pgsql: Remove dependency to system calls for memory allocation in refin

Remove dependency to system calls for memory allocation in refint

Failures in allocations could lead to crashes with NULL pointer
dereferences .  Memory context TopMemoryContext is used instead to keep
alive the plans allocated in the session.  A more specific context could
be used here, but this is left for later.

Reported-by: Jian Zhang
Author: Michael Paquier
Reviewed-by: Tom Lane, Andres Freund
Discussion: https://postgr.es/m/16190-70181c803641c3dc@postgresql.org

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/b0b6196386681383b8f0cb76df4fd35178a7371e

Modified Files
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contrib/spi/refint.c | 26 ++++++++++++++++++++------
1 file changed, 20 insertions(+), 6 deletions(-)