Hash index creation warning
Now that we have the create hash index warning in 9.5, I realized that
we don't warn about hash indexes with PITR, only crash recovery and
streaming. This patch fixes that.
Is the wording "cannot be used" too vague. The CREATE INDEX manual
page has the words "give wrong answers to queries", which might be
better, but is kind of long for an error message. Suggestions?
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EnterpriseDB http://enterprisedb.com
+ Everyone has their own god. +
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Bruce Momjian wrote
Now that we have the create hash index warning in 9.5, I realized that
we don't warn about hash indexes with PITR, only crash recovery and
streaming. This patch fixes that.Is the wording "cannot be used" too vague. The CREATE INDEX manual
page has the words "give wrong answers to queries", which might be
better, but is kind of long for an error message. Suggestions?
Something like the following is more specific without being more wordy:
"hash indexes are not WAL-logged: they are corrupted during recovery and
changes do not replicate to standby servers."
The question is whether we explain the implications of not being WAL-logged
in an error message or simply state the fact and let the documentation
explain the hazards - basically just output:
"hash indexes are not WAL-logged and their use is discouraged"
David J.
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David G Johnston <david.g.johnston@gmail.com> writes:
The question is whether we explain the implications of not being WAL-logged
in an error message or simply state the fact and let the documentation
explain the hazards - basically just output:
"hash indexes are not WAL-logged and their use is discouraged"
+1. The warning message is not the place to be trying to explain all the
details.
regards, tom lane
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On Fri, Oct 17, 2014 at 12:56:52PM -0400, Tom Lane wrote:
David G Johnston <david.g.johnston@gmail.com> writes:
The question is whether we explain the implications of not being WAL-logged
in an error message or simply state the fact and let the documentation
explain the hazards - basically just output:
"hash indexes are not WAL-logged and their use is discouraged"+1. The warning message is not the place to be trying to explain all the
details.
OK, updated patch attached.
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Bruce Momjian <bruce@momjian.us> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ Everyone has their own god. +
Attachments:
hash.difftext/x-diff; charset=us-asciiDownload+21-21
On Fri, Oct 17, 2014 at 02:36:55PM -0400, Bruce Momjian wrote:
On Fri, Oct 17, 2014 at 12:56:52PM -0400, Tom Lane wrote:
David G Johnston <david.g.johnston@gmail.com> writes:
The question is whether we explain the implications of not being WAL-logged
in an error message or simply state the fact and let the documentation
explain the hazards - basically just output:
"hash indexes are not WAL-logged and their use is discouraged"+1. The warning message is not the place to be trying to explain all the
details.OK, updated patch attached.
Patch applied.
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Bruce Momjian <bruce@momjian.us> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ Everyone has their own god. +
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On 18 October 2014 at 15:36, Bruce Momjian <bruce@momjian.us> wrote:
On Fri, Oct 17, 2014 at 02:36:55PM -0400, Bruce Momjian wrote:
On Fri, Oct 17, 2014 at 12:56:52PM -0400, Tom Lane wrote:
David G Johnston <david.g.johnston@gmail.com> writes:
The question is whether we explain the implications of not being WAL-logged
in an error message or simply state the fact and let the documentation
explain the hazards - basically just output:
"hash indexes are not WAL-logged and their use is discouraged"+1. The warning message is not the place to be trying to explain all the
details.OK, updated patch attached.
Patch applied.
I only just noticed this item when I read the release notes. Should
we bother warning when used on an unlogged table?
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On 6/12/15 5:00 PM, Thom Brown wrote:
On 18 October 2014 at 15:36, Bruce Momjian <bruce@momjian.us> wrote:
On Fri, Oct 17, 2014 at 02:36:55PM -0400, Bruce Momjian wrote:
On Fri, Oct 17, 2014 at 12:56:52PM -0400, Tom Lane wrote:
David G Johnston <david.g.johnston@gmail.com> writes:
The question is whether we explain the implications of not being WAL-logged
in an error message or simply state the fact and let the documentation
explain the hazards - basically just output:
"hash indexes are not WAL-logged and their use is discouraged"+1. The warning message is not the place to be trying to explain all the
details.OK, updated patch attached.
Patch applied.
I only just noticed this item when I read the release notes. Should
we bother warning when used on an unlogged table?
Not really; but I think the bigger question at this point is if we want
to change it this late in the game.
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Jim Nasby, Data Architect, Blue Treble Consulting, Austin TX
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On Tue, Jun 23, 2015 at 9:06 AM, Jim Nasby <Jim.Nasby@bluetreble.com> wrote:
On 6/12/15 5:00 PM, Thom Brown wrote:
On 18 October 2014 at 15:36, Bruce Momjian <bruce@momjian.us> wrote:
On Fri, Oct 17, 2014 at 02:36:55PM -0400, Bruce Momjian wrote:
On Fri, Oct 17, 2014 at 12:56:52PM -0400, Tom Lane wrote:
David G Johnston <david.g.johnston@gmail.com> writes:
The question is whether we explain the implications of not being
WAL-logged
in an error message or simply state the fact and let the documentation
explain the hazards - basically just output:
"hash indexes are not WAL-logged and their use is discouraged"+1. The warning message is not the place to be trying to explain all
the
details.OK, updated patch attached.
Patch applied.
I only just noticed this item when I read the release notes. Should
we bother warning when used on an unlogged table?Not really; but I think the bigger question at this point is if we want to
change it this late in the game.
Changing it even during beta looks acceptable to me. I think that it
is mainly a matter to have a patch (here is one), and someone to push
it as everybody here seem to agree that for UNLOGGED tables this
warning has little sense.
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Michael
Attachments:
20150623_hash_index_unlogged.patchtext/x-patch; charset=US-ASCII; name=20150623_hash_index_unlogged.patchDownload+9-1
On Mon, Jun 22, 2015 at 8:46 PM, Michael Paquier
<michael.paquier@gmail.com> wrote:
On Tue, Jun 23, 2015 at 9:06 AM, Jim Nasby <Jim.Nasby@bluetreble.com> wrote:
On 6/12/15 5:00 PM, Thom Brown wrote:
On 18 October 2014 at 15:36, Bruce Momjian <bruce@momjian.us> wrote:
On Fri, Oct 17, 2014 at 02:36:55PM -0400, Bruce Momjian wrote:
On Fri, Oct 17, 2014 at 12:56:52PM -0400, Tom Lane wrote:
David G Johnston <david.g.johnston@gmail.com> writes:
The question is whether we explain the implications of not being
WAL-logged
in an error message or simply state the fact and let the documentation
explain the hazards - basically just output:
"hash indexes are not WAL-logged and their use is discouraged"+1. The warning message is not the place to be trying to explain all
the
details.OK, updated patch attached.
Patch applied.
I only just noticed this item when I read the release notes. Should
we bother warning when used on an unlogged table?Not really; but I think the bigger question at this point is if we want to
change it this late in the game.Changing it even during beta looks acceptable to me. I think that it
is mainly a matter to have a patch (here is one), and someone to push
it as everybody here seem to agree that for UNLOGGED tables this
warning has little sense.
I think you should be testing RelationNeedsWAL(), not the
relpersistence directly. The same point applies for temporary
indexes.
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Robert Haas
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On Wed, Jun 24, 2015 at 12:27 AM, Robert Haas wrote:
I think you should be testing RelationNeedsWAL(), not the
relpersistence directly. The same point applies for temporary
indexes.
Indeed. Patch updated attached.
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Michael
Attachments:
20150624_hash_index_unlogged_v2.patchapplication/x-patch; name=20150624_hash_index_unlogged_v2.patchDownload+9-1
On 18 October 2014 at 02:36, Bruce Momjian <bruce@momjian.us> wrote:
On Fri, Oct 17, 2014 at 12:56:52PM -0400, Tom Lane wrote:
David G Johnston <david.g.johnston@gmail.com> writes:
The question is whether we explain the implications of not being WAL-logged
in an error message or simply state the fact and let the documentation
explain the hazards - basically just output:
"hash indexes are not WAL-logged and their use is discouraged"+1. The warning message is not the place to be trying to explain all the
details.
While I don't think it should explain all the details, "WAL-logged"
will mean *nothing* to most users, including most of those who're
using streaming replication, PITR, etc.
I would strongly prefer to see something that conveys some meaning to
a user who doesn't know PostgreSQL's innards, since by the time "WAL
logged" means much to you, you've got a good chance of having already
learned that hash indexes aren't crash-safe. Or of reading the manual.
Perhaps:
WARNING: hash indexes are not crash-safe, not replicated, and their
use is discouraged
?
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On Wed, Jun 24, 2015 at 1:45 AM, Craig Ringer <craig@2ndquadrant.com> wrote:
WARNING: hash indexes are not crash-safe, not replicated, and their
use is discouraged
+1
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On Wed, Jun 24, 2015 at 3:06 AM, Michael Paquier
<michael.paquier@gmail.com> wrote:
On Wed, Jun 24, 2015 at 12:27 AM, Robert Haas wrote:
I think you should be testing RelationNeedsWAL(), not the
relpersistence directly. The same point applies for temporary
indexes.Indeed. Patch updated attached.
Committed.
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On Wed, Jun 24, 2015 at 4:53 AM, Peter Geoghegan <pg@heroku.com> wrote:
On Wed, Jun 24, 2015 at 1:45 AM, Craig Ringer <craig@2ndquadrant.com> wrote:
WARNING: hash indexes are not crash-safe, not replicated, and their
use is discouraged+1
I'm not wild about this rewording; I think that if users don't know
what WAL is, they probably need to know that in order to make good
decisions about whether to use hash indexes. But I don't feel
super-strongly about it.
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EnterpriseDB: http://www.enterprisedb.com
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On Fri, Jun 26, 2015 at 11:40:27AM -0400, Robert Haas wrote:
On Wed, Jun 24, 2015 at 4:53 AM, Peter Geoghegan <pg@heroku.com> wrote:
On Wed, Jun 24, 2015 at 1:45 AM, Craig Ringer <craig@2ndquadrant.com> wrote:
WARNING: hash indexes are not crash-safe, not replicated, and their
use is discouraged+1
I'm not wild about this rewording; I think that if users don't know
what WAL is, they probably need to know that in order to make good
decisions about whether to use hash indexes. But I don't feel
super-strongly about it.
Coming late to this, but I think Robert is right. WAL is used for crash
recovery, PITR, and streaming replication, and I am not sure we want to
specify all of those in the warning message.
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Bruce Momjian <bruce@momjian.us> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ Everyone has their own god. +
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