16.01.2017 19:42, Dmitry Yemanov wrote: > But I fail to see how these ideas are > going to work for table format changes. How would records be stored > accordingly to the "virtual" formats? How are formats going to be > uniquely (but without gaps!) numbered across uncommitted transactions?
Why "without gaps"? In my vision the first step is to modify garbage collector/sweeper to clean unused formats out. In this case new formats can fill the gaps the same way as this can be done with ordinary records in ordinary table: try first free - get conflict - try next. DDL is not so frequent operation to get high tension here. > How concurrent readers should access/skip physically stored records if > their format is unknown/invisible for them? If they can read records, they can read formats. Careful writes should take care to write format before any data - no difference from ordinary master-detail relationship. Garbage collector should be clever enough to wipe data before metadata. -- WBR, SD. ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot Firebird-Devel mailing list, web interface at https://lists.sourceforge.net/lists/listinfo/firebird-devel
