/// <summary>
/// Returns the mimimum spherical distance between Point or MultiPoint arguments on a sphere in meters,
/// by using the specified algorithm.
/// It is assumed that `g1` and `g2` are associated with an SRID of `4326`.
/// </summary>
/// <param name="_">The DbFunctions instance.</param>
/// <param name="g1">First geometry argument.</param>
/// <param name="g2">Second geometry argument.</param>
/// <param name="algorithm">The algorithm to use. Must be directly supplied as a constant.</param>
/// <returns>Distance betweeen g1 and g2.</returns>
public static double SpatialDistanceSphere(
[CanBeNull] this DbFunctions _,
Geometry g1,
Geometry g2,
SpatialDistanceAlgorithm algorithm)
{
throw new InvalidOperationException(MySqlStrings.FunctionOnClient(nameof(SpatialDistanceSphere)));
}
public static SqlExpression GetStDistanceSphereFunctionCall(
SqlExpression left,
SqlExpression right,
SpatialDistanceAlgorithm algorithm,
Type resultType,
RelationalTypeMapping resultTypeMapping,
MySqlSqlExpressionFactory sqlExpressionFactory,
IMySqlOptions options)
{
if (options.ServerVersion.Supports.SpatialDistanceSphereFunction)
{
if (algorithm == SpatialDistanceAlgorithm.Native)
{
// Returns null for empty geometry arguments.
return(sqlExpressionFactory.NullableFunction(
"ST_Distance_Sphere",
new[] { left, right },
resultType,
resultTypeMapping,
false));
}
if (algorithm == SpatialDistanceAlgorithm.Andoyer &&
options.ServerVersion.Supports.SpatialDistanceFunctionImplementsAndoyer)
{
// The `ST_Distance()` in MySQL already uses the Andoyer algorithm, when SRID 4326 is associated
// with the geometry.
// CHECK: It might be faster to just run the custom implementation, if `ST_SRID()` does not support
// a second parameter yet (see SetSrid()).
return(sqlExpressionFactory.Case(
new[]
{
new CaseWhenClause(
sqlExpressionFactory.Equal(
sqlExpressionFactory.NullableFunction(
"ST_SRID",
new[] { left },
typeof(int)),
sqlExpressionFactory.Constant(4326)),
GetStDistanceFunctionCall(
left,
right,
resultType,
resultTypeMapping,
sqlExpressionFactory))
},
GetStDistanceFunctionCall(
SetSrid(left, 4326, sqlExpressionFactory, options),
SetSrid(right, 4326, sqlExpressionFactory, options),
resultType,
resultTypeMapping,
sqlExpressionFactory)));
}
if (algorithm == SpatialDistanceAlgorithm.Haversine)
{
// The Haversine algorithm assumes planar coordinates.
return(sqlExpressionFactory.Case(
new[]
{
new CaseWhenClause(
sqlExpressionFactory.Equal(
sqlExpressionFactory.NullableFunction(
"ST_SRID",
new[] { left },
typeof(int)),
sqlExpressionFactory.Constant(0)),
GetHaversineDistance(
left,
right,
resultType,
sqlExpressionFactory))
},
GetHaversineDistance(
SetSrid(left, 0, sqlExpressionFactory, options),
SetSrid(right, 0, sqlExpressionFactory, options),
resultType,
sqlExpressionFactory)));
}
}
if (algorithm == SpatialDistanceAlgorithm.Haversine)
{
return(GetHaversineDistance(left, right, resultType, sqlExpressionFactory));
}
return(GetAndoyerDistance(left, right, resultType, sqlExpressionFactory));
}
