[HACKERS] May cause infinite loop when initializing rel-cache contains partitioned table

[甄明洋]

The function of  initializing rel-cache is RelationCacheInitializePhase3 and in 
src/backend/utils/cache/relcache.c file.
When initializing the partition description information, we forget to check if 
partition key or descriptor is NULL. 
Therefore, after the loop restarts, the partition information will be 
initialized again, resulting in an infinite loop.
Code:
/*
* Reload partition key and descriptor for a partitioned table.
*/
if (relation->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
{
RelationBuildPartitionKey(relation);
Assert(relation->rd_partkey != NULL);


RelationBuildPartitionDesc(relation);
Assert(relation->rd_partdesc != NULL);


restart = true;
}