Re: [HACKERS] recover corrupted pg_controldata from WAL
Hi Tom I agree that it is wrong to use the information from the file name itself. I will try to read the xlp_pageaddr out from the segment header to figure out which one is the lastest one. In the mutilple time lines scenario, if the pg_control file crashed, and the current time line information will be lost. Altough we can let the user the select the possible time line, but the implementation until now is using the highest time line number. --- Tom Lane [EMAIL PROTECTED] wrote: yuanjia lee [EMAIL PROTECTED] writes: The algorithm of searching the WAL is like this: 1. Read name of the segment files from xlog directory, and put all of their name into an one way list, the list is descending according to the time line, xlog id, segement id. (Athough I use only the lastest file in the implementation, but the list can be used for the feature like dump log in future.) You do realize that in most situations, the segment files with the newest-looking names have not been used yet, and contain older rather than newer data? When multiple timelines are present, I'm not sure I care for the heuristic use the highest timeline number, either. regards, tom lane Start your day with Yahoo! - make it your home page http://www.yahoo.com/r/hs ---(end of broadcast)--- TIP 9: In versions below 8.0, the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match
[HACKERS] recover corrupted pg_controldata from WAL
Hi, All I am preparing to enhance the pg_resetlog to support recover corrupted pg_control data from WAL. I had finised the code now and testing it, but before I bring it out for patch review, I want to discuss some issues here to get some advice. The functionality of reset the xlog is the same as before, except for extracting the exactly information from WAL. I also had added a new option to recovery the pg_control file only but not to touch the xlog files. My question is that should we separate the funtionality of recovery the pg_control file and reset log? I am questioning about should we make a new name instead of pg_resetlog, we can use the name like pg_xlog and put the funtionalities (like reset log, recovery pg_control file, dump binary log) into the same tool. The algorithm of searching the WAL is like this: 1. Read name of the segment files from xlog directory, and put all of their name into an one way list, the list is descending according to the time line, xlog id, segement id. (Athough I use only the lastest file in the implementation, but the list can be used for the feature like dump log in future.) 2. Scan the records from the beginning of the latest segement file, if checkpoint is found then update the lastcheckpoint information. One concern for just using the last segement file is that, in some situation, the last checkpoint record may not in the last segement file but in the prevoius segement file of last segement file, this is the limitation. Although I can search from the prevoius segement file of last segement file, but the implementation now just using the last segement file. Regards Yuanjia Lee Start your day with Yahoo! - make it your home page
Re: [HACKERS] recover corrupted pg_controldata from WAL
I cant contribute with any technical advice, but as a user I had to resort to using pg_resetxlog few times. I wonder if it is possible to make it more user-friendly. It was never clear to me whether it was sufficient to run it without any arguments, and if not what these arguments should be. Perhaps at the minimum the help option could be extended? Thank you, Mike From: yuanjia lee [mailto:[EMAIL PROTECTED] Sent: Thursday, July 21, 2005 7:09 AM To: pgsql-hackers@postgresql.org Subject: [HACKERS] recover corrupted pg_controldata from WAL Hi, All I am preparing to enhance the pg_resetlog to support recover corrupted pg_control data from WAL. I had finised the code now and testing it, but before I bring it out for patch review, I want to discuss some issues here to get some advice. .. Regards Yuanjia Lee
Re: [HACKERS] recover corrupted pg_controldata from WAL
yuanjia lee [EMAIL PROTECTED] writes: The algorithm of searching the WAL is like this: 1. Read name of the segment files from xlog directory, and put all of their name into an one way list, the list is descending according to the time line, xlog id, segement id. (Athough I use only the lastest file in the implementation, but the list can be used for the feature like dump log in future.) You do realize that in most situations, the segment files with the newest-looking names have not been used yet, and contain older rather than newer data? When multiple timelines are present, I'm not sure I care for the heuristic use the highest timeline number, either. regards, tom lane ---(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
