Handle exceptions caused by partitioned tables

[Leo-XM-Zeng]

Because we do not yet have good support for partitioned tables, the following code triggers assertions. #409

/*
 * RelationGetNumberOfBlocksInFork
 *		Determines the current number of pages in the specified relation fork.
 *
 * Note that the accuracy of the result will depend on the details of the
 * relation's storage. For builtin AMs it'll be accurate, but for external AMs
 * it might not be.
 */
BlockNumber
RelationGetNumberOfBlocksInFork(Relation relation, ForkNumber forkNum)
{
	if (RELKIND_HAS_TABLE_AM(relation->rd_rel->relkind))
	{
		/*
		 * Not every table AM uses BLCKSZ wide fixed size blocks. Therefore
		 * tableam returns the size in bytes - but for the purpose of this
		 * routine, we want the number of blocks. Therefore divide, rounding
		 * up.
		 */
		uint64		szbytes;

		szbytes = table_relation_size(relation, forkNum);

		return (szbytes + (BLCKSZ - 1)) / BLCKSZ;
	}
	else if (RELKIND_HAS_STORAGE(relation->rd_rel->relkind))
	{
		return smgrnblocks(RelationGetSmgr(relation), forkNum);
	}
	else
		Assert(false);

	return 0;					/* keep compiler quiet */
}

What does this PR do?

When accessing the partition table, we temporarily let PG handle it instead of DuckDB.
This temporarily avoids the unavailability of the system due to an assertion.

[JelteF]

Thank you for the fix. Some small naming suggestions, but other than that this looks good.

[JelteF]

I think Is is the wrong prefix here and the argument name tables is also confusing. We pass it a list of tables RTEs not a single table. I realize the problem is the case for IsCatalogTable, but we should change this there too (not in this PR though).

Suggested change

	IsPartitionedTable(List *tables) {
	ContainsPartitionedTable(List *rtes) {

[Leo-XM-Zeng]

Updated the IsCatalogTable function information #417

[JelteF]

Suggested change

	/* Check whether the table in the subquery is a partitioned table */
	/* Check whether any table in the subquery is a partitioned table */