On Wed, 26 Jul 2023 at 19:46, gzh <gzhcoder@126.com> wrote:
> QUERY PLAN (enable_seqscan=on)
> Execution Time: 167183.133 ms
> QUERY PLAN (enable_seqscan=off)
> Execution Time: 22320.153 ms
effective_cache_size and random_page_cost are the settings you should
be adjusting to coax the planner into using the index.
A rule of thumb for effective_cache_size would be to set it to about
75% of RAM. There are certainly cases where lower would make more
sense, certainly, 75% will make more sense than the default 4GB value
in the majority of cases.
For random_page_cost, the default of 4.0 has been the default since
HDDs were common. SSDs are common now and, comparatively to sequential
I/O, their random I/O is faster than that of an HDD, so you may get
better results by lowering random_page_cost.
David