/// <summary>Return all the keys that share a common prefix</summary>
/// <param name="query">Source database query</param>
/// <param name="prefix">Shared prefix</param>
/// <returns>Query that will return the keys that share the specified <paramref name="prefix"/></returns>
public static IFdbAsyncSequenceQueryable <KeyValuePair <Slice, Slice> > RangeStartsWith(this IFdbDatabaseQueryable query, Slice prefix)
{
if (query == null)
{
throw new ArgumentNullException(nameof(query));
}
var expr = FdbQueryExpressions.RangeStartsWith(prefix);
return(query.Provider.CreateSequenceQuery(expr));
}
public void Test_FdbQueryFilterExpression()
{
var expr = FdbQueryExpressions.Filter(
FdbQueryExpressions.RangeStartsWith(TuPack.EncodeKey("Hello", "World")),
(kvp) => kvp.Value.ToInt32() % 2 == 0
);
Log(expr);
Assert.That(expr, Is.Not.Null);
Assert.That(expr.Source, Is.Not.Null.And.InstanceOf <FdbQueryRangeExpression>());
Assert.That(expr.Filter, Is.Not.Null);
Assert.That(expr.Type, Is.EqualTo(typeof(IAsyncEnumerable <KeyValuePair <Slice, Slice> >)));
Assert.That(expr.ElementType, Is.EqualTo(typeof(KeyValuePair <Slice, Slice>)));
Log(FdbQueryExpressions.ExplainSequence(expr));
}
public void Test_FdbQueryTransformExpression()
{
var expr = FdbQueryExpressions.Transform(
FdbQueryExpressions.RangeStartsWith(TuPack.EncodeKey("Hello", "World")),
(kvp) => kvp.Value.ToUnicode()
);
Log(expr);
Assert.That(expr, Is.Not.Null);
Assert.That(expr.Source, Is.Not.Null.And.InstanceOf <FdbQueryRangeExpression>());
Assert.That(expr.Transform, Is.Not.Null);
Assert.That(expr.Type, Is.EqualTo(typeof(IAsyncEnumerable <string>)));
Assert.That(expr.ElementType, Is.EqualTo(typeof(string)));
Log(FdbQueryExpressions.ExplainSequence(expr));
}
