pgsql: Teach bitmap heap scan to cope with absence of a DSA.

Teach bitmap heap scan to cope with absence of a DSA.

If we have a plan that uses parallelism but are unable to execute it
using parallelism, for example due to a lack of available DSM
segments, then the EState's es_query_dsa will be NULL. Parallel
bitmap heap scan needs to fall back to a non-parallel scan in such
cases.

Patch by me, reviewed by Dilip Kumar

Discussion: http://postgr.es/m/CAEepm=0kADK5inNf_KuemjX=HQ=PuTP0DykM--fO5jS5ePVFEA@mail.gmail.com

Branch
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REL_10_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/ec7629dfb98a34cf4e459cf6b27febfd33ae9ad5

Modified Files
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src/backend/executor/nodeBitmapHeapscan.c | 11 +++++++++++
1 file changed, 11 insertions(+)