Querying a view fails if the base table has new columns added about citus

[tejeswarm]

In the Citus, the range table entries in a query are mocked as RTE_FUNCTION entries.

	MultiLogicalPlanCreate 
		MultiNodeTree takes { List *rangeTableList = queryTree->rtable }
			MultiTableNodeList(tableEntryList, rangeTableList);
				{ for each table in Join tableNode->referenceNames = rangeTableEntry->eref; }
                                   BaseRangeTableList
			              { RTE_FUNCTION rangeTableEntry->eref = multiTable->referenceNames; }
		                           SetRangeTblExtraData { funccolcount = list_length(rte->eref->colnames); }

Here the funccolcount gets the unaltered table's column count, i.e. 1, from the parse tree

During the runtime

AcquireRewriteLocks
   foreach(l, parsetree->rtable)
   	RTE_JOIN entry for each rte->joinaliasvars
               {rte->joinaliasvars gets the latest columns in expandRTE() -- expand the columns of a rangetable entry}
               and for each Var it calls
   	{ if (get_rte_attribute_is_dropped(curinputrte, aliasvar->varattno)) to check if any column is dropped }

This results in the ERROR as the curinputrte (RTE_FUNCTION) till has old column count in funccolcount.

ERROR: column 2 of relation "r" does not exist

This could be related to this change where we added expandRTE to accommodate dropped columns.

#4242

[tejeswarm]

This simple fix appears to have resolved the issue, but it may have other consequences, so we need to take a comprehensive look.

diff --git a/src/backend/distributed/utils/citus_nodefuncs.c b/src/backend/distributed/utils/citus_nodefuncs.c
index 55b83e6c5..110c61d1c 100644
--- a/src/backend/distributed/utils/citus_nodefuncs.c
+++ b/src/backend/distributed/utils/citus_nodefuncs.c
@@ -142,7 +142,16 @@ SetRangeTblExtraData(RangeTblEntry *rte, CitusRTEKind rteKind, char *fragmentSch
        fauxFunction->funcexpr = (Node *) fauxFuncExpr;

        /* set the column count to pass ruleutils checks, not used elsewhere */
+#if 0
        fauxFunction->funccolcount = list_length(rte->eref->colnames);
+#endif
+       if (rte->relid != 0)
+       {
+               Relation rel = RelationIdGetRelation(rte->relid);
+               fauxFunction->funccolcount = RelationGetNumberOfAttributes(rel);
+               RelationClose(rel);
+       }
+
        fauxFunction->funccolnames = funcColumnNames;
        fauxFunction->funccoltypes = funcColumnTypes;
        fauxFunction->funccoltypmods = funcColumnTypeMods;