Обсуждение: pgsql: Doc: clarify locking requirements for ALTER TABLE ADD FOREIGN KE

Doc: clarify locking requirements for ALTER TABLE ADD FOREIGN KEY.

The docs explained that a SHARE ROW EXCLUSIVE lock is needed on the
referenced table, but failed to say the same about the table being
altered.  Since the page says that ACCESS EXCLUSIVE lock is taken
unless otherwise stated, this left readers with the wrong conclusion.

Discussion: https://postgr.es/m/834603375.3470346.1586482852542@mail.yahoo.com

Branch
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REL9_5_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/2cab4ad81bcb44ccd6591ed1fb54495c7301b42d

Modified Files
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doc/src/sgml/ref/alter_table.sgml | 21 ++++++++++++++++-----
1 file changed, 16 insertions(+), 5 deletions(-)