Re: pgsql: Allow HOT updates for some expression indexes

On 27 March 2018 at 22:26, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> I wrote:
>> The test script appears to imagine that pgstats outputs update
>> instantaneously.
>
> Oh, wait, it's looking at pg_stat_xact, which is the *local*, unsent
> stats information.  So your problem is actually the reverse of that:
> if the test runs too slowly, it fails, because at some point the
> unsent stats information will get flushed out to the collector and
> disappear from the pg_stat_xact view.
>
> You could probably make this more reliable by wrapping each test
> stanza in a transaction, ie instead of
>
> create table keyvalue ...;
> ... do something to table ...
> select pg_stat_get_xact_tuples_hot_updated('keyvalue'::regclass);
> drop table keyvalue;
>
> do
>
> begin;
> create table keyvalue ...;
> ... do something to table ...
> select pg_stat_get_xact_tuples_hot_updated('keyvalue'::regclass);
> rollback;
>
> (no need for a DROP if you're rolling it all back)

Oh wow, thanks. Fixed.

-- 
Simon Riggs                http://www.2ndQuadrant.com/
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