-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 07/31/2011 12:58 PM, Simon Slavin wrote: > Datestamp every value (document) and whichever one has the lastest date is > the one you want.
That isn't always the correct approach and requires clocks to be synchronized - something that is challenging when peers get disconnected for periods, and can be fairly crappy devices. CouchDB does not use timestamps - - instead a DAG is built using revisions where the revision is derived from the MD5 of the document so it is completely unambiguous. None of the DVCS use timestamps either because they are more fragile and less "truthful". > One reason multi-master replication of SQL databases is hard to do properly You can't do multi-master replication in general with SQL because SQL requires transactions which means every peer has to agree. Additionally because data for any one logical item is scattered across several tables and rows you can't just use table granularity. Even sharding requires a lot of coordination. *If* you are prepared to have looser transactions and you know your data well then various things can be hacked together. But at that point you are effectively re-implementing what the various document/key-value store databases provide builtin. It is notable that SQL and the relational model are not used for the newer database implementations. UnQL appears to be an attempt to shoehorn SQL like syntax into another new database, but I'm very sceptical it will go anywhere - note how many have been developed and are in use without SQL syntax holding back adoption. Obligatory: One size does not fit all, no one piece of software is perfect, different solutions for different problems, developers and administrators make decisions for themselves, you can mangle many pieces of softwares to behave like other software etc Roger -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) iEYEARECAAYFAk41yoMACgkQmOOfHg372QTn+QCgvuU5aprsjm+0MAsP2tKPdQ46 hX4AnjWA47mwoVJRkEIpqX8jnlG3h5mE =8AD6 -----END PGP SIGNATURE----- _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
