Re: [HACKERS] A few user-level questions on Streaming Replication and pg_upgrade
On Tue, Jul 19, 2011 at 8:45 PM, Bruce Momjian br...@momjian.us wrote: Gurjeet Singh wrote: [ CC to general removed --- emailing only hackers; cross-posting is frowned upon. ] I thought these questions were of interest to the general public too. .) Is Streaming Replication supported across minor releases, in reverse direction; e.g. 9.0.3 to 9.0.1 I think the answer is it depends, since it would depend upon whether any SR related bug has been fixed in the 'greater' of the minor releases. I am assuming that smaller minor release to bigger minor release will always be supported (e.g. 9.0.1 to 9.0.3) Yes. I am assuming that's a yes to both the directions: older - newer , and newer - older minor releases. We could mention in the minor release notes if we break streaming replication for a minor release --- or someone will tell us when we do. I am pretty sure the Postgres community would notify its user base via release notes. .) How reliable is `pg_upgrade -c` (dry run) currently; that is, how accurate is pg_upgrade at predicting any potential problem with the eventual in-place upgrade. I'd say it is as reliable as it gets since this is the official tool supported by the project, and it should not contain any known bugs. One has to use the latest and greatest 'minor' version of the tool for the major release they are upgrading to, though. Well, we make no guarantees about the software at all, so it is hard to make any guarantee about pg_upgrade either. :) Given the BSD-style license, that's a fair point. Thanks, -- Gurjeet Singh EnterpriseDB Corporation The Enterprise PostgreSQL Company
Re: [HACKERS] A few user-level questions on Streaming Replication and pg_upgrade
Gurjeet Singh wrote: On Tue, Jul 19, 2011 at 8:45 PM, Bruce Momjian br...@momjian.us wrote: Gurjeet Singh wrote: [ CC to general removed --- emailing only hackers; cross-posting is frowned upon. ] I thought these questions were of interest to the general public too. What I usually do is to discuss on hackers and post a summary of information 'general' would find interesting. .) Is Streaming Replication supported across minor releases, in reverse direction; e.g. 9.0.3 to 9.0.1 I think the answer is it depends, since it would depend upon whether any SR related bug has been fixed in the 'greater' of the minor releases. I am assuming that smaller minor release to bigger minor release will always be supported (e.g. 9.0.1 to 9.0.3) Yes. I am assuming that's a yes to both the directions: older - newer , and newer - older minor releases. Yes, I believe both directions would work unless we mentioned it the release notes, in which cases it might not work, or might work older to newer but newer to older. We could mention in the minor release notes if we break streaming replication for a minor release --- or someone will tell us when we do. I am pretty sure the Postgres community would notify its user base via release notes. We will if we know it, but it is possible to have rare cases where we don't find out until after the minor release. .) How reliable is `pg_upgrade -c` (dry run) currently; that is, how accurate is pg_upgrade at predicting any potential problem with the eventual in-place upgrade. I'd say it is as reliable as it gets since this is the official tool supported by the project, and it should not contain any known bugs. One has to use the latest and greatest 'minor' version of the tool for the major release they are upgrading to, though. Well, we make no guarantees about the software at all, so it is hard to make any guarantee about pg_upgrade either. :) Given the BSD-style license, that's a fair point. I just found out, thanks to EnterpriseDB testing, that pg_upgrade -l doesn't work on Windows. I will post the fix in an hour for all released versions of pg_upgrade. You will find it entertaining that -l works in check mode but not in actual upgrade mode. -- Bruce Momjian br...@momjian.ushttp://momjian.us EnterpriseDB http://enterprisedb.com + It's impossible for everything to be true. + -- 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] A few user-level questions on Streaming Replication and pg_upgrade
On Wed, Jul 20, 2011 at 2:53 PM, Bruce Momjian br...@momjian.us wrote: I am assuming that's a yes to both the directions: older - newer , and newer - older minor releases. Yes, I believe both directions would work unless we mentioned it the release notes, in which cases it might not work, or might work older to newer but newer to older. I don't see how this would get broken in a minor release. We'd have to change the WAL format or the tuple format, which is definitely not minor release material. -- 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] A few user-level questions on Streaming Replication and pg_upgrade
Robert Haas wrote: On Wed, Jul 20, 2011 at 2:53 PM, Bruce Momjian br...@momjian.us wrote: I am assuming that's a yes to both the directions: older - newer , and newer - older minor releases. Yes, I believe both directions would work unless we mentioned it the release notes, in which cases it might not work, or might work older to newer but newer to older. I don't see how this would get broken in a minor release. We'd have to change the WAL format or the tuple format, which is definitely not minor release material. If there was a bug in the xlog stream content we might not be able to fix it without breaking compatibility. Rare, but possible. -- Bruce Momjian br...@momjian.ushttp://momjian.us EnterpriseDB http://enterprisedb.com + It's impossible for everything to be true. + -- 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] A few user-level questions on Streaming Replication and pg_upgrade
On Wed, Jul 20, 2011 at 3:29 PM, Bruce Momjian br...@momjian.us wrote: Robert Haas wrote: On Wed, Jul 20, 2011 at 2:53 PM, Bruce Momjian br...@momjian.us wrote: I am assuming that's a yes to both the directions: older - newer , and newer - older minor releases. Yes, I believe both directions would work unless we mentioned it the release notes, in which cases it might not work, or might work older to newer but newer to older. I don't see how this would get broken in a minor release. We'd have to change the WAL format or the tuple format, which is definitely not minor release material. If there was a bug in the xlog stream content we might not be able to fix it without breaking compatibility. Rare, but possible. OK, fair enough. But I think the likelihood is extremely low. -- 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] A few user-level questions on Streaming Replication and pg_upgrade
Robert Haas wrote: On Wed, Jul 20, 2011 at 3:29 PM, Bruce Momjian br...@momjian.us wrote: Robert Haas wrote: On Wed, Jul 20, 2011 at 2:53 PM, Bruce Momjian br...@momjian.us wrote: I am assuming that's a yes to both the directions: older - newer , and newer - older minor releases. Yes, I believe both directions would work unless we mentioned it the release notes, in which cases it might not work, or might work older to newer but newer to older. I don't see how this would get broken in a minor release. ?We'd have to change the WAL format or the tuple format, which is definitely not minor release material. If there was a bug in the xlog stream content we might not be able to fix it without breaking compatibility. ?Rare, but possible. OK, fair enough. But I think the likelihood is extremely low. It would require a case where we couldn't distinguish a valid from an invalid WAL entry, or the streaming used by the old server was sufficiently broken that we didn't want to support it. -- Bruce Momjian br...@momjian.ushttp://momjian.us EnterpriseDB http://enterprisedb.com + It's impossible for everything to be true. + -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
[HACKERS] A few user-level questions on Streaming Replication and pg_upgrade
Hi, Here are a few questions that were asked by a customer, who are trying to assess the pros and cons of using Postgres and its SR feature. I would like to get an opinion of someone more involved with the community than me. .) Will Postgres support Streaming Replication from 9.0.x to 9.1.x; i.e. across major releases. I am pretty sure the answer is no, it won't, but just double-checking with the community. .) Is Streaming Replication supported across minor releases, in reverse direction; e.g. 9.0.3 to 9.0.1 I think the answer is it depends, since it would depend upon whether any SR related bug has been fixed in the 'greater' of the minor releases. I am assuming that smaller minor release to bigger minor release will always be supported (e.g. 9.0.1 to 9.0.3) .) How reliable is `pg_upgrade -c` (dry run) currently; that is, how accurate is pg_upgrade at predicting any potential problem with the eventual in-place upgrade. I'd say it is as reliable as it gets since this is the official tool supported by the project, and it should not contain any known bugs. One has to use the latest and greatest 'minor' version of the tool for the major release they are upgrading to, though. I'd also like to mention a piece of information that may be surprising to some. Per Tom at a PGCon dinner, Postgres project does not promise continued guarantee of in-place upgrades across future major releases. Although the project will try hard to avoid having to make any changes that may affect in-place upgrade capability, but if a case can be made that a feature would give a significant improvement at the cost of compromising this capability, then the in-place upgrade capability may be forgone for that release. Thanks in advance, -- Gurjeet Singh EnterpriseDB Corporation The Enterprise PostgreSQL Company
Re: [HACKERS] A few user-level questions on Streaming Replication and pg_upgrade
Gurjeet Singh wrote: Hi, Here are a few questions that were asked by a customer, who are trying to assess the pros and cons of using Postgres and its SR feature. I would like to get an opinion of someone more involved with the community than me. .) Will Postgres support Streaming Replication from 9.0.x to 9.1.x; i.e. across major releases. I am pretty sure the answer is no, it won't, but just double-checking with the community. [ CC to general removed --- emailing only hackers; cross-posting is frowned upon. ] Right. .) Is Streaming Replication supported across minor releases, in reverse direction; e.g. 9.0.3 to 9.0.1 I think the answer is it depends, since it would depend upon whether any SR related bug has been fixed in the 'greater' of the minor releases. I am assuming that smaller minor release to bigger minor release will always be supported (e.g. 9.0.1 to 9.0.3) Yes. We could mention in the minor release notes if we break streaming replication for a minor release --- or someone will tell us when we do. .) How reliable is `pg_upgrade -c` (dry run) currently; that is, how accurate is pg_upgrade at predicting any potential problem with the eventual in-place upgrade. I'd say it is as reliable as it gets since this is the official tool supported by the project, and it should not contain any known bugs. One has to use the latest and greatest 'minor' version of the tool for the major release they are upgrading to, though. Well, we make no guarantees about the software at all, so it is hard to make any guarantee about pg_upgrade either. I'd also like to mention a piece of information that may be surprising to some. Per Tom at a PGCon dinner, Postgres project does not promise continued guarantee of in-place upgrades across future major releases. Although the project will try hard to avoid having to make any changes that may affect in-place upgrade capability, but if a case can be made that a feature would give a significant improvement at the cost of compromising this capability, then the in-place upgrade capability may be forgone for that release. Doesn't surprise me --- I know a time will come when we must change the data format enough to break pg_upgrade's ability to perform major upgrades. It is not 'if', but 'when'. -- Bruce Momjian br...@momjian.ushttp://momjian.us EnterpriseDB http://enterprisedb.com + It's impossible for everything to be true. + -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
