pgsql: During pg_dump startup, acquire table locks in batches.

During pg_dump startup, acquire table locks in batches.

Combine multiple LOCK TABLE commands to reduce the number of
round trips to the server. This is particularly helpful when
dumping from a remote server, but it seems useful even without
that. In particular, shortening the time from seeing a table
in pg_class to acquiring lock on it reduces the window for
trouble from concurrent DDL.

Aleksander Alekseev, reviewed by Fabrízio de Royes Mello,
Gilles Darold, and Andres Freund

Discussion: https://postgr.es/m/CAJ7c6TO4z1+OBa-R+fC8FnaUgbEWJUf2Kq=nRngTW5EXtKru2g@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/5f53b42cfd053a724fcbe0712a9d5716e576a3e6

Modified Files
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src/bin/pg_dump/pg_dump.c | 36 +++++++++++++++++++++++++++++++-----
1 file changed, 31 insertions(+), 5 deletions(-)