On 2/26/26 01:45, Ilia Evdokimov wrote:
> About op_is_reserved. It seems we should assign op_is_reserved = true,
> because we don't reverse types like eqjoinsel_semi(). If IN-list
> smaller than MCV-list we reverse it by fmgr_info(hash_mcv ? hashLeft :
> hashRight, &hash_proc). Thanks for this remark.
>
I guess I rushed to conclusions. This assignment op_is_reversed = true
was incorrect. During lookups, simplehash passes: key0 as the value
stored in the hash table, key1 as the probe value. Since MCV entries
correspond to the variable's statistics, the correct argument order
depends on which side we build the hash table on. If we hash MCV values
(hash_mcv = true), then key0 = MCV value, key1 = IN-list value, so we
must call operator(key0, key1). If we hash IN-list elements (hash_mcv =
fasle), then key0 = IN-list value, key1 = MCV value and we must call
operator(key1, key0). Therefore the correct assignment is
hashContext.op_is_reversed = hash_mcv.
If you have another suggestions to v6 patches, send them, and I'll fix
them with hashContext.op_is_reversed = hash_mcv.
--
Best regards,
Ilia Evdokimov,
Tantor Labs LLC,
https://tantorlabs.com/
