pgsql: vacuumlazy.c: Standardize rel_pages terminology.

vacuumlazy.c: Standardize rel_pages terminology.

VACUUM's rel_pages field indicates the size of the target heap rel just
after the table_relation_vacuum() operation began. There are specific
expectations around how rel_pages can be related to other nearby state.
In particular, the range of rel_pages must contain every tuple in the
relation whose tuple headers might contain an XID < OldestXmin.

Consistently refer to the field as rel_pages to make this clearer and
more discoverable.

This is follow-up work to commit 73f6ec3d from earlier today.

Author: Peter Geoghegan <pg(at)bowt(dot)ie>
Reviewed-By: Andres Freund <andres(at)anarazel(dot)de>
Discussion: https://postgr.es/m/20220311031351.sbge5m2bpvy2ttxg@alap3.anarazel.de

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/e370f100f05d77eec258fb430009c16c0e315065

Modified Files
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src/backend/access/heap/vacuumlazy.c | 22 +++++++++++-----------
1 file changed, 11 insertions(+), 11 deletions(-)