Re: Sync Rep: First Thoughts on Code

Markus Wanner wrote:<br /><blockquote cite="mid:494421B1.7040707@bluegap.ch" type="cite"><pre wrap="">Tom Lane wrote:
</pre><blockquotetype="cite"><pre wrap="">We won't call it anything, because we never will or can implement that.
 
See the theory of relativity: the notion of exactly simultaneous events
at distinct locations isn't even well-defined   </pre></blockquote><pre wrap="">
That has never been the point of the discussion. It's rather about the
question if changes from transactions are guaranteed to be visible on
remote nodes immediately after commit acknowledgment. Whether or not
this is guaranteed, in both cases the term "synchronous replication" is
commonly used, which is causing confusion. </pre></blockquote><br /> Might it not be true that anybody unfamiliar would
beconfused and that this is a bit of a straw man?<br /><br /> I don't think synchronous replication guarantees that it
willbe immediately visible. Even if it did push the change to the other machine, and the other machine had committed
it,that doesn't guarantee that any reader sees it any more than if I commit to the same machine (no replication), I am
guaranteedto see the change from another session. Synchronous replication only means that I can be assured that my
changehas been saved permanently by the time my commit completes. It doesn't mean anybody else can see my change or is
guaranteedto see my change if the query from another session.<br /><br /> If my application assumes that it can commit
toone server, and then read back the commit from another server, and my application breaks as a result, it's because I
didn'tunderstand the problem. Even if PostgreSQL didn't use the word "synchronous replication", I could still be
confused.I need to understand the problem no matter what words are used.<br /><br /> Cheers,<br /> mark<br /><br /><pre
class="moz-signature"cols="72">-- 
 
Mark Mielke <a class="moz-txt-link-rfc2396E" href="mailto:mark@mielke.cc"><mark@mielke.cc></a>
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