Function get_hash_memory_limit

src/backend/executor/nodeHash.c:4111–4123

* Calculate the limit on how much memory can be used by Hash and similar * plan types. This is work_mem times hash_mem_multiplier, and is * expressed in bytes. * * Exported for use by the planner, as well as other hash-like executor * nodes. This is a rather random place for this, but there is no better * place. * * GPDB_14_MERGE_FIXME: Postgres uses work_mem to control the memory usage

 * and no other places actually need it to multiply with work_mem.
 */
size_t
get_hash_memory_limit(void)
{
	double		mem_limit;

	/* Do initial calculation in double arithmetic */
	mem_limit = (double) work_mem * hash_mem_multiplier * 1024.0;

	/* Clamp in case it doesn't fit in size_t */
	mem_limit = Min(mem_limit, (double) SIZE_MAX);

	return (size_t) mem_limit;
}

/*
 * Convert the hash memory limit to an integer number of kilobytes,