Add GET STACKED DIAGNOSTICS plpgsql command to retrieve exception info.

This is more SQL-spec-compliant, more easily extensible, and better
performing than the old method of inventing special variables.

Pavel Stehule, reviewed by Shigeru Hanada and David Wheeler

5 files changed, 198 insertions, 27 deletions

diff --git a/src/pl/plpgsql/src/gram.y b/src/pl/plpgsql/src/gram.y
index 4e2b7058f0c..92b54dd9cf6 100644
--- a/src/pl/plpgsql/src/gram.y
+++ b/src/pl/plpgsql/src/gram.y
@@ -203,6 +203,7 @@ static	List			*read_raise_options(void);
 %type <casewhen>	case_when
 %type <list>	case_when_list opt_case_else
 
+%type <boolean>	getdiag_area_opt
 %type <list>	getdiag_list
 %type <diagitem> getdiag_list_item
 %type <ival>	getdiag_item getdiag_target
@@ -251,6 +252,7 @@ static	List			*read_raise_options(void);
 %token <keyword>	K_COLLATE
 %token <keyword>	K_CONSTANT
 %token <keyword>	K_CONTINUE
+%token <keyword>	K_CURRENT
 %token <keyword>	K_CURSOR
 %token <keyword>	K_DEBUG
 %token <keyword>	K_DECLARE
@@ -284,6 +286,7 @@ static	List			*read_raise_options(void);
 %token <keyword>	K_LOG
 %token <keyword>	K_LOOP
 %token <keyword>	K_MESSAGE
+%token <keyword>	K_MESSAGE_TEXT
 %token <keyword>	K_MOVE
 %token <keyword>	K_NEXT
 %token <keyword>	K_NO
@@ -294,18 +297,23 @@ static	List			*read_raise_options(void);
 %token <keyword>	K_OPTION
 %token <keyword>	K_OR
 %token <keyword>	K_PERFORM
+%token <keyword>	K_PG_EXCEPTION_CONTEXT
+%token <keyword>	K_PG_EXCEPTION_DETAIL
+%token <keyword>	K_PG_EXCEPTION_HINT
 %token <keyword>	K_PRIOR
 %token <keyword>	K_QUERY
 %token <keyword>	K_RAISE
 %token <keyword>	K_RELATIVE
 %token <keyword>	K_RESULT_OID
 %token <keyword>	K_RETURN
+%token <keyword>	K_RETURNED_SQLSTATE
 %token <keyword>	K_REVERSE
 %token <keyword>	K_ROWTYPE
 %token <keyword>	K_ROW_COUNT
 %token <keyword>	K_SCROLL
 %token <keyword>	K_SLICE
 %token <keyword>	K_SQLSTATE
+%token <keyword>	K_STACKED
 %token <keyword>	K_STRICT
 %token <keyword>	K_THEN
 %token <keyword>	K_TO
@@ -832,19 +840,74 @@ stmt_assign		: assign_var assign_operator expr_until_semi
 					}
 				;
 
-stmt_getdiag	: K_GET K_DIAGNOSTICS getdiag_list ';'
+stmt_getdiag	: K_GET getdiag_area_opt K_DIAGNOSTICS getdiag_list ';'
 					{
 						PLpgSQL_stmt_getdiag	 *new;
+						ListCell		*lc;
 
 						new = palloc0(sizeof(PLpgSQL_stmt_getdiag));
 						new->cmd_type = PLPGSQL_STMT_GETDIAG;
 						new->lineno   = plpgsql_location_to_lineno(@1);
-						new->diag_items  = $3;
+						new->is_stacked = $2;
+						new->diag_items = $4;
+
+						/*
+						 * Check information items are valid for area option.
+						 */
+						foreach(lc, new->diag_items)
+						{
+							PLpgSQL_diag_item *ditem = (PLpgSQL_diag_item *) lfirst(lc);
+
+							switch (ditem->kind)
+							{
+								/* these fields are disallowed in stacked case */
+								case PLPGSQL_GETDIAG_ROW_COUNT:
+								case PLPGSQL_GETDIAG_RESULT_OID:
+									if (new->is_stacked)
+										ereport(ERROR,
+												(errcode(ERRCODE_SYNTAX_ERROR),
+												 errmsg("diagnostics item %s is not allowed in GET STACKED DIAGNOSTICS",
+														plpgsql_getdiag_kindname(ditem->kind)),
+												 parser_errposition(@1)));
+									break;
+								/* these fields are disallowed in current case */
+								case PLPGSQL_GETDIAG_ERROR_CONTEXT:
+								case PLPGSQL_GETDIAG_ERROR_DETAIL:
+								case PLPGSQL_GETDIAG_ERROR_HINT:
+								case PLPGSQL_GETDIAG_RETURNED_SQLSTATE:
+								case PLPGSQL_GETDIAG_MESSAGE_TEXT:
+									if (!new->is_stacked)
+										ereport(ERROR,
+												(errcode(ERRCODE_SYNTAX_ERROR),
+												 errmsg("diagnostics item %s is not allowed in GET CURRENT DIAGNOSTICS",
+														plpgsql_getdiag_kindname(ditem->kind)),
+												 parser_errposition(@1)));
+									break;
+								default:
+									elog(ERROR, "unrecognized diagnostic item kind: %d",
+										 ditem->kind);
+									break;
+							}
+						}
 
 						$$ = (PLpgSQL_stmt *)new;
 					}
 				;
 
+getdiag_area_opt :
+					{
+						$$ = false;
+					}
+				| K_CURRENT
+					{
+						$$ = false;
+					}
+				| K_STACKED
+					{
+						$$ = true;
+					}
+				;
+
 getdiag_list : getdiag_list ',' getdiag_list_item
 					{
 						$$ = lappend($1, $3);
@@ -877,6 +940,21 @@ getdiag_item :
 						else if (tok_is_keyword(tok, &yylval,
 												K_RESULT_OID, "result_oid"))
 							$$ = PLPGSQL_GETDIAG_RESULT_OID;
+						else if (tok_is_keyword(tok, &yylval,
+												K_PG_EXCEPTION_DETAIL, "pg_exception_detail"))
+							$$ = PLPGSQL_GETDIAG_ERROR_DETAIL;
+						else if (tok_is_keyword(tok, &yylval,
+												K_PG_EXCEPTION_HINT, "pg_exception_hint"))
+							$$ = PLPGSQL_GETDIAG_ERROR_HINT;
+						else if (tok_is_keyword(tok, &yylval,
+												K_PG_EXCEPTION_CONTEXT, "pg_exception_context"))
+							$$ = PLPGSQL_GETDIAG_ERROR_CONTEXT;
+						else if (tok_is_keyword(tok, &yylval,
+												K_MESSAGE_TEXT, "message_text"))
+							$$ = PLPGSQL_GETDIAG_MESSAGE_TEXT;
+						else if (tok_is_keyword(tok, &yylval,
+												K_RETURNED_SQLSTATE, "returned_sqlstate"))
+							$$ = PLPGSQL_GETDIAG_RETURNED_SQLSTATE;
 						else
 							yyerror("unrecognized GET DIAGNOSTICS item");
 					}
@@ -2135,6 +2213,7 @@ unreserved_keyword	:
 				| K_ARRAY
 				| K_BACKWARD
 				| K_CONSTANT
+				| K_CURRENT
 				| K_CURSOR
 				| K_DEBUG
 				| K_DETAIL
@@ -2149,20 +2228,26 @@ unreserved_keyword	:
 				| K_LAST
 				| K_LOG
 				| K_MESSAGE
+				| K_MESSAGE_TEXT
 				| K_NEXT
 				| K_NO
 				| K_NOTICE
 				| K_OPTION
+				| K_PG_EXCEPTION_CONTEXT
+				| K_PG_EXCEPTION_DETAIL
+				| K_PG_EXCEPTION_HINT
 				| K_PRIOR
 				| K_QUERY
 				| K_RELATIVE
 				| K_RESULT_OID
+				| K_RETURNED_SQLSTATE
 				| K_REVERSE
 				| K_ROW_COUNT
 				| K_ROWTYPE
 				| K_SCROLL
 				| K_SLICE
 				| K_SQLSTATE
+				| K_STACKED
 				| K_TYPE
 				| K_USE_COLUMN
 				| K_USE_VARIABLE
diff --git a/src/pl/plpgsql/src/pl_exec.c b/src/pl/plpgsql/src/pl_exec.c
index b7ffb717f9a..de1aece92a1 100644
--- a/src/pl/plpgsql/src/pl_exec.c
+++ b/src/pl/plpgsql/src/pl_exec.c
@@ -151,6 +151,9 @@ static bool exec_eval_simple_expr(PLpgSQL_execstate *estate,
 static void exec_assign_expr(PLpgSQL_execstate *estate,
 				 PLpgSQL_datum *target,
 				 PLpgSQL_expr *expr);
+static void exec_assign_c_string(PLpgSQL_execstate *estate,
+					 PLpgSQL_datum *target,
+					 const char *str);
 static void exec_assign_value(PLpgSQL_execstate *estate,
 				  PLpgSQL_datum *target,
 				  Datum value, Oid valtype, bool *isNull);
@@ -1421,6 +1424,17 @@ exec_stmt_getdiag(PLpgSQL_execstate *estate, PLpgSQL_stmt_getdiag *stmt)
 {
 	ListCell   *lc;
 
+	/*
+	 * GET STACKED DIAGNOSTICS is only valid inside an exception handler.
+	 *
+	 * Note: we trust the grammar to have disallowed the relevant item kinds
+	 * if not is_stacked, otherwise we'd dump core below.
+	 */
+	if (stmt->is_stacked && estate->cur_error == NULL)
+		ereport(ERROR,
+				(errcode(ERRCODE_STACKED_DIAGNOSTICS_ACCESSED_WITHOUT_ACTIVE_HANDLER),
+				 errmsg("GET STACKED DIAGNOSTICS cannot be used outside an exception handler")));
+
 	foreach(lc, stmt->diag_items)
 	{
 		PLpgSQL_diag_item *diag_item = (PLpgSQL_diag_item *) lfirst(lc);
@@ -1438,21 +1452,44 @@ exec_stmt_getdiag(PLpgSQL_execstate *estate, PLpgSQL_stmt_getdiag *stmt)
 		switch (diag_item->kind)
 		{
 			case PLPGSQL_GETDIAG_ROW_COUNT:
-
 				exec_assign_value(estate, var,
 								  UInt32GetDatum(estate->eval_processed),
 								  INT4OID, &isnull);
 				break;
 
 			case PLPGSQL_GETDIAG_RESULT_OID:
-
 				exec_assign_value(estate, var,
 								  ObjectIdGetDatum(estate->eval_lastoid),
 								  OIDOID, &isnull);
 				break;
 
+			case PLPGSQL_GETDIAG_ERROR_CONTEXT:
+				exec_assign_c_string(estate, var,
+									 estate->cur_error->context);
+				break;
+
+			case PLPGSQL_GETDIAG_ERROR_DETAIL:
+				exec_assign_c_string(estate, var,
+									 estate->cur_error->detail);
+				break;
+
+			case PLPGSQL_GETDIAG_ERROR_HINT:
+				exec_assign_c_string(estate, var,
+									 estate->cur_error->hint);
+				break;
+
+			case PLPGSQL_GETDIAG_RETURNED_SQLSTATE:
+				exec_assign_c_string(estate, var,
+									 unpack_sql_state(estate->cur_error->sqlerrcode));
+				break;
+
+			case PLPGSQL_GETDIAG_MESSAGE_TEXT:
+				exec_assign_c_string(estate, var,
+									 estate->cur_error->message);
+				break;
+
 			default:
-				elog(ERROR, "unrecognized attribute request: %d",
+				elog(ERROR, "unrecognized diagnostic item kind: %d",
 					 diag_item->kind);
 		}
 	}
@@ -2634,7 +2671,7 @@ exec_stmt_raise(PLpgSQL_execstate *estate, PLpgSQL_stmt_raise *stmt)
 			ReThrowError(estate->cur_error);
 		/* oops, we're not inside a handler */
 		ereport(ERROR,
-				(errcode(ERRCODE_SYNTAX_ERROR),
+				(errcode(ERRCODE_STACKED_DIAGNOSTICS_ACCESSED_WITHOUT_ACTIVE_HANDLER),
 				 errmsg("RAISE without parameters cannot be used outside an exception handler")));
 	}
 
@@ -3650,8 +3687,7 @@ exec_stmt_close(PLpgSQL_execstate *estate, PLpgSQL_stmt_close *stmt)
 
 
 /* ----------
- * exec_assign_expr			Put an expression's result into
- *					a variable.
+ * exec_assign_expr			Put an expression's result into a variable.
  * ----------
  */
 static void
@@ -3669,6 +3705,29 @@ exec_assign_expr(PLpgSQL_execstate *estate, PLpgSQL_datum *target,
 
 
 /* ----------
+ * exec_assign_c_string		Put a C string into a text variable.
+ *
+ * We take a NULL pointer as signifying empty string, not SQL null.
+ * ----------
+ */
+static void
+exec_assign_c_string(PLpgSQL_execstate *estate, PLpgSQL_datum *target,
+					 const char *str)
+{
+	text	   *value;
+	bool		isnull = false;
+
+	if (str != NULL)
+		value = cstring_to_text(str);
+	else
+		value = cstring_to_text("");
+	exec_assign_value(estate, target, PointerGetDatum(value),
+					  TEXTOID, &isnull);
+	pfree(value);
+}
+
+
+/* ----------
  * exec_assign_value			Put a value into a target field
  *
  * Note: in some code paths, this may leak memory in the eval_econtext;
diff --git a/src/pl/plpgsql/src/pl_funcs.c b/src/pl/plpgsql/src/pl_funcs.c
index 1f83114d9b1..030ed07ac55 100644
--- a/src/pl/plpgsql/src/pl_funcs.c
+++ b/src/pl/plpgsql/src/pl_funcs.c
@@ -265,6 +265,33 @@ plpgsql_stmt_typename(PLpgSQL_stmt *stmt)
 	return "unknown";
 }
 
+/*
+ * GET DIAGNOSTICS item name as a string, for use in error messages etc.
+ */
+const char *
+plpgsql_getdiag_kindname(int kind)
+{
+	switch (kind)
+	{
+		case PLPGSQL_GETDIAG_ROW_COUNT:
+			return "ROW_COUNT";
+		case PLPGSQL_GETDIAG_RESULT_OID:
+			return "RESULT_OID";
+		case PLPGSQL_GETDIAG_ERROR_CONTEXT:
+			return "PG_EXCEPTION_CONTEXT";
+		case PLPGSQL_GETDIAG_ERROR_DETAIL:
+			return "PG_EXCEPTION_DETAIL";
+		case PLPGSQL_GETDIAG_ERROR_HINT:
+			return "PG_EXCEPTION_HINT";
+		case PLPGSQL_GETDIAG_RETURNED_SQLSTATE:
+			return "RETURNED_SQLSTATE";
+		case PLPGSQL_GETDIAG_MESSAGE_TEXT:
+			return "MESSAGE_TEXT";
+	}
+
+	return "unknown";
+}
+
 
 /**********************************************************************
  * Release memory when a PL/pgSQL function is no longer needed
@@ -1389,7 +1416,7 @@ dump_getdiag(PLpgSQL_stmt_getdiag *stmt)
 	ListCell   *lc;
 
 	dump_ind();
-	printf("GET DIAGNOSTICS ");
+	printf("GET %s DIAGNOSTICS ", stmt->is_stacked ? "STACKED" : "CURRENT");
 	foreach(lc, stmt->diag_items)
 	{
 		PLpgSQL_diag_item *diag_item = (PLpgSQL_diag_item *) lfirst(lc);
@@ -1397,22 +1424,8 @@ dump_getdiag(PLpgSQL_stmt_getdiag *stmt)
 		if (lc != list_head(stmt->diag_items))
 			printf(", ");
 
-		printf("{var %d} = ", diag_item->target);
-
-		switch (diag_item->kind)
-		{
-			case PLPGSQL_GETDIAG_ROW_COUNT:
-				printf("ROW_COUNT");
-				break;
-
-			case PLPGSQL_GETDIAG_RESULT_OID:
-				printf("RESULT_OID");
-				break;
-
-			default:
-				printf("???");
-				break;
-		}
+		printf("{var %d} = %s", diag_item->target,
+			   plpgsql_getdiag_kindname(diag_item->kind));
 	}
 	printf("\n");
 }
diff --git a/src/pl/plpgsql/src/pl_scanner.c b/src/pl/plpgsql/src/pl_scanner.c
index e1c0b625954..76e8436e50e 100644
--- a/src/pl/plpgsql/src/pl_scanner.c
+++ b/src/pl/plpgsql/src/pl_scanner.c
@@ -110,6 +110,7 @@ static const ScanKeyword unreserved_keywords[] = {
 	PG_KEYWORD("array", K_ARRAY, UNRESERVED_KEYWORD)
 	PG_KEYWORD("backward", K_BACKWARD, UNRESERVED_KEYWORD)
 	PG_KEYWORD("constant", K_CONSTANT, UNRESERVED_KEYWORD)
+	PG_KEYWORD("current", K_CURRENT, UNRESERVED_KEYWORD)
 	PG_KEYWORD("cursor", K_CURSOR, UNRESERVED_KEYWORD)
 	PG_KEYWORD("debug", K_DEBUG, UNRESERVED_KEYWORD)
 	PG_KEYWORD("detail", K_DETAIL, UNRESERVED_KEYWORD)
@@ -124,20 +125,26 @@ static const ScanKeyword unreserved_keywords[] = {
 	PG_KEYWORD("last", K_LAST, UNRESERVED_KEYWORD)
 	PG_KEYWORD("log", K_LOG, UNRESERVED_KEYWORD)
 	PG_KEYWORD("message", K_MESSAGE, UNRESERVED_KEYWORD)
+	PG_KEYWORD("message_text", K_MESSAGE_TEXT, UNRESERVED_KEYWORD)
 	PG_KEYWORD("next", K_NEXT, UNRESERVED_KEYWORD)
 	PG_KEYWORD("no", K_NO, UNRESERVED_KEYWORD)
 	PG_KEYWORD("notice", K_NOTICE, UNRESERVED_KEYWORD)
 	PG_KEYWORD("option", K_OPTION, UNRESERVED_KEYWORD)
+	PG_KEYWORD("pg_exception_context", K_PG_EXCEPTION_CONTEXT, UNRESERVED_KEYWORD)
+	PG_KEYWORD("pg_exception_detail", K_PG_EXCEPTION_DETAIL, UNRESERVED_KEYWORD)
+	PG_KEYWORD("pg_exception_hint", K_PG_EXCEPTION_HINT, UNRESERVED_KEYWORD)
 	PG_KEYWORD("prior", K_PRIOR, UNRESERVED_KEYWORD)
 	PG_KEYWORD("query", K_QUERY, UNRESERVED_KEYWORD)
 	PG_KEYWORD("relative", K_RELATIVE, UNRESERVED_KEYWORD)
 	PG_KEYWORD("result_oid", K_RESULT_OID, UNRESERVED_KEYWORD)
+	PG_KEYWORD("returned_sqlstate", K_RETURNED_SQLSTATE, UNRESERVED_KEYWORD)
 	PG_KEYWORD("reverse", K_REVERSE, UNRESERVED_KEYWORD)
 	PG_KEYWORD("row_count", K_ROW_COUNT, UNRESERVED_KEYWORD)
 	PG_KEYWORD("rowtype", K_ROWTYPE, UNRESERVED_KEYWORD)
 	PG_KEYWORD("scroll", K_SCROLL, UNRESERVED_KEYWORD)
 	PG_KEYWORD("slice", K_SLICE, UNRESERVED_KEYWORD)
 	PG_KEYWORD("sqlstate", K_SQLSTATE, UNRESERVED_KEYWORD)
+	PG_KEYWORD("stacked", K_STACKED, UNRESERVED_KEYWORD)
 	PG_KEYWORD("type", K_TYPE, UNRESERVED_KEYWORD)
 	PG_KEYWORD("use_column", K_USE_COLUMN, UNRESERVED_KEYWORD)
 	PG_KEYWORD("use_variable", K_USE_VARIABLE, UNRESERVED_KEYWORD)
diff --git a/src/pl/plpgsql/src/plpgsql.h b/src/pl/plpgsql/src/plpgsql.h
index 89103aea8c5..c543f1cf9dd 100644
--- a/src/pl/plpgsql/src/plpgsql.h
+++ b/src/pl/plpgsql/src/plpgsql.h
@@ -120,13 +120,18 @@ enum
 };
 
 /* ----------
- * GET DIAGNOSTICS system attrs
+ * GET DIAGNOSTICS information items
  * ----------
  */
 enum
 {
 	PLPGSQL_GETDIAG_ROW_COUNT,
-	PLPGSQL_GETDIAG_RESULT_OID
+	PLPGSQL_GETDIAG_RESULT_OID,
+	PLPGSQL_GETDIAG_ERROR_CONTEXT,
+	PLPGSQL_GETDIAG_ERROR_DETAIL,
+	PLPGSQL_GETDIAG_ERROR_HINT,
+	PLPGSQL_GETDIAG_RETURNED_SQLSTATE,
+	PLPGSQL_GETDIAG_MESSAGE_TEXT
 };
 
 /* --------
@@ -376,6 +381,7 @@ typedef struct
 {								/* Get Diagnostics statement		*/
 	int			cmd_type;
 	int			lineno;
+	bool		is_stacked;		/* STACKED or CURRENT diagnostics area? */
 	List	   *diag_items;		/* List of PLpgSQL_diag_item */
 } PLpgSQL_stmt_getdiag;
 
@@ -929,6 +935,7 @@ extern PLpgSQL_nsitem *plpgsql_ns_lookup_label(PLpgSQL_nsitem *ns_cur,
  * ----------
  */
 extern const char *plpgsql_stmt_typename(PLpgSQL_stmt *stmt);
+extern const char *plpgsql_getdiag_kindname(int kind);
 extern void plpgsql_free_function_memory(PLpgSQL_function *func);
 extern void plpgsql_dumptree(PLpgSQL_function *func);