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TinyDrivers: Getting Started

Introduction​

The TinyDrivers library is an underlying SQL database layer for TinyORM. It can be used instead of the QtSql module, can be swapped at compile, and has 1:1 API as the QtSql module. 😮 Swapping is controlled by the qmake and CMake build system options.

It was designed to drop the QtSql dependency while maintaining backward compatibility and without the need for any code changes after the swap.

Features summary​
  • both, normal and prepared statements are supported
  • TLS/SSL connections using MYSQL_OPT_SSL_MODE (verify_ca, verify_identity) 🔥
  • setting many other connection options (see mysqldriver_p.cpp)
  • building and linking against the MariaDB Connector/C
  • transactions
  • re-using the current SqlQuery instance to re-execute the same or another query
  • detaching from the result set (associated to release memory)
  • query size, number of affected rows, last inserted ID, testing isNull(), ...
  • all 3366 unit tests passed 😮
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Currently, only the MySQL database driver is supported and finished.

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TinyDrivers can only be built with Qt v6, Qt v5.15 isn't supported.

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TinyDrivers library supports both build systems qmake and also CMake.

Differences from QtSql​

TinyDrivers doesn't return errors the the same way as the QtSql module, which means return a bool and if it's the result false then obtain the SqlError instance using the lastError() method from SqlDatabase or SqlQuery instances. Instead, it throws exceptions, and methods returning a bool type to report an error state always return true.

Naming conventions​
  • QtSql module -> TinyDrivers library
  • QMYSQL driver -> TinyMySql driver
MySQL driver​

The following describes the differences between QMYSQL and TinyMySql drivers.

The QMYSQL driver doesn't support setting MySQL non-flag connection options like MYSQL_OPT_RECONNECT without the value, it needs to be defined with value like =1 or =TRUE (case-sensitive), only real flag options like CLIENT_INTERACTIVE can be set without the value and = character.

On the other hand, the TinyMySql driver allows setting non-flag connection options options without the value and = character, which are considered enabled (ON or TRUE).

Removed features​

Simulation of prepared statements while calling SqlQuery::exec(QString), this functionality is useless because you can call regular prepared statements using SqlQuery::prepare(QString) and then SqlQuery::exec().

Missing features​

Fetching multiple result sets using SqlQuery::nextResult(). Multiple statement queries are supported they will be executed correctly (they can return multiple result sets), but only the first result set can be fetched currently. However, destroying multiple result sets is handled correctly.

Build system​

Another difference is that you can build the TinyDrivers and its SQL drivers (TinyMySql) in 3 different ways; Shared, Static, and as a Loadable library at runtime using LoadLibrary() on Windows or dlopen() on Linux.

The Shared library build​

It builds two shared libraries, the TinyDrivers shared library that contains the core/common code and the TinyMySql shared library that contains MySQL implementation. The TinyOrm links only against the TinyDrivers shared library and TinyMySql is a private implementation.

The Static build​

It builds one TinyDrivers static archive that contains the core/common code and SQL drivers (TinyMySql). This static library is linked or merged into the TinyOrm shared or static library (both variants are supported).

The Loadable SQL drivers build​

It builds two shared libraries, the TinyDrivers shared library that contains the core/common code and TinyMySql shared library (module) that contains MySQL implementation that is loaded at runtime using LoadLibrary() on Windows or dlopen() on Linux. The SQL driver library loader throws an exception if it cannot find this library at runtime.

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The TinyMySql links directly against the MySQL C connector (libmysql or mysqlclient library).

CMake/qmake build options​

For CMake​

See CMake build options, related CMake build options are:
BUILD_DRIVERS, BUILD_MYSQL_DRIVER, and DRIVERS_TYPE

To control shared and static build use BUILD_SHARED_LIBS CMake configuration option.

For qmake​

See qmake build options, related qmake configuration options are:
build_loadable_drivers, build_mysql_driver, build_shared_drivers, and build_static_drivers

To control shared and static build use static qmake configuration option.

Performance​

Performance is several milliseconds faster compared to QtSql with the QMYSQL driver. It was tuned using the KCacheGrind to be so. It's ~40ms faster on TinyOrmPlayground project with 620 database queries compiled using GCC v13.2.1 Debug build on Linux. Similar results can be expected on other platforms but it's not guaranteed.

This means performance is very similar to QtSql. There is not much to speed up because TinyDrivers code is swift and 90% of the time is spent inside the MySQL C API because we always have to wait for the database server, especially when creating database connections using eg. mysql_real_connect() (this function is king among the slowest functions 😎, which is understandable of course).

Internals​

TinyDrivers internal design can be divided into 3 different layers:

  • Driver layer
  • SQL API layer
  • Public API layer

The Driver layer is eg. TinyMySql library which is responsible for communicating with the underlying database driver (eg. MySQL C API).

The SQL API layer is a semi-layer that glues everything up and sits between the Public interface API and the Driver layer.

The Public interface API layer are the end classes like SqlDatabase and SqlQuery which are exposed to the end user.

SqlDatabase​

One more thing worth mentioning is the SqlDatabase API. It's one class that has two responsibilities! All static methods act as the database connection manager and an instance of the SqlDatabase represents a physical database connection. It's not a good design because it breaks the Single Responsibility principle, but it's what it is.

Namespaces​

TinyDrivers classes are defined in the Orm::Drivers namespace and TinyMySql classes in the Orm::Drivers::MySql namespace.

Documentation​

For all other APIs you can follow the QtSql documentation as the API is 1:1. The exception is of course the build system, TinyOrm has its own build system that doesn't follow the QtSql module.