Fix BitmapHeapScan non-parallel-aware EXPLAIN ANALYZE Allocates shared bitmap table scan instrumentation for all parallel scans. Previously, the instrumentation was only allocated for parallel-aware scans, other bitmap heap scans in the parallel query had no shared instrumentation and EXPLAIN didn't report exact/lossy pages. This affected cases like scans on the outside of a parallel join or queries run with debug_parallel_query=regress.
Fixed by allocating a separate DSM chunk for shared instrumentation and doing so regardless of parallel-awareness. The instrumentation is allocated in its own DSM chunk, separate from ParallelBitmapHeapState. Report an initial patch by me. The approach with a separate DSM was proposed and implemented by Melanie. Not backpatched. The issue affects Postgres 18 (since 5a1e6df3b84c), but having multiple DSM chunks is possible only since dd78e69cfc33. If we decide to fix this in backbranches too, it will need to be done in a less invasive way. Author: Melanie Plageman <[email protected]> Reviewed-by: Tomas Vondra <[email protected]> Reviewed-by: Lukas Fittl <[email protected]> Discussion: https://postgr.es/m/flat/a177a6dd-240b-455a-8f25-aca0b1c08c6e%40vondra.me Branch ------ master Details ------- https://git.postgresql.org/pg/commitdiff/9c18b47e61071cf1395620f182b07a7ab9aac263 Modified Files -------------- src/backend/commands/explain.c | 2 +- src/backend/executor/execParallel.c | 9 +++ src/backend/executor/nodeBitmapHeapscan.c | 111 ++++++++++++++++++------------ src/include/executor/nodeBitmapHeapscan.h | 6 ++ 4 files changed, 83 insertions(+), 45 deletions(-)
