);
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EXPECT_EQ(user2.name, "John");
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EXPECT_EQ(user2.age, 30);
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EXPECT_EQ(cached_query.cache(conn).size(), 1);
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EXPECT_EQ(user3.name, "John");
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EXPECT_EQ(user3.age, 30);
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auto test_cache_population = [&]() {
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const auto user1 = conn.and_then(cache<100>(query)).value();
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EXPECT_EQ(cached_query.cache(conn).size(), 1);
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const auto user2 = cached_query(conn).value();
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const auto user3 = cached_query(conn).value();
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EXPECT_EQ(user1.name, "John");
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EXPECT_EQ(user1.age, 30);
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EXPECT_EQ(user2.name, "John");
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EXPECT_EQ(user2.age, 30);
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EXPECT_EQ(cached_query.cache(conn).size(), 1);
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EXPECT_EQ(user3.name, "John");
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EXPECT_EQ(user3.age, 30);
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};
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test_cache_population();
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// Test cache invalidation
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cached_query.clear(conn);
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EXPECT_EQ(cached_query.cache(conn).size(), 0);
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test_cache_population();
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}
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} // namespace test_cache

‎tests/sqlite/test_cache.cpp‎

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@@ -26,20 +26,28 @@ TEST(sqlite, test_cache) {
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const auto cached_query = sqlgen::cache<100>(query);
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const auto user1 = conn.and_then(cache<100>(query)).value();
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EXPECT_EQ(cached_query.cache(conn).size(), 1);
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const auto user2 = cached_query(conn).value();
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const auto user3 = cached_query(conn).value();
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EXPECT_EQ(user1.name, "John");
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EXPECT_EQ(user1.age, 30);
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EXPECT_EQ(user2.name, "John");
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EXPECT_EQ(user2.age, 30);
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EXPECT_EQ(cached_query.cache(conn).size(), 1);
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EXPECT_EQ(user3.name, "John");
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EXPECT_EQ(user3.age, 30);
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auto test_cache_population = [&]() {
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const auto user1 = conn.and_then(cache<100>(query)).value();
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EXPECT_EQ(cached_query.cache(conn).size(), 1);
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const auto user2 = cached_query(conn).value();
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const auto user3 = cached_query(conn).value();
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EXPECT_EQ(user1.name, "John");
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EXPECT_EQ(user1.age, 30);
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EXPECT_EQ(user2.name, "John");
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EXPECT_EQ(user2.age, 30);
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EXPECT_EQ(cached_query.cache(conn).size(), 1);
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EXPECT_EQ(user3.name, "John");
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EXPECT_EQ(user3.age, 30);
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};
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test_cache_population();
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// Test cache invalidation
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cached_query.clear(conn);
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EXPECT_EQ(cached_query.cache(conn).size(), 0);
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test_cache_population();
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}
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} // namespace test_cache

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