Make new event trigger facility actually do something.

Commit 3855968f32 added syntax, pg_dump,
psql support, and documentation, but the triggers didn't actually fire.
With this commit, they now do.  This is still a pretty basic facility
overall because event triggers do not get a whole lot of information
about what the user is trying to do unless you write them in C; and
there's still no option to fire them anywhere except at the very
beginning of the execution sequence, but it's better than nothing,
and a good building block for future work.

Along the way, add a regression test for ALTER LARGE OBJECT, since
testing of event triggers reveals that we haven't got one.

Dimitri Fontaine and Robert Haas

src/include/commands/event_trigger.h

@@ -16,6 +16,21 @@
 #include "catalog/pg_event_trigger.h"
 #include "nodes/parsenodes.h"
 
+typedef struct EventTriggerData
+{
+	NodeTag		type;
+	char	   *event;				/* event name */
+	Node	   *parsetree;			/* parse tree */
+	const char *tag;				/* command tag */
+} EventTriggerData;
+
+/*
+ * EventTriggerData is the node type that is passed as fmgr "context" info
+ * when a function is called by the event trigger manager.
+ */
+#define CALLED_AS_EVENT_TRIGGER(fcinfo) \
+	((fcinfo)->context != NULL && IsA((fcinfo)->context, EventTriggerData))
+
 extern void CreateEventTrigger(CreateEventTrigStmt *stmt);
 extern void RemoveEventTriggerById(Oid ctrigOid);
 extern Oid	get_event_trigger_oid(const char *trigname, bool missing_ok);
@@ -25,4 +40,7 @@ extern void RenameEventTrigger(const char* trigname, const char *newname);
 extern void AlterEventTriggerOwner(const char *name, Oid newOwnerId);
 extern void AlterEventTriggerOwner_oid(Oid, Oid newOwnerId);
 
+extern bool EventTriggerSupportsObjectType(ObjectType obtype);
+extern void EventTriggerDDLCommandStart(Node *parsetree);
+
 #endif   /* EVENT_TRIGGER_H */

src/include/nodes/nodes.h

@@ -415,6 +415,7 @@ typedef enum NodeTag
 	 * pass multiple object types through the same pointer).
 	 */
 	T_TriggerData = 950,		/* in commands/trigger.h */
+	T_EventTriggerData,			/* in commands/event_trigger.h */
 	T_ReturnSetInfo,			/* in nodes/execnodes.h */
 	T_WindowObjectData,			/* private in nodeWindowAgg.c */
 	T_TIDBitmap,				/* in nodes/tidbitmap.h */

src/include/port.h

@@ -443,6 +443,7 @@ extern int pqGethostbyname(const char *name,
 
 extern void pg_qsort(void *base, size_t nel, size_t elsize,
 		 int (*cmp) (const void *, const void *));
+extern int pg_qsort_strcmp(const void *a, const void *b);
 
 #define qsort(a,b,c,d) pg_qsort(a,b,c,d)
 

src/include/tcop/utility.h

@@ -16,19 +16,27 @@
 
 #include "tcop/tcopprot.h"
 
+typedef enum
+{
+	PROCESS_UTILITY_TOPLEVEL,		/* toplevel interactive command */
+	PROCESS_UTILITY_QUERY,			/* a complete query, but not toplevel */
+	PROCESS_UTILITY_SUBCOMMAND,		/* a piece of a query */
+	PROCESS_UTILITY_GENERATED		/* internally generated node query node */
+} ProcessUtilityContext;
 
 /* 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);
+			  const char *queryString, ParamListInfo params,
+			  DestReceiver *dest, char *completionTag,
+			  ProcessUtilityContext context);
 extern PGDLLIMPORT ProcessUtility_hook_type ProcessUtility_hook;
 
 extern void ProcessUtility(Node *parsetree, const char *queryString,
-			   ParamListInfo params, bool isTopLevel,
-			   DestReceiver *dest, char *completionTag);
+			   ParamListInfo params, DestReceiver *dest, char *completionTag,
+			   ProcessUtilityContext context);
 extern void standard_ProcessUtility(Node *parsetree, const char *queryString,
-						ParamListInfo params, bool isTopLevel,
-						DestReceiver *dest, char *completionTag);
+						ParamListInfo params, DestReceiver *dest,
+						char *completionTag, ProcessUtilityContext context);
 
 extern bool UtilityReturnsTuples(Node *parsetree);
 

src/include/utils/evtcache.h

@@ -0,0 +1,34 @@
+/*-------------------------------------------------------------------------
+ *
+ * evtcache.c
+ *	  Special-purpose cache for event trigger data.
+ *
+ * Portions Copyright (c) 1996-2012, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/cache/evtcache.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef EVTCACHE_H
+#define EVTCACHE_H
+
+#include "nodes/pg_list.h"
+
+typedef enum
+{
+	EVT_DDLCommandStart
+} EventTriggerEvent;
+
+typedef struct
+{
+	Oid			fnoid;				/* function to be called */
+	char		enabled;			/* as SESSION_REPLICATION_ROLE_* */
+	int			ntags;				/* number of command tags */
+	char	  **tag;				/* command tags in SORTED order */
+} EventTriggerCacheItem;
+
+extern List *EventCacheLookup(EventTriggerEvent event);
+
+#endif   /* EVTCACHE_H */