| From: | Justin Pryzby <pryzby(at)telsasoft(dot)com> |
|---|---|
| To: | Michael Lewis <mlewis(at)entrata(dot)com> |
| Cc: | Simon Riggs <simon(at)2ndquadrant(dot)com>, Chris Wilson <chris(dot)wilson(at)cantabcapital(dot)com>, pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: EXPLAIN ANALYZE of BRIN bitmap index scan with disjunction |
| Date: | 2019-06-20 18:13:35 |
| Message-ID: | 20190620181335.GY16019@telsasoft.com |
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| Lists: | pgsql-performance |
On Thu, Jun 20, 2019 at 12:09:13PM -0600, Michael Lewis wrote:
> For kicks I tried the example given and got the below which seems more
> expected.
Do you just mean that it ran faster the 2nd time ? Isn't that just due just to
cache effects ? Rerun them both back to back.
See that the "actual" rowcount of the Index Scan is higher with tigher
condition:
> -> Bitmap Index Scan on idx_brin_test_brin (cost=0.00..3.32 rows=14286 width=0) (actual time=0.018..0.019 rows=640 loops=1)
> Index Cond: (id >= 90000)
> -> Bitmap Index Scan on idx_brin_test_brin (cost=0.00..3.31 rows=7143 width=0) (actual time=0.026..0.027 rows=1280 loops=1)
> Index Cond: ((id >= 90000) AND (r = ANY ('{1,3}'::integer[])))
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