Make new event trigger facility actually do something.

Commit 3855968f328918b6cd1401dd11d109d471a54d40 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

4 files changed, 171 insertions, 14 deletions

diff --git a/src/pl/plpgsql/src/pl_comp.c b/src/pl/plpgsql/src/pl_comp.c
index 5d2f818dacb..0dc0e0b37ed 100644
--- a/src/pl/plpgsql/src/pl_comp.c
+++ b/src/pl/plpgsql/src/pl_comp.c
@@ -263,7 +263,8 @@ do_compile(FunctionCallInfo fcinfo,
 		   bool forValidator)
 {
 	Form_pg_proc procStruct = (Form_pg_proc) GETSTRUCT(procTup);
-	bool		is_trigger = CALLED_AS_TRIGGER(fcinfo);
+	bool		is_dml_trigger = CALLED_AS_TRIGGER(fcinfo);
+	bool		is_event_trigger = CALLED_AS_EVENT_TRIGGER(fcinfo);
 	Datum		prosrcdatum;
 	bool		isnull;
 	char	   *proc_source;
@@ -345,12 +346,18 @@ do_compile(FunctionCallInfo fcinfo,
 	function->fn_oid = fcinfo->flinfo->fn_oid;
 	function->fn_xmin = HeapTupleHeaderGetXmin(procTup->t_data);
 	function->fn_tid = procTup->t_self;
-	function->fn_is_trigger = is_trigger;
 	function->fn_input_collation = fcinfo->fncollation;
 	function->fn_cxt = func_cxt;
 	function->out_param_varno = -1;		/* set up for no OUT param */
 	function->resolve_option = plpgsql_variable_conflict;
 
+	if (is_dml_trigger)
+		function->fn_is_trigger = PLPGSQL_DML_TRIGGER;
+	else if (is_event_trigger)
+		function->fn_is_trigger = PLPGSQL_EVENT_TRIGGER;
+	else
+		function->fn_is_trigger = PLPGSQL_NOT_TRIGGER;
+
 	/*
 	 * Initialize the compiler, particularly the namespace stack.  The
 	 * outermost namespace contains function parameters and other special
@@ -367,9 +374,9 @@ do_compile(FunctionCallInfo fcinfo,
 									 sizeof(PLpgSQL_datum *) * datums_alloc);
 	datums_last = 0;
 
-	switch (is_trigger)
+	switch (function->fn_is_trigger)
 	{
-		case false:
+		case PLPGSQL_NOT_TRIGGER:
 
 			/*
 			 * Fetch info about the procedure's parameters. Allocations aren't
@@ -529,7 +536,7 @@ do_compile(FunctionCallInfo fcinfo,
 				if (rettypeid == VOIDOID ||
 					rettypeid == RECORDOID)
 					 /* okay */ ;
-				else if (rettypeid == TRIGGEROID)
+				else if (rettypeid == TRIGGEROID || rettypeid == EVTTRIGGEROID)
 					ereport(ERROR,
 							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 							 errmsg("trigger functions can only be called as triggers")));
@@ -568,7 +575,7 @@ do_compile(FunctionCallInfo fcinfo,
 			ReleaseSysCache(typeTup);
 			break;
 
-		case true:
+		case PLPGSQL_DML_TRIGGER:
 			/* Trigger procedure's return type is unknown yet */
 			function->fn_rettype = InvalidOid;
 			function->fn_retbyval = false;
@@ -672,8 +679,39 @@ do_compile(FunctionCallInfo fcinfo,
 
 			break;
 
+		case PLPGSQL_EVENT_TRIGGER:
+			function->fn_rettype = VOIDOID;
+			function->fn_retbyval = false;
+			function->fn_retistuple = true;
+			function->fn_retset = false;
+
+			/* shouldn't be any declared arguments */
+			if (procStruct->pronargs != 0)
+				ereport(ERROR,
+						(errcode(ERRCODE_INVALID_FUNCTION_DEFINITION),
+						 errmsg("event trigger functions cannot have declared arguments")));
+
+			/* Add the variable tg_event */
+			var = plpgsql_build_variable("tg_event", 0,
+										 plpgsql_build_datatype(TEXTOID,
+																-1,
+											   function->fn_input_collation),
+										 true);
+			function->tg_event_varno = var->dno;
+
+			/* Add the variable tg_tag */
+			var = plpgsql_build_variable("tg_tag", 0,
+										 plpgsql_build_datatype(TEXTOID,
+																-1,
+											   function->fn_input_collation),
+										 true);
+			function->tg_tag_varno = var->dno;
+
+			break;
+
 		default:
-			elog(ERROR, "unrecognized function typecode: %d", (int) is_trigger);
+			elog(ERROR, "unrecognized function typecode: %d",
+				 (int) function->fn_is_trigger);
 			break;
 	}
 
@@ -803,7 +841,7 @@ plpgsql_compile_inline(char *proc_source)
 	compile_tmp_cxt = MemoryContextSwitchTo(func_cxt);
 
 	function->fn_signature = pstrdup(func_name);
-	function->fn_is_trigger = false;
+	function->fn_is_trigger = PLPGSQL_NOT_TRIGGER;
 	function->fn_input_collation = InvalidOid;
 	function->fn_cxt = func_cxt;
 	function->out_param_varno = -1;		/* set up for no OUT param */
diff --git a/src/pl/plpgsql/src/pl_exec.c b/src/pl/plpgsql/src/pl_exec.c
index 11a56c9a8f1..8b649a4e5dc 100644
--- a/src/pl/plpgsql/src/pl_exec.c
+++ b/src/pl/plpgsql/src/pl_exec.c
@@ -773,6 +773,99 @@ plpgsql_exec_trigger(PLpgSQL_function *func,
 	return rettup;
 }
 
+void
+plpgsql_exec_event_trigger(PLpgSQL_function *func, EventTriggerData *trigdata)
+{
+	PLpgSQL_execstate estate;
+	ErrorContextCallback plerrcontext;
+	int			i;
+	int			rc;
+	PLpgSQL_var *var;
+
+	/*
+	 * Setup the execution state
+	 */
+	plpgsql_estate_setup(&estate, func, NULL);
+
+	/*
+	 * Setup error traceback support for ereport()
+	 */
+	plerrcontext.callback = plpgsql_exec_error_callback;
+	plerrcontext.arg = &estate;
+	plerrcontext.previous = error_context_stack;
+	error_context_stack = &plerrcontext;
+
+	/*
+	 * Make local execution copies of all the datums
+	 */
+	estate.err_text = gettext_noop("during initialization of execution state");
+	for (i = 0; i < estate.ndatums; i++)
+		estate.datums[i] = copy_plpgsql_datum(func->datums[i]);
+
+	/*
+	 * Assign the special tg_ variables
+	 */
+	var = (PLpgSQL_var *) (estate.datums[func->tg_event_varno]);
+	var->value = CStringGetTextDatum(trigdata->event);
+	var->isnull = false;
+	var->freeval = true;
+
+	var = (PLpgSQL_var *) (estate.datums[func->tg_tag_varno]);
+	var->value = CStringGetTextDatum(trigdata->tag);
+	var->isnull = false;
+	var->freeval = true;
+
+	/*
+	 * Let the instrumentation plugin peek at this function
+	 */
+	if (*plugin_ptr && (*plugin_ptr)->func_beg)
+		((*plugin_ptr)->func_beg) (&estate, func);
+
+	/*
+	 * Now call the toplevel block of statements
+	 */
+	estate.err_text = NULL;
+	estate.err_stmt = (PLpgSQL_stmt *) (func->action);
+	rc = exec_stmt_block(&estate, func->action);
+	if (rc != PLPGSQL_RC_RETURN)
+	{
+		estate.err_stmt = NULL;
+		estate.err_text = NULL;
+
+		/*
+		 * Provide a more helpful message if a CONTINUE or RAISE has been used
+		 * outside the context it can work in.
+		 */
+		if (rc == PLPGSQL_RC_CONTINUE)
+			ereport(ERROR,
+					(errcode(ERRCODE_SYNTAX_ERROR),
+					 errmsg("CONTINUE cannot be used outside a loop")));
+		else
+			ereport(ERROR,
+			   (errcode(ERRCODE_S_R_E_FUNCTION_EXECUTED_NO_RETURN_STATEMENT),
+				errmsg("control reached end of trigger procedure without RETURN")));
+	}
+
+	estate.err_stmt = NULL;
+	estate.err_text = gettext_noop("during function exit");
+
+	/*
+	 * Let the instrumentation plugin peek at this function
+	 */
+	if (*plugin_ptr && (*plugin_ptr)->func_end)
+		((*plugin_ptr)->func_end) (&estate, func);
+
+	/* Clean up any leftover temporary memory */
+	plpgsql_destroy_econtext(&estate);
+	exec_eval_cleanup(&estate);
+
+	/*
+	 * Pop the error context stack
+	 */
+	error_context_stack = plerrcontext.previous;
+
+	return;
+}
 
 /*
  * error context callback to let us supply a call-stack traceback
diff --git a/src/pl/plpgsql/src/pl_handler.c b/src/pl/plpgsql/src/pl_handler.c
index 022ec3f334c..2adf166164e 100644
--- a/src/pl/plpgsql/src/pl_handler.c
+++ b/src/pl/plpgsql/src/pl_handler.c
@@ -91,7 +91,7 @@ plpgsql_call_handler(PG_FUNCTION_ARGS)
 {
 	PLpgSQL_function *func;
 	PLpgSQL_execstate *save_cur_estate;
-	Datum		retval;
+	Datum		retval = 0;		/* make compiler happy */
 	int			rc;
 
 	/*
@@ -118,6 +118,9 @@ plpgsql_call_handler(PG_FUNCTION_ARGS)
 		if (CALLED_AS_TRIGGER(fcinfo))
 			retval = PointerGetDatum(plpgsql_exec_trigger(func,
 										   (TriggerData *) fcinfo->context));
+		else if (CALLED_AS_EVENT_TRIGGER(fcinfo))
+			plpgsql_exec_event_trigger(func,
+									   (EventTriggerData *) fcinfo->context);
 		else
 			retval = plpgsql_exec_function(func, fcinfo);
 	}
@@ -224,7 +227,8 @@ plpgsql_validator(PG_FUNCTION_ARGS)
 	Oid		   *argtypes;
 	char	  **argnames;
 	char	   *argmodes;
-	bool		istrigger = false;
+	bool		is_dml_trigger = false;
+	bool		is_event_trigger = false;
 	int			i;
 
 	/* Get the new function's pg_proc entry */
@@ -242,7 +246,9 @@ plpgsql_validator(PG_FUNCTION_ARGS)
 		/* we assume OPAQUE with no arguments means a trigger */
 		if (proc->prorettype == TRIGGEROID ||
 			(proc->prorettype == OPAQUEOID && proc->pronargs == 0))
-			istrigger = true;
+			is_dml_trigger = true;
+		else if (proc->prorettype == EVTTRIGGEROID)
+			is_event_trigger = true;
 		else if (proc->prorettype != RECORDOID &&
 				 proc->prorettype != VOIDOID &&
 				 !IsPolymorphicType(proc->prorettype))
@@ -273,7 +279,6 @@ plpgsql_validator(PG_FUNCTION_ARGS)
 	{
 		FunctionCallInfoData fake_fcinfo;
 		FmgrInfo	flinfo;
-		TriggerData trigdata;
 		int			rc;
 
 		/*
@@ -291,12 +296,20 @@ plpgsql_validator(PG_FUNCTION_ARGS)
 		fake_fcinfo.flinfo = &flinfo;
 		flinfo.fn_oid = funcoid;
 		flinfo.fn_mcxt = CurrentMemoryContext;
-		if (istrigger)
+		if (is_dml_trigger)
 		{
+			TriggerData trigdata;
 			MemSet(&trigdata, 0, sizeof(trigdata));
 			trigdata.type = T_TriggerData;
 			fake_fcinfo.context = (Node *) &trigdata;
 		}
+		else if (is_event_trigger)
+		{
+			EventTriggerData trigdata;
+			MemSet(&trigdata, 0, sizeof(trigdata));
+			trigdata.type = T_EventTriggerData;
+			fake_fcinfo.context = (Node *) &trigdata;
+		}
 
 		/* Test-compile the function */
 		plpgsql_compile(&fake_fcinfo, true);
diff --git a/src/pl/plpgsql/src/plpgsql.h b/src/pl/plpgsql/src/plpgsql.h
index b63f336825d..dcf80743b88 100644
--- a/src/pl/plpgsql/src/plpgsql.h
+++ b/src/pl/plpgsql/src/plpgsql.h
@@ -19,6 +19,7 @@
 #include "postgres.h"
 
 #include "access/xact.h"
+#include "commands/event_trigger.h"
 #include "commands/trigger.h"
 #include "executor/spi.h"
 
@@ -675,6 +676,12 @@ typedef struct PLpgSQL_func_hashkey
 	Oid			argtypes[FUNC_MAX_ARGS];
 } PLpgSQL_func_hashkey;
 
+typedef enum PLpgSQL_trigtype
+{
+	PLPGSQL_DML_TRIGGER,
+	PLPGSQL_EVENT_TRIGGER,
+	PLPGSQL_NOT_TRIGGER
+} PLpgSQL_trigtype;
 
 typedef struct PLpgSQL_function
 {								/* Complete compiled function	  */
@@ -682,7 +689,7 @@ typedef struct PLpgSQL_function
 	Oid			fn_oid;
 	TransactionId fn_xmin;
 	ItemPointerData fn_tid;
-	bool		fn_is_trigger;
+	PLpgSQL_trigtype fn_is_trigger;
 	Oid			fn_input_collation;
 	PLpgSQL_func_hashkey *fn_hashkey;	/* back-link to hashtable key */
 	MemoryContext fn_cxt;
@@ -713,6 +720,10 @@ typedef struct PLpgSQL_function
 	int			tg_nargs_varno;
 	int			tg_argv_varno;
 
+	/* for event triggers */
+	int			tg_event_varno;
+	int			tg_tag_varno;
+
 	PLpgSQL_resolve_option resolve_option;
 
 	int			ndatums;
@@ -920,6 +931,8 @@ extern Datum plpgsql_exec_function(PLpgSQL_function *func,
 					  FunctionCallInfo fcinfo);
 extern HeapTuple plpgsql_exec_trigger(PLpgSQL_function *func,
 					 TriggerData *trigdata);
+extern void plpgsql_exec_event_trigger(PLpgSQL_function *func,
+					 EventTriggerData *trigdata);
 extern void plpgsql_xact_cb(XactEvent event, void *arg);
 extern void plpgsql_subxact_cb(SubXactEvent event, SubTransactionId mySubid,
 				   SubTransactionId parentSubid, void *arg);