Re: [HACKERS] Commitfest Status: Sudden Death Overtime
On Thu, 2011-07-21 at 00:21 +0200, Florian Pflug wrote: There's a small additional concern, though, which is that there's an XPath 2.0 spec out there, and it modifies the type system and data model rather heavily. So before we go adding functions, it'd probably be wise to check that we're not painting ourselves into a corner. Why not just write XPATH2() function conforming to XPath 2.0 spec if the new spec is substancially different ? -- --- Hannu Krosing PostgreSQL Infinite Scalability and Performance Consultant PG Admin Book: http://www.2ndQuadrant.com/books/ -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] Commitfest Status: Sudden Death Overtime
[ having now read the relevant threads a bit more carefully ... ] Florian Pflug f...@phlo.org writes: On Jul18, 2011, at 22:19 , Tom Lane wrote: Yeah, it's not clear to me either which of those are still reasonable candidates for committing as-is. There are actually three XML-related patches from me in the queue. I'll try to give an overview of their states - as perceived by me, of course. If people want to comment on this, I suggest to do that that either on the existing threads from these patches or on new ones, but not on this one - lest confusion ensues. * Bugfix for XPATH() if text or attribute nodes are selected https://commitfest.postgresql.org/action/patch_view?id=580 Makes XPATH() return valid XML if text or attribute are selected. I'm not aware of any issues with that one, other than Radoslaw's unhappiness about the change of behaviour. Since the current behaviour is very clearly broken (as in dump, reload, ka-Woom), I'm not prepared to accept that as a show-stopper. I think we ought to apply this one. I agree that returning invalid XML is not acceptable. * Bugfix for XPATH() if expression returns a scalar value https://commitfest.postgresql.org/action/patch_view?id=565 Makes XPATH() support XPath expressions which compute a scalar value, not a node set (i.e. apply a top-level function such as name()). Currently, we return an empty array in that case. Peter Eisentraut initially seemed to prefer creating separate functions for that (XPATH_STRING, ...). I argued against that, on the grounds that that'd make it impossible to evaluate user-supplied XPath expression (since you wouldn't know which function to use). I haven't heard back from him after that argument. I find your argument against XPATH_STRING() a bit unconvincing. The use case for that is not where you are trying to evaluate an unknown, arbitrary XPath expression; it's where you are evaluating an expression that you *know* returns string (ie, it has name() or some other string returning function at top level) and you'd like a string, thanks, not something that you have to de-escape in order to get a string. Of course this use-case could also be addressed by providing a de-escape function, but I don't really think that de_escape(xpath(...)[1]) is a particularly friendly or efficient notation. Now, these statements are not arguments against the patch --- as is, XPATH() is entirely useless for expressions that return scalars, and with the patch it at least does something usable. So I think we should apply it. But there is room here for more function(s) to provide more convenient functionality for the special case of expressions returning strings. I'd be inclined to provide xpath_number and xpath_bool too, although those are less essential since a cast will get the job done. There's some code-style aspects I don't care for in the submitted patch, but I'll go clean those up and commit it. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] Commitfest Status: Sudden Death Overtime
On Jul20, 2011, at 23:35 , Tom Lane wrote: I find your argument against XPATH_STRING() a bit unconvincing. The use case for that is not where you are trying to evaluate an unknown, arbitrary XPath expression; it's where you are evaluating an expression that you *know* returns string (ie, it has name() or some other string returning function at top level) and you'd like a string, thanks, not something that you have to de-escape in order to get a string. Hm, maybe I didn't make myself clear. I'm not against having special-case functions like XPATH_STRING() at all, as long as there's a general-purpuse function like XPATH() that deal with every expression you throw at it. There's a small additional concern, though, which is that there's an XPath 2.0 spec out there, and it modifies the type system and data model rather heavily. So before we go adding functions, it'd probably be wise to check that we're not painting ourselves into a corner. Of course this use-case could also be addressed by providing a de-escape function, but I don't really think that de_escape(xpath(...)[1]) is a particularly friendly or efficient notation. Yeah, that's pretty ugly. Having XMLESCAPE/XMLUNESCAPE (with types TEXT - XML and XML - TEXT) would probably still be a good idea though, even if it no replacement for XPATH_STRING(). Now, these statements are not arguments against the patch --- as is, XPATH() is entirely useless for expressions that return scalars, and with the patch it at least does something usable. So I think we should apply it. Cool, so we're on the same page. But there is room here for more function(s) to provide more convenient functionality for the special case of expressions returning strings. I'd be inclined to provide xpath_number and xpath_bool too, although those are less essential since a cast will get the job done. No objection here. I do have a number of XML-related stuff that I'd like to do for 9.2, actually. I'll write up a proposal once this commit-fest is over, and I'll include XPATH_STRINGS and friends. There's some code-style aspects I don't care for in the submitted patch, but I'll go clean those up and commit it. I'd offer to fix them, but I somehow have the feeling that you're already in the middle of it ;-) best regards, Florian Pflug -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] Commitfest Status: Sudden Death Overtime
Florian Pflug f...@phlo.org writes: There's a small additional concern, though, which is that there's an XPath 2.0 spec out there, and it modifies the type system and data model rather heavily. So before we go adding functions, it'd probably be wise to check that we're not painting ourselves into a corner. Good point. Has anybody here looked at that? regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] Commitfest Status: Sudden Death Overtime
On 2011-07-18 21:59, Robert Haas wrote: There are only two patches left and I think we really ought to try to take a crack at doing something with them. Yeb is working on the userspace access vector cache patch, which I think is going drag on longer than we want keep the CommitFest open, but I'm OK with giving it a day or two to shake out. At the end if this day I'm nearing the 'my head a splode' moment, which is more caused by trying to get my brain around selinux and it's postgresql policy, than the actual patch to review. I've verified that the patch works as indicated by KaiGai-san, but reading and understanding the code to say anything useful about it will take a few more hours, which will be tomorrow. regards, Yeb -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] Commitfest Status: Sudden Death Overtime
Robert Haas robertmh...@gmail.com writes: On Mon, Jul 18, 2011 at 4:19 PM, Tom Lane t...@sss.pgh.pa.us wrote: If you mean the business about allowing GUCs in postgresql.conf to be applied even if there are semantic errors elsewhere, I'm just as happy to let Alexey or Florian have a go at it first, if they want. The real question at the moment is do we have consensus about changing that? Because if we do, the submitted patch is certainly not something to commit as-is, and should be marked Returned With Feedback. I'm not totally convinced. The proposed patch is pretty small, and seems to stand on its own two feet. I don't hear anyone objecting to your proposed plan, but OTOH it doesn't strike me as such a good plan that we should reject all other improvements in the meantime. Maybe I'm missing something... To me, the proposed patch adds another layer of contortionism on top of code that's already logically messy. I find it pretty ugly, and would prefer to try to simplify the code before not after we attempt to deal with the feature the patch wants to add. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] Commitfest Status: Sudden Death Overtime
Excerpts from Tom Lane's message of mar jul 19 12:09:24 -0400 2011: Robert Haas robertmh...@gmail.com writes: On Mon, Jul 18, 2011 at 4:19 PM, Tom Lane t...@sss.pgh.pa.us wrote: If you mean the business about allowing GUCs in postgresql.conf to be applied even if there are semantic errors elsewhere, I'm just as happy to let Alexey or Florian have a go at it first, if they want. The real question at the moment is do we have consensus about changing that? Because if we do, the submitted patch is certainly not something to commit as-is, and should be marked Returned With Feedback. I'm not totally convinced. The proposed patch is pretty small, and seems to stand on its own two feet. I don't hear anyone objecting to your proposed plan, but OTOH it doesn't strike me as such a good plan that we should reject all other improvements in the meantime. Maybe I'm missing something... To me, the proposed patch adds another layer of contortionism on top of code that's already logically messy. I find it pretty ugly, and would prefer to try to simplify the code before not after we attempt to deal with the feature the patch wants to add. +1. Alexey stated that he would get back on this patch for reworks. -- Álvaro Herrera alvhe...@commandprompt.com The PostgreSQL Company - Command Prompt, Inc. PostgreSQL Replication, Consulting, Custom Development, 24x7 support -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] Commitfest Status: Sudden Death Overtime
On Fri, Jul 15, 2011 at 5:05 PM, Josh Berkus j...@agliodbs.com wrote: As you can probably tell, we are not ready to end the commitfest. (I think Robert gave me this CF to show why even talking about a one-week mini-fest is a fantasy. If so, successful.). Heh, heh. Well, it wasn't that premeditated, but I'm always glad to reach a meeting of the minds. :-) These are complex and need review by advanced hackers. They are also often interdependant. As such, I'd like to automatically move his patches to the next CF and ask that hackers who are engaged in working on them continue to do so between CFs. There are only two patches left and I think we really ought to try to take a crack at doing something with them. Yeb is working on the userspace access vector cache patch, which I think is going drag on longer than we want keep the CommitFest open, but I'm OK with giving it a day or two to shake out. Aside from the benefit of reviewing the actual patch, I see that Yeb is pushing on KaiGai to do further work on the documentation, which I think is of great value. I will review the other patch - on shared object labels - RSN. PATCHES WHICH I MOVED TO THE NEXT CF 9-2011: * Collect frequency statistics and selectivity estimation for arrays * Allow multiple Postgres clusters running on the same machine to distinguish themselves in the event log * lazy vxid locks I'm not clear on your criteria for moving these patches, as they seem to be in somewhat different states. The first one is WIP, and it doesn't really matter whether you move it to the next CommitFest or just mark it returned with feedback. There is active development work going on there, so it's not going to get committed at this point. But the other two are basically just things we didn't get around to reviewing. With respect to the lazy vxid lock patch, it looks to me like Jeff has done a bit of review, and I think the real question here is whether or not we want to go ahead and make that change (with some stylistic and cosmetic corrections) or wait until we have a more complex solution to the spinlock contention problems mapped out. On a pgbench run with 8 clients on a 32-core machine, I see about a 2% speedup from that patch on pgbench -S, and it grows to 8% at 32 clients. At 80 clients (but still just a 32-core box), the results bounce around more, but taking the median of three five-minute runs, it's an 11% improvement. To me, that's enough to make it worth applying, especially considering that what is 11% on today's master is, in raw TPS, equivalent to maybe 30% of yesterday's master (prior to the fast relation lock patch being applied). More, it seems pretty clear that this is the conceptually right thing to do, even if it's going to require some work elsewhere to file down all the rough edges thus exposed. If someone objects to that, then OK, we should talk about that: but so far I don't think anyone has expressed strong opposition: in which case I'd like to fix it up and get it in. With respect to the event-log patch, MauMau has resubmitted that to the next CommitFest, so that's fine as far as it goes. But it might make sense to see if we can twist Magnus's arm into re-reviewing it now while it's fresh in his mind, rather than waiting another two or three months. PATCHES WHICH HAVE BEEN UPDATED AND NEED FURTHER REVIEW: * Cascade Replication No update. PATCHES STILL UNDER ACTIVE DISCUSSION: * Add ability to constrain backend temporary file space Now committed, by Tom. PATCHES I CAN'T FIGURE OUT THE STATUS OF: * pg_comments system view I reviewed this and marked it Returned with Feedback. * Bugfix for XPATH() if expression returns a scalar value No update. So, down to a fairly limited list, except that we need a lot of committing. We're down to three patches that fall into this category: two XML patches by Florian, which have been somewhat derailed by an argument about whether values of type xml should, in fact, be required to be valid xml (I think you know my vote on this one...); and an error-reporting patch that Tom weighed in on over the weekend. This last suffers from the issue that it's not quite clear whether Tom is going to do the work or whether he's expecting the submitter to do it. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] Commitfest Status: Sudden Death Overtime
On Fri, Jul 15, 2011 at 10:05 PM, Josh Berkus j...@agliodbs.com wrote: PATCHES WHICH HAVE BEEN UPDATED AND NEED FURTHER REVIEW: * Cascade Replication Sorry, too busy reviewing to take note of this. I expect to commit when its tested and ready. -- Simon Riggs 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
Re: [HACKERS] Commitfest Status: Sudden Death Overtime
Robert Haas robertmh...@gmail.com writes: We're down to three patches that fall into this category: two XML patches by Florian, which have been somewhat derailed by an argument about whether values of type xml should, in fact, be required to be valid xml (I think you know my vote on this one...); Yeah, it's not clear to me either which of those are still reasonable candidates for committing as-is. and an error-reporting patch that Tom weighed in on over the weekend. This last suffers from the issue that it's not quite clear whether Tom is going to do the work or whether he's expecting the submitter to do it. If you mean the business about allowing GUCs in postgresql.conf to be applied even if there are semantic errors elsewhere, I'm just as happy to let Alexey or Florian have a go at it first, if they want. The real question at the moment is do we have consensus about changing that? Because if we do, the submitted patch is certainly not something to commit as-is, and should be marked Returned With Feedback. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] Commitfest Status: Sudden Death Overtime
Simon, * Cascade Replication Sorry, too busy reviewing to take note of this. I expect to commit when its tested and ready. So, would that be this commitfest, or next commitfest? -- Josh Berkus PostgreSQL Experts Inc. http://pgexperts.com -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] Commitfest Status: Sudden Death Overtime
Robert, * Collect frequency statistics and selectivity estimation for arrays * Allow multiple Postgres clusters running on the same machine to distinguish themselves in the event log * lazy vxid locks I'm not clear on your criteria for moving these patches, as they seem to be in somewhat different states. For the array criteria, it took me until the last week of the CF to find a reviewer. That reviewer found a number of issues, and the submitter submitted an updated patch. It looks quite likely that work on that patch will get updated in the next couple weeks but not immediately. For the eventlog, MauMau had submitted an updated patch, but all of our Windows hackers had let me know that they were unavailable for the next couple weeks for review or commit. For lazy VXID locks, I'd the impression that we had an ongoing discussion about whether we were going to apply it or not, and you were on vacation for the last week of the CF. -- Josh Berkus PostgreSQL Experts Inc. http://pgexperts.com -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] Commitfest Status: Sudden Death Overtime
On Mon, Jul 18, 2011 at 4:19 PM, Tom Lane t...@sss.pgh.pa.us wrote: and an error-reporting patch that Tom weighed in on over the weekend. This last suffers from the issue that it's not quite clear whether Tom is going to do the work or whether he's expecting the submitter to do it. If you mean the business about allowing GUCs in postgresql.conf to be applied even if there are semantic errors elsewhere, I'm just as happy to let Alexey or Florian have a go at it first, if they want. The real question at the moment is do we have consensus about changing that? Because if we do, the submitted patch is certainly not something to commit as-is, and should be marked Returned With Feedback. I'm not totally convinced. The proposed patch is pretty small, and seems to stand on its own two feet. I don't hear anyone objecting to your proposed plan, but OTOH it doesn't strike me as such a good plan that we should reject all other improvements in the meantime. Maybe I'm missing something... -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] Commitfest Status: Sudden Death Overtime
On Jul18, 2011, at 22:19 , Tom Lane wrote: Robert Haas robertmh...@gmail.com writes: We're down to three patches that fall into this category: two XML patches by Florian, which have been somewhat derailed by an argument about whether values of type xml should, in fact, be required to be valid xml (I think you know my vote on this one...); Yeah, it's not clear to me either which of those are still reasonable candidates for committing as-is. There are actually three XML-related patches from me in the queue. I'll try to give an overview of their states - as perceived by me, of course. If people want to comment on this, I suggest to do that that either on the existing threads from these patches or on new ones, but not on this one - lest confusion ensues. * Bugfix for XPATH() if text or attribute nodes are selected https://commitfest.postgresql.org/action/patch_view?id=580 Makes XPATH() return valid XML if text or attribute are selected. I'm not aware of any issues with that one, other than Radoslaw's unhappiness about the change of behaviour. Since the current behaviour is very clearly broken (as in dump, reload, ka-Woom), I'm not prepared to accept that as a show-stopper. The question about whether values of type XML should or should not be in fact valid XML is a red herring. That question has long ago been settles by the XML type's input function, which has a pretty clear and consistent idea about what constitutes a valid value of type XML. The patch simply makes XPATH() abide by those rules, instead of making up rules of it's own pretty nilly-willy. * Bugfix for XPATH() if expression returns a scalar value https://commitfest.postgresql.org/action/patch_view?id=565 Makes XPATH() support XPath expressions which compute a scalar value, not a node set (i.e. apply a top-level function such as name()). Currently, we return an empty array in that case. Peter Eisentraut initially seemed to prefer creating separate functions for that (XPATH_STRING, ...). I argued against that, on the grounds that that'd make it impossible to evaluate user-supplied XPath expression (since you wouldn't know which function to use). I haven't heard back from him after that argument. Radoslaw liked the patch, but wanted the quoting removed - same theme as with the other patch. * XML error handling improvement to fix XPATH bug https://commitfest.postgresql.org/action/patch_view?id=579 Like that first patch, it fixes a bug where XPATH() returns invalid XML. The cause is completely different though. Here, libxml is (partially) at fault - it's parsing methods always return a document instance if a document is *structurally* valid, even if it contains semantic error like invalid namespace references. But it isn't fully prepared to actually handle these inconsistent documents - for example, when asked to render a namespace URI as text, it unconditionally assumes it doesn't have to escape it, because it may not contain special characters anway. Which, if course, isn't necessarily true for structurally valid but semantically invalid documents... valid... Fixing that wasn't possible without a major rewrite of the XML support's error handling - one must use the modern version of libxml's error handling infrastructure to actually be able to detect these semantic error reliably and distinguish them from mere warnings. Noah Misch has reviewed that patch pretty extensively (Thanks again, Noah!), and I've resolved all his concerns regarding the implementation. I haven't seen a single argument *against* applying this so far. best regards, Florian Pflug -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] Commitfest Status: Sudden Death Overtime
On Jul18, 2011, at 22:19 , Tom Lane wrote: and an error-reporting patch that Tom weighed in on over the weekend. This last suffers from the issue that it's not quite clear whether Tom is going to do the work or whether he's expecting the submitter to do it. If you mean the business about allowing GUCs in postgresql.conf to be applied even if there are semantic errors elsewhere, I'm just as happy to let Alexey or Florian have a go at it first, if they want. The real question at the moment is do we have consensus about changing that? Because if we do, the submitted patch is certainly not something to commit as-is, and should be marked Returned With Feedback. Just to avoid false expectations here: I'd be happy to review further versions of this patch, but I won't write them. best regards, Florian Pflug -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] Commitfest Status: Sudden Death Overtime
On Mon, 2011-07-18 at 15:59 -0400, Robert Haas wrote: On a pgbench run with 8 clients on a 32-core machine, I see about a 2% speedup from that patch on pgbench -S, and it grows to 8% at 32 clients. At 80 clients (but still just a 32-core box), the results bounce around more, but taking the median of three five-minute runs, it's an 11% improvement. To me, that's enough to make it worth applying, especially considering that what is 11% on today's master is, in raw TPS, equivalent to maybe 30% of yesterday's master (prior to the fast relation lock patch being applied). More, it seems pretty clear that this is the conceptually right thing to do, even if it's going to require some work elsewhere to file down all the rough edges thus exposed. If someone objects to that, then OK, we should talk about that: but so far I don't think anyone has expressed strong opposition: in which case I'd like to fix it up and get it in. Agreed. I certainly like the concept of the lazy vxid patch. Regards, Jeff Davis -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] Commitfest Status: Sudden Death Overtime
On Jul15, 2011, at 23:05 , Josh Berkus wrote: * Bugfix for XPATH() if expression returns a scalar value Well, Peter Eisentraut seemed to disagree with my approach initially, and seemed to prefer a separate function for XPATH expressions which return a scalar value. http://archives.postgresql.org/pgsql-hackers/2011-06/msg00401.php I considered that, but came to the conclusion that it has problems of it's own, described here: http://archives.postgresql.org/pgsql-hackers/2011-06/msg00608.php Peter stopped responding at that point, so I assumed that my argument convinced him. Radoslaw complained about the fact the results of scalar values come back escaped from XPATH() with the patch applied (without it, an empty array is returned) and wanted that changed - Basically the same objection he had to my other patch which made sure text nodes are properly escaped (The fine print here is that text nodes *aren't* scalar values, they're nodes. What fun.). He did upgrade that other patch to Ready for Committer despite his objections, though. I don't know whether he wanted to do the same with this one or not, and my inquiry was left unanswered http://archives.postgresql.org/pgsql-hackers/2011-07/msg00783.php I also don't know much code review the patch has received. I didn't receive any complaints, but whether that reflects the quality of the patch or the quantity of review I leave for someone else to judge. I dunno what the best way forward is, but I'd hate to see this being bumped to the next commit-fest. best regards, Florian Pflug -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
