pgsql: bloom: Optimize bitmap scan path with streaming read

bloom: Optimize bitmap scan path with streaming read

This commit replaces the per-page buffer read look in blgetbitmap() with
a reading stream, to improve scan efficiency, particularly useful for
large bloom indexes.  Some benchmarking with a large number of rows has
shown a very nice improvement in terms of runtime and IO read reduction
with test cases up to 10M rows for a bloom index scan.

For the io_uring method, The author has reported a 3x in runtime with
io_uring while I was at close to a 7x.  For the worker method with 3
workers, the author has reported better numbers than myself in runtime,
with the reduction in IO stats being appealing for all the cases
measured.

Author: Xuneng Zhou <xunengzhou@gmail.com>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Reviewed-by: Nazir Bilal Yavuz <byavuz81@gmail.com>
Discussion: https://postgr.es/m/CABPTF7VrqfbcDXqGrdLQ2xaQ=K0RzExNuw6U_GGqzSJu32wfdQ@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/4c910f3bbe92aa4e84ff15fa27b4de2da0d7ae50

Modified Files
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contrib/bloom/blscan.c | 29 +++++++++++++++++++++++++----
1 file changed, 25 insertions(+), 4 deletions(-)