Extend EXPLAIN to allow generic options to be specified.

The original syntax made it difficult to add options without making them
into reserved words.  This change parenthesizes the options to avoid that
problem, and makes provision for an explicit (and perhaps non-Boolean)
value for each option.  The original syntax is still supported, but only
for the two original options ANALYZE and VERBOSE.

As a test case, add a COSTS option that can suppress the planner cost
estimates.  This may be useful for including EXPLAIN output in the regression
tests, which are otherwise unable to cope with cross-platform variations in
cost estimates.

Robert Haas

src/include/commands/explain.h

@@ -6,7 +6,7 @@
  * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994-5, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/commands/explain.h,v 1.39 2009/06/11 14:49:11 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/commands/explain.h,v 1.40 2009/07/26 23:34:18 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -15,12 +15,23 @@
 
 #include "executor/executor.h"
 
+typedef struct ExplainState
+{
+	StringInfo	str;			/* output buffer */
+	/* options */
+	bool		verbose;		/* print plan targetlists */
+	bool		analyze;		/* print actual times */
+	bool		costs;			/* print costs */
+	/* other states */
+	PlannedStmt *pstmt;			/* top of plan */
+	List	   *rtable;			/* range table */
+} ExplainState;
+
 /* Hook for plugins to get control in ExplainOneQuery() */
 typedef void (*ExplainOneQuery_hook_type) (Query *query,
-													   ExplainStmt *stmt,
-													 const char *queryString,
-													   ParamListInfo params,
-													 TupOutputState *tstate);
+										   ExplainState *es,
+										   const char *queryString,
+										   ParamListInfo params);
 extern PGDLLIMPORT ExplainOneQuery_hook_type ExplainOneQuery_hook;
 
 /* Hook for plugins to get control in explain_get_index_name() */
@@ -31,19 +42,16 @@ extern PGDLLIMPORT explain_get_index_name_hook_type explain_get_index_name_hook;
 extern void ExplainQuery(ExplainStmt *stmt, const char *queryString,
 			 ParamListInfo params, DestReceiver *dest);
 
+extern void ExplainInitState(ExplainState *es);
+
 extern TupleDesc ExplainResultDesc(ExplainStmt *stmt);
 
-extern void ExplainOneUtility(Node *utilityStmt, ExplainStmt *stmt,
-				  const char *queryString,
-				  ParamListInfo params,
-				  TupOutputState *tstate);
+extern void ExplainOneUtility(Node *utilityStmt, ExplainState *es,
+				  const char *queryString, ParamListInfo params);
 
-extern void ExplainOnePlan(PlannedStmt *plannedstmt, ExplainStmt *stmt,
-			   const char *queryString,
-			   ParamListInfo params,
-			   TupOutputState *tstate);
+extern void ExplainOnePlan(PlannedStmt *plannedstmt, ExplainState *es,
+			   const char *queryString, ParamListInfo params);
 
-extern void ExplainPrintPlan(StringInfo str, QueryDesc *queryDesc,
-				 bool analyze, bool verbose);
+extern void ExplainPrintPlan(ExplainState *es, QueryDesc *queryDesc);
 
 #endif   /* EXPLAIN_H */

src/include/commands/prepare.h

@@ -6,14 +6,14 @@
  *
  * Copyright (c) 2002-2009, PostgreSQL Global Development Group
  *
- * $PostgreSQL: pgsql/src/include/commands/prepare.h,v 1.30 2009/01/01 17:23:58 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/commands/prepare.h,v 1.31 2009/07/26 23:34:18 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
 #ifndef PREPARE_H
 #define PREPARE_H
 
-#include "executor/executor.h"
+#include "commands/explain.h"
 #include "utils/plancache.h"
 #include "utils/timestamp.h"
 
@@ -40,9 +40,8 @@ extern void ExecuteQuery(ExecuteStmt *stmt, const char *queryString,
 			 ParamListInfo params,
 			 DestReceiver *dest, char *completionTag);
 extern void DeallocateQuery(DeallocateStmt *stmt);
-extern void ExplainExecuteQuery(ExecuteStmt *execstmt, ExplainStmt *stmt,
-					const char *queryString,
-					ParamListInfo params, TupOutputState *tstate);
+extern void ExplainExecuteQuery(ExecuteStmt *execstmt, ExplainState *es,
+					const char *queryString, ParamListInfo params);
 
 /* Low-level access to stored prepared statements */
 extern void StorePreparedStatement(const char *stmt_name,