(I sent this to -docs already, but it didn't get through for some reason.) >From the current 8.3 docs:
Section 24.3.3.1 states about restore_command: "The command will be asked for file names that are not present in the archive; it must return nonzero when so asked." Section 24.4.1 further states: "The magic that makes the two loosely coupled servers work together is simply a restore_command used on the standby that waits for the next WAL file to become available from the primary." It is not clear from the first paragraph, whether the non-existing file that restore_command is being asked for is a not-yet-generated WAL file or something different. If it was a not-yet-generated WAL file, restore_command for replication would have to wait for it to appear. If it was something different, restore_command for replication would have to return an error right away. (Because else it would hang indefinitely, waiting for a file that is not going to appear). Yet I couldn't find hints in the documentation as to how these two cases can be detected by restore_command, i.e. how restore_command should tell a request for a WAL file from a request for a non-WAL file. Practice (http://archives.postgresql.org/sydpug/2006-10/msg00001.php) shows that this is a problem, and people use unproved heuristics ('history' substring in the requested file name). Additionally, 24.3.3 contains slightly misleading information: "It is important that the command return nonzero exit status on failure. The command will be asked for log files that are not present in the archive; it must return nonzero when so asked. This is not an error condition." This suggests that all non-existing files that restore_command will be asked for are log files. One could therefore reasonably assume that restore_command for replication should wait on all non-existing files. 24.3.3.1 later corrects this by stating that not only log files may be requested, but nevertheless. Markus ---------------------------(end of broadcast)--------------------------- TIP 1: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly
