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thin and lightweight, fast, ODBC API wrapper for modern C++ uses

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LASTRADA-Software/Lightweight

Lightweight is a thin and modern C++ ODBC wrapper foreasy andfast raw database access.Documentation is available athttps://lastrada-software.github.io/Lightweight/.

It supports both low-level access to the SQL API as well as provides hight level abstraction that allow easy database access.

Here you can see an example of datamapper usage (our tool for the high level abstraction)

Supported platforms

Only ODBC is supported, so it should work on any platform that has an ODBC driver anda modern enough C++ compiler.

  • Windows (Visual Studio 2022, toolkit v143)
  • Linux (GCC 14, Clang 19)

Supported databases

  • Microsoft SQL
  • PostgreSQL
  • SQLite3
  • Oracle database (work in progress)

Namespace

All functionality is placed inside aLightweight namespace, we also provide an alias for this namespaceLight, that is slightly shorter.

High level API

High level API of the library provided by the typeDataMapper

Simple one record example

Example of its usage to save/load/update/delete entry in the database for one table

#include<Lightweight/Lightweight.hpp>// Define a person structure, mapping to a table from the databasestructPerson{    Field<SqlGuid, PrimaryKey::AutoAssign> id;    Field<SqlAnsiString<25>> name;    Field<bool> is_active {true };    Field<std::optional<int>> age;};voidCRUD(DataMapper& dm){// Creates the table if it does not exist    dm.CreateTable<Person>();// Create a new person and create a database entryauto person = Person {.name ="John Doe", .is_active =true, .age =24};    dm.Create(person);// Update the age and save to the database    person.age =25;    dm.Update(person);// Query the person by primary keyif (autoconst po = dm.Query<Person>(person.id); po)std::println("Person: {} ({})", po->name,DataMapper::Inspect(*po));// Query all persons    std::vector<Person>const persons = dm.Query<Person>().All();// Query all persons with some filter and order by nameautoconst records = dm.Query<Person>()                             .Where(FieldNameOf<&Person::is_active>,"=",true)                             .OrderBy(FieldNameOf<&Person::name>)                             .All();// Delete the person    dm.Delete(person);}

Foreign keys relation

Now consider the following example we have two tablesUser andEmail, with foreign key inEmail pointing to theUserthis will translate in the following structs

structUser{    Light::Field<Light::SqlGuid, Light::PrimaryKey::AutoAssign, SqlRealName {"user_id" }> id {};    Light::Field<Light::SqlAnsiString<30>> name {};};structEmail{    Light::Field<Light::SqlGuid, Light::PrimaryKey::AutoAssign> id {};    Light::Field<Light::SqlAnsiString<30>> address {};    Light::BelongsTo<&User::id, Light::SqlRealName {"user_id" }> user {};};

In the presented example we used rename of the columns, for more details see how-to#rename-column-name page.you can query the email and get access to the user record as well

auto dm = Light::DataMapper::Create();auto email = dm->QuerySingle<Email>(some_email_id).value_or(Email{});auto user_name = email.user->name;// lazily loads the user record

Mapping query results to a simple struct

If you have a SQL query that returns some values, but it does not corresponds to the existing table in the database, you can map the result to a simple struct.The struct must have fields that match the columns in the query. The fields can be of any type that can be converted from the column type. The struct can have more fields than the columns in the query, but the fields that match the columns must be in the same order as the columns in the query.

#include<Lightweight/Lightweight.hpp>structSimpleStruct{uint64_t pkFromA;uint64_t pkFromB;    SqlAnsiString<30> c1FromA;    SqlAnsiString<30> c2FromA;    SqlAnsiString<30> c1FromB;    SqlAnsiString<30> c2FromB;};voidSimpleStructExample(DataMapper& dm){if (auto maybeObject = dm.Query<SimpleString>("SELECT A.pk, B.pk, A.c1, A.c2, B.c1, B.c2 FROM A LEFT JOIN B ON A.pk = B.pk"); maybeObject)    ))    {for (autoconst& obj : *maybeObject)std::println("{}",DataMapper::Inspect(obj));    }}

Mapping query to multiple struct

We also provide an API to create SQL queries, this can be usefull if you want to use information from existing structures.The following example shows how to create a query that joins multiple tables and maps the result to multiple structs.Consider the following structs

structCustomBindingA{    Field<uint64_t, PrimaryKey::ServerSideAutoIncrement> id {};    Field<int> number {};    Field<SqlAnsiString<20>> name {};    Field<SqlDynamicWideString<1000>> description {};};structCustomBindingB{    Field<uint64_t, PrimaryKey::ServerSideAutoIncrement> id {};    Field<SqlAnsiString<20>> title {};    Field<SqlDateTime> date_time {};    Field<uint64_t> a_id {};    Field<uint64_t> c_id {};};structCustomBindingC{    Field<uint64_t, PrimaryKey::ServerSideAutoIncrement> id {};    Field<double> value {};    Field<SqlAnsiString<20>> comment {};};

Create a query to join those tables to get in a single query

auto dm = Light::DataMapper::Create();auto query = dm->FromTable(RecordTableName<CustomBindingA>)                 .Select()                 .Fields<CustomBindingA, CustomBindingB>()                 .Field(QualifiedColumnName<"C.id">)                 .Field(QualifiedColumnName<"C.comment">)                 .InnerJoin<&CustomBindingB::a_id, &CustomBindingA::id>()                 .InnerJoin<&CustomBindingC::id, &CustomBindingB::c_id>()                 .OrderBy(QualifiedColumnName<"A.id">)                 .All();

This create the following SQL query

SELECT"A"."id","A"."number","A"."name","A"."description","B"."id","B"."title","B"."date_time","B"."a_id","B"."c_id",""C"."id"","C"."comment"FROM"A"INNER JOIN"B"ON"B"."a_id"="A"."id"INNER JOIN"C"ON"C"."id"="B"."c_id"ORDER BY"A"."id"ASC

Now you can execute it and get the result as astd::vector<std::tuple<CustomBindingA, CustomBindingB, ParfOfC> like this

structPartOfC{uint64_t id {};    SqlAnsiString<20> comment {};};autoconst records = dm->Query<CustomBindingA, CustomBindingB, PartOfC>(query);for (autoconst& [a, b, c]: records){// ...}

Using SQLite for testing on Windows operating system

You need to have the SQLite3 ODBC driver for SQLite installed.

SQLite ODBC driver installation on other operating systems

# Fedora Linuxsudo dnf install sqliteodbc# Ubuntu Linuxsudo apt install sqliteodbc# macOSarch -arm64 brew install sqliteodbc

Generate example for the existing database

You can useddl2cpp to generate header file for you database schema as well as an example file that you can compile

First, configure cmake project and compileddl2cpp target

cmake --build build --target ddl2cpp

Generate header file from the existing database by providing connection string to the tool

 ./build/src/tools/ddl2cpp --connection-string"DRIVER=SQLite3;Database=test.db" --make-aliases --naming-convention CamelCase  --output ./src/examples/example.hpp --generate-example

You can also avoid all those command line arguments by creating a config file that muts be in yourcurrent working directory or in one of its parent directories.The config file must be namedddl2cpp.yml and must contain the following content:

ConnectionString:'DSN=YourDSN;UID=YourUser;PWD=YourSecret'OutputDirectory:'src/entities'MakeAliases:trueNamingConvention:CamelCase

Now you can configure cmake to compile example

cmake --preset linux-clang-debug -DLIGHWEIGHT_EXAMPLE=ON -B build

Finally, compile and run the example

cmake --build build&& ./build/src/examples/example

Compile using C++26 reflection support

docker buildx build --progress=plain -f .github/DockerReflection --load.
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