The previous topic became too long for a wiki article... so this is the short version

• to add names to CSV columns you do

->pipe(new ColumnRename(array(
                    "Column 0" => "your_name_for_column_0",
                    "Column 1" => "your_name_for_column_1",
                    "Column 2" => "your_name_for_column_2",
                    ...
                )))

see ColumnRename process in the documentation

• to have separate access to date and time if you have mixed datetime column you do

->pipe(new CopyColumn(array(
                "date"=>"datetime",
                "time"=>"datetime",
            )))
->pipe(new DateTimeFormat(array(
                "date" => "Y-m-d",
                "time" => "H:i:s"
            )))

see CopyColumn process and DateTimeFormat processin the documentation

• to select data with AND conditions you do

->pipe(new Filter(array(
    array("code","=",1000),
    array("date",">=","2019-02-01"),
    array("date","<=","2019-02-28"),
    array("flag","=",0)
)))

(using >= and <= for the date works like BETWEEN) see Filter process in the documentation

• to select data with OR conditions you do

->pipe(new Filter(array(
    array("value","<",10),
 'or',
    array("value",">",30),
)))

After the operator or, all the condition below will use or, if you want and again, you need to use 'and'

• for more complicated conditions like (a AND b) OR (c AND d) you do

->pipe(new Custom(function($row){
    if( (($row["a"] && $row["b"]) || ($row["c"] && $row["d"]) )
    {
        return $row;
    }
}))

see Custom process in the documentation

• to group data you do

->pipe(new Group(array(
    "by"=>"date",
    "max"=>"datetime"
)))

"max" - is an example only see Group process in the documentation

• to join CSV with another data source you do

 $join = new Join($first_source, $second_source, 
                   array("matching column1" => "matching column2"));

see Join process in the documentation