A Named Selection in 4D is an ordered list of records for a file in a 4D process. This list of records is given a name and preserved in memory. Multiple named selections can be kept in memory simultaneously. It is possible to copy the current selection to a named selection, or temporary selection. This is a copy of the selection table which is kept in memory, where each record takes up 4 bytes of memory space.
- This selection will remain sorted.
- It is also named, as a set would be named.
- It maintains a current record pointer.
- There is one selection for each process in each file.
- With 4D Server a temporary (saved) selection can be local or global, but it can only belong to a single user.
The exception to the 4 bytes per record rule is a selection that was created with ALL RECORDS. This command is optimized in 4D by storing an exception table that contains the addresses of the records that have been deleted (usually this will be less than the number of active records.
There are four commands that an be used to manipulate named selections:
COPY NAMED SELECTION
CUT NAMED SELECTION
USE NAMED SELECTION
CLEAR NAMED SELECTION