Fix CREATE VIEW to allow zero-column views.

tglsfdc · tglsfdc · commit 9fdc49d08fe4 · 2019-02-17T12:37:32.000-05:00
We should logically have allowed this case when we allowed zero-column tables, but it was overlooked. Although this might be thought a feature addition, it's really a bug fix, because it was possible to create a zero-column view via the convert-table-to-view code path, and then you'd have a situation where dump/reload would fail. Hence, back-patch to all supported branches. Arrange the added test cases to provide coverage of the related pg_dump code paths (since these views will be dumped and reloaded during the pg_upgrade regression test). I also made them test the case where pg_dump has to postpone the view rule into post-data, which disturbingly had no regression coverage before. Report and patch by Ashutosh Sharma (test case by me) Discussion: https://postgr.es/m/CAE9k0PkmHdeSaeZt2ujnb_cKucmK3sDDceDzw7+d5UZoNJPYOg@mail.gmail.com
diff --git a/src/backend/commands/view.c b/src/backend/commands/view.c
@@ -109,11 +109,6 @@ DefineVirtualRelation(RangeVar *relation, List *tlist, bool replace,
 		}
 	}
 
-	if (attrList == NIL)
-		ereport(ERROR,
-				(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
-				 errmsg("view must have at least one column")));
-
 	/*
 	 * Look up, check permissions on, and lock the creation namespace; also
 	 * check for a preexisting view with the same name.  This will also set
diff --git a/src/test/regress/expected/create_view.out b/src/test/regress/expected/create_view.out
@@ -20,6 +20,16 @@ COMMENT ON VIEW noview IS 'no view';
 ERROR:  relation "noview" does not exist
 COMMENT ON VIEW toyemp IS 'is a view';
 COMMENT ON VIEW toyemp IS NULL;
+-- These views are left around mainly to exercise special cases in pg_dump.
+CREATE TABLE view_base_table (key int PRIMARY KEY, data varchar(20));
+CREATE VIEW key_dependent_view AS
+   SELECT * FROM view_base_table GROUP BY key;
+ALTER TABLE view_base_table DROP CONSTRAINT view_base_table_pkey;  -- fails
+ERROR:  cannot drop constraint view_base_table_pkey on table view_base_table because other objects depend on it
+DETAIL:  view key_dependent_view depends on constraint view_base_table_pkey on table view_base_table
+HINT:  Use DROP ... CASCADE to drop the dependent objects too.
+CREATE VIEW key_dependent_view_no_cols AS
+   SELECT FROM view_base_table GROUP BY key HAVING length(data) > 0;
 --
 -- CREATE OR REPLACE VIEW
 --
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
@@ -1285,6 +1285,14 @@ iexit| SELECT ih.name,
    FROM ihighway ih,
     ramp r
   WHERE (ih.thepath ## r.thepath);
+key_dependent_view| SELECT view_base_table.key,
+    view_base_table.data
+   FROM view_base_table
+  GROUP BY view_base_table.key;
+key_dependent_view_no_cols| SELECT
+   FROM view_base_table
+  GROUP BY view_base_table.key
+ HAVING (length((view_base_table.data)::text) > 0);
 pg_available_extension_versions| SELECT e.name,
     e.version,
     (x.extname IS NOT NULL) AS installed,
diff --git a/src/test/regress/expected/sanity_check.out b/src/test/regress/expected/sanity_check.out
@@ -167,6 +167,7 @@ timestamp_tbl|f
 timestamptz_tbl|f
 timetz_tbl|f
 varchar_tbl|f
+view_base_table|t
 -- restore normal output mode
 \a\t
 --
diff --git a/src/test/regress/sql/create_view.sql b/src/test/regress/sql/create_view.sql
@@ -24,6 +24,18 @@ COMMENT ON VIEW noview IS 'no view';
 COMMENT ON VIEW toyemp IS 'is a view';
 COMMENT ON VIEW toyemp IS NULL;
 
+-- These views are left around mainly to exercise special cases in pg_dump.
+
+CREATE TABLE view_base_table (key int PRIMARY KEY, data varchar(20));
+
+CREATE VIEW key_dependent_view AS
+   SELECT * FROM view_base_table GROUP BY key;
+
+ALTER TABLE view_base_table DROP CONSTRAINT view_base_table_pkey;  -- fails
+
+CREATE VIEW key_dependent_view_no_cols AS
+   SELECT FROM view_base_table GROUP BY key HAVING length(data) > 0;
+
 --
 -- CREATE OR REPLACE VIEW
 --

Original file line number	Diff line number	Diff line change
`@@ -109,11 +109,6 @@ DefineVirtualRelation(RangeVar relation, List tlist, bool replace,`
`109`	`109`	`}`
`110`	`110`	`}`
`111`	`111`
`112`		`- if (attrList == NIL)`
`113`		`- ereport(ERROR,`
`114`		`- (errcode(ERRCODE_INVALID_TABLE_DEFINITION),`
`115`		`- errmsg("view must have at least one column")));`
`116`		`-`
`117`	`112`	`/*`
`118`	`113`	`* Look up, check permissions on, and lock the creation namespace; also`
`119`	`114`	`* check for a preexisting view with the same name. This will also set`