Fix planner error when estimating SubPlan cost SubPlan nodes are typically built very early, before any RelOptInfos have been constructed for the parent query level. As a result, the simple_rel_array in the parent root has not yet been initialized. Currently, during cost estimation of a SubPlan's testexpr, we may call examine_variable() to look up statistical data about the expressions. This can lead to "no relation entry for relid" errors.
To fix, pass root as NULL to cost_qual_eval() in cost_subplan(), since the root does not yet contain enough information to safely consult statistics. One exception is SubPlan nodes built for the initplans of MIN/MAX aggregates from indexes. In this case, having a NULL root is safe because testexpr will be NULL. Additionally, an initplan will by definition not consult anything from the parent plan. Backpatch to all supported branches. Although the reported call path that triggers this error is not reachable prior to v17, there's no guarantee that other code paths -- especially in extensions -- could not encounter the same issue when cost_qual_eval() is called with a root that lacks a valid simple_rel_array. The test case is not included in pre-v17 branches though. Bug: #19037 Reported-by: Alexander Lakhin <exclus...@gmail.com> Diagnosed-by: Tom Lane <t...@sss.pgh.pa.us> Author: Richard Guo <guofengli...@gmail.com> Reviewed-by: Tom Lane <t...@sss.pgh.pa.us> Discussion: https://postgr.es/m/19037-3d1c7bb553c7c...@postgresql.org Backpatch-through: 13 Branch ------ master Details ------- https://git.postgresql.org/pg/commitdiff/aba8f61c30911cbac1a310b7d21777e04711c66e Modified Files -------------- src/backend/optimizer/path/costsize.c | 18 ++++++++++++++++-- src/test/regress/expected/subselect.out | 19 +++++++++++++++++++ src/test/regress/sql/subselect.sql | 9 +++++++++ 3 files changed, 44 insertions(+), 2 deletions(-)
