fix: guard against NULL subplan in full-path MERGE sub-case 1 (#2536) - #2546
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fix: guard against NULL subplan in full-path MERGE sub-case 1 (#2536)#2546waterWang wants to merge 1 commit into
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…#2536) When MERGE is the first clause followed by WITH (Case 3, sub-case 1), the code assumes the child execution node is always a SubqueryScanState and dereferences sss->subplan to obtain the tuple descriptor for the remade scan slot. When the MERGE path pattern produces no base-relation scan (e.g. empty graph), the planner emits a plain Result plan instead of a SubqueryScan, the cast-to-SubqueryScanState reads through the wrong struct layout, sss->subplan is NULL, and ExecGetResultType(NULL) segfaults. Fix: check IsA(lefttree, SubqueryScanState) before using SubqueryScanState internals. When the child is a SubqueryScan the original code path (remake child scan slot via sss->ss + ExecGetResultType(sss->subplan)) is preserved without regression. When the child is a Result plan, use the generic PlanState API (ExecGetResultType(lefttree)) and store the remade slot in the MERGE node's own ScanState. Fixes apache#2536.
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Fixes #2536.
Root cause: When a full-path MERGE is the first clause followed by a
WITH (Case 3, sub-case 1, path-not-found → create path), the code assumes
node->ss.ps.lefttreeis always aSubqueryScanStateand readsExecGetResultType(sss->subplan). When the MERGE path pattern producesno base-relation scan (e.g. empty graph), the planner emits a plain
Resultplan, theSubqueryScanStatecast reads through the wrong structlayout,
sss->subplanisNULL, andExecGetResultType(NULL)segfaults.Fix: check
IsA(lefttree, SubqueryScanState)before usingSubqueryScanStateinternals. For aSubqueryScanchild the originalcode path (remake child scan slot via
sss->ss+ExecGetResultType(sss->subplan))is preserved. For a
Resultchild, use the genericPlanStateAPI(
ExecGetResultType(lefttree)) and store the remade slot in the MERGEnode's own
ScanState.Tests: 41/43 regression tests pass (age_load and age_upgrade are
pre-existing environment failures). New regression test added to
regress/sql/expr.sqlreproduces the exact query shape from #2536.