Delete records in a random file

[SMcNeill]

Let me give you the world's most hidden secret in how to delete files from a database:

Code: (Select All)

Type Warenposten
  invalid As _BYTE
  nummer As String * 4
  artikel As String * 10
  preis As Double
End Type

Now, compare that to what you have in your own code above. See the extra entry?

With a flip of that single byte in each record, you can flag a record as being "deleted" or "invalid".... And, most amazingly, since the record is still there -- just flagged "invalid" -- you can now also add an option to "undelete" and validate that record once again!

Yo just built a RECYCLE BIN into your database! That's all it takes to expand that random record that much!

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Now, if you want to PACK the database, or PURGE deleted files, all you do is basically write a short routine to run the length of the database:

FOR i = 1 TO Record_Length
GET #1,i, record
IF record(i).invalid THEN
'skip record
ELSE
PUT #2, ,record
END IF
NEXT

Copy all the records from the old database over to a new database, as long as that "invalid" flag hasn't been set for them.

It's much more efficient than trying to rebuild/reindex the database with every "delete", and you have the option of scheduling it for times when the user isn't using the database for anything else. (Like a 2AM repacking time every Sunday night...)