Include a pointer to the query's source text in QueryDesc structs. This is

practically free given prior 8.4 changes in plancache and portal management,
and it makes it a lot easier for ExecutorStart/Run/End hooks to get at the
query text.  Extracted from Itagaki Takahiro's pg_stat_statements patch,
with minor editorialization.

src/include/executor/execdesc.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/executor/execdesc.h,v 1.39 2009/01/01 17:23:59 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/executor/execdesc.h,v 1.40 2009/01/02 20:42:00 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -37,6 +37,7 @@ typedef struct QueryDesc
 	CmdType		operation;		/* CMD_SELECT, CMD_UPDATE, etc. */
 	PlannedStmt *plannedstmt;	/* planner's output, or null if utility */
 	Node	   *utilitystmt;	/* utility statement, or null */
+	const char *sourceText;		/* source text of the query */
 	Snapshot	snapshot;		/* snapshot to use for query */
 	Snapshot	crosscheck_snapshot;	/* crosscheck for RI update/delete */
 	DestReceiver *dest;			/* the destination for tuple output */
@@ -54,6 +55,7 @@ typedef struct QueryDesc
 
 /* in pquery.c */
 extern QueryDesc *CreateQueryDesc(PlannedStmt *plannedstmt,
+				const char *sourceText,
 				Snapshot snapshot,
 				Snapshot crosscheck_snapshot,
 				DestReceiver *dest,
@@ -61,6 +63,7 @@ extern QueryDesc *CreateQueryDesc(PlannedStmt *plannedstmt,
 				bool doInstrument);
 
 extern QueryDesc *CreateUtilityQueryDesc(Node *utilitystmt,
+					   const char *sourceText,
 					   Snapshot snapshot,
 					   DestReceiver *dest,
 					   ParamListInfo params);