Fix the incorrect column count after ALTER TABLE, this fixes the bug #7378 (please read the analysis in the bug for more information)

(cherry picked from commit 00068e07c5)

src/backend/distributed/deparser/ruleutils_13.c

@@ -1397,8 +1397,15 @@ set_join_column_names(deparse_namespace *dpns, RangeTblEntry *rte,
 
 	/* Assert we processed the right number of columns */
 #ifdef USE_ASSERT_CHECKING
-	while (i < colinfo->num_cols && colinfo->colnames[i] == NULL)
+	for (int col_index = 0; col_index < colinfo->num_cols; col_index++)
-		i++;
+	{
+		/*
+		 * In the above processing-loops, "i" advances only if
+		 * the column is not new, check if this is a new column.
+		 */
+		if (colinfo->is_new_col[col_index])
+			i++;
+	}
 	Assert(i == colinfo->num_cols);
 	Assert(j == nnewcolumns);
 #endif

src/backend/distributed/utils/citus_nodefuncs.c

@@ -141,7 +141,17 @@ SetRangeTblExtraData(RangeTblEntry *rte, CitusRTEKind rteKind, char *fragmentSch
 	fauxFunction->funcexpr = (Node *) fauxFuncExpr;
 
 	/* set the column count to pass ruleutils checks, not used elsewhere */
-	fauxFunction->funccolcount = list_length(rte->eref->colnames);
+	if (rte->relid != 0)
+	{
+		Relation rel = RelationIdGetRelation(rte->relid);
+		fauxFunction->funccolcount = RelationGetNumberOfAttributes(rel);
+		RelationClose(rel);
+	}
+	else
+	{
+		fauxFunction->funccolcount = list_length(rte->eref->colnames);
+	}
+
 	fauxFunction->funccolnames = funcColumnNames;
 	fauxFunction->funccoltypes = funcColumnTypes;
 	fauxFunction->funccoltypmods = funcColumnTypeMods;

src/test/regress/input/multi_alter_table_statements.source

@@ -631,3 +631,29 @@ CREATE TABLE referenced_table(i int UNIQUE);
 SELECT create_distributed_table('referenced_table', 'i');
 ALTER TABLE test_table_1 ADD COLUMN test_col int REFERENCES referenced_table(i);
 DROP TABLE referenced_table, test_table_1;
+
+-- Bug: https://github.com/citusdata/citus/issues/7378
+
+-- Create a reference table
+CREATE TABLE tbl_ref(row_id integer primary key);
+INSERT INTO tbl_ref VALUES (1), (2);
+SELECT create_reference_table('tbl_ref');
+
+-- Create a distributed table
+CREATE TABLE tbl_dist(series_id integer);
+INSERT INTO tbl_dist VALUES (1), (1), (2), (2);
+SELECT create_distributed_table('tbl_dist', 'series_id');
+
+-- Create a view that joins the distributed table with the reference table on the distribution key.
+CREATE VIEW vw_citus_views as
+SELECT d.series_id FROM tbl_dist d JOIN tbl_ref r ON d.series_id = r.row_id;
+
+-- The view initially works fine
+SELECT * FROM vw_citus_views ORDER BY 1;
+-- Now, alter the table
+ALTER TABLE tbl_ref ADD COLUMN category1 varchar(50);
+SELECT * FROM vw_citus_views ORDER BY 1;
+ALTER TABLE tbl_ref ADD COLUMN category2 varchar(50);
+SELECT * FROM vw_citus_views ORDER BY 1;
+ALTER TABLE tbl_ref DROP COLUMN category1;
+SELECT * FROM vw_citus_views ORDER BY 1;

src/test/regress/output/multi_alter_table_statements.source

@@ -1261,3 +1261,74 @@ ALTER TABLE test_table_1 ADD COLUMN test_col int REFERENCES referenced_table(i);
 ERROR:  cannot create foreign key constraint
 DETAIL:  Foreign keys are supported in two cases, either in between two colocated tables including partition column in the same ordinal in the both tables or from distributed to reference tables
 DROP TABLE referenced_table, test_table_1;
+-- Bug: https://github.com/citusdata/citus/issues/7378
+-- Create a reference table
+CREATE TABLE tbl_ref(row_id integer primary key);
+INSERT INTO tbl_ref VALUES (1), (2);
+SELECT create_reference_table('tbl_ref');
+NOTICE:  Copying data from local table...
+NOTICE:  copying the data has completed
+DETAIL:  The local data in the table is no longer visible, but is still on disk.
+HINT:  To remove the local data, run: SELECT truncate_local_data_after_distributing_table($$public.tbl_ref$$)
+ create_reference_table
+---------------------------------------------------------------------
+
+(1 row)
+
+-- Create a distributed table
+CREATE TABLE tbl_dist(series_id integer);
+INSERT INTO tbl_dist VALUES (1), (1), (2), (2);
+SELECT create_distributed_table('tbl_dist', 'series_id');
+NOTICE:  Copying data from local table...
+NOTICE:  copying the data has completed
+DETAIL:  The local data in the table is no longer visible, but is still on disk.
+HINT:  To remove the local data, run: SELECT truncate_local_data_after_distributing_table($$public.tbl_dist$$)
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+-- Create a view that joins the distributed table with the reference table on the distribution key.
+CREATE VIEW vw_citus_views as
+SELECT d.series_id FROM tbl_dist d JOIN tbl_ref r ON d.series_id = r.row_id;
+-- The view initially works fine
+SELECT * FROM vw_citus_views ORDER BY 1;
+ series_id
+---------------------------------------------------------------------
+         1
+         1
+         2
+         2
+(4 rows)
+
+-- Now, alter the table
+ALTER TABLE tbl_ref ADD COLUMN category1 varchar(50);
+SELECT * FROM vw_citus_views ORDER BY 1;
+ series_id
+---------------------------------------------------------------------
+         1
+         1
+         2
+         2
+(4 rows)
+
+ALTER TABLE tbl_ref ADD COLUMN category2 varchar(50);
+SELECT * FROM vw_citus_views ORDER BY 1;
+ series_id
+---------------------------------------------------------------------
+         1
+         1
+         2
+         2
+(4 rows)
+
+ALTER TABLE tbl_ref DROP COLUMN category1;
+SELECT * FROM vw_citus_views ORDER BY 1;
+ series_id
+---------------------------------------------------------------------
+         1
+         1
+         2
+         2
+(4 rows)
+