Fix plancache so that any required replanning is done with the same

search_path that was active when the plan was first made.  To do this,
improve namespace.c to support a stack of "override" search path settings
(we must have a stack since nested replan events are entirely possible).
This facility replaces the "special namespace" hack formerly used by
CREATE SCHEMA, and should be able to support per-function search path
settings as well.

src/backend/commands/schemacmds.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/schemacmds.c,v 1.44 2007/03/13 00:33:39 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/schemacmds.c,v 1.45 2007/03/23 19:53:51 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -43,6 +43,7 @@ CreateSchemaCommand(CreateSchemaStmt *stmt, const char *queryString)
 	const char *schemaName = stmt->schemaname;
 	const char *authId = stmt->authid;
 	Oid			namespaceId;
+	OverrideSearchPath *overridePath;
 	List	   *parsetree_list;
 	ListCell   *parsetree_item;
 	Oid			owner_uid;
@@ -102,7 +103,10 @@ CreateSchemaCommand(CreateSchemaStmt *stmt, const char *queryString)
 	 * well as the default creation target namespace.  This will be undone at
 	 * the end of this routine, or upon error.
 	 */
-	PushSpecialNamespace(namespaceId);
+	overridePath = GetOverrideSearchPath(CurrentMemoryContext);
+	overridePath->schemas = lcons_oid(namespaceId, overridePath->schemas);
+	/* XXX should we clear overridePath->useTemp? */
+	PushOverrideSearchPath(overridePath);
 
 	/*
 	 * Examine the list of commands embedded in the CREATE SCHEMA command, and
@@ -143,7 +147,7 @@ CreateSchemaCommand(CreateSchemaStmt *stmt, const char *queryString)
 	}
 
 	/* Reset search path to normal state */
-	PopSpecialNamespace(namespaceId);
+	PopOverrideSearchPath();
 
 	/* Reset current user */
 	SetUserId(saved_uid);

src/backend/utils/cache/plancache.c

@@ -33,13 +33,14 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/cache/plancache.c,v 1.3 2007/03/19 23:38:29 wieck Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/cache/plancache.c,v 1.4 2007/03/23 19:53:51 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
 #include "postgres.h"
 
 #include "utils/plancache.h"
+#include "catalog/namespace.h"
 #include "executor/executor.h"
 #include "optimizer/clauses.h"
 #include "storage/lmgr.h"
@@ -120,6 +121,7 @@ CreateCachedPlan(Node *raw_parse_tree,
 				 bool fixed_result)
 {
 	CachedPlanSource *plansource;
+	OverrideSearchPath *search_path;
 	MemoryContext source_context;
 	MemoryContext oldcxt;
 
@@ -133,6 +135,12 @@ CreateCachedPlan(Node *raw_parse_tree,
 										   ALLOCSET_SMALL_INITSIZE,
 										   ALLOCSET_SMALL_MAXSIZE);
 
+	/*
+	 * Fetch current search_path into new context, but do any recalculation
+	 * work required in caller's context.
+	 */
+	search_path = GetOverrideSearchPath(source_context);
+
 	/*
 	 * Create and fill the CachedPlanSource struct within the new context.
 	 */
@@ -151,6 +159,7 @@ CreateCachedPlan(Node *raw_parse_tree,
 	plansource->num_params = num_params;
 	plansource->fully_planned = fully_planned;
 	plansource->fixed_result = fixed_result;
+	plansource->search_path = search_path;
 	plansource->generation = 0;			/* StoreCachedPlan will increment */
 	plansource->resultDesc = PlanCacheComputeResultDesc(stmt_list);
 	plansource->plan = NULL;
@@ -209,8 +218,15 @@ FastCreateCachedPlan(Node *raw_parse_tree,
 					 MemoryContext context)
 {
 	CachedPlanSource *plansource;
+	OverrideSearchPath *search_path;
 	MemoryContext oldcxt;
 
+	/*
+	 * Fetch current search_path into given context, but do any recalculation
+	 * work required in caller's context.
+	 */
+	search_path = GetOverrideSearchPath(context);
+
 	/*
 	 * Create and fill the CachedPlanSource struct within the given context.
 	 */
@@ -223,6 +239,7 @@ FastCreateCachedPlan(Node *raw_parse_tree,
 	plansource->num_params = num_params;
 	plansource->fully_planned = fully_planned;
 	plansource->fixed_result = fixed_result;
+	plansource->search_path = search_path;
 	plansource->generation = 0;			/* StoreCachedPlan will increment */
 	plansource->resultDesc = PlanCacheComputeResultDesc(stmt_list);
 	plansource->plan = NULL;
@@ -420,6 +437,12 @@ RevalidateCachedPlan(CachedPlanSource *plansource, bool useResOwner)
 		List   *slist;
 		TupleDesc resultDesc;
 
+		/*
+		 * Restore the search_path that was in use when the plan was made.
+		 * (XXX is there anything else we really need to restore?)
+		 */
+		PushOverrideSearchPath(plansource->search_path);
+
 		/*
 		 * Run parse analysis and rule rewriting.  The parser tends to
 		 * scribble on its input, so we must copy the raw parse tree to
@@ -469,6 +492,9 @@ RevalidateCachedPlan(CachedPlanSource *plansource, bool useResOwner)
 			MemoryContextSwitchTo(oldcxt);
 		}
 
+		/* Now we can restore current search path */
+		PopOverrideSearchPath();
+
 		/*
 		 * Store the plans into the plancache entry, advancing the generation
 		 * count.

src/include/catalog/namespace.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/catalog/namespace.h,v 1.44 2007/01/05 22:19:52 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/catalog/namespace.h,v 1.45 2007/03/23 19:53:52 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -32,6 +32,16 @@ typedef struct _FuncCandidateList
 	Oid			args[1];		/* arg types --- VARIABLE LENGTH ARRAY */
 }	*FuncCandidateList;	/* VARIABLE LENGTH STRUCT */
 
+/*
+ *	Structure for xxxOverrideSearchPath functions
+ */
+typedef struct OverrideSearchPath
+{
+	List	   *schemas;		/* OIDs of explicitly named schemas */
+	bool		addCatalog;		/* implicitly prepend pg_catalog? */
+	bool		addTemp;		/* implicitly prepend temp schema? */
+} OverrideSearchPath;
+
 
 extern Oid	RangeVarGetRelid(const RangeVar *relation, bool failOK);
 extern Oid	RangeVarGetCreationNamespace(const RangeVar *newRelation);
@@ -72,8 +82,9 @@ extern bool isTempNamespace(Oid namespaceId);
 extern bool isAnyTempNamespace(Oid namespaceId);
 extern bool isOtherTempNamespace(Oid namespaceId);
 
-extern void PushSpecialNamespace(Oid namespaceId);
-extern void PopSpecialNamespace(Oid namespaceId);
+extern OverrideSearchPath *GetOverrideSearchPath(MemoryContext context);
+extern void PushOverrideSearchPath(OverrideSearchPath *newpath);
+extern void PopOverrideSearchPath(void);
 
 extern Oid	FindConversionByName(List *conname);
 extern Oid	FindDefaultConversionProc(int4 for_encoding, int4 to_encoding);

src/include/utils/plancache.h

@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/utils/plancache.h,v 1.3 2007/03/19 23:38:32 wieck Exp $
+ * $PostgreSQL: pgsql/src/include/utils/plancache.h,v 1.4 2007/03/23 19:53:52 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -53,6 +53,7 @@ typedef struct CachedPlanSource
 	int			num_params;		/* length of param_types array */
 	bool		fully_planned;	/* do we cache planner or rewriter output? */
 	bool		fixed_result;	/* disallow change in result tupdesc? */
+	struct OverrideSearchPath *search_path;		/* saved search_path */
 	int			generation;		/* counter, starting at 1, for replans */
 	TupleDesc	resultDesc;		/* result type; NULL = doesn't return tuples */
 	struct CachedPlan *plan;	/* link to plan, or NULL if not valid */

src/test/regress/expected/plancache.out

@@ -163,3 +163,42 @@ select cache_test_2();
         10007
 (1 row)
 
+--- Check that change of search_path is ignored by replans
+create schema s1
+  create table abc (f1 int);
+create schema s2
+  create table abc (f1 int);
+insert into s1.abc values(123);
+insert into s2.abc values(456);
+set search_path = s1;
+prepare p1 as select f1 from abc;
+execute p1;
+ f1  
+-----
+ 123
+(1 row)
+
+set search_path = s2;
+select f1 from abc;
+ f1  
+-----
+ 456
+(1 row)
+
+execute p1;
+ f1  
+-----
+ 123
+(1 row)
+
+alter table s1.abc add column f2 float8;   -- force replan
+execute p1;
+ f1  
+-----
+ 123
+(1 row)
+
+drop schema s1 cascade;
+NOTICE:  drop cascades to table s1.abc
+drop schema s2 cascade;
+NOTICE:  drop cascades to table abc

src/test/regress/sql/plancache.sql

@@ -93,3 +93,33 @@ select cache_test_2();
 create or replace temp view v1 as
   select 2+2+4+(select max(unique1) from tenk1) as f1;
 select cache_test_2();
+
+--- Check that change of search_path is ignored by replans
+
+create schema s1
+  create table abc (f1 int);
+
+create schema s2
+  create table abc (f1 int);
+
+insert into s1.abc values(123);
+insert into s2.abc values(456);
+
+set search_path = s1;
+
+prepare p1 as select f1 from abc;
+
+execute p1;
+
+set search_path = s2;
+
+select f1 from abc;
+
+execute p1;
+
+alter table s1.abc add column f2 float8;   -- force replan
+
+execute p1;
+
+drop schema s1 cascade;
+drop schema s2 cascade;