Fix Assert failure in WITH RECURSIVE UNION queries If the non-recursive part of a recursive CTE ended up using TTSOpsBufferHeapTuple as the table slot type, then a duplicate value could cause an Assert failure in CheckOpSlotCompatibility() when checking the hash table for the duplicate value. The expected slot type for the deform step was TTSOpsMinimalTuple so the Assert failed when the TTSOpsBufferHeapTuple slot was used.
This is a long-standing bug which we likely didn't notice because it seems much more likely that the non-recursive term would have required projection and used a TTSOpsVirtual slot, which CheckOpSlotCompatibility is ok with. There doesn't seem to be any harm done here other than the Assert failure. Both TTSOpsMinimalTuple and TTSOpsBufferHeapTuple slot types require tuple deformation, so the EEOP_*_FETCHSOME ExprState step would have properly existed in the ExprState. The solution is to pass NULL for the ExecBuildGroupingEqual's 'lops' parameter. This means the ExprState's EEOP_*_FETCHSOME step won't expect a fixed slot type. This makes CheckOpSlotCompatibility() happy as no checking is performed when the ExprEvalStep is not expecting a fixed slot type. Reported-by: Richard Guo Reviewed-by: Tom Lane Discussion: https://postgr.es/m/cambws4-8u9q2latf8+ghv11zeurea3amrykxzbev0vkndxw...@mail.gmail.com Backpatch-through: 13, all supported versions Branch ------ master Details ------- https://git.postgresql.org/pg/commitdiff/8f4ee962691ed36302be3333c65422ed9e082743 Modified Files -------------- src/backend/executor/execGrouping.c | 3 +-- src/test/regress/expected/with.out | 15 +++++++++++++++ src/test/regress/sql/with.sql | 12 ++++++++++++ 3 files changed, 28 insertions(+), 2 deletions(-)
