Source Information

Before reading or writing form a source you may want to understand the source better. For this we need to obtain the schema of the source.

Get Schema of Source

There following function can be used to obtain the schema of a source. Whether the type can be determined depends on the provider.

dl::GetDataSourceSchema(DataSource, ColumnName, ColumnType, DataSourceAttributes)

Arguments

• DataSource – Name of the data source (string)

• ColumnName – Output String Parameter giving the column names for tables and column numbers

• ColumnType – Output String Parameter giving the column types for tables and column numbers

• DataSourceAttributes – The Read/write attribute specifying the provider

Before we call this function we have to specify the outputs:

StringParameter Schema {
    IndexDomain: (
        dl::dt,      ! table name
        dl::cn       ! column number
    );
}
ElementParameter ColumnType {
    IndexDomain: (
        dl::dt,      ! table name
        dl::cn       ! column number
    );
    Range: dl::ColumnTypes;
}

Now we can call:

dl::GetDataSourceSchema(
    "TheSource.xlsx",          ! choose a source
    Schema,                    ! outputs the colum names
    ColumnType,                ! outputs the types
    ReadWriteAttribute         ! only needed to choose a provider
);

We have to make sure that we choose the right provider fitting for the source. In the example above we see that we need the XLSProvider. So ReadWriteAttribute needs to have defined this as provider:

ReadWriteAttribute := {'DataProvider' : xlsprov::DataLink };