pgsql: Avoid SIGSEGV in pg_get_database_ddl() on NULL tablespace

Avoid SIGSEGV in pg_get_database_ddl() on NULL tablespace

There is a narrow race in which a concurrent ALTER DATABASE ... SET
TABLESPACE moves the database off the tablespace and a DROP TABLESPACE
removes it between the syscache lookup and the catalog scan. If that
happens, output an error.

Author: Chao Li <lic(at)highgo(dot)com>
Reviewed-by: Jack Bonatakis <jack(at)bonatak(dot)is>
Reviewed-by: Satyanarayana Narlapuram <satyanarlapuram(at)gmail(dot)com>
Reviewed-by: Japin Li <japinli(at)hotmail(dot)com>
Discussion: https://postgr.es/m/573E45C1-31A4-4885-A00C-1A2171159A2A@gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/5642a0367c2fe69684800c5d5c5929c20d99ef72

Modified Files
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src/backend/utils/adt/ddlutils.c | 7 +++++++
1 file changed, 7 insertions(+)