Physical ODS Changes for ODS 12

Posted to the Firebird Development list by Dimitry Yeamanov:

Below is the initial proposal (to be corrected/extended by others) that
describes the physical ODS changes we'd like to see in ODS 12.

Header page

* rework implementation ID to simplify the porting split into endianness and swap_double flags?)

* deprecate page buffers and sweep interval (in favor of the per-database values defined in .conf)


Pointer page / data page

* add "swept" flag
(allows to skip pages that have no dead or backversions, thus improving the GC / sweep performance)

Page inventory page

* use its own field instead of common "pag::reserved" (related to the misuse by PAG_allocate() happened in ODS 11.1)

New page type (bitmap?) to link SCNs to page numbers.
This may noticeably improve the incremental NBackup performance, avoiding reading pages not changed since the last backup.

Switch from SLONG to ULONG for transaction numbers and page numbers.

Extend blob length field from ULONG to UINT64 (and maybe allow blob levels higher than 2?).

Consider better alternative (instead of SQZ) for record compression.
Tests are required.
If not found, extend SQZ for sequences longer than 127 bytes.

Consider better packing of index key data (record numbers) and compound index keys (described by Jim in fb-architect).
Tests are required.
Extend the ACL format to cover new permission types and objects.

Additions are welcome, as well as questions/comments re. the
aforementioned items.