sqlite: Improve precision for floating-point types

adamdruppe / arsd

This is a collection of modules that I've released over the years. Most of them stand alone, or have just one or two dependencies in here, so you don't have to download this whole repo.

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Sqlite is able to store 64 bit floating-point values, but the arsd.sqlite diver does not support this.

This adds support for values of type double when binding values to a query. Prior to this, doubles would be converted to a string and only be stored with 6 digits of precision in the database.

Additionally, floats stored in the database were converted to strings when retrieved and therefore be reduced to 6 digits of precision, too. This behavior is now fixed for floats and doubles.

This unittest checks that doubles now work as expected.

unittest
{
    import arsd.database;
    import arsd.sqlite;
    import std.math : feqrel;
    import std.conv : to;

    double d = 1.0/3.0;
    auto db = new Sqlite(":memory:");
    db.query("CREATE TABLE test(d REAL);");
    db.query("INSERT INTO test VALUES (?)", d);
    auto result = db.query("SELECT d FROM test;").front[0];
    assert(feqrel(d, to!double(result)) >= 52);
}

adamdruppe / arsd

sqlite: Improve precision for floating-point types #400