pgsql: Fix memory leak and inefficiency in CREATE DATABASE ... STRATEGY

Fix memory leak and inefficiency in CREATE DATABASE ... STRATEGY WAL_LOG

RelationCopyStorageUsingBuffer() did not free the strategies used to access
the source / target relation. They memory was released at the end of the
transaction, but when using a template database with a lot of relations, the
temporary leak can become big prohibitively big.

RelationCopyStorageUsingBuffer() acquired the buffer for the target relation
with RBM_NORMAL, therefore requiring a read of a block guaranteed to be
zero. Use RBM_ZERO_AND_LOCK instead.

Reviewed-by: Robert Haas <robertmhaas(at)gmail(dot)com>
Discussion: https://postgr.es/m/20230321070113.o2vqqxogjykwgfrr@awork3.anarazel.de
Backpatch: 15-, where STRATEGY WAL_LOG was introduced

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/5df319f3d55d09fadb4f7e4b58c5b476a3aeceb4

Modified Files
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src/backend/storage/buffer/bufmgr.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)