Re: pgsql: Allow HOT updates for some expression indexes

On 28.03.2018 07:23, Simon Riggs wrote:
> On 27 March 2018 at 22:26, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)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.
>

I am sorry, I missed the fact that local stat information can be reset.
Attached please find updated version of the patch with func_index.sql
test fixed.
Also I have renamed rd_indexattr to rd_nprjindexattr to avoid confusions.

--
Konstantin Knizhnik
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The Russian Postgres Company