pgsql: bloom: Optimize VACUUM and bulk-deletion with streaming read

bloom: Optimize VACUUM and bulk-deletion with streaming read

This commit replaces the synchronous ReadBufferExtended() loops done in
blbulkdelete() and blvacuumcleanup() with the streaming read equivalent,
to improve I/O efficiency during bloom index vacuum cleanup operations.

Under the same test conditions as 6c228755add8, the runtime is proving
to gain around 30% better, with most the benefits coming from a large
reduction of the IO operation based on the stats retrieved in the
scenarios run.

Author: Xuneng Zhou <xunengzhou(at)gmail(dot)com>
Reviewed-by: Michael Paquier <michael(at)paquier(dot)xyz>
Reviewed-by: Nazir Bilal Yavuz <byavuz81(at)gmail(dot)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/d841ca2d149666b823525e7f5258efd9ef9d7fb1

Modified Files
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contrib/bloom/blvacuum.c | 55 ++++++++++++++++++++++++++++++++++++++++++++----
1 file changed, 51 insertions(+), 4 deletions(-)