zhangwenchao-123 opened a new pull request, #1860:
URL: https://github.com/apache/cloudberry/pull/1860
ORCA-translated plans get their extParam/allParam bitmapsets from
SetParamIds(), called piecemeal by every translator function. These bitmaps
are what rescan correctness hangs on: the executor propagates chgParam to a
child only if the child's allParam contains the changed param
(UpdateChangedParamSet()), and a Material node relies on that to discard its
tuplestore when a param of an enclosing SubPlan changes. Any translator path
that misses the call leaves a node with an empty bitmap, which silently breaks
the chgParam chain below it: a Material sitting above a subtree that consumes a
correlated param then replays the first outer row's result for every subsequent
row. GPDB 7.5.x shipped exactly this class of wrong-results regression for
correlated subqueries computing UNNEST over an outer column (fixed in 7.6.0).
Two hardenings:
1. Replace the per-translator SetParamIds() calls with one authoritative
pass in the ORCA post-processing (orca.c), run over the final shape of the plan
after all plan mutations. Every plan node, in the main tree and in every
subplan, now gets its bitmaps computed in one place, so a future translator
path cannot reintroduce the wrong-results hazard by forgetting a call.
The pass counts only PARAM_EXEC params, matching the regular planner's
finalize_primnode(): PARAM_EXTERN paramids live in a separate numbering space
(the client's $n) and never change during execution, so including them would
alias unrelated exec params and trigger spurious rescans of materialized
subtrees.
2. Set Material's cdb_shield_child_from_rescans only when the subtree below
actually contains a Motion. That flag exists to protect Motions, which cannot
be rescanned, from rescan and squelch (see the planner-side uses in
pathnode.c); the ORCA translator set it unconditionally on every Material. For
a Motion-free subtree the shield adds no benefit, and if the subtree consumes
params of an enclosing SubPlan it needlessly makes the cached result's
invalidation depend solely on the param bitmaps being right.
The ORCA optimizer model itself is sound and unchanged: a Spool over a
subtree with outer refs requests Rescannable from its children
(CPhysicalSpool::PrsRequired), i.e. it already assumes the executor rebuilds
the spooled result whenever the correlated params change.
The new orca_material_rescan regression test pins the vulnerable plan shape
- a correlated SubPlan whose nestloop inner side is a Material over a
Motion-free ProjectSet computing UNNEST over an outer column - and verifies
per-row results. Its tables are left unanalyzed on purpose: with default
cardinalities ORCA places the ProjectSet under the inner-side Material, which
is the shape this fix protects.
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Fixes #ISSUE_Number
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