LuciferYang commented on PR #68018:
URL: https://github.com/apache/doris/pull/68018#issuecomment-5747709933

   Thanks for the re-review. Agreed there is no new inline finding here; the 
three P1s it re-raises (r4017097815, r4025665398, r4032777651) are the same 
placeholder-index exposure, and I want to state how it is fenced rather than 
leave the deferral implicit.
   
   This PR is not meant to merge independently. It is ordered behind #67995, 
which moves placeholder handling into `Segment::new_index_iterator` (and the 
zone-map builders and the pushed-agg gate), keyed on the column's schema 
ordinal rather than on which reader happens to be cached. Until #67995 is in, 
"this head is not independently safe to merge" is accurate and expected, not an 
oversight.
   
   The reason the guard is not in this diff is the same evidence those three 
findings provide. A reader-type check cannot carry the invariant: eviction 
(r4032777651) and a concurrent bare miss (r4025665398) both rebuild a physical 
reader for a placeholder column, and the bare index path passes no constant, so 
the check is bypassed. That is why I removed the 
`ConstantColumnReader::new_index_iterator` override. Residency and arrival 
order are not a place to store a correctness property; the schema is.
   
   So this PR stays scoped to the cache contract: a request carrying a constant 
is not dropped on a hit, and the entry is replaced in place. That part its two 
unit tests cover on their own. #67995 lands first, then this one.


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