| From: | "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> |
|---|---|
| To: | srkrishna1(at)aol(dot)com |
| Cc: | "pgsql-generallists(dot)postgresql(dot)org" <pgsql-general(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: Truncation of UNLOGGED tables upon restart. |
| Date: | 2018-11-01 20:58:12 |
| Message-ID: | CAKFQuwaXNVdT6N75ZbjvO8+wySn=iW5xyc3Ox+faZ=XP_gz3rw@mail.gmail.com |
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| Lists: | pgsql-general |
On Thu, Nov 1, 2018 at 1:49 PM Ravi Krishna <srkrishna1(at)aol(dot)com> wrote:
> Per documentation unlogged tables are not crash safe and PG will truncate
> it when it restarts after a crash. Does this apply to even read only
> unlogged tables.
>
> For example:
>
> On Monday I load data into unlogged tables.
>
> Then from Tue onwards the table is only read by application.
>
> On Fri morning PG crashes. When it restarts will it truncate all unlogged
> tables even though they remained
> unchanged. I hope it does not.
"an unlogged table is automatically truncated after a crash or unclean
shutdown." - there are no exceptions noted.
There is no such thing as a "read only" table in PostgreSQL. All tables
are read/write no matter that frequency of either event. There is nothing
inherently special about "no writes for 4 days" and "no writes for 10
seconds" that would allow for a distinction to be made. There could be
write in progress on the table just as it crashes Friday.
David J.
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