On Mon, Sep 3, 2018 at 2:44 PM Dilip Kumar <dilipbal...@gmail.com> wrote: > On Mon, Sep 3, 2018 at 8:37 AM, Amit Kapila <amit.kapil...@gmail.com> wrote: > > On Sat, Sep 1, 2018 at 10:28 AM Dilip Kumar <dilipbal...@gmail.com> wrote: > >> > >> I think if we compute with below formula which I suggested upthread > >> > >> #define HASH_MAX_BITMAPS Min(BLCKSZ / 8, 1024) > >> > >> then for BLCKSZ 8K and bigger, it will remain the same value where it > >> does not overrun. And, for the small BLCKSZ, I think it will give > >> sufficient space for the hash map. If the BLCKSZ is 1K then the sizeof > >> (HashMetaPageData) + sizeof (HashPageOpaque) = 968 which is very close > >> to the BLCKSZ. > >> > > > > Yeah, so at 1K, the value of HASH_MAX_BITMAPS will be 128 as per above > > formula which is what it was its value prior to the commit 620b49a1. > > I think it will be better if you add a comment in your patch > > indicating the importance/advantage of such a formula. > > > I have added the comments. >
Thanks, I will look into it. Can you please do some pg_upgrade tests to ensure that this doesn't impact the upgrade? You can create hash-index and populate it with some data in version 10 and try upgrading to 11 after applying this patch. You can also try it with different block-sizes. -- With Regards, Amit Kapila. EnterpriseDB: http://www.enterprisedb.com
