PG_FINALLY

This gives an alternative way of catching exceptions, for the common
case where the cleanup code is the same in the error and non-error
cases.  So instead of

    PG_TRY();
    {
        ... code that might throw ereport(ERROR) ...
    }
    PG_CATCH();
    {
        cleanup();
	PG_RE_THROW();
    }
    PG_END_TRY();
    cleanup();

one can write

    PG_TRY();
    {
        ... code that might throw ereport(ERROR) ...
    }
    PG_FINALLY();
    {
        cleanup();
    }
    PG_END_TRY();

Discussion: https://www.postgresql.org/message-id/flat/95a822c3-728b-af0e-d7e5-71890507ae0c%402ndquadrant.com

src/backend/catalog/index.c

@@ -3449,14 +3449,12 @@ reindex_index(Oid indexId, bool skip_constraint_checks, char persistence,
 		/* Note: we do not need to re-establish pkey setting */
 		index_build(heapRelation, iRel, indexInfo, true, true);
 	}
-	PG_CATCH();
+	PG_FINALLY();
 	{
 		/* Make sure flag gets cleared on error exit */
 		ResetReindexProcessing();
-		PG_RE_THROW();
 	}
 	PG_END_TRY();
-	ResetReindexProcessing();
 
 	/*
 	 * If the index is marked invalid/not-ready/dead (ie, it's from a failed
@@ -3676,14 +3674,12 @@ reindex_relation(Oid relid, int flags, int options)
 			i++;
 		}
 	}
-	PG_CATCH();
+	PG_FINALLY();
 	{
 		/* Make sure list gets cleared on error exit */
 		ResetReindexPending();
-		PG_RE_THROW();
 	}
 	PG_END_TRY();
-	ResetReindexPending();
 
 	/*
 	 * Close rel, but continue to hold the lock.

src/backend/commands/async.c

@@ -2028,22 +2028,15 @@ asyncQueueReadAllNotifications(void)
 													   snapshot);
 		} while (!reachedStop);
 	}
-	PG_CATCH();
+	PG_FINALLY();
 	{
 		/* Update shared state */
 		LWLockAcquire(AsyncQueueLock, LW_SHARED);
 		QUEUE_BACKEND_POS(MyBackendId) = pos;
 		LWLockRelease(AsyncQueueLock);
-
-		PG_RE_THROW();
 	}
 	PG_END_TRY();
 
-	/* Update shared state */
-	LWLockAcquire(AsyncQueueLock, LW_SHARED);
-	QUEUE_BACKEND_POS(MyBackendId) = pos;
-	LWLockRelease(AsyncQueueLock);
-
 	/* Done with snapshot */
 	UnregisterSnapshot(snapshot);
 }

src/backend/commands/copy.c

@@ -1916,13 +1916,11 @@ BeginCopyTo(ParseState *pstate,
 			{
 				cstate->copy_file = AllocateFile(cstate->filename, PG_BINARY_W);
 			}
-			PG_CATCH();
+			PG_FINALLY();
 			{
 				umask(oumask);
-				PG_RE_THROW();
 			}
 			PG_END_TRY();
-			umask(oumask);
 			if (cstate->copy_file == NULL)
 			{
 				/* copy errno because ereport subfunctions might change it */

src/backend/commands/event_trigger.c

@@ -934,13 +934,11 @@ EventTriggerSQLDrop(Node *parsetree)
 	{
 		EventTriggerInvoke(runlist, &trigdata);
 	}
-	PG_CATCH();
+	PG_FINALLY();
 	{
 		currentEventTriggerState->in_sql_drop = false;
-		PG_RE_THROW();
 	}
 	PG_END_TRY();
-	currentEventTriggerState->in_sql_drop = false;
 
 	/* Cleanup. */
 	list_free(runlist);
@@ -1007,17 +1005,13 @@ EventTriggerTableRewrite(Node *parsetree, Oid tableOid, int reason)
 	{
 		EventTriggerInvoke(runlist, &trigdata);
 	}
-	PG_CATCH();
+	PG_FINALLY();
 	{
 		currentEventTriggerState->table_rewrite_oid = InvalidOid;
 		currentEventTriggerState->table_rewrite_reason = 0;
-		PG_RE_THROW();
 	}
 	PG_END_TRY();
 
-	currentEventTriggerState->table_rewrite_oid = InvalidOid;
-	currentEventTriggerState->table_rewrite_reason = 0;
-
 	/* Cleanup. */
 	list_free(runlist);
 

src/backend/commands/extension.c

@@ -942,17 +942,13 @@ execute_extension_script(Oid extensionOid, ExtensionControlFile *control,
 
 		execute_sql_string(c_sql);
 	}
-	PG_CATCH();
+	PG_FINALLY();
 	{
 		creating_extension = false;
 		CurrentExtensionObject = InvalidOid;
-		PG_RE_THROW();
 	}
 	PG_END_TRY();
 
-	creating_extension = false;
-	CurrentExtensionObject = InvalidOid;
-
 	/*
 	 * Restore the GUC variables we set above.
 	 */

src/backend/commands/subscriptioncmds.c

@@ -493,16 +493,11 @@ CreateSubscription(CreateSubscriptionStmt *stmt, bool isTopLevel)
 								slotname)));
 			}
 		}
-		PG_CATCH();
+		PG_FINALLY();
 		{
-			/* Close the connection in case of failure. */
 			walrcv_disconnect(wrconn);
-			PG_RE_THROW();
 		}
 		PG_END_TRY();
-
-		/* And we are done with the remote side. */
-		walrcv_disconnect(wrconn);
 	}
 	else
 		ereport(WARNING,
@@ -1023,16 +1018,12 @@ DropSubscription(DropSubscriptionStmt *stmt, bool isTopLevel)
 
 		walrcv_clear_result(res);
 	}
-	PG_CATCH();
+	PG_FINALLY();
 	{
-		/* Close the connection in case of failure */
 		walrcv_disconnect(wrconn);
-		PG_RE_THROW();
 	}
 	PG_END_TRY();
 
-	walrcv_disconnect(wrconn);
-
 	pfree(cmd.data);
 
 	table_close(rel, NoLock);

src/backend/commands/trigger.c

@@ -2431,13 +2431,11 @@ ExecCallTriggerFunc(TriggerData *trigdata,
 	{
 		result = FunctionCallInvoke(fcinfo);
 	}
-	PG_CATCH();
+	PG_FINALLY();
 	{
 		MyTriggerDepth--;
-		PG_RE_THROW();
 	}
 	PG_END_TRY();
-	MyTriggerDepth--;
 
 	pgstat_end_function_usage(&fcusage, true);
 

src/backend/commands/vacuum.c

@@ -430,17 +430,13 @@ vacuum(List *relations, VacuumParams *params,
 			}
 		}
 	}
-	PG_CATCH();
+	PG_FINALLY();
 	{
 		in_vacuum = false;
 		VacuumCostActive = false;
-		PG_RE_THROW();
 	}
 	PG_END_TRY();
 
-	in_vacuum = false;
-	VacuumCostActive = false;
-
 	/*
 	 * Finish up processing.
 	 */

src/backend/libpq/be-fsstubs.c

@@ -503,13 +503,11 @@ be_lo_export(PG_FUNCTION_ARGS)
 		fd = OpenTransientFilePerm(fnamebuf, O_CREAT | O_WRONLY | O_TRUNC | PG_BINARY,
 								   S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
 	}
-	PG_CATCH();
+	PG_FINALLY();
 	{
 		umask(oumask);
-		PG_RE_THROW();
 	}
 	PG_END_TRY();
-	umask(oumask);
 	if (fd < 0)
 		ereport(ERROR,
 				(errcode_for_file_access(),

src/backend/tcop/utility.c

@@ -1514,13 +1514,11 @@ ProcessUtilitySlow(ParseState *pstate,
 					address = ExecRefreshMatView((RefreshMatViewStmt *) parsetree,
 												 queryString, params, completionTag);
 				}
-				PG_CATCH();
+				PG_FINALLY();
 				{
 					EventTriggerUndoInhibitCommandCollection();
-					PG_RE_THROW();
 				}
 				PG_END_TRY();
-				EventTriggerUndoInhibitCommandCollection();
 				break;
 
 			case T_CreateTrigStmt:
@@ -1716,16 +1714,12 @@ ProcessUtilitySlow(ParseState *pstate,
 			EventTriggerDDLCommandEnd(parsetree);
 		}
 	}
-	PG_CATCH();
+	PG_FINALLY();
 	{
 		if (needCleanup)
 			EventTriggerEndCompleteQuery();
-		PG_RE_THROW();
 	}
 	PG_END_TRY();
-
-	if (needCleanup)
-		EventTriggerEndCompleteQuery();
 }
 
 /*

src/backend/utils/adt/xml.c

@@ -1193,13 +1193,11 @@ xml_pstrdup_and_free(xmlChar *str)
 		{
 			result = pstrdup((char *) str);
 		}
-		PG_CATCH();
+		PG_FINALLY();
 		{
 			xmlFree(str);
-			PG_RE_THROW();
 		}
 		PG_END_TRY();
-		xmlFree(str);
 	}
 	else
 		result = NULL;
@@ -3866,19 +3864,14 @@ xml_xmlnodetoxmltype(xmlNodePtr cur, PgXmlErrorContext *xmlerrcxt)
 
 			result = xmlBuffer_to_xmltype(buf);
 		}
-		PG_CATCH();
+		PG_FINALLY()
 		{
 			if (nodefree)
 				nodefree(cur_copy);
 			if (buf)
 				xmlBufferFree(buf);
-			PG_RE_THROW();
 		}
 		PG_END_TRY();
-
-		if (nodefree)
-			nodefree(cur_copy);
-		xmlBufferFree(buf);
 	}
 	else
 	{
@@ -3893,13 +3886,11 @@ xml_xmlnodetoxmltype(xmlNodePtr cur, PgXmlErrorContext *xmlerrcxt)
 			result = (xmltype *) cstring_to_text(escaped);
 			pfree(escaped);
 		}
-		PG_CATCH();
+		PG_FINALLY();
 		{
 			xmlFree(str);
-			PG_RE_THROW();
 		}
 		PG_END_TRY();
-		xmlFree(str);
 	}
 
 	return result;
@@ -4734,16 +4725,13 @@ XmlTableGetValue(TableFuncScanState *state, int colnum,
 									   state->typioparams[colnum],
 									   typmod);
 	}
-	PG_CATCH();
+	PG_FINALLY();
 	{
 		if (xpathobj != NULL)
 			xmlXPathFreeObject(xpathobj);
-		PG_RE_THROW();
 	}
 	PG_END_TRY();
 
-	xmlXPathFreeObject(xpathobj);
-
 	return result;
 #else
 	NO_XML_SUPPORT();

src/include/utils/elog.h

@@ -277,6 +277,25 @@ extern PGDLLIMPORT ErrorContextCallback *error_context_stack;
  * (sub)transaction abort. Failure to do so may leave the system in an
  * inconsistent state for further processing.
  *
+ * For the common case that the error recovery code and the cleanup in the
+ * normal code path are identical, the following can be used instead:
+ *
+ *		PG_TRY();
+ *		{
+ *			... code that might throw ereport(ERROR) ...
+ *		}
+ *		PG_FINALLY();
+ *		{
+ *			... cleanup code ...
+ *		}
+ *      PG_END_TRY();
+ *
+ * The cleanup code will be run in either case, and any error will be rethrown
+ * afterwards.
+ *
+ * You cannot use both PG_CATCH() and PG_FINALLY() in the same
+ * PG_TRY()/PG_END_TRY() block.
+ *
  * Note: while the system will correctly propagate any new ereport(ERROR)
  * occurring in the recovery section, there is a small limit on the number
  * of levels this will work for.  It's best to keep the error recovery
@@ -300,24 +319,33 @@ extern PGDLLIMPORT ErrorContextCallback *error_context_stack;
  */
 #define PG_TRY()  \
 	do { \
-		sigjmp_buf *save_exception_stack = PG_exception_stack; \
-		ErrorContextCallback *save_context_stack = error_context_stack; \
-		sigjmp_buf local_sigjmp_buf; \
-		if (sigsetjmp(local_sigjmp_buf, 0) == 0) \
+		sigjmp_buf *_save_exception_stack = PG_exception_stack; \
+		ErrorContextCallback *_save_context_stack = error_context_stack; \
+		sigjmp_buf _local_sigjmp_buf; \
+		bool _do_rethrow = false; \
+		if (sigsetjmp(_local_sigjmp_buf, 0) == 0) \
 		{ \
-			PG_exception_stack = &local_sigjmp_buf
+			PG_exception_stack = &_local_sigjmp_buf
 
 #define PG_CATCH()	\
 		} \
 		else \
 		{ \
-			PG_exception_stack = save_exception_stack; \
-			error_context_stack = save_context_stack
+			PG_exception_stack = _save_exception_stack; \
+			error_context_stack = _save_context_stack
+
+#define PG_FINALLY() \
+		} \
+		else \
+			_do_rethrow = true; \
+		{
 
 #define PG_END_TRY()  \
 		} \
-		PG_exception_stack = save_exception_stack; \
-		error_context_stack = save_context_stack; \
+		PG_exception_stack = _save_exception_stack; \
+		error_context_stack = _save_context_stack; \
+		if (_do_rethrow) \
+				PG_RE_THROW(); \
 	} while (0)
 
 /*

src/pl/plperl/plperl.c

@@ -1862,20 +1862,15 @@ plperl_call_handler(PG_FUNCTION_ARGS)
 		else
 			retval = plperl_func_handler(fcinfo);
 	}
-	PG_CATCH();
+	PG_FINALLY();
 	{
 		current_call_data = save_call_data;
 		activate_interpreter(oldinterp);
 		if (this_call_data.prodesc)
 			decrement_prodesc_refcount(this_call_data.prodesc);
-		PG_RE_THROW();
 	}
 	PG_END_TRY();
 
-	current_call_data = save_call_data;
-	activate_interpreter(oldinterp);
-	if (this_call_data.prodesc)
-		decrement_prodesc_refcount(this_call_data.prodesc);
 	return retval;
 }
 
@@ -1958,22 +1953,15 @@ plperl_inline_handler(PG_FUNCTION_ARGS)
 		if (SPI_finish() != SPI_OK_FINISH)
 			elog(ERROR, "SPI_finish() failed");
 	}
-	PG_CATCH();
+	PG_FINALLY();
 	{
 		if (desc.reference)
 			SvREFCNT_dec_current(desc.reference);
 		current_call_data = save_call_data;
 		activate_interpreter(oldinterp);
-		PG_RE_THROW();
 	}
 	PG_END_TRY();
 
-	if (desc.reference)
-		SvREFCNT_dec_current(desc.reference);
-
-	current_call_data = save_call_data;
-	activate_interpreter(oldinterp);
-
 	error_context_stack = pl_error_context.previous;
 
 	PG_RETURN_VOID();

src/pl/plpgsql/src/pl_handler.c

@@ -264,19 +264,14 @@ plpgsql_call_handler(PG_FUNCTION_ARGS)
 		else
 			retval = plpgsql_exec_function(func, fcinfo, NULL, !nonatomic);
 	}
-	PG_CATCH();
+	PG_FINALLY();
 	{
-		/* Decrement use-count, restore cur_estate, and propagate error */
+		/* Decrement use-count, restore cur_estate */
 		func->use_count--;
 		func->cur_estate = save_cur_estate;
-		PG_RE_THROW();
 	}
 	PG_END_TRY();
 
-	func->use_count--;
-
-	func->cur_estate = save_cur_estate;
-
 	/*
 	 * Disconnect from SPI manager
 	 */

src/pl/plpython/plpy_cursorobject.c

@@ -228,13 +228,11 @@ PLy_cursor_plan(PyObject *ob, PyObject *args)
 				plan->values[j] = PLy_output_convert(arg, elem, &isnull);
 				nulls[j] = isnull ? 'n' : ' ';
 			}
-			PG_CATCH();
+			PG_FINALLY();
 			{
 				Py_DECREF(elem);
-				PG_RE_THROW();
 			}
 			PG_END_TRY();
-			Py_DECREF(elem);
 		}
 
 		portal = SPI_cursor_open(NULL, plan->plan, plan->values, nulls,

src/pl/plpython/plpy_elog.c

@@ -141,7 +141,7 @@ PLy_elog_impl(int elevel, const char *fmt,...)
 				 (constraint_name) ? err_generic_string(PG_DIAG_CONSTRAINT_NAME,
 														constraint_name) : 0));
 	}
-	PG_CATCH();
+	PG_FINALLY();
 	{
 		if (fmt)
 			pfree(emsg.data);
@@ -151,19 +151,8 @@ PLy_elog_impl(int elevel, const char *fmt,...)
 			pfree(tbmsg);
 		Py_XDECREF(exc);
 		Py_XDECREF(val);
-
-		PG_RE_THROW();
 	}
 	PG_END_TRY();
-
-	if (fmt)
-		pfree(emsg.data);
-	if (xmsg)
-		pfree(xmsg);
-	if (tbmsg)
-		pfree(tbmsg);
-	Py_XDECREF(exc);
-	Py_XDECREF(val);
 }
 
 /*

src/pl/plpython/plpy_exec.c

@@ -403,18 +403,13 @@ PLy_exec_trigger(FunctionCallInfo fcinfo, PLyProcedure *proc)
 			}
 		}
 	}
-	PG_CATCH();
+	PG_FINALLY();
 	{
 		Py_XDECREF(plargs);
 		Py_XDECREF(plrv);
-
-		PG_RE_THROW();
 	}
 	PG_END_TRY();
 
-	Py_DECREF(plargs);
-	Py_DECREF(plrv);
-
 	return rv;
 }
 
@@ -1052,15 +1047,12 @@ PLy_procedure_call(PLyProcedure *proc, const char *kargs, PyObject *vargs)
 		 */
 		Assert(list_length(explicit_subtransactions) >= save_subxact_level);
 	}
-	PG_CATCH();
+	PG_FINALLY();
 	{
 		PLy_abort_open_subtransactions(save_subxact_level);
-		PG_RE_THROW();
 	}
 	PG_END_TRY();
 
-	PLy_abort_open_subtransactions(save_subxact_level);
-
 	/* If the Python code returned an error, propagate it */
 	if (rv == NULL)
 		PLy_elog(ERROR, NULL);

src/pl/plpython/plpy_spi.c

@@ -249,13 +249,11 @@ PLy_spi_execute_plan(PyObject *ob, PyObject *list, long limit)
 				plan->values[j] = PLy_output_convert(arg, elem, &isnull);
 				nulls[j] = isnull ? 'n' : ' ';
 			}
-			PG_CATCH();
+			PG_FINALLY();
 			{
 				Py_DECREF(elem);
-				PG_RE_THROW();
 			}
 			PG_END_TRY();
-			Py_DECREF(elem);
 		}
 
 		rv = SPI_execute_plan(plan->plan, plan->values, nulls,

src/pl/plpython/plpy_typeio.c

@@ -925,15 +925,12 @@ PLyObject_ToBytea(PLyObToDatum *arg, PyObject *plrv,
 		memcpy(VARDATA(result), plrv_sc, len);
 		rv = PointerGetDatum(result);
 	}
-	PG_CATCH();
+	PG_FINALLY();
 	{
 		Py_XDECREF(plrv_so);
-		PG_RE_THROW();
 	}
 	PG_END_TRY();
 
-	Py_XDECREF(plrv_so);
-
 	return rv;
 }
 

src/pl/tcl/pltcl.c

@@ -765,9 +765,10 @@ pltcl_handler(PG_FUNCTION_ARGS, bool pltrusted)
 			retval = pltcl_func_handler(fcinfo, &current_call_state, pltrusted);
 		}
 	}
-	PG_CATCH();
+	PG_FINALLY();
 	{
 		/* Restore static pointer, then clean up the prodesc refcount if any */
+		/* (We're being paranoid in case an error is thrown in context deletion) */
 		pltcl_current_call_state = save_call_state;
 		if (current_call_state.prodesc != NULL)
 		{
@@ -775,20 +776,9 @@ pltcl_handler(PG_FUNCTION_ARGS, bool pltrusted)
 			if (--current_call_state.prodesc->fn_refcount == 0)
 				MemoryContextDelete(current_call_state.prodesc->fn_cxt);
 		}
-		PG_RE_THROW();
 	}
 	PG_END_TRY();
 
-	/* Restore static pointer, then clean up the prodesc refcount if any */
-	/* (We're being paranoid in case an error is thrown in context deletion) */
-	pltcl_current_call_state = save_call_state;
-	if (current_call_state.prodesc != NULL)
-	{
-		Assert(current_call_state.prodesc->fn_refcount > 0);
-		if (--current_call_state.prodesc->fn_refcount == 0)
-			MemoryContextDelete(current_call_state.prodesc->fn_cxt);
-	}
-
 	return retval;
 }