How to hdf5 (Hdfsl ) file (One Column Read) read (Big Size file) - hdf5

Question

I am using the HDF5DotNet with C# and I can read only full data as the attached image in the dataset.
The hdf5 file is too big, up to nearly 1.4GB, and if I load the whole array into the memory then it will be out of memory.
I would like to read all data from One columns
double[] values = new double[203572];
string m_Doc_01 = "data/sample/line";
HDFql.Execute("USE DIRECTORY " + "\"" + File_Directory + "\"");
HDFql.Execute("USE FILE " + "\"" + File_Name + "\"");
HDFql.Execute("CREATE CHUNKED(1, 203572) DATASET my_dataset_BS AS DOUBLE(2050, 203572)");
How to "m_Doc_01 ==> my_dataset_BS" Data
???
???
for (int i = 0; i < 2050; i++)
{
HDFql.Execute("SELECT FROM " + "\"" + m_Doc_01 + "\"" + "(1:::1) INTO MEMORY " + HDFql.VariableRegister(values));
}

Answer 1

To read the column that you have highlighted in the screenshot (i.e. column #0), you have to change the hyperslab to (please note the 0):
HDFql.Execute("SELECT FROM " + "\"" + m_Doc_01 + "\"" + "(, 0:::1) INTO MEMORY " + HDFql.VariableRegister(values));
That said, if you want to loop through the dataset and read one column at the time do the following (also better to register variable values before the loop starts and unregister it after the loop is done - this will increase performance):
number = HDFql.VariableRegister(values);
for(int i = 0; i < 2050; i++)
{
HDFql.Execute("SELECT FROM " + "\"" + m_Doc_01 + "\"" + "(, " + i + ":::1) INTO MEMORY " + number);
// do something with variable "values" (which contains the values of column #i)
}
HDFql.VariableUnregister(values);