[doc](query-cache) Document incremental merge (experimental)#3975
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asdf2014 wants to merge 1 commit into
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[doc](query-cache) Document incremental merge (experimental)#3975asdf2014 wants to merge 1 commit into
asdf2014 wants to merge 1 commit into
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Document the experimental incremental merge of the query cache in both the English and Chinese dev docs: how a stale entry is reused by scanning only the delta rowsets, the prerequisites (append-only index: duplicate-key, or merge-on-write unique-key verified through the delete bitmap window; non-finalize aggregation directly above the scan; local storage; capturable delta without delete predicates), the compaction threshold, and the observability surface (profile fields and BE metrics). Add five self-contained hand-drawn SVG diagrams: the full recompute vs incremental merge comparison, the merge-on-write delete bitmap window check, the per-instance dataflow, the decision flow with all fallback reasons, and an overview across FE, BE and storage.
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What does this PR do?
Documents the experimental incremental merge feature of the query cache
in the dev docs, English and Chinese. The feature itself is proposed in a
companion PR in apache/doris, which links back to this document PR:
keep invalidating the hot partition's entries), how a stale entry is reused
by scanning only
(cached_version, current_version], the prerequisites(append-only index: DUP_KEYS, or merge-on-write UNIQUE_KEYS whose delta
window did not rewrite pre-existing keys; non-finalize aggregation directly
above the scan; local storage mode; capturable delta with no delete
predicates), entry compaction via
query_cache_max_incremental_merge_count, and observability (profilefields and BE metrics).
enable_query_cache_incrementalandquery_cache_max_incremental_merge_count, plus a cross reference from theinvalidation table.
under
static/images/next/query-cache/, one per subsection: comparison,merge-on-write delete bitmap window, per-instance dataflow, decision flow
with all fallback reasons, and the overall architecture.
The feature ships default-off behind the experimental session switch; the
docs mark it as experimental accordingly.