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 Mon, 29 Jun 2020 22:57:44 -0700 (PDT)
Date: Tue, 30 Jun 2020 13:57:40 +0800
From: "movead.li@highgo.ca" <movead.li@highgo.ca>
To: michael <michael@paquier.xyz>,
	"Madan Kumar" <madankumar1993@gmail.com>
Cc: pgsql-hackers <pgsql-hackers@lists.postgresql.org>,
	craig <craig@2ndquadrant.com>,
	petr <petr@2ndquadrant.com>,
	"Alvaro Herrera" <alvherre@2ndquadrant.com>,
	andres <andres@anarazel.de>,
	soumyadeep2007 <soumyadeep2007@gmail.com>,
	peter.eisentraut <peter.eisentraut@2ndquadrant.com>
Subject: Re: A patch for get origin from commit_ts.
References: <2020051116430836450630@highgo.ca>,
	<20200512014537.GF88791@paquier.xyz>,
	<2020051316291300911447@highgo.ca>,
	<CAMtsaPEm47-mD5br8O8fVsZ0PnowtNij4O3UNsuG6Zb7dSCAaQ@mail.gmail.com>,
	<20200630044114.GA67289@paquier.xyz>
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	charset="ISO-8859-1"
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<html><head><meta http-equiv=3D"content-type" content=3D"text/html; charse=
t=3DISO-8859-1"><style>body { line-height: 1.5; }blockquote { margin-top: =
0px; margin-bottom: 0px; margin-left: 0.5em; }body { font-size: 10.5pt; fo=
nt-family: 'Microsoft YaHei UI'; color: rgb(0, 0, 0); line-height: 1.5; }<=
/style></head><body>=0A<div><span></span><br></div>=0A<div><div><span styl=
e=3D"font-size: 10.5pt; line-height: 1.5; background-color: transparent;">=
&gt;</span>&gt; A second thing is that TransactionIdGetCommitTsData() was =
introdued in</div><div><span style=3D"font-size: 10.5pt; line-height: 1.5;=
 background-color: transparent;">&gt;</span>&gt; core(73c986add). It has o=
nly one caller pg_xact_commit_timestamp() which</div><div><span style=3D"f=
ont-size: 10.5pt; line-height: 1.5; background-color: transparent;">&gt;</=
span>&gt; passes RepOriginId as NULL, making last argument to the</div><di=
v><span style=3D"font-size: 10.5pt; line-height: 1.5; background-color: tr=
ansparent;">&gt;</span>&gt; TransactionIdGetCommitTsData() a dead code in =
core.</div><div><span style=3D"font-size: 10.5pt; line-height: 1.5; backgr=
ound-color: transparent;">&gt;</span>&gt;</div><div><span style=3D"font-si=
ze: 10.5pt; line-height: 1.5; background-color: transparent;">&gt;</span>&=
gt; Quick code search shows that it is getting used by pglogical (caller:<=
/div><div><span style=3D"font-size: 10.5pt; line-height: 1.5; background-c=
olor: transparent;">&gt;</span>&gt; https://sources.debian.org/src/pglogic=
al/2.3.2-1/pglogical_conflict.c/?hl=3D509#L509).</div><div><span style=3D"=
font-size: 10.5pt; line-height: 1.5; background-color: transparent;">&gt;<=
/span>&gt; CCing Craig Ringer and Petr Jelinek for the inputs.</div><div>&=
nbsp;</div><div><span style=3D"font-size: 10.5pt; line-height: 1.5; backgr=
ound-color: transparent;">&gt;</span>Another question that has popped up w=
hen doing this review is what</div><div><span style=3D"font-size: 10.5pt; =
line-height: 1.5; background-color: transparent;">&gt;</span>would be the =
use-case of adding this information at SQL level knowing</div><div><span s=
tyle=3D"font-size: 10.5pt; line-height: 1.5; background-color: transparent=
;">&gt;</span>t<span style=3D"font-size: 10.5pt; line-height: 1.5; backgro=
und-color: transparent;">hat logical replication exists since 10?&nbsp; Ha=
ving dead code in the</span></div><div><span style=3D"font-size: 10.5pt; l=
ine-height: 1.5; background-color: transparent;">&gt;</span>backend tree i=
s not a good idea of course, so we can also have as</div><div><span style=
=3D"font-size: 10.5pt; line-height: 1.5; background-color: transparent;">&=
gt;</span>argument to simplify TransactionIdGetCommitTsData().&nbsp; Now, =
pglogical</div><div><span style=3D"font-size: 10.5pt; line-height: 1.5; ba=
ckground-color: transparent;">&gt;</span>has pglogical_xact_commit_timesta=
mp_origin() to get the replication</div><div><span style=3D"font-size: 10.=
5pt; line-height: 1.5; background-color: transparent;">&gt;</span>origin w=
ith its own function so providing an extending equivalent</div><div><span =
style=3D"font-size: 10.5pt; line-height: 1.5; background-color: transparen=
t;">&gt;</span>r<span style=3D"font-size: 10.5pt; line-height: 1.5; backgr=
ound-color: transparent;">eturning one row with two fields would be nice f=
or pglogical so as</span></div><div><span style=3D"font-size: 10.5pt; line=
-height: 1.5; background-color: transparent;">&gt;</span>this function is =
not necessary.&nbsp; As mentioned by Madan, the portion of</div><div><span=
 style=3D"font-size: 10.5pt; line-height: 1.5; background-color: transpare=
nt;">&gt;</span>the code using TransactionIdGetCommitTsData() relies on it=
 for</div><div><span style=3D"font-size: 10.5pt; line-height: 1.5; backgro=
und-color: transparent;">&gt;</span>conflicts of updates (the first win, l=
ast win logic at quick glance).</div><div><br></div><div><div>Thanks for t=
he explanation, the origin in commit_ts seems useless, I am just</div><div=
>want to know why it appears there. It's ok to close this issue if we do n=
ot</div><div>want to touch it now.</div><div><br></div><div>And I am more =
interest in origin in wal, if data from a logical replicate or a&nbsp;</di=
v><div>manual origin then many wal records will get a 'RepOriginId', &nbsp=
;'RepOriginId'</div><div>in 'xact' wal record may help to do some filter, =
the other same dead code</div><div>too. So can&nbsp;<span style=3D"font-si=
ze: 10.5pt; line-height: 1.5; background-color: transparent;">you help me =
to understand why or the historical reason for that?</span></div></div></d=
iv><div><br></div><div><br></div><hr style=3D"width: 210px; height: 1px;" =
color=3D"#b5c4df" size=3D"1" align=3D"left">=0A<div><span><div style=3D"MA=
RGIN: 10px; FONT-FAMILY: verdana; FONT-SIZE: 10pt"><span style=3D"color: r=
gb(13, 10, 11); font-family: monospace, monospace; font-size: 10.7333px; f=
ont-variant-ligatures: normal; orphans: 2; white-space: pre-wrap; widows: =
2;">Regards,</span></div><div style=3D"MARGIN: 10px; FONT-FAMILY: verdana;=
 FONT-SIZE: 10pt"><span style=3D"color: rgb(13, 10, 11); font-family: mono=
space, monospace; font-size: 10.7333px; font-variant-ligatures: normal; or=
phans: 2; white-space: pre-wrap; widows: 2;">Highgo Software (Canada/China=
/Pakistan) </span><br style=3D"box-sizing: border-box; color: rgb(13, 10, =
11); font-family: monospace, monospace; font-size: 10.7333px; font-variant=
-ligatures: normal; orphans: 2; white-space: pre-wrap; widows: 2;"><span s=
tyle=3D"color: rgb(13, 10, 11); font-family: monospace, monospace; font-si=
ze: 10.7333px; font-variant-ligatures: normal; orphans: 2; white-space: pr=
e-wrap; widows: 2;">URL : </span><a href=3D"http://www.highgo.ca/" rel=3D"=
nofollow" style=3D"box-sizing: border-box; color: rgb(132, 0, 50); text-de=
coration: none; font-weight: 600; transition: color 0.2s ease-in-out 0s; f=
ont-family: monospace, monospace; font-size: 10.7333px; font-variant-ligat=
ures: normal; orphans: 2; white-space: pre-wrap; widows: 2;">www.highgo.ca=
</a><span style=3D"color: rgb(13, 10, 11); font-family: monospace, monospa=
ce; font-size: 10.7333px; font-variant-ligatures: normal; orphans: 2; whit=
e-space: pre-wrap; widows: 2;"> </span><br style=3D"box-sizing: border-box=
; color: rgb(13, 10, 11); font-family: monospace, monospace; font-size: 10=
.7333px; font-variant-ligatures: normal; orphans: 2; white-space: pre-wrap=
; widows: 2;"><span style=3D"color: rgb(13, 10, 11); font-family: monospac=
e, monospace; font-size: 10.7333px; font-variant-ligatures: normal; orphan=
s: 2; white-space: pre-wrap; widows: 2;">EMAIL: mailto:movead(dot)li(at)hi=
ghgo(dot)ca</span></div></span></div><blockquote style=3D"margin-Top: 0px;=
 margin-Bottom: 0px; margin-Left: 0.5em; margin-Right: inherit"><div>=0A</=
div></blockquote>=0A</body></html>
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