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/backend/commands/copy.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/copy.c,v 1.303 2009/01/01 17:23:37 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/copy.c,v 1.304 2009/01/02 20:42:00 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1054,7 +1054,8 @@ DoCopy(const CopyStmt *stmt, const char *queryString)
 		((DR_copy *) dest)->cstate = cstate;
 
 		/* Create a QueryDesc requesting no output */
-		cstate->queryDesc = CreateQueryDesc(plan, GetActiveSnapshot(),
+		cstate->queryDesc = CreateQueryDesc(plan, queryString,
+											GetActiveSnapshot(),
 											InvalidSnapshot,
 											dest, NULL, false);
 

src/backend/commands/explain.c

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994-5, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/explain.c,v 1.183 2009/01/01 17:23:37 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/explain.c,v 1.184 2009/01/02 20:42:00 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -172,7 +172,7 @@ ExplainOneQuery(Query *query, ExplainStmt *stmt, const char *queryString,
 		plan = pg_plan_query(query, 0, params);
 
 		/* run it (if needed) and produce output */
-		ExplainOnePlan(plan, params, stmt, tstate);
+		ExplainOnePlan(plan, stmt, queryString, params, tstate);
 	}
 }
 
@@ -218,8 +218,9 @@ ExplainOneUtility(Node *utilityStmt, ExplainStmt *stmt,
  * to call it.
  */
 void
-ExplainOnePlan(PlannedStmt *plannedstmt, ParamListInfo params,
-			   ExplainStmt *stmt, TupOutputState *tstate)
+ExplainOnePlan(PlannedStmt *plannedstmt, ExplainStmt *stmt,
+			   const char *queryString, ParamListInfo params,
+			   TupOutputState *tstate)
 {
 	QueryDesc  *queryDesc;
 	instr_time	starttime;
@@ -234,7 +235,7 @@ ExplainOnePlan(PlannedStmt *plannedstmt, ParamListInfo params,
 	PushUpdatedSnapshot(GetActiveSnapshot());
 
 	/* Create a QueryDesc requesting no output */
-	queryDesc = CreateQueryDesc(plannedstmt,
+	queryDesc = CreateQueryDesc(plannedstmt, queryString,
 								GetActiveSnapshot(), InvalidSnapshot,
 								None_Receiver, params,
 								stmt->analyze);

src/backend/commands/prepare.c

@@ -10,7 +10,7 @@
  * Copyright (c) 2002-2009, PostgreSQL Global Development Group
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/prepare.c,v 1.95 2009/01/01 17:23:39 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/prepare.c,v 1.96 2009/01/02 20:42:00 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -636,6 +636,9 @@ DropAllPreparedStatements(void)
 
 /*
  * Implements the 'EXPLAIN EXECUTE' utility statement.
+ *
+ * Note: the passed-in queryString is that of the EXPLAIN EXECUTE,
+ * not the original PREPARE; we get the latter string from the plancache.
  */
 void
 ExplainExecuteQuery(ExecuteStmt *execstmt, ExplainStmt *stmt,
@@ -643,6 +646,7 @@ ExplainExecuteQuery(ExecuteStmt *execstmt, ExplainStmt *stmt,
 					ParamListInfo params, TupOutputState *tstate)
 {
 	PreparedStatement *entry;
+	const char *query_string;
 	CachedPlan *cplan;
 	List	   *plan_list;
 	ListCell   *p;
@@ -659,6 +663,8 @@ ExplainExecuteQuery(ExecuteStmt *execstmt, ExplainStmt *stmt,
 	if (!entry->plansource->fixed_result)
 		elog(ERROR, "EXPLAIN EXECUTE does not support variable-result cached plans");
 
+	query_string = entry->plansource->query_string;
+
 	/* Replan if needed, and acquire a transient refcount */
 	cplan = RevalidateCachedPlan(entry->plansource, true);
 
@@ -701,11 +707,12 @@ ExplainExecuteQuery(ExecuteStmt *execstmt, ExplainStmt *stmt,
 				pstmt->intoClause = execstmt->into;
 			}
 
-			ExplainOnePlan(pstmt, paramLI, stmt, tstate);
+			ExplainOnePlan(pstmt, stmt, query_string,
+						   paramLI, tstate);
 		}
 		else
 		{
-			ExplainOneUtility((Node *) pstmt, stmt, queryString,
+			ExplainOneUtility((Node *) pstmt, stmt, query_string,
 							  params, tstate);
 		}