design: correct the fetch plan's ordering - #145
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…he check The plan put a needed-columns bitmap first, on the argument that the uniqueness check only needs the key columns. Reading the call path before writing any of it says otherwise: core's table_index_fetch_tuple_check creates a slot, calls table_index_fetch_tuple, and discards it, so the access method cannot tell that call from a real fetch and columnar_index_fetch_tuple fills every column either way. The caller that would benefit most has no way to declare what it needs. The statement-scoped decoded-group cache moves first, since it is the only piece that helps every caller. Also records that GetCurrentCommandId is enough to scope it, so an in-transaction vacuum invalidates the entry without a dedicated hook. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_012uKWWwBDt5TWWS5DR2tzDb
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Follow-up to #144, design document only.
I checked the call path before writing the piece the plan listed first, and it does not do what the plan assumed. The uniqueness check reaches
columnar_index_fetch_tuplethrough core'stable_index_fetch_tuple_check, which builds a slot, calls the ordinary fetch callback, and throws the slot away. The access method cannot distinguish that from a real fetch, so a needed-columns bitmap cannot help the caller it was aimed at.Reordered: the statement-scoped decoded-group cache goes first, since it helps every caller including the check. Also recorded that
GetCurrentCommandId(false)is enough to scope the cache to a statement, so apgcolumnar.vacuumin the same transaction invalidates it without a dedicated hook.