Add support for invoking parser callback hooks via SPI and in cached plans.

As proof of concept, modify plpgsql to use the hooks.  plpgsql is still
inserting $n symbols textually, but the "back end" of the parsing process now
goes through the ParamRef hook instead of using a fixed parameter-type array,
and then execution only fetches actually-referenced parameters, using a hook
added to ParamListInfo.

Although there's a lot left to be done in plpgsql, this already cures the
"if (TG_OP = 'INSERT' and NEW.foo ...)"  problem, as illustrated by the
changed regression test.

5 files changed, 51 insertions, 9 deletions

diff --git a/src/include/executor/spi.h b/src/include/executor/spi.h
index 5bdde2d5241..42ba4e464d1 100644
--- a/src/include/executor/spi.h
+++ b/src/include/executor/spi.h
@@ -6,7 +6,7 @@
  * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/executor/spi.h,v 1.72 2009/06/11 14:49:11 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/executor/spi.h,v 1.73 2009/11/04 22:26:06 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -73,6 +73,9 @@ extern void SPI_restore_connection(void);
 extern int	SPI_execute(const char *src, bool read_only, long tcount);
 extern int SPI_execute_plan(SPIPlanPtr plan, Datum *Values, const char *Nulls,
 				 bool read_only, long tcount);
+extern int SPI_execute_plan_with_paramlist(SPIPlanPtr plan,
+										   ParamListInfo params,
+										   bool read_only, long tcount);
 extern int	SPI_exec(const char *src, long tcount);
 extern int SPI_execp(SPIPlanPtr plan, Datum *Values, const char *Nulls,
 		  long tcount);
@@ -88,6 +91,10 @@ extern int SPI_execute_with_args(const char *src,
 extern SPIPlanPtr SPI_prepare(const char *src, int nargs, Oid *argtypes);
 extern SPIPlanPtr SPI_prepare_cursor(const char *src, int nargs, Oid *argtypes,
 				   int cursorOptions);
+extern SPIPlanPtr SPI_prepare_params(const char *src,
+									 ParserSetupHook parserSetup,
+									 void *parserSetupArg,
+									 int cursorOptions);
 extern SPIPlanPtr SPI_saveplan(SPIPlanPtr plan);
 extern int	SPI_freeplan(SPIPlanPtr plan);
 
@@ -122,6 +129,8 @@ extern Portal SPI_cursor_open_with_args(const char *name,
 						  int nargs, Oid *argtypes,
 						  Datum *Values, const char *Nulls,
 						  bool read_only, int cursorOptions);
+extern Portal SPI_cursor_open_with_paramlist(const char *name, SPIPlanPtr plan,
+							   ParamListInfo params, bool read_only);
 extern Portal SPI_cursor_find(const char *name);
 extern void SPI_cursor_fetch(Portal portal, bool forward, long count);
 extern void SPI_cursor_move(Portal portal, bool forward, long count);
diff --git a/src/include/executor/spi_priv.h b/src/include/executor/spi_priv.h
index ef50a9013e8..a0dee126952 100644
--- a/src/include/executor/spi_priv.h
+++ b/src/include/executor/spi_priv.h
@@ -6,7 +6,7 @@
  * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/executor/spi_priv.h,v 1.32 2009/01/01 17:23:59 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/executor/spi_priv.h,v 1.33 2009/11/04 22:26:06 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -68,6 +68,8 @@ typedef struct _SPI_plan
 	int			cursor_options; /* Cursor options used for planning */
 	int			nargs;			/* number of plan arguments */
 	Oid		   *argtypes;		/* Argument types (NULL if nargs is 0) */
+	ParserSetupHook parserSetup;	/* alternative parameter spec method */
+	void	   *parserSetupArg;	
 } _SPI_plan;
 
 #endif   /* SPI_PRIV_H */
diff --git a/src/include/nodes/params.h b/src/include/nodes/params.h
index adc58710553..96cbf5267a4 100644
--- a/src/include/nodes/params.h
+++ b/src/include/nodes/params.h
@@ -7,13 +7,16 @@
  * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/nodes/params.h,v 1.38 2009/01/01 17:24:00 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/nodes/params.h,v 1.39 2009/11/04 22:26:06 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
 #ifndef PARAMS_H
 #define PARAMS_H
 
+/* To avoid including a pile of parser headers, reference ParseState thus: */
+struct ParseState;
+
 
 /* ----------------
  *	  ParamListInfo
@@ -26,10 +29,20 @@
  *	  Although parameter numbers are normally consecutive, we allow
  *	  ptype == InvalidOid to signal an unused array entry.
  *
+ *	  pflags is a flags field.  Currently the only used bit is:
  *	  PARAM_FLAG_CONST signals the planner that it may treat this parameter
  *	  as a constant (i.e., generate a plan that works only for this value
  *	  of the parameter).
  *
+ *	  There are two hook functions that can be associated with a ParamListInfo
+ *	  array to support dynamic parameter handling.  First, if paramFetch
+ *	  isn't null and the executor requires a value for an invalid parameter
+ *	  (one with ptype == InvalidOid), the paramFetch hook is called to give
+ *	  it a chance to fill in the parameter value.  Second, a parserSetup
+ *	  hook can be supplied to re-instantiate the original parsing hooks if
+ *	  a query needs to be re-parsed/planned (as a substitute for supposing
+ *	  that the current ptype values represent a fixed set of parameter types).
+
  *	  Although the data structure is really an array, not a list, we keep
  *	  the old typedef name to avoid unnecessary code changes.
  * ----------------
@@ -45,14 +58,22 @@ typedef struct ParamExternData
 	Oid			ptype;			/* parameter's datatype, or 0 */
 } ParamExternData;
 
+typedef struct ParamListInfoData *ParamListInfo;
+
+typedef void (*ParamFetchHook) (ParamListInfo params, int paramid);
+
+typedef void (*ParserSetupHook) (struct ParseState *pstate, void *arg);
+
 typedef struct ParamListInfoData
 {
+	ParamFetchHook paramFetch;	/* parameter fetch hook */
+	void	   *paramFetchArg;
+	ParserSetupHook parserSetup; /* parser setup hook */
+	void	   *parserSetupArg;
 	int			numParams;		/* number of ParamExternDatas following */
 	ParamExternData params[1];	/* VARIABLE LENGTH ARRAY */
 } ParamListInfoData;
 
-typedef ParamListInfoData *ParamListInfo;
-
 
 /* ----------------
  *	  ParamExecData
@@ -82,7 +103,7 @@ typedef struct ParamExecData
 /* Functions found in src/backend/nodes/params.c */
 extern ParamListInfo copyParamList(ParamListInfo from);
 
-extern void getParamListTypes(ParamListInfo params,
-				  Oid **param_types, int *num_params);
+extern void setupParserWithParamList(struct ParseState *pstate,
+									 ParamListInfo params);
 
 #endif   /* PARAMS_H */
diff --git a/src/include/tcop/tcopprot.h b/src/include/tcop/tcopprot.h
index b1c8b77bd5c..103a22fbc53 100644
--- a/src/include/tcop/tcopprot.h
+++ b/src/include/tcop/tcopprot.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/tcop/tcopprot.h,v 1.100 2009/09/01 00:09:42 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/tcop/tcopprot.h,v 1.101 2009/11/04 22:26:07 tgl Exp $
  *
  * OLD COMMENTS
  *	  This file was created so that other c files could get the two
@@ -49,6 +49,10 @@ extern List *pg_parse_and_rewrite(const char *query_string,
 extern List *pg_parse_query(const char *query_string);
 extern List *pg_analyze_and_rewrite(Node *parsetree, const char *query_string,
 					   Oid *paramTypes, int numParams);
+extern List *pg_analyze_and_rewrite_params(Node *parsetree,
+										   const char *query_string,
+										   ParserSetupHook parserSetup,
+										   void *parserSetupArg);
 extern PlannedStmt *pg_plan_query(Query *querytree, int cursorOptions,
 			  ParamListInfo boundParams);
 extern List *pg_plan_queries(List *querytrees, int cursorOptions,
diff --git a/src/include/utils/plancache.h b/src/include/utils/plancache.h
index ea919bd4566..68e3f72b195 100644
--- a/src/include/utils/plancache.h
+++ b/src/include/utils/plancache.h
@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/utils/plancache.h,v 1.15 2009/01/01 17:24:02 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/utils/plancache.h,v 1.16 2009/11/04 22:26:07 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -16,6 +16,7 @@
 #define PLANCACHE_H
 
 #include "access/tupdesc.h"
+#include "nodes/params.h"
 
 /*
  * CachedPlanSource represents the portion of a cached plan that persists
@@ -50,6 +51,8 @@ typedef struct CachedPlanSource
 	const char *commandTag;		/* command tag (a constant!), or NULL */
 	Oid		   *param_types;	/* array of parameter type OIDs, or NULL */
 	int			num_params;		/* length of param_types array */
+	ParserSetupHook parserSetup;	/* alternative parameter spec method */
+	void	   *parserSetupArg;	
 	int			cursor_options; /* cursor options used for planning */
 	bool		fully_planned;	/* do we cache planner or rewriter output? */
 	bool		fixed_result;	/* disallow change in result tupdesc? */
@@ -105,6 +108,9 @@ extern CachedPlanSource *FastCreateCachedPlan(Node *raw_parse_tree,
 					 bool fully_planned,
 					 bool fixed_result,
 					 MemoryContext context);
+extern void CachedPlanSetParserHook(CachedPlanSource *plansource,
+									ParserSetupHook parserSetup,
+									void *parserSetupArg);
 extern void DropCachedPlan(CachedPlanSource *plansource);
 extern CachedPlan *RevalidateCachedPlan(CachedPlanSource *plansource,
 					 bool useResOwner);