Function getPolicyForDistributedBy

src/backend/parser/parse_utilcmd.c:3110–3167

* Given a DistributedBy clause, construct a GpPolicy for it. */

 * Given a DistributedBy clause, construct a GpPolicy for it.
 */
GpPolicy *
getPolicyForDistributedBy(DistributedBy *distributedBy, TupleDesc tupdesc)
{
	List	   *policykeys;
	List	   *policyopclasses;
	ListCell   *lc;

	if (!distributedBy)
		return NULL; /* XXX or should we complain? */

	switch(distributedBy->ptype)
	{
		case POLICYTYPE_PARTITIONED:
			/* Look up the attribute numbers for each column */
			policykeys = NIL;
			policyopclasses = NIL;
			foreach(lc, distributedBy->keyCols)
			{
				DistributionKeyElem *dkelem = (DistributionKeyElem *) lfirst(lc);
				char	   *colname = dkelem->name;
				int			i;
				bool		found = false;

				for (i = 0; i < tupdesc->natts; i++)
				{
					Form_pg_attribute attr = TupleDescAttr(tupdesc, i);

					if (strcmp(colname, NameStr(attr->attname)) == 0)
					{
						Oid			opclass;

						opclass = cdb_get_opclass_for_column_def(dkelem->opclass, attr->atttypid);

						policykeys = lappend_int(policykeys, attr->attnum);
						policyopclasses = lappend_oid(policyopclasses, opclass);
						found = true;
					}
				}
				if (!found)
					ereport(ERROR,
							(errcode(ERRCODE_UNDEFINED_COLUMN),
							 errmsg("column \"%s\" does not exist", colname)));
			}

			return createHashPartitionedPolicy(policykeys,
											   policyopclasses,
											   distributedBy->numsegments);;

		case POLICYTYPE_ENTRY:
			elog(ERROR, "unexpected entry distribution policy");
			return NULL;

		case POLICYTYPE_REPLICATED:
			return createReplicatedGpPolicy(distributedBy->numsegments);
	}
	elog(ERROR, "unrecognized policy type %d", distributedBy->ptype);
	return NULL;
}