Re: Truncation of UNLOGGED tables upon restart.

On 11/01/2018 03:58 PM, David G. Johnston wrote:
> On Thu, Nov 1, 2018 at 1:49 PM Ravi Krishna <srkrishna1(at)aol(dot)com
> <mailto: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.

Too bad you can't say ALTER TABLESPACE foo SET READONLY = false;

That would effectively give you read only tables.  I've done that before on
the legacy RDBMS I managed.

--
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