Re: Why a bitmap scan in this case? - Mailing list pgsql-performance

From Frédéric Yhuel
Subject Re: Why a bitmap scan in this case?
Date
Msg-id 43c7d623-1805-4db2-a8fc-9a99d3633320@dalibo.com
Whole thread Raw
In response to Re: Why a bitmap scan in this case?  (Jon Zeppieri <zeppieri@gmail.com>)
Responses Re: Why a bitmap scan in this case?
List pgsql-performance

On 12/19/24 20:09, Jon Zeppieri wrote:
> The table is freshly vacuumed. If I disable bitmap scans, it will do
> an index only scan, which performs better. For the bitmap heap scan,
> it says "Heap Blocks: exact=27393," whereas for the index only scan,
> it's "Heap Fetches: 27701."

So you have 100% heap fetches. Are you sure that your table is freshly 
vacuumed? Please note that VACUUM FULL doesn't create the visibility 
map, so you still have to run a plain VACUUM for this.




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