Support for weak binding views to allow dropping of underlying objects

src/backend/commands/dropcmds.c

@@ -22,6 +22,7 @@
 #include "catalog/pg_namespace.h"
 #include "catalog/pg_proc.h"
 #include "commands/defrem.h"
+#include "commands/tablecmds.h"
 #include "miscadmin.h"
 #include "parser/parser.h"
 #include "parser/parse_type.h"
@@ -131,6 +132,13 @@ RemoveObjects(DropStmt *stmt)
 			table_close(relation, NoLock);
 
 		add_exact_object_address(&address, objects);
+
+		/* Check for strong views and handle weak views */
+		if ((stmt->removeType == OBJECT_FUNCTION) && view_dependency_hook)
+		{			
+			if (!(*view_dependency_hook)(&address, NULL, NULL))
+				continue;
+		}
 	}
 
 	/* Here we really delete them. */

src/backend/commands/tablecmds.c

@@ -138,6 +138,7 @@ InvokePreDropColumnHook_type InvokePreDropColumnHook = NULL;
 check_extended_attoptions_hook_type check_extended_attoptions_hook = NULL;
 find_attr_by_name_from_column_def_list_hook_type
 	find_attr_by_name_from_column_def_list_hook = NULL;
+view_dependency_hook_type view_dependency_hook = NULL;
 
 /*
  * State information for ALTER TABLE
@@ -1676,6 +1677,13 @@ RemoveRelations(DropStmt *drop)
 		{
 			InvokeObjectDropHook(RelationRelationId,relOid,0);
 		}
+
+		/* Check for strong views and handle weak views */
+		if ((drop->removeType == OBJECT_TABLE || drop->removeType == OBJECT_VIEW) && view_dependency_hook)
+		{			
+			if (!(*view_dependency_hook)(&obj, NULL, NULL))
+				continue;
+		}
 	}
 
 	performMultipleDeletions(objects, drop->behavior, flags);

src/backend/commands/view.c

@@ -22,6 +22,7 @@
 #include "nodes/makefuncs.h"
 #include "nodes/nodeFuncs.h"
 #include "parser/analyze.h"
+#include "parser/parser.h"
 #include "parser/parse_relation.h"
 #include "rewrite/rewriteDefine.h"
 #include "rewrite/rewriteHandler.h"
@@ -36,6 +37,8 @@ static void checkViewColumns(TupleDesc newdesc, TupleDesc olddesc);
 
 inherit_view_constraints_from_table_hook_type inherit_view_constraints_from_table_hook = NULL;
 
+check_view_dependencies_hook_type check_view_dependencies_hook = NULL;
+
 /*---------------------------------------------------------------------
  * DefineVirtualRelation
  *
@@ -381,6 +384,9 @@ DefineView(ViewStmt *stmt, const char *queryString,
 
 	viewParse = parse_analyze_fixedparams(rawstmt, queryString, NULL, 0, NULL);
 
+	if (check_view_dependencies_hook)
+			(*check_view_dependencies_hook)(viewParse);
+
 	/*
 	 * The grammar should ensure that the result is a single SELECT Query.
 	 * However, it doesn't forbid SELECT INTO, so we have to check for that.

src/backend/rewrite/rewriteHandler.c

@@ -47,6 +47,7 @@
 #include "utils/rel.h"
 
 bbfViewHasInsteadofTrigger_hook_type bbfViewHasInsteadofTrigger_hook = NULL; /** BBF Hook to check Instead Of trigger on View */
+view_repair_hook_type view_repair_hook = NULL;
 
 /* We use a list of these to detect recursion in RewriteQuery */
 typedef struct rewrite_event
@@ -4403,7 +4404,6 @@ RewriteQuery(Query *parsetree, List *rewrite_events, int orig_rt_length)
 	return rewritten;
 }
 
-
 /*
  * QueryRewrite -
  *	  Primary entry point to the query rewriter.
@@ -4431,6 +4431,14 @@ QueryRewrite(Query *parsetree)
 	Assert(parsetree->canSetTag);
 
 	/*
+     * Step 0 (Babelfish extension)
+     *
+     * If this is a view with broken rules, try to repair it
+     * using the definition from babelfish_view_def
+     */
+	if (view_repair_hook)
+		(*view_repair_hook)(parsetree);
+	/*
 	 * Step 1
 	 *
 	 * Apply all non-SELECT rules possibly getting 0 or many queries

src/bin/pg_dump/pg_dump.c

@@ -344,7 +344,7 @@ static void setupDumpWorker(Archive *AH);
 static TableInfo *getRootTableInfo(const TableInfo *tbinfo);
 static bool forcePartitionRootLoad(const TableInfo *tbinfo);
 static void read_dump_filters(const char *filename, DumpOptions *dopt);
-
+static PQExpBuffer createDummyViewAsClause(Archive *fout, const TableInfo *tbinfo);
 
 int
 main(int argc, char **argv)
@@ -15856,8 +15856,19 @@ createViewAsClause(Archive *fout, const TableInfo *tbinfo)
 	len = PQgetlength(res, 0, 0);
 
 	if (len == 0)
-		pg_fatal("definition of view \"%s\" appears to be empty (length zero)",
-				 tbinfo->dobj.name);
+	{
+		/* 
+		 * Handle broken views (with empty definitions)
+		 * Instead of failing, create a dummy SELECT that preserves the structure
+		 */
+		PQclear(res);
+		destroyPQExpBuffer(query);
+
+		/* Use createDummyViewAsClause to generate a compatible structure */
+		result = createDummyViewAsClause(fout, tbinfo);
+
+		return result;
+	}
 
 	/* Strip off the trailing semicolon so that other things may follow. */
 	Assert(PQgetvalue(res, 0, 0)[len - 1] == ';');

src/include/commands/tablecmds.h

@@ -122,4 +122,8 @@ typedef int (*find_attr_by_name_from_column_def_list_hook_type) (
 extern PGDLLEXPORT find_attr_by_name_from_column_def_list_hook_type
 	find_attr_by_name_from_column_def_list_hook;
 
+/* Hook for handling view dependencies during table drops */
+typedef bool (*view_dependency_hook_type) (const ObjectAddress *droppedObject, Relation depRel, ViewStmt *viewstmt);
+extern PGDLLIMPORT view_dependency_hook_type view_dependency_hook;
+
 #endif							/* TABLECMDS_H */

src/include/commands/view.h

@@ -27,4 +27,7 @@ extern PGDLLEXPORT store_view_definition_hook_type	store_view_definition_hook;
 
 typedef void (*inherit_view_constraints_from_table_hook_type) (ColumnDef  *col, Oid tableOid, AttrNumber colId);
 extern PGDLLEXPORT inherit_view_constraints_from_table_hook_type inherit_view_constraints_from_table_hook;
+
+typedef bool (*check_view_dependencies_hook_type) (Query *viewParse);
+extern check_view_dependencies_hook_type check_view_dependencies_hook;
 #endif							/* VIEW_H */

src/include/rewrite/rewriteHandler.h

@@ -38,4 +38,8 @@ extern void error_view_not_updatable(Relation view,
 									 List *mergeActionList,
 									 const char *detail);
 
+/* View repair hook */
+typedef bool (*view_repair_hook_type) (Query *parsetree);
+extern PGDLLEXPORT view_repair_hook_type view_repair_hook;									 
+
 #endif							/* REWRITEHANDLER_H */