Add a hook to let loadable modules get control at ProcessUtility execution,

and use it to extend contrib/pg_stat_statements to track utility commands.

Itagaki Takahiro, reviewed by Euler Taveira de Oliveira.

2 files changed, 36 insertions, 2 deletions

diff --git a/src/backend/tcop/utility.c b/src/backend/tcop/utility.c
index 2fd4b9923f5..10fb728fc79 100644
--- a/src/backend/tcop/utility.c
+++ b/src/backend/tcop/utility.c
@@ -10,7 +10,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/tcop/utility.c,v 1.323 2009/12/11 03:34:55 itagaki Exp $
+ *	  $PostgreSQL: pgsql/src/backend/tcop/utility.c,v 1.324 2009/12/15 20:04:49 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -58,6 +58,10 @@
 #include "utils/syscache.h"
 
 
+/* Hook for plugins to get control in ProcessUtility() */
+ProcessUtility_hook_type ProcessUtility_hook = NULL;
+
+
 /*
  * Verify user has ownership of specified relation, else ereport.
  *
@@ -274,6 +278,27 @@ ProcessUtility(Node *parsetree,
 {
 	Assert(queryString != NULL);	/* required as of 8.4 */
 
+	/*
+	 * We provide a function hook variable that lets loadable plugins
+	 * get control when ProcessUtility is called.  Such a plugin would
+	 * normally call standard_ProcessUtility().
+	 */
+	if (ProcessUtility_hook)
+		(*ProcessUtility_hook) (parsetree, queryString, params,
+								isTopLevel, dest, completionTag);
+	else
+		standard_ProcessUtility(parsetree, queryString, params,
+								isTopLevel, dest, completionTag);
+}
+
+void
+standard_ProcessUtility(Node *parsetree,
+						const char *queryString,
+						ParamListInfo params,
+						bool isTopLevel,
+						DestReceiver *dest,
+						char *completionTag)
+{
 	check_xact_readonly(parsetree);
 
 	if (completionTag)
diff --git a/src/include/tcop/utility.h b/src/include/tcop/utility.h
index 271a97d690a..8db35f6a01a 100644
--- a/src/include/tcop/utility.h
+++ b/src/include/tcop/utility.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/utility.h,v 1.37 2009/12/01 02:31:13 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/tcop/utility.h,v 1.38 2009/12/15 20:04:49 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -17,9 +17,18 @@
 #include "tcop/tcopprot.h"
 
 
+/* Hook for plugins to get control in ProcessUtility() */
+typedef void (*ProcessUtility_hook_type) (Node *parsetree,
+			   const char *queryString, ParamListInfo params, bool isTopLevel,
+			   DestReceiver *dest, char *completionTag);
+extern PGDLLIMPORT ProcessUtility_hook_type ProcessUtility_hook;
+
 extern void ProcessUtility(Node *parsetree, const char *queryString,
 			   ParamListInfo params, bool isTopLevel,
 			   DestReceiver *dest, char *completionTag);
+extern void standard_ProcessUtility(Node *parsetree, const char *queryString,
+			   ParamListInfo params, bool isTopLevel,
+			   DestReceiver *dest, char *completionTag);
 
 extern bool UtilityReturnsTuples(Node *parsetree);