Threadsafe connection #1395
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Threadsafe connection #1395
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The connection holder should be performant in all variants: 1. single-threaded use 2. opened once (open forever) 3. concurrent open/close Hence, a light-weight binary semaphore is used to synchronize opening and closing a database connection.
A user-provided 'on open' handler and connection control options can now be specified in a declarative way when making the 'storage' object.
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fnc12
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Feb 11, 2025
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| void release() { | ||
| // last one closes the connection. | ||
| // we assume that this might happen by any thread, therefore the counter must serve as a synchronization point. | ||
| if (this->_retain_count.fetch_sub(1, std::memory_order_acq_rel) == 1) { | ||
| if (_retainCount.fetch_sub(1, std::memory_order_acq_rel) == 1) { |
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We have code that omits this if the member variable starts with an underscore, so I removed it here as well.
What do you think? I find it easier to read and it's clear enough.
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| #ifdef SQLITE_ORM_CTAD_SUPPORTED | ||
| template<template<typename...> class R, class Tpl, size_t... Idx, class Projection = polyfill::identity> | ||
| constexpr auto create_from_tuple(Tpl&& tpl, std::index_sequence<Idx...>, Projection project = {}) { |
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would be nice to have it covered with unit tests
| @@ -4,6 +4,26 @@ | |||
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| using namespace sqlite_orm; | |||
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| #ifdef SQLITE_ORM_CTAD_SUPPORTED | |||
| TEST_CASE("connection control") { | |||
| const auto openForever = GENERATE(false, true); | |||
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A Catch2 data generator.
| const auto openForever = GENERATE(false, true); | ||
| SECTION("") { | ||
| SECTION("empty") { | ||
| auto storage = make_storage("", connection_control{openForever}, on_open([](sqlite3*) {})); |
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probably we may add also on_open call counter increment inside on_open and checking that is was or wasn't called
| #ifdef SQLITE_ORM_CTAD_SUPPORTED | ||
| TEST_CASE("connection control") { | ||
| const auto openForever = GENERATE(false, true); | ||
| SECTION("") { |
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what is the purpose of empty single session?
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GENERATE repeats the SECTION following it.
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With C++20 a more light-weight binary semaphore can be conditionally used to synchronize opening and closing a database connection.
Therefore, the connection holder should be minimally invasive and performant in all variants:
Note: One important change is that things involved around setting up a database connection - like creating application-defined functions, setting pragma or limit values - must be done under the same synchronization point right after opening the database.
Caveat: Currently the connection cannot yet be recursively retained; think: user-provided 'on open' handlers.