Re: Avoid stuck of pbgench due to skipped transactions

Hello Fujii-san, ISTM that the patch changes pgbench so that it can skip counting some skipped transactions here even for realistic rates under -T. Of course, which would happen very rarely. Is this understanding right? Yes. The point is to get out of the scheduling loop when time has expire

Re: Postgres perl module namespace

On Fri, Sep 03, 2021 at 03:34:24PM -0400, Andrew Dunstan wrote: > On 8/25/21 10:08 AM, Robert Haas wrote: > > On Wed, Aug 25, 2021 at 1:48 AM Michael Paquier wrote: > >> On Mon, Aug 23, 2021 at 03:39:15PM -0400, Robert Haas wrote: > >>> On Mon, Aug 23, 2021 at 3:03 PM Andrew Dunstan > >>> wrote:

Re: A reloption for partitioned tables - parallel_workers

> On 4 Sep 2021, at 01:17, Amit Langote wrote: > On Sat, Sep 4, 2021 at 3:10 Laurenz Albe > wrote: > On Fri, 2021-09-03 at 18:24 +0200, Daniel Gustafsson wrote: > > This thread has stalled and the patch no longer applies. I propose that we > > mark this Returned

Re: Column Filtering in Logical Replication

On Sat, Sep 4, 2021 at 10:12 AM Amit Kapila wrote: > > On Thu, Sep 2, 2021 at 2:51 AM Rahila Syed wrote: > > > >>> > >>> Do we want to consider that the columns specified in the filter must > >>> not have NOT NULL constraint? Because, otherwise, the subscriber will > >>> error out inserting such

Re: Column Filtering in Logical Replication

On Thu, Sep 2, 2021 at 2:51 AM Rahila Syed wrote: > >>> >>> Do we want to consider that the columns specified in the filter must >>> not have NOT NULL constraint? Because, otherwise, the subscriber will >>> error out inserting such rows? >>> >> I think you mean columns *not* specified in the filte

Re: Column Filtering in Logical Replication

On Thu, Sep 2, 2021 at 2:19 PM Alvaro Herrera wrote: > > On 2021-Sep-02, Rahila Syed wrote: > > > After thinking about this, I think it is best to remove the entire table > > from publication, > > if a column specified in the column filter is dropped from the table. > > Hmm, I think it would be cl

Re: Skipping logical replication transactions on subscriber side

On Sat, Sep 4, 2021 at 8:54 AM Amit Kapila wrote: > > On Fri, Sep 3, 2021 at 2:15 AM Mark Dilger > wrote: > > > > > On Aug 30, 2021, at 12:06 AM, Masahiko Sawada > > > wrote: > > > > > > I've attached rebased patches. > > For the v12-0003 patch: > > > > I believe this feature is needed, but it

Re: Skipping logical replication transactions on subscriber side

On Fri, Sep 3, 2021 at 2:15 AM Mark Dilger wrote: > > > On Aug 30, 2021, at 12:06 AM, Masahiko Sawada wrote: > > > > I've attached rebased patches. > For the v12-0003 patch: > > I believe this feature is needed, but it also seems like a very powerful > foot-gun. Can we do anything to make it le

Re: when the startup process doesn't (logging startup delays)

On Fri, Sep 03, 2021 at 01:23:56PM +0530, Nitin Jadhav wrote: > Please find the updated patch attached. Please check CA+TgmoZtbqxaOLdpNkBcDbz=41tWALA8kpH4M=rwtpyhc7-...@mail.gmail.com I agree with Robert that a standby server should not continuously show timing messages for WAL replay. Some doc

Re: [PATCH] pg_ctl should not truncate command lines at 1024 characters

Phil Krylov writes: > Attaching the new version, with the test case and free-before-exit > removed. Pushed with minor cosmetic adjustments. Thanks for the patch! regards, tom lane

Re: prevent immature WAL streaming

Hi, On 2021-09-03 20:01:50 -0400, Alvaro Herrera wrote: > From 6abc5026f92b99d704bff527d1306eb8588635e9 Mon Sep 17 00:00:00 2001 > From: Alvaro Herrera > Date: Tue, 31 Aug 2021 20:55:10 -0400 > Subject: [PATCH v3 1/5] Revert "Avoid creating archive status ".ready" files > too early" > This reve

Re: pgstat_send_connstats() introduces unnecessary timestamp and UDP overhead

Hi, On 2021-08-31 21:56:50 -0700, Andres Freund wrote: > On 2021-08-27 13:57:45 +0900, Michael Paquier wrote: > > On Wed, Aug 25, 2021 at 01:20:03AM -0700, Andres Freund wrote: > > > On 2021-08-25 12:51:58 +0900, Michael Paquier wrote: > > > As I said before, this ship has long sailed: > > > > > >

Re: prevent immature WAL streaming

I thought that the way to have debug output for this new WAL code is to use WAL_DEBUG; that way it won't bother anyone and we can remove them later if necessary. Also, I realized that we should cause any error in the path that assembles a record from contrecords is to set a flag that we can test a

Re: [PATCH] support tab-completion for single quote input with equal sign

Hi Tang, On Fri, 2021-09-03 at 04:32 +, tanghy.f...@fujitsu.com wrote: > I'd appreciate it if you can share your test results with me. Sure! Here's my output (after a `make clean && make`): cd . && TESTDIR='/home/pchampion/workspace/postgres/src/bin/psql' PATH="/home/pchampion/workspace

Re: [PATCH] test/ssl: rework the sslfiles Makefile target

On Fri, 2021-09-03 at 09:46 +0900, Michael Paquier wrote: > Nice. This is neat. The split helps a lot to understand how you've > changed things from the original implementation. As a whole, this > looks rather committable to me. Great! > One small-ish comment that I have is about all the .conf

Re: A reloption for partitioned tables - parallel_workers

On Sat, Sep 4, 2021 at 3:10 Laurenz Albe wrote: > On Fri, 2021-09-03 at 18:24 +0200, Daniel Gustafsson wrote: > > > On 6 Apr 2021, at 09:46, Amit Langote wrote: > > > On Fri, Apr 2, 2021 at 11:36 PM Laurenz Albe > wrote: > > > > > > I don't know if Seamus is still working on that; if not, we mi

Re: [Proposal] Fully WAL logged CREATE DATABASE - No Checkpoints

Hi, On 2021-09-03 14:25:10 +0530, Dilip Kumar wrote: > Yeah, we can surely lock the relation as described by Robert, but IMHO, > while creating the database we are already holding the exclusive lock on > the database and there is no one else allowed to be connected to the > database, so do we actu

Re: Add guc to enable send SIGSTOP to peers when backend exits abnormally

Alvaro Herrera writes: > On 2021-Sep-03, Tom Lane wrote: >> TBH, I'd sooner rip out SendStop, and simplify the related postmaster >> logic. > I wrote a patch to do that in 2012, after this exchange: > https://postgr.es/m/1333124720-sup-6...@alvh.no-ip.org > I obviously doesn't apply at all anymor

Re: Add guc to enable send SIGSTOP to peers when backend exits abnormally

On 2021-Sep-03, Tom Lane wrote: > "=?UTF-8?B?6JSh5qKm5aifKOeOiuS6jik=?=" writes: > > I want to share a patch with you, in which I add a guc parameter > > 'enable_send_stop' to enable set the value of SendStop in postmaster.c more > > conveniently. SendStop enable postmaster to send SIGSTOP rat

Re: ORDER BY pushdowns seem broken in postgres_fdw

The following review has been posted through the commitfest application: make installcheck-world: tested, failed Implements feature: tested, passed Spec compliant: not tested Documentation:not tested Applied the v6 patch to master branch and ran regression test for con

Re: pgsql: Set the volatility of the timestamptz version of date_bin() back

Alvaro Herrera writes: > On 2021-Sep-03, John Naylor wrote: >> On Fri, Sep 3, 2021 at 1:46 PM Alvaro Herrera >> wrote: >>> These catversion bumps in branch 14 this late in the cycle seem suspect. >>> Didn't we have some hesitation to push multirange unnest around beta2 >>> precisely because of a

Re: Estimating HugePages Requirements?

Hi, On 2021-09-01 15:53:52 +0900, Michael Paquier wrote: > Hmm. I am not sure about the addition of huge_pages_required, knowing > that we would have shared_memory_size. I'd rather let the calculation > part to the user with a scan of /proc/meminfo. -1. We can easily do better, what do we gain

Re: Bug fix for tab completion of ALTER TABLE ... VALIDATE CONSTRAINT ...

> On 19 May 2021, at 09:53, Michael Paquier wrote: > > On Tue, Apr 27, 2021 at 12:58:52PM +0300, Aleksander Alekseev wrote: >> I've noticed there is no tab completion for ALTER TABLE xxx ADD. Here >> is an alternative version of the patch that fixes this as well. Not >> sure if this should be in

Re: pgsql: Set the volatility of the timestamptz version of date_bin() back

On Fri, Sep 03, 2021 at 01:56:50PM -0400, Alvaro Herrera wrote: > On 2021-Sep-03, John Naylor wrote: > > > On Fri, Sep 3, 2021 at 1:46 PM Alvaro Herrera > > wrote: > > > > > > On 2021-Sep-03, John Naylor wrote: > > > These catversion bumps in branch 14 this late in the cycle seem suspect. > > > D

Re: A reloption for partitioned tables - parallel_workers

On Fri, 2021-09-03 at 18:24 +0200, Daniel Gustafsson wrote: > > On 6 Apr 2021, at 09:46, Amit Langote wrote: > > On Fri, Apr 2, 2021 at 11:36 PM Laurenz Albe > > wrote: > > > > I don't know if Seamus is still working on that; if not, we might > > > mark it as "returned with feedback". > > > >

Re: pgsql: Set the volatility of the timestamptz version of date_bin() back

On 2021-Sep-03, John Naylor wrote: > On Fri, Sep 3, 2021 at 1:46 PM Alvaro Herrera > wrote: > > > > On 2021-Sep-03, John Naylor wrote: > > These catversion bumps in branch 14 this late in the cycle seem suspect. > > Didn't we have some hesitation to push multirange unnest around beta2 > > precise

Re: prevent immature WAL streaming

On 2021-Sep-03, Andres Freund wrote: > Hi, > > On 2021-09-03 12:55:23 -0400, Alvaro Herrera wrote: > > Oh, but of course we can't modify XLogReaderState in backbranches to add > > the new struct member abortedContrecordPtr (or whatever we end up naming > > that.) > > Why is that? Afaict it's alw

Re: pgsql: Set the volatility of the timestamptz version of date_bin() back

On Fri, Sep 3, 2021 at 1:46 PM Alvaro Herrera wrote: > > On 2021-Sep-03, John Naylor wrote: > These catversion bumps in branch 14 this late in the cycle seem suspect. > Didn't we have some hesitation to push multirange unnest around beta2 > precisely because of a desire to avoid catversion bumps?

Re: prevent immature WAL streaming

Hi, On 2021-09-03 12:55:23 -0400, Alvaro Herrera wrote: > Oh, but of course we can't modify XLogReaderState in backbranches to add > the new struct member abortedContrecordPtr (or whatever we end up naming > that.) Why is that? Afaict it's always allocated via XLogReaderAllocate(), so adding a ne

Re: Estimating HugePages Requirements?

On 9/2/21, 10:12 PM, "Kyotaro Horiguchi" wrote: > By the way I noticed that postgres -C huge_page_size shows 0, which I > think should have the number used for the calculation if we show > huge_page_required. I would agree with this if huge_page_size was a runtime-computed GUC, but since it's int

Re: pgsql: Set the volatility of the timestamptz version of date_bin() back

On 2021-Sep-03, John Naylor wrote: > Set the volatility of the timestamptz version of date_bin() back to immutable > > 543f36b43d was too hasty in thinking that the volatility of date_bin() > had to match date_trunc(), since only the latter references > session_timezone. > > Bump catversion The

Re: prevent immature WAL streaming

On 2021-Sep-03, Kyotaro Horiguchi wrote: > At Thu, 2 Sep 2021 18:43:33 -0400, Alvaro Herrera > wrote in > The name sounds like the start LSN. doesn't contrecordAbort(ed)Ptr work? > > > if (!(pageHeader->xlp_info & XLP_FIRST_IS_CONTRECORD)) > > { > >

Re: prevent immature WAL streaming

Oh, but of course we can't modify XLogReaderState in backbranches to add the new struct member abortedContrecordPtr (or whatever we end up naming that.) I think I'm going to fix this, in backbranches only, by having xlogreader.c have a global variable, which is going to be used by ReadRecord inste

Re: Allow escape in application_name (was: [postgres_fdw] add local pid to fallback_application_name)

On 2021/09/03 14:56, kuroda.hay...@fujitsu.com wrote: Dear Fujii-san, Thank you for your great works. Attached is the latest version. Thanks a lot! I set four testcases: (1) Sets neither GUC nor server option (2) Sets server option, but not GUC (3) Sets GUC but not server option (4) Sets

Re: psql: \dl+ to list large objects privileges

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 Hi, There is something I forgot to mention in my previous review. Typically

Re: Improve logging when using Huge Pages

On 2021/09/03 23:27, Tom Lane wrote: Fujii Masao writes: IMO, if the level is promoted to LOG, the message should be updated so that it follows the error message style guide. But I agree that simpler message would be better in this case. So what about something like the following? LOG: co

Re: psql: \dl+ to list large objects privileges

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 Hi, thank you for the patch, I personally think it is a useful addition and

Re: A reloption for partitioned tables - parallel_workers

> On 6 Apr 2021, at 09:46, Amit Langote wrote: > On Fri, Apr 2, 2021 at 11:36 PM Laurenz Albe wrote: >> I don't know if Seamus is still working on that; if not, we might >> mark it as "returned with feedback". > > I have to agree given the time left. This thread has stalled and the patch no lo

Re: pg_receivewal starting position

On Fri, Sep 3, 2021 at 3:28 PM Ronan Dunklau wrote: > There is still the concern raised by Bharath about being able to select the > way to fetch the replication slot information for the user, and what should or > should not be included in the documentation. I am in favor of documenting the > proce

Re: Trap errors from streaming child in pg_basebackup to exit early

On Fri, Sep 3, 2021 at 3:23 PM Daniel Gustafsson wrote: > > 4) Instead of just exiting from the main pg_basebackup process when > > the child WAL receiver dies, can't we think of restarting the child > > process, probably with the WAL streaming position where it left off or > > stream from the beg

Re: [PATCH] Make pkg-config files cross-compile friendly

On 05.03.20 22:38, Sebastian Kemper wrote: This commit addresses this by doing the following two things: 1. Instead of hard coding the paths in "Cflags" and "Libs" "${includedir}" and "${libdir}" are used. Note: these variables can be overriden on the pkg-config command line

Re: Add guc to enable send SIGSTOP to peers when backend exits abnormally

"=?UTF-8?B?6JSh5qKm5aifKOeOiuS6jik=?=" writes: > I want to share a patch with you, in which I add a guc parameter > 'enable_send_stop' to enable set the value of SendStop in postmaster.c more > conveniently. SendStop enable postmaster to send SIGSTOP rather than SIGQUIT > to its children when

Re: [Proposal] Fully WAL logged CREATE DATABASE - No Checkpoints

On Fri, Sep 3, 2021 at 6:23 AM Dilip Kumar wrote: >> + /* Built-in oids are mapped directly */ >> + if (classForm->oid < FirstGenbkiObjectId) >> + relfilenode = classForm->oid; >> + else if (OidIsValid(classForm->relfilenode)) >> + relfilenode = classForm->relfilenode; >> + else >> + continue; >>

Re: Improve logging when using Huge Pages

Fujii Masao writes: > IMO, if the level is promoted to LOG, the message should be updated > so that it follows the error message style guide. But I agree that simpler > message would be better in this case. So what about something like > the following? > LOG: could not map anonymous shared memory

Re: using an end-of-recovery record in all cases

On Fri, Sep 3, 2021 at 12:52 AM Kyotaro Horiguchi wrote: > I tried to reproduce this but just replacing the end-of-recovery > checkpoint request with issuing an end-of-recovery record didn't cause > make check-workd fail for me. Do you have an idea of any other > requirement to cause that? Did y

Re: replay of CREATE TABLESPACE eats data at wal_level=minimal

On Thu, Sep 2, 2021 at 10:56 PM Noah Misch wrote: > > Is there anything still standing in the way of committing this? > > I pushed it as commit 97ddda8. Oh, thanks. Sorry, I had missed that. -- Robert Haas EDB: http://www.enterprisedb.com

Re: prevent immature WAL streaming

On 2021-Sep-03, Kyotaro Horiguchi wrote: > At Thu, 2 Sep 2021 18:43:33 -0400, Alvaro Herrera > wrote in > 0002: > > + XLogRecPtr abortedContrecordPtr; /* LSN of incomplete record at > > end of > > + * > > WAL */ > >

Re: Multi-Column List Partitioning

On Wed, Sep 1, 2021 at 2:31 PM Amit Langote wrote: > On Tue, Aug 31, 2021 at 8:02 PM Nitin Jadhav > wrote: > > The attached patch also fixes the above comments. > > I noticed that multi-column list partitions containing NULLs don't > work correctly with partition pruning yet. > > create table p0

Re: psql: \dl+ to list large objects privileges

Hello, Thank you very mush for review. I will prepare a new version of the patch according to your comments. For now, I will answer this question: I will also inquire as to the need for renaming the function `do_lo_list` to `listLargeObjects` and its move to describe.c. from large_obj.c. In

Re: Improve logging when using Huge Pages

On 2021/09/03 16:49, Kyotaro Horiguchi wrote: IF you are thinking to show that in GUC, you might want to look into the nearby thread [1] Yes, let's discuss this feature at that thread. I have some comment about the patch. - if (huge_pages == HUGE_PAGES_TRY && ptr == MAP_FAI

Re: psql: \dl+ to list large objects privileges

Hello, Thank you very much for review. Since '\dl' already contains description, it might be worthwhile to consider to add the column `Access privileges` without introducing a verbose version. I thought about it. The reason why I decided to add the verbose version is because of backward com

Re: .ready and .done files considered harmful

Hi, Thanks for the feedback. > Which approach do you think we should use? I think we have decent > patches for both approaches at this point, so perhaps we should see if > we can get some additional feedback from the community on which one we > should pursue further. In my opinion both the appr

Re: Avoid stuck of pbgench due to skipped transactions

On 2021/06/17 1:23, Yugo NAGATA wrote: I attached the v2 patch to clarify that I withdrew the v3 patch. Thanks for the patch! +* For very unrealistic rates under -T, some skipped +

Re: Added schema level support for publication.

On Thu, Sep 2, 2021 at 5:12 PM Amit Kapila wrote: > > On Thu, Sep 2, 2021 at 11:58 AM vignesh C wrote: > > > > Below are few comments on v23. If you have already addressed anything > in v24, then ignore it. > More Review comments (on latest version v24): === 1

Re: Added schema level support for publication.

On Wed, Sep 1, 2021 at 12:05 PM Amit Kapila wrote: > > On Wed, Sep 1, 2021 at 8:52 AM Greg Nancarrow wrote: > > > > > I'd expect a lot of users to naturally think that "ALTER PUBLICATION > > pub1 DROP ALL TABLES IN SCHEMA sc1;" would drop from the publication > > all tables that are in schema "sc

Re: using an end-of-recovery record in all cases

On Fri, Sep 3, 2021 at 10:23 AM Kyotaro Horiguchi wrote: > > At Thu, 2 Sep 2021 11:30:59 -0400, Robert Haas wrote > in > > On Mon, Aug 9, 2021 at 3:00 PM Robert Haas wrote: > > > I decided to try writing a patch to use an end-of-recovery record > > > rather than a checkpoint record in all cases

Re: [Proposal] Fully WAL logged CREATE DATABASE - No Checkpoints

On Thu, Sep 2, 2021 at 8:52 PM Robert Haas wrote: > On Thu, Sep 2, 2021 at 2:06 AM Dilip Kumar wrote: > > 0003- The main patch for WAL logging the created database operation. > > Andres pointed out that this approach ends up accessing relations > without taking a lock on them. It doesn't look li

Re: pg_receivewal starting position

Le jeudi 2 septembre 2021, 10:37:20 CEST Michael Paquier a écrit : > On Thu, Sep 02, 2021 at 10:08:26AM +0200, Ronan Dunklau wrote: > > I could see the use for sending active_pid for use within pg_basebackup: > > at > > least we could fail early if the slot is already in use. But at the same > > ti

Re: Trap errors from streaming child in pg_basebackup to exit early

> On 1 Sep 2021, at 12:28, Bharath Rupireddy > wrote: > > On Wed, Sep 1, 2021 at 1:56 PM Daniel Gustafsson wrote: >> A v2 with the above fixes is attached. > > Thanks for the updated patch. Here are some comments: > > 1) Do we need to set bgchild = -1 before the exit(1); in the code > below s

Re: Added schema level support for publication.

On Mon, Aug 30, 2021 at 8:56 PM vignesh C wrote: > > On Mon, Aug 30, 2021 at 9:10 AM houzj.f...@fujitsu.com > wrote: > > > > > 5) > > + if (list_length(pubobj->name) == 1 && > > + (strcmp(relname, "CURRENT_SCHEMA") == 0)) > > +

Re: Question about an Extension Project

Hi, I don't want to sound overly rude, but I suggest not spamming this list with the same message when you don't get an answer right away. If no one answered the first time, they're not going to answer the second time. Providing a quote usually requires some sort of a business relationship,

Re: [Proposal] Fully WAL logged CREATE DATABASE - No Checkpoints

On Fri, Jun 18, 2021 at 12:18 AM Andres Freund wrote: > Hi, > > On 2021-06-17 14:22:52 -0400, Robert Haas wrote: > > On Thu, Jun 17, 2021 at 2:17 PM Andres Freund > wrote: > > > Adding a hacky special case implementation for cross-database relation > > > accesses that violates all kinds of assum

Re: [PATCH] pg_ctl should not truncate command lines at 1024 characters

On 2021-09-03 02:09, Tom Lane wrote: I think that these free() calls you propose to add are a complete waste of code space. Certainly a free() right before an exit() call is that; if anything, it's *delaying* recycling the memory space for some useful purpose. But no part of pg_ctl runs long en

Question about an Extension Project

To who it may concern, I am trying to get a project completed to enhance PostgreSQL arithmetic and elementary functions prowess by means of two new High Precision mixed decimal number types in a self installing extension. Hopefully, I want this to be a free or low cost project. Is there anyone

Re: corruption of WAL page header is never reported

At Fri, 03 Sep 2021 16:55:36 +0900 (JST), Kyotaro Horiguchi wrote in > > Yes, I'm fine with your latest patch. > > Thanks. Maybe some additional comment is needed. Something like this. regards. -- Kyotaro Horiguchi NTT Open Source Software Center diff --git a/src/backend/access/transam/xlog

Re: corruption of WAL page header is never reported

At Thu, 2 Sep 2021 21:52:00 +0900, Fujii Masao wrote in > > > On 2021/09/02 16:26, Kyotaro Horiguchi wrote: > > I believe errmsg_buf is an interface to emit error messages dedicated > > to xlogreader that doesn't have an access to elog facility, and > > xlogreader doesn't (or ought not to or e

Re: when the startup process doesn't (logging startup delays)

> > Anything that's not used in other files should be declared static in > > the file itself, and not present in the header. Once you fix this for > > reset_startup_progress_timeout, the header won't need to include > > datatype/timestamp.h any more, which is good, because we don't want > > header

Re: Improve logging when using Huge Pages

Hello. At Fri, 3 Sep 2021 06:28:58 +, "Shinoda, Noriyoshi (PN Japan FSIP)" wrote in > Fujii-san, Julien-san > > Thank you very much for your comment. > I followed your comment and changed the elog function to ereport function and > also changed the log level. The output message is the sam

Re: prevent immature WAL streaming

At Thu, 2 Sep 2021 18:43:33 -0400, Alvaro Herrera wrote in > On 2021-Sep-02, Kyotaro Horiguchi wrote: > > > So, this is a crude PoC of that. > > I had ended up with something very similar, except I was trying to cram > the flag via the checkpoint record instead of hacking > AdvanceXLInsertBuff

Re: Unused variable in TAP tests file

On Fri, Sep 03, 2021 at 10:53:19AM +0530, Amul Sul wrote: > Few tap test files have the "tempdir_short" variable which isn't in > use. The attached patch removes the same Indeed. Let's clean up that. Thanks! -- Michael signature.asc Description: PGP signature

Add guc to enable send SIGSTOP to peers when backend exits abnormally

Hi all I want to share a patch with you, in which I add a guc parameter 'enable_send_stop' to enable set the value of SendStop in postmaster.c more conveniently. SendStop enable postmaster to send SIGSTOP rather than SIGQUIT to its children when some backend dumps core, and this variable is o