On 2013-10-15 10:15:14 -0400, Robert Haas wrote: > On Tue, Oct 15, 2013 at 9:47 AM, Andres Freund <and...@2ndquadrant.com> wrote: > > On 2013-10-15 15:17:58 +0200, Andres Freund wrote: > >> If we go for CSV I think we should put the entire primary key as one > >> column (containing all the columns) and the entire row another. > > > > What about columns like: > > * action B|I|U|D|C > > BEGIN and COMMIT?
That's B and C, yes. You'd rather not have them? When would you replay the commit without an explicit message telling you to? > Repeating the column names for every row strikes me as a nonstarter. > [...] > Sure, some people may want JSON or XML > output that reiterates the labels every time, but for a lot of people > that's going to greatly increase the size of the output and be > undesirable for that reason. But I argue that most simpler users - which are exactly the ones a generic output plugin is aimed at - will want all column names since it makes replay far easier. > If the plugin interface isn't rich enough to provide a convenient way > to avoid that, then it needs to be fixed so that it is, because it > will be a common requirement. Oh, it surely is possibly to avoid repeating it. The output plugin interface simply gives you a relcache entry, that contains everything necessary. The output plugin would need to keep track of whether it has output data for a specific relation and it would need to check whether the table definition has changed, but I don't see how we could avoid that? > > What still need to be determined is: > > * how do we separate and escape multiple values in one CSV column > > * how do we represent NULLs > > I consider the escaping a key design decision. Ideally, it should be > something that's easy to reverse from a scripting language; ideally > also, it should be something similar to how we handle COPY. These > goals may be in conflict; we'll have to pick something. Note that parsing COPYs is a major PITA from most languages... Perhaps we should make the default output json instead? With every action terminated by a nullbyte? That's probably easier to parse from various scripting languages than anything else. Greetings, Andres Freund -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
