Large index files over 4GB length in DBFs
Posted: Fri Oct 17, 2014 4:32 pm
2014-10-17 14:55 UTC+0200 Przemyslaw Czerpak (druzus/at/poczta.onet.pl)
+ added support for large index files over 4GB length.
These are slightly modified CDX indexes which stores index page numbers
instead of index page offsets inside index file. This trick increase
maximum index files size from 2^32 (4GB) to 2^41 (2TB). This index
format is enabled automatically when DB_DBFLOCK_HB64 is used. This is
the same behavior as in DBFNTX and DBFNSX for which I added support
for large indexes (up to 4TB) few years ago.
Warning: new CDX indexes are not backward compatible and cannot be
read by other systems or older [x]Harbour versions.
If you try to open new indexes using older [x]Harbour RDDs
then RTE "DBFCDX/1012 Corruption detected" is generated.
When current Harbour *DBFCDX/SIXCDX RDD open index file
then it automatically recognize type of index file so it
will work correctly with both versions without any problem.
In short words: People using DB_DBFLOCK_HB64 should remember
that after reindexing with new Harbour applications old ones
cannot read new CDX indexes.
; In next step I plan to add support for user defined page size in CDX
* added information about extended CDX format to section "NATIVE RDDs"
* disable record readahead buffer used during indexing when only
one record can be stored inside
! generate RTE when data cannot be read into record readahead buffer