Re: Unclear\mistakable description of UPDATE behaviour in "13.2.1. Read Committed Isolation Level"
| От | radiodiversion |
|---|---|
| Тема | Re: Unclear\mistakable description of UPDATE behaviour in "13.2.1. Read Committed Isolation Level" |
| Дата | |
| Msg-id | CAP7bpbDbieo4qkzVm+7Uk=Bx+zFnh5m6eYh-kZJaLuC8sTDAXw@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: Unclear\mistakable description of UPDATE behaviour in "13.2.1. Read Committed Isolation Level" ("David G. Johnston" <david.g.johnston@gmail.com>) |
| Ответы |
Re: Unclear\mistakable description of UPDATE behaviour in "13.2.1. Read Committed Isolation Level"
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| Список | pgsql-docs |
David, I have some suggestions.
but first i want to show how the current version of doc may look like for new readers. and why.
I am sure that it looks pretty logical if you KNOW how it works, but it is not so clear if you WANT to learn that from documentation.
explanation:
first sentence: "they will only find target rows that were committed as of the command start time."
how a naive user (me) read that: "okay. at the start of command we find only committed rows. LETS SEE WHAT HAPPENS NEXT!".
second sentence: "The search condition of the command (the
WHERE clause) is re-evaluated to see if the updated version of the row still matches the search condition."how it looks: "The command will be RE-EVALUATED for all rows in the current snapshot (i.e. against new state of db after first updater commits) to RE-CHECK the WHERE condition. AT THE SAME TIME (AS AN EFFECT) we see if the updated version of the row still matches the search condition."
For me RE-evaluating is an ACTION and "to see..that still matches" is ONE of the accompanying options.
As if I said: "I mowed all the grass to avoid seeing the dandelions again."
suggestion:
change sentence: "The search condition of the command (the
WHERE clause) is re-evaluated to see if the updated version of the row still matches the search condition."with sentence: "The search condition of the command (the
WHERE clause) is re-evaluated only for updated versions of rows to see if they still match the search condition. Note that this is different from re-executing the command."I tried to explain as best I could.
Of course, I dare not insist on anything.
Of course, I dare not insist on anything.
thanks!
On Wed, 18 Aug 2021 at 03:47, David G. Johnston <david.g.johnston@gmail.com> wrote:
On Tue, Aug 17, 2021 at 4:17 PM radiodiversion <radiodiversion@gmail.com> wrote:I still think it would be great if this doc point was worded a little differently in new editions.Suggestions are welcome.Without some idea of why you seemed to miss the two seemingly obvious references that I pointed out (including a fragment you quoted) it's hard to decide what might be an improvement. It's unappealing to consider rewriting the documentation based upon the experiences of a sample size of one without a clear rationale.David J.
with best regards,
radiodiversion
radiodiversion
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