Re: [WIP] Zipfian distribution in pgbench

> On 7 Jul 2017, at 21:53, Peter Geoghegan <pg@bowt.ie> wrote:
> 
> Is it possible for you to instrument the number of B-Tree page
> accesses using custom instrumentation for pgbench_accounts_pkey?
> 
> If that seems like too much work, then it would still be interesting
> to see what the B-Tree keyspace looks like before and after varying
> the "nclient" count from, say, 32 to 128. Maybe there is a significant
> difference in how balanced or skewed it is in each case. Or, the index
> could simply be more bloated.
> 
> There is a query that I sometimes use, that itself uses pageinspect,
> to summarize the keyspace quickly. It shows you the highkey for every
> internal page, starting from the root and working down to the lowest
> internal page level (the one just before the leaf level -- level 1),
> in logical/keyspace order. You can use it to visualize the
> distribution of values. It could easily include the leaf level, too,
> but that's less interesting and tends to make the query take ages. I
> wonder what the query will show here.
> 
> Here is the query:
> …

I am attaching results of query that you sent. It shows that there is nothing have changed after executing tests. 

—
Thanks and Regards,
Alik Khilazhev
Postgres Professional:
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