Re: [PATCH] ANALYZE: hash-accelerate MCV tracking for equality-only types

Hi,

Thank you for the detailed explanation! Your explanation helped me
understand the design much better.
I hope my understanding is now on the right track.

I tested v3 both approaches:

1. Ilia's proposal with corrected increment and <= condition:
   if (was_count1 && j <= firstcount1)
       firstcount1++;

2. The original patch with while loop:
   while (use_hash && firstcount1 < track_cnt &&
          track[firstcount1].count > 1)
       firstcount1++;

I verified the following cases and both approaches produced correct
track array values after the loop completed:

Case 1: c1_cursor == match_index
  c1_cursor points to a singleton, that singleton is matched again,
  bubble-up occurs, then a new value arrives triggering eviction.

Case 2: c1_cursor < match_index
  c1_cursor is in the earlier part of the singleton region,
  and a singleton further back is matched.

Case 3: c1_cursor > match_index
  c1_cursor has advanced past match_index due to previous evictions,
  and an earlier singleton is matched.

Both approaches seem to work correctly. The code reduction from 1 is
minimal, so either approach should be fine.
I believe the while loop exists to handle potential edge cases,
though in typical scenarios firstcount1 would only increment once per match
(since one singleton is promoted at a time).

Overall, the patch looks good to me.

Regards,
Tatsuya Kawata