Re: WIP: Avoid creation of the free space map for small tables

2019-03-13 Thread John Naylor
On Wed, Mar 13, 2019 at 8:18 PM Amit Kapila wrote: > > First, I had a problem: On MacOS with their "gcc" wrapper around > > clang, I got a segfault 11 when compiled with no debugging symbols. > > > > Did you get this problem with the patch or both with and without the > patch? If it is only with

GIN indexes on an = ANY(array) clause

2019-03-13 Thread Corey Huinker
(moving this over from pgsql-performance) A client had an issue with a where that had a where clause something like this: WHERE 123456 = ANY(integer_array_column) I was surprised that this didn't use the pre-existing GIN index on integer_array_column, whereas recoding as WHERE ARRAY[123456]

Re: performance issue in remove_from_unowned_list()

2019-03-13 Thread Robert Haas
On Wed, Mar 13, 2019 at 9:47 AM Tomas Vondra wrote: > AFAICS we already maintain a hash table of the smgr relations, and we > look them up in this table. We don't need to look them up in the list of > unowned relations - the whole problem is that with the current > single-linked list, we need to

Re: performance issue in remove_from_unowned_list()

2019-03-13 Thread Tomas Vondra
On 3/13/19 1:12 PM, Robert Haas wrote: > On Tue, Mar 12, 2019 at 6:54 PM Tomas Vondra > wrote: >> Attached is a patch adopting the dlist approach - it seems to be working >> quite fine, and is a bit cleaner than just slapping another pointer into >> the SMgrRelationData struct. So I'd say this is

Re: [WIP] CREATE SUBSCRIPTION with FOR TABLES clause (table filter)

2019-03-13 Thread Robert Haas
On Mon, Mar 4, 2019 at 1:55 AM Michael Paquier wrote: > - To create a subscription, the user must be a superuser. > + To add tables to a subscription, the user must have ownership rights on > the > + table. > [...] > + /* must have CREATE privilege on database */ > + aclresult =

Re: Special role for subscriptions

2019-03-13 Thread Robert Haas
On Mon, Mar 11, 2019 at 10:39 PM Michael Paquier wrote: > On Mon, Mar 11, 2019 at 06:32:10PM -0700, Jeff Davis wrote: > > * Is the original idea of a special role still viable? > > In my opinion, that part may be valuable. The latest patches proposed > change the way tables are filtered and

Re: PATCH: Include all columns in default names for foreign key constraints.

2019-03-13 Thread Peter Eisentraut
On 2019-03-09 22:27, Paul Martinez wrote: > Yikes, sorry about that. Some tests are failing on my machine because of > dynamic > linking issues and I totally missed all the foreign key failures. I think I've > fixed all the tests. I changed the test I added to test the 63-character > limit. > >

Re: Should we add GUCs to allow partition pruning to be disabled?

2019-03-13 Thread Robert Haas
On Tue, Mar 12, 2019 at 7:28 PM David Rowley wrote: > I think I've done that in the attached patch. Cool, thanks. > However, do think the > just saying "excessive memory usage" seems strange without prefixing > it with "can result in" and dropping the "especially". I'm fairly > used to having

Re: using index or check in ALTER TABLE SET NOT NULL

2019-03-13 Thread Sergei Kornilov
Wow, thank you! 13.03.2019, 15:57, "Robert Haas" : > On Tue, Mar 12, 2019 at 4:27 PM Sergei Kornilov wrote: >>  Agreed, in attached new version ... > > Committed with a little more nitpicking. > > -- > Robert Haas > EnterpriseDB: http://www.enterprisedb.com > The Enterprise PostgreSQL Company

Re: using index or check in ALTER TABLE SET NOT NULL

2019-03-13 Thread Robert Haas
On Tue, Mar 12, 2019 at 4:27 PM Sergei Kornilov wrote: > Agreed, in attached new version ... Committed with a little more nitpicking. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company

Re: [PATCH] Remove stray comma from heap_page_item_attrs() docs

2019-03-13 Thread Magnus Hagander
On Wed, Mar 13, 2019 at 1:26 PM Christoph Berg wrote: > (This seems to be the only occurrence of this error, after about 2 > minutes of git-grep-ing.) > Thanks, pushed! -- Magnus Hagander Me: https://www.hagander.net/ Work: https://www.redpill-linpro.com/

Re: GSOC Application

2019-03-13 Thread Andrey Borodin
Hi, Pavan! > 12 марта 2019 г., в 12:01, pavan gudivada > написал(а): > > I am Pavan_Gudivada.I have good knowledge in HTML, CSS,JAVASCRIPT,PYTHON and > SQL.After i know about PostgreSQL and its contributions through open source > .i am also intersted to take part in Read/write

Re: What to name the current heap after pluggable storage / what to rename?

2019-03-13 Thread Robert Haas
On Tue, Mar 12, 2019 at 8:39 PM Andres Freund wrote: > > I like that option. > > In that vein, does anybody have an opinion about the naming of > a) HeapUpdateFailureData, which will be used for different AMs > b) HTSU_Result itself, which'll be the return parameter for >update/delete via

[PATCH] Remove stray comma from heap_page_item_attrs() docs

2019-03-13 Thread Christoph Berg
(This seems to be the only occurrence of this error, after about 2 minutes of git-grep-ing.) >From 42b2a82f8e06beb0de3b3b15ded85fc905fb9edd Mon Sep 17 00:00:00 2001 From: Christoph Berg Date: Wed, 13 Mar 2019 13:24:22 +0100 Subject: [PATCH] Remove stray comma from heap_page_item_attrs() docs ---

Re: Offline enabling/disabling of data checksums

2019-03-13 Thread Michael Paquier
On Wed, Mar 13, 2019 at 02:43:39PM +0300, Sergei Kornilov wrote: > Seems good. And I think we need backpath this check to pg11. similar > to cross-version compatibility checks Good point raised, a backpatch looks adapted. It would be nice to get into something more dynamic, but

Re: WIP: Avoid creation of the free space map for small tables

2019-03-13 Thread Amit Kapila
On Wed, Mar 13, 2019 at 4:57 PM John Naylor wrote: > > On Fri, Mar 8, 2019 at 7:43 PM Amit Kapila wrote: > > > Have you done any performance testing of this patch? I mean to say > > now that we added a new stat call for each table, we should see if > > that has any impact. Ideally, that should

Re: Using condition variables to wait for checkpoints

2019-03-13 Thread Robert Haas
On Tue, Mar 12, 2019 at 7:12 PM Andres Freund wrote: > Having useful infrastructure is sure cool. Yay! -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company

Re: performance issue in remove_from_unowned_list()

2019-03-13 Thread Robert Haas
On Tue, Mar 12, 2019 at 6:54 PM Tomas Vondra wrote: > Attached is a patch adopting the dlist approach - it seems to be working > quite fine, and is a bit cleaner than just slapping another pointer into > the SMgrRelationData struct. So I'd say this is the way to go. What about using a data

Fix handling of unlogged tables in FOR ALL TABLES publications

2019-03-13 Thread Peter Eisentraut
If a FOR ALL TABLES publication exists, unlogged tables are ignored for publishing changes. But CheckCmdReplicaIdentity() would still check in that case that such a table has a replica identity set before accepting updates. That is useless, so check first whether the given table is publishable

Re: Use nanosleep(2) in pg_usleep, if available?

2019-03-13 Thread Magnus Hagander
On Tue, Mar 12, 2019 at 6:13 PM Tom Lane wrote: > Robert Haas writes: > > On Mon, Mar 11, 2019 at 8:03 PM Tom Lane wrote: > >> While the WaitLatch alternative avoids the problem, I doubt > >> we're ever going to remove pg_usleep entirely, so it'd be > >> good if it had fewer sharp edges.

Re: Offline enabling/disabling of data checksums

2019-03-13 Thread Michael Paquier
On Wed, Mar 13, 2019 at 12:09:24PM +0100, Michael Banck wrote: > The attached patch should do the above, on top of Michael's last > patchset. What you are doing here looks like a good defense in itself. -- Michael signature.asc Description: PGP signature

RE: SQL statement PREPARE does not work in ECPG

2019-03-13 Thread Matsumura, Ryo
Hi Meskes-san cc: Takahashi-san, Kuroda-san, Ideriha-san I attach a new patch. Please review it. Excuse: It doesn't include regression tests and pass them. Because I must reset all expected C program of regression. # I add an argument to ECPGdo(). I explain the patch as follows: 1.

Re: Offline enabling/disabling of data checksums

2019-03-13 Thread Sergei Kornilov
Hi, >>  > Also we support ./configure --with-blocksize=(not equals 8)? make >>  > check on HEAD fails for me. If we support this - i think we need >>  > recheck BLCKSZ between compiled pg_checksum and used in PGDATA >> >>  You mean if the backend and pg_checksums is built with different >>  

Re: Offline enabling/disabling of data checksums

2019-03-13 Thread Magnus Hagander
On Wed, Mar 13, 2019 at 12:40 PM Sergei Kornilov wrote: > Hi > > >> One new question from me: how about replication? > >> Case: primary+replica, we shut down primary and enable checksum, and > "started streaming WAL from primary" without any issue. I have master with > checksums, but replica

Re: Offline enabling/disabling of data checksums

2019-03-13 Thread Sergei Kornilov
Hi >> One new question from me: how about replication? >> Case: primary+replica, we shut down primary and enable checksum, and >> "started streaming WAL from primary" without any issue. I have master with >> checksums, but replica without. >> Or cluster with checksums, then disable checksums on

Re: Unified logging system for command-line programs

2019-03-13 Thread Arthur Zakirov
Hello, On 22.02.2019 11:39, Peter Eisentraut wrote: Here is an updated patch. I've finished the functionality to the point where I'm content with it. I fixed up some of the remaining special cases in pg_dump that I hadn't sorted out last time. I also moved the scattered setvbuf(stderr, ...)

Re: Offline enabling/disabling of data checksums

2019-03-13 Thread Michael Banck
Hi, Am Mittwoch, den 13.03.2019, 12:24 +0100 schrieb Magnus Hagander: > > Also we support ./configure --with-blocksize=(not equals 8)? make > > check on HEAD fails for me. If we support this - i think we need > > recheck BLCKSZ between compiled pg_checksum and used in PGDATA > > You mean if the

Re: WIP: Avoid creation of the free space map for small tables

2019-03-13 Thread John Naylor
On Fri, Mar 8, 2019 at 7:43 PM Amit Kapila wrote: > Have you done any performance testing of this patch? I mean to say > now that we added a new stat call for each table, we should see if > that has any impact. Ideally, that should be compensated by the fact > that we are now not transferring

Re: Offline enabling/disabling of data checksums

2019-03-13 Thread Magnus Hagander
On Wed, Mar 13, 2019 at 11:54 AM Sergei Kornilov wrote: > Hi > > One new question from me: how about replication? > Case: primary+replica, we shut down primary and enable checksum, and > "started streaming WAL from primary" without any issue. I have master with > checksums, but replica without.

Re: Offline enabling/disabling of data checksums

2019-03-13 Thread Michael Banck
Hi, Am Mittwoch, den 13.03.2019, 11:47 +0100 schrieb Magnus Hagander: > On Wed, Mar 13, 2019 at 11:41 AM Michael Banck > wrote: > > I propose we re-read the control file for the enable case after we > > finished operating on all files and (i) check the instance is still > > offline and (ii)

Re: WIP: BRIN multi-range indexes

2019-03-13 Thread Alexander Korotkov
On Wed, Mar 13, 2019 at 12:52 PM Tomas Vondra wrote: > On 3/13/19 9:15 AM, Alexander Korotkov wrote: > > On Tue, Mar 12, 2019 at 8:15 PM Tomas Vondra > > wrote: > >>> 0001. Pass all keys to BRIN consistent function at once. > >>> > >>> I think that changing the signature of consistent function

Re: Offline enabling/disabling of data checksums

2019-03-13 Thread Fabien COELHO
Hallo Michael, I propose we re-read the control file for the enable case after we finished operating on all files and (i) check the instance is still offline and (ii) update the checksums version from there. That should be a small but worthwhile change that could be done anyway. That looks

Re: Offline enabling/disabling of data checksums

2019-03-13 Thread Sergei Kornilov
Hi One new question from me: how about replication? Case: primary+replica, we shut down primary and enable checksum, and "started streaming WAL from primary" without any issue. I have master with checksums, but replica without. Or cluster with checksums, then disable checksums on primary, but

Re: Offline enabling/disabling of data checksums

2019-03-13 Thread Magnus Hagander
On Wed, Mar 13, 2019 at 11:41 AM Michael Banck wrote: > Am Mittwoch, den 13.03.2019, 18:31 +0900 schrieb Michael Paquier: > > On Wed, Mar 13, 2019 at 10:08:33AM +0100, Fabien COELHO wrote: > > > I'm not sure of the punctuation logic on the help line: the first > sentence > > > does not end with

Re: Offline enabling/disabling of data checksums

2019-03-13 Thread Fabien COELHO
Hello, Yep. That is the issue I think is preventable by fsyncing updated data *then* writing & syncing the control file, and that should be done by pg_checksums. Well, pg_rewind works similarly: control file gets updated and then the whole data directory gets flushed. So it is basically

Re: Offline enabling/disabling of data checksums

2019-03-13 Thread Michael Banck
Am Mittwoch, den 13.03.2019, 18:31 +0900 schrieb Michael Paquier: > On Wed, Mar 13, 2019 at 10:08:33AM +0100, Fabien COELHO wrote: > > I'm not sure of the punctuation logic on the help line: the first sentence > > does not end with a ".". I could not find an instance of this style in other > >

RE: speeding up planning with partitions

2019-03-13 Thread Imai, Yoshikazu
Amit-san, On Tue, Mar 12, 2019 at 2:34 PM, Amit Langote wrote: > Thanks for the heads up. > > On Tue, Mar 12, 2019 at 10:23 PM Jesper Pedersen > wrote: > > After applying 0004 check-world fails with the attached. CFBot agrees > [1]. > > Fixed. I had forgotten to re-run postgres_fdw tests

RE: [PATCH] remove repetitive characters in fdwhandler.sgml

2019-03-13 Thread Zhang, Jie
> This function should store the tuple into the provided slot, no? Yes, this modification is easier to understand. -Original Message- From: Michael Paquier [mailto:mich...@paquier.xyz] Sent: Wednesday, March 13, 2019 1:02 PM To: Zhang, Jie/张 杰 Cc: pgsql-hack...@postgresql.org Subject:

Re: Offline enabling/disabling of data checksums

2019-03-13 Thread Michael Paquier
On Wed, Mar 13, 2019 at 10:44:03AM +0100, Fabien COELHO wrote: > Yep. That is the issue I think is preventable by fsyncing updated data > *then* writing & syncing the control file, and that should be done by > pg_checksums. Well, pg_rewind works similarly: control file gets updated and then the

Re: Compressed TOAST Slicing

2019-03-13 Thread Tomas Vondra
On 3/13/19 3:19 AM, Michael Paquier wrote: > On Tue, Mar 12, 2019 at 07:01:17PM -0700, Andres Freund wrote: >> I don't think this is even close to popular enough to incur the >> maybe of a separate function / more complicated interface. By this >> logic we can change basically no APIs anymore. >

Re: CPU costs of random_zipfian in pgbench

2019-03-13 Thread Georgios Kokolatos
The following review has been posted through the commitfest application: make installcheck-world: not tested Implements feature: not tested Spec compliant: not tested Documentation:not tested Version 3 of the patch looks ready for committer. Thank you for taking the

Re: WIP: BRIN multi-range indexes

2019-03-13 Thread Tomas Vondra
On 3/13/19 9:15 AM, Alexander Korotkov wrote: > On Tue, Mar 12, 2019 at 8:15 PM Tomas Vondra > wrote: >>> 0001. Pass all keys to BRIN consistent function at once. >>> >>> I think that changing the signature of consistent function is bad, because >>> then >>> the authors of existing BRIN

Re: CPU costs of random_zipfian in pgbench

2019-03-13 Thread Fabien COELHO
For whatever it is worth, the patch looks good to me. A minor nitpick would be to use a verb in the part: `cost when the parameter in (0, 1)` maybe: `cost when the parameter's value is in (0, 1)` or similar. Looks ok. Apart from that, I would suggest it that the patch could be moved

Re: Inadequate executor locking of indexes

2019-03-13 Thread Amit Langote
Hi David, On 2019/03/13 10:38, David Rowley wrote: > I had another go at this patch and fixed the problem by just setting > the idxlockmode inside the planner just before the call to > expand_inherited_tables(). This allows the lockmode to be copied into > child RTEs. I have one question about

Re: Offline enabling/disabling of data checksums

2019-03-13 Thread Fabien COELHO
I do not think it is a good thing that two commands can write to the data directory at the same time, really. We don't prevent either a pg_resetwal and a pg_basebackup to run in parallel. That would be... Interesting. Yep, I'm trying again to suggest that this kind of thing should be

Re: Offline enabling/disabling of data checksums

2019-03-13 Thread Michael Paquier
On Wed, Mar 13, 2019 at 10:08:33AM +0100, Fabien COELHO wrote: > I'm not sure of the punctuation logic on the help line: the first sentence > does not end with a ".". I could not find an instance of this style in other > help on pg commands. I'd suggest "check data checksums (default)" would work

Re: Fix volatile vs. pointer confusion

2019-03-13 Thread Peter Eisentraut
On 2019-03-11 12:57, Alvaro Herrera wrote: > Looking at recently committed 2e616dee9e60, we have introduced this: > > + volatile xmlBufferPtr buf = NULL; > + volatile xmlNodePtr cur_copy = NULL; > > where the pointer-ness nature of the object is inside the typedef. I > *suppose*

Re: Fix volatile vs. pointer confusion

2019-03-13 Thread Peter Eisentraut
On 2019-03-11 09:31, Michael Paquier wrote: > On Mon, Mar 11, 2019 at 08:23:39AM +0100, Peter Eisentraut wrote: >> Attached patch fixes a couple of cases of that. Most instances were >> already correct. > > It seems to me that you should look at that: >

Re: Offline enabling/disabling of data checksums

2019-03-13 Thread Fabien COELHO
Michaël-san, Now the set of patches is: - 0001, add --enable and --disable. I have tweaked a bit the patch so as "action" is replaced by "mode" which is more consistent with other tools like pg_ctl. pg_indent was also complaining about one of the new enum structures. Patch applies cleanly,

Re: CPU costs of random_zipfian in pgbench

2019-03-13 Thread Georgios Kokolatos
The following review has been posted through the commitfest application: make installcheck-world: not tested Implements feature: not tested Spec compliant: not tested Documentation:not tested For whatever it is worth, the patch looks good to me. A minor nitpick would

Re: Introduce timeout capability for ConditionVariableSleep

2019-03-13 Thread Kyotaro HORIGUCHI
Hello. At Tue, 12 Mar 2019 17:53:43 -0700, Shawn Debnath wrote in <20190313005342.ga8...@f01898859afd.ant.amazon.com> > Hi Thomas, > > Thanks for reviewing! > > On Wed, Mar 13, 2019 at 12:40:57PM +1300, Thomas Munro wrote: > > Can we just refer to the other function's documentation for this?

Re: WIP: BRIN multi-range indexes

2019-03-13 Thread Alexander Korotkov
On Tue, Mar 12, 2019 at 8:15 PM Tomas Vondra wrote: > > 0001. Pass all keys to BRIN consistent function at once. > > > > I think that changing the signature of consistent function is bad, because > > then > > the authors of existing BRIN opclasses will need to maintain two variants of > > the

Re: pg_rewind : feature to rewind promoted standby is broken!

2019-03-13 Thread Michael Paquier
On Tue, Mar 12, 2019 at 06:23:01PM +0900, Michael Paquier wrote: > And you are pointing out to the correct commit. The issue is that > process_target_file() has added a call to check_file_excluded(), and > this skips all the folders which it thinks can be skipped. One > problem though is that we

RE: Timeout parameters

2019-03-13 Thread Nagaura, Ryohei
Hello Robert-san. > From: Robert Haas > So this says that it works on systems that have TCP_USER_TIMEOUT or an > equivalent socket option and that it also works on Windows, and then a few > lines > later > > + This parameter is not supported on Windows, and must be zero. > > This

RE: Timeout parameters

2019-03-13 Thread Nagaura, Ryohei
Hello Mikalai-san. > From: mikalaike...@ibagroup.eu > The main idea of my comment was to avoid handling logical errors ( > "client-side > timeout") in advance to the detection of network problems > Therefore, I suggested setting "client-side timeout" greater of equal to the >

Re: Offline enabling/disabling of data checksums

2019-03-13 Thread Michael Paquier
On Wed, Mar 13, 2019 at 07:18:32AM +0100, Fabien COELHO wrote: > I probably can do that before next Monday. I'll prioritize reviewing the > latest instance of this patch, though. Thanks. The core code of the feature has not really changed with the last reviews, except for the tweaks in the

Re: Progress reporting for pg_verify_checksums

2019-03-13 Thread Michael Paquier
On Wed, Mar 13, 2019 at 07:22:28AM +0100, Fabien COELHO wrote: > Does not apply because of the renaming committed by Michaël. > > Could you rebase? This stuff touches pg_checksums.c, so you may want to wait one day or two to avoid extra work... I think that I'll be able to finish the addition

Re: Adding a TAP test checking data consistency on standby with minRecoveryPoint

2019-03-13 Thread Michael Paquier
On Tue, Mar 12, 2019 at 01:16:14PM +0300, Arthur Zakirov wrote: > On my environment installcheck passes as well as check. Also I ran tests > with reverted c186ba13, 016_min_consistency.pl doesn't pass as expected. Thanks all for the feedback! I have done an extra pass on the new, tweaking some

Re: ToDo: show size of partitioned table

2019-03-13 Thread Amit Langote
On 2019/02/22 1:41, Pavel Stehule wrote: > čt 21. 2. 2019 v 0:56 odesílatel Justin Pryzby > napsal: > >> On Sat, Feb 16, 2019 at 10:52:35PM +0100, Pavel Stehule wrote: >>> I like your changes. I merged all - updated patch is attached >> >> I applied and tested your v10 patch. >> >> Find attached

Re: [HACKERS] PATCH: multivariate histograms and MCV lists

2019-03-13 Thread David Rowley
On Wed, 13 Mar 2019 at 17:20, Kyotaro HORIGUCHI wrote: > bms_member_index seems working differently than maybe expected. > > bms_member_index((2, 4), 0) => 0, (I think) should be -1 > bms_member_index((2, 4), 1) => 0, should be -1 > bms_member_index((2, 4), 2) => 0, should be 0 >

Re: Progress reporting for pg_verify_checksums

2019-03-13 Thread Fabien COELHO
Hallo Michael, I would bother rounding down < 100% to 100, because then you would get 1560/1492 MB (100\%, X MB/s) which is kind of silly. No, we cap the total_size to current_size so you won't see that (but total_size will potentially gradually increase). pg_basebackup has the same

Re: [PATCH] remove repetitive characters in fdwhandler.sgml

2019-03-13 Thread Andres Freund
On 2019-03-13 14:55:59 +0900, Etsuro Fujita wrote: > (2019/03/13 14:02), Michael Paquier wrote: > > On Tue, Mar 12, 2019 at 01:37:04AM +, Zhang, Jie wrote: > > > Here is a tiny patch removing repetitive characters [if] in > > > fdwhandler.sgml. > > > > > > - This function should

Re: Offline enabling/disabling of data checksums

2019-03-13 Thread Fabien COELHO
Bonjour Michaël, Yes, that would be nice, for now I have focused. For pg_resetwal yes we could do it easily. Would you like to send a patch? I probably can do that before next Monday. I'll prioritize reviewing the latest instance of this patch, though. This seem contradictory to me:

Re: BUG #15668: Server crash in transformPartitionRangeBounds

2019-03-13 Thread Amit Langote
On 2019/03/13 14:15, Amit Langote wrote: > On 2019/03/11 16:21, Michael Paquier wrote: >> On Mon, Mar 11, 2019 at 03:44:39PM +0900, Amit Langote wrote: >>> We could make the error message more meaningful depending on the context, >>> but maybe it'd better be pursue it as a separate project. >> >>

Re: COPY FREEZE and setting PD_ALL_VISIBLE/visibility map bits

2019-03-13 Thread Masahiko Sawada
On Tue, Mar 12, 2019 at 4:54 PM Pavan Deolasee wrote: > > > On Mon, Mar 11, 2019 at 1:37 PM Masahiko Sawada wrote: >> >> >> >> I might be missing something but why do we need to recheck whether >> each pages is all-frozen after insertion? I wonder if we can set >> all-frozen without checking all

Re: Timeout parameters

2019-03-13 Thread Fabien COELHO
Hello Robert, wrote: The main purpose of this parameter is to avoid client's waiting for DB server infinitely, not reducing the server's burden. This results in not waiting end-user, which is most important. +1. If the server fails to detect that the client has gone away, that's the

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