From: | Alik Khilazhev <a(dot)khilazhev(at)postgrespro(dot)ru> |
---|---|
To: | Peter Geoghegan <pg(at)bowt(dot)ie> |
Cc: | PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: [WIP] Zipfian distribution in pgbench |
Date: | 2017-07-12 11:28:58 |
Message-ID: | 998D4787-D98D-4FCC-A456-A2B56933E3E6@postgrespro.ru |
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Thread: | |
Lists: | pgsql-hackers |
> On 7 Jul 2017, at 21:53, Peter Geoghegan <pg(at)bowt(dot)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:
http://www.postgrespro.com <http://www.postgrespro.com/>
The Russian Postgres Company
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