plpgsql: Add new option print_strict_params.

This option provides more detailed error messages when STRICT is used
and the number of rows returned is not one.

Marko Tiikkaja, reviewed by Ian Lawrence Barwick

Author: robertmhaas

doc/src/sgml/plpgsql.sgml

@@ -1076,6 +1076,30 @@ END;
      always sets <literal>FOUND</literal> to true.
     </para>
 
+    <para>
+     If <literal>print_strict_params</> is enabled for the function,
+     you will get information about the parameters passed to the
+     query in the <literal>DETAIL</> part of the error message produced
+     when the requirements of STRICT are not met.  You can change this
+     setting on a system-wide basis by setting
+     <varname>plpgsql.print_strict_params</>, though only subsequent
+     function compilations will be affected.  You can also enable it
+     on a per-function basis by using a compiler option:
+<programlisting>
+CREATE FUNCTION get_userid(username text) RETURNS int
+AS $$
+#print_strict_params on
+DECLARE
+userid int;
+BEGIN
+    SELECT users.userid INTO STRICT userid
+        FROM users WHERE users.username = get_userid.username;
+    RETURN userid;
+END
+$$ LANGUAGE plpgsql;
+</programlisting>
+    </para>
+
     <para>
      For <command>INSERT</>/<command>UPDATE</>/<command>DELETE</> with
      <literal>RETURNING</>, <application>PL/pgSQL</application> reports

src/pl/plpgsql/src/pl_comp.c

@@ -351,6 +351,7 @@ do_compile(FunctionCallInfo fcinfo,
 	function->fn_cxt = func_cxt;
 	function->out_param_varno = -1;		/* set up for no OUT param */
 	function->resolve_option = plpgsql_variable_conflict;
+	function->print_strict_params = plpgsql_print_strict_params;
 
 	if (is_dml_trigger)
 		function->fn_is_trigger = PLPGSQL_DML_TRIGGER;
@@ -847,6 +848,7 @@ plpgsql_compile_inline(char *proc_source)
 	function->fn_cxt = func_cxt;
 	function->out_param_varno = -1;		/* set up for no OUT param */
 	function->resolve_option = plpgsql_variable_conflict;
+	function->print_strict_params = plpgsql_print_strict_params;
 
 	plpgsql_ns_init();
 	plpgsql_ns_push(func_name);

src/pl/plpgsql/src/pl_exec.c

@@ -221,6 +221,11 @@ static Portal exec_dynquery_with_params(PLpgSQL_execstate *estate,
 						  PLpgSQL_expr *dynquery, List *params,
 						  const char *portalname, int cursorOptions);
 
+static char *format_expr_params(PLpgSQL_execstate *estate,
+					  			const PLpgSQL_expr *expr);
+static char *format_preparedparamsdata(PLpgSQL_execstate *estate,
+									   const PreparedParamsData *ppd);
+
 
 /* ----------
  * plpgsql_exec_function	Called by the call handler for
@@ -3391,18 +3396,40 @@ exec_stmt_execsql(PLpgSQL_execstate *estate,
 		if (n == 0)
 		{
 			if (stmt->strict)
+			{
+				char *errdetail;
+
+				if (estate->func->print_strict_params)
+					errdetail = format_expr_params(estate, expr);
+				else
+					errdetail = NULL;
+
 				ereport(ERROR,
 						(errcode(ERRCODE_NO_DATA_FOUND),
-						 errmsg("query returned no rows")));
+						 errmsg("query returned no rows"),
+						 errdetail ?
+						 	errdetail_internal("parameters: %s", errdetail) : 0));
+			}
 			/* set the target to NULL(s) */
 			exec_move_row(estate, rec, row, NULL, tuptab->tupdesc);
 		}
 		else
 		{
 			if (n > 1 && (stmt->strict || stmt->mod_stmt))
+			{
+				char *errdetail;
+
+				if (estate->func->print_strict_params)
+					errdetail = format_expr_params(estate, expr);
+				else
+					errdetail = NULL;
+
 				ereport(ERROR,
 						(errcode(ERRCODE_TOO_MANY_ROWS),
-						 errmsg("query returned more than one row")));
+						 errmsg("query returned more than one row"),
+						 errdetail ?
+						 	errdetail_internal("parameters: %s", errdetail) : 0));
+			}
 			/* Put the first result row into the target */
 			exec_move_row(estate, rec, row, tuptab->vals[0], tuptab->tupdesc);
 		}
@@ -3442,6 +3469,7 @@ exec_stmt_dynexecute(PLpgSQL_execstate *estate,
 	Oid			restype;
 	char	   *querystr;
 	int			exec_res;
+	PreparedParamsData *ppd = NULL;
 
 	/*
 	 * First we evaluate the string expression after the EXECUTE keyword. Its
@@ -3466,14 +3494,11 @@ exec_stmt_dynexecute(PLpgSQL_execstate *estate,
 	 */
 	if (stmt->params)
 	{
-		PreparedParamsData *ppd;
-
 		ppd = exec_eval_using_params(estate, stmt->params);
 		exec_res = SPI_execute_with_args(querystr,
 										 ppd->nargs, ppd->types,
 										 ppd->values, ppd->nulls,
 										 estate->readonly_func, 0);
-		free_params_data(ppd);
 	}
 	else
 		exec_res = SPI_execute(querystr, estate->readonly_func, 0);
@@ -3565,18 +3590,41 @@ exec_stmt_dynexecute(PLpgSQL_execstate *estate,
 		if (n == 0)
 		{
 			if (stmt->strict)
+			{
+				char *errdetail;
+
+				if (estate->func->print_strict_params)
+					errdetail = format_preparedparamsdata(estate, ppd);
+				else
+					errdetail = NULL;
+
 				ereport(ERROR,
 						(errcode(ERRCODE_NO_DATA_FOUND),
-						 errmsg("query returned no rows")));
+						 errmsg("query returned no rows"),
+						 errdetail ?
+						 	errdetail_internal("parameters: %s", errdetail) : 0));
+			}
 			/* set the target to NULL(s) */
 			exec_move_row(estate, rec, row, NULL, tuptab->tupdesc);
 		}
 		else
 		{
 			if (n > 1 && stmt->strict)
+			{
+				char *errdetail;
+
+				if (estate->func->print_strict_params)
+					errdetail = format_preparedparamsdata(estate, ppd);
+				else
+					errdetail = NULL;
+
 				ereport(ERROR,
 						(errcode(ERRCODE_TOO_MANY_ROWS),
-						 errmsg("query returned more than one row")));
+						 errmsg("query returned more than one row"),
+						 errdetail ?
+						 	errdetail_internal("parameters: %s", errdetail) : 0));
+			}
+
 			/* Put the first result row into the target */
 			exec_move_row(estate, rec, row, tuptab->vals[0], tuptab->tupdesc);
 		}
@@ -3592,6 +3640,9 @@ exec_stmt_dynexecute(PLpgSQL_execstate *estate,
 		 */
 	}
 
+	if (ppd)
+		free_params_data(ppd);
+
 	/* Release any result from SPI_execute, as well as the querystring */
 	SPI_freetuptable(SPI_tuptable);
 	pfree(querystr);
@@ -6456,3 +6507,103 @@ exec_dynquery_with_params(PLpgSQL_execstate *estate,
 
 	return portal;
 }
+
+/*
+ * Return a formatted string with information about an expression's parameters,
+ * or NULL if the expression does not take any parameters.
+ */
+static char *
+format_expr_params(PLpgSQL_execstate *estate,
+				   const PLpgSQL_expr *expr)
+{
+	int paramno;
+	int dno;
+	StringInfoData paramstr;
+	Bitmapset *tmpset;
+
+	if (!expr->paramnos)
+		return NULL;
+
+	initStringInfo(&paramstr);
+	tmpset = bms_copy(expr->paramnos);
+	paramno = 0;
+	while ((dno = bms_first_member(tmpset)) >= 0)
+	{
+		Datum paramdatum;
+		Oid paramtypeid;
+		bool paramisnull;
+		int32 paramtypmod;
+		PLpgSQL_var *curvar;
+
+		curvar = (PLpgSQL_var *) estate->datums[dno];
+
+		exec_eval_datum(estate, (PLpgSQL_datum *) curvar, &paramtypeid,
+						&paramtypmod, &paramdatum, &paramisnull);
+
+		appendStringInfo(&paramstr, "%s%s = ",
+						 paramno > 0 ? ", " : "",
+						 curvar->refname);
+
+		if (paramisnull)
+			appendStringInfoString(&paramstr, "NULL");
+		else
+		{
+			char *value = convert_value_to_string(estate, paramdatum, paramtypeid);
+			char *p;
+			appendStringInfoCharMacro(&paramstr, '\'');
+			for (p = value; *p; p++)
+			{
+				if (*p == '\'') /* double single quotes */
+					appendStringInfoCharMacro(&paramstr, *p);
+				appendStringInfoCharMacro(&paramstr, *p);
+			}
+			appendStringInfoCharMacro(&paramstr, '\'');
+		}
+
+		paramno++;
+	}
+	bms_free(tmpset);
+
+	return paramstr.data;
+}
+
+/*
+ * Return a formatted string with information about PreparedParamsData, or NULL
+ * if the there are no parameters.
+ */
+static char *
+format_preparedparamsdata(PLpgSQL_execstate *estate,
+						  const PreparedParamsData *ppd)
+{
+	int paramno;
+	StringInfoData paramstr;
+
+	if (!ppd)
+		return NULL;
+
+	initStringInfo(&paramstr);
+	for (paramno = 0; paramno < ppd->nargs; paramno++)
+	{
+		appendStringInfo(&paramstr, "%s$%d = ",
+						 paramno > 0 ? ", " : "",
+						 paramno + 1);
+
+		if (ppd->nulls[paramno] == 'n')
+			appendStringInfoString(&paramstr, "NULL");
+		else
+		{
+			char *value = convert_value_to_string(estate, ppd->values[paramno], ppd->types[paramno]);
+			char *p;
+			appendStringInfoCharMacro(&paramstr, '\'');
+			for (p = value; *p; p++)
+			{
+				if (*p == '\'') /* double single quotes */
+					appendStringInfoCharMacro(&paramstr, *p);
+				appendStringInfoCharMacro(&paramstr, *p);
+			}
+			appendStringInfoCharMacro(&paramstr, '\'');
+		}
+	}
+
+	return paramstr.data;
+}

src/pl/plpgsql/src/pl_gram.y

@@ -185,7 +185,7 @@ static	List			*read_raise_options(void);
 %type <forvariable>	for_variable
 %type <stmt>	for_control
 
-%type <str>		any_identifier opt_block_label opt_label
+%type <str>		any_identifier opt_block_label opt_label option_value 
 
 %type <list>	proc_sect proc_stmts stmt_elsifs stmt_else
 %type <loop_body>	loop_body
@@ -308,6 +308,7 @@ static	List			*read_raise_options(void);
 %token <keyword>	K_PG_EXCEPTION_CONTEXT
 %token <keyword>	K_PG_EXCEPTION_DETAIL
 %token <keyword>	K_PG_EXCEPTION_HINT
+%token <keyword>	K_PRINT_STRICT_PARAMS
 %token <keyword>	K_PRIOR
 %token <keyword>	K_QUERY
 %token <keyword>	K_RAISE
@@ -354,6 +355,15 @@ comp_option		: '#' K_OPTION K_DUMP
 					{
 						plpgsql_DumpExecTree = true;
 					}
+				| '#' K_PRINT_STRICT_PARAMS option_value
+					{
+						if (strcmp($3, "on") == 0)
+							plpgsql_curr_compile->print_strict_params = true;
+						else if (strcmp($3, "off") == 0)
+							plpgsql_curr_compile->print_strict_params = false;
+						else
+							elog(ERROR, "unrecognized print_strict_params option %s", $3);
+					}
 				| '#' K_VARIABLE_CONFLICT K_ERROR
 					{
 						plpgsql_curr_compile->resolve_option = PLPGSQL_RESOLVE_ERROR;
@@ -368,6 +378,15 @@ comp_option		: '#' K_OPTION K_DUMP
 					}
 				;
 
+option_value : T_WORD
+				{
+					$$ = $1.ident;
+				}
+			 | unreserved_keyword
+				{
+					$$ = pstrdup($1);
+				}
+
 opt_semi		:
 				| ';'
 				;
@@ -2300,6 +2319,7 @@ unreserved_keyword	:
 				| K_PG_EXCEPTION_DETAIL
 				| K_PG_EXCEPTION_HINT
 				| K_PRIOR
+				| K_PRINT_STRICT_PARAMS
 				| K_QUERY
 				| K_RELATIVE
 				| K_RESULT_OID

src/pl/plpgsql/src/pl_handler.c

@@ -37,6 +37,8 @@ static const struct config_enum_entry variable_conflict_options[] = {
 
 int			plpgsql_variable_conflict = PLPGSQL_RESOLVE_ERROR;
 
+bool		plpgsql_print_strict_params = false;
+
 /* Hook for plugins */
 PLpgSQL_plugin **plugin_ptr = NULL;
 
@@ -66,6 +68,14 @@ _PG_init(void)
 							 PGC_SUSET, 0,
 							 NULL, NULL, NULL);
 
+	DefineCustomBoolVariable("plpgsql.print_strict_params",
+							 gettext_noop("Print information about parameters in the DETAIL part of the error messages generated on INTO .. STRICT failures."),
+							 NULL,
+							 &plpgsql_print_strict_params,
+							 false,
+							 PGC_USERSET, 0,
+							 NULL, NULL, NULL);
+
 	EmitWarningsOnPlaceholders("plpgsql");
 
 	plpgsql_HashTableInit();

src/pl/plpgsql/src/pl_scanner.c

@@ -140,6 +140,7 @@ static const ScanKeyword unreserved_keywords[] = {
 	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("print_strict_params", K_PRINT_STRICT_PARAMS, UNRESERVED_KEYWORD)
 	PG_KEYWORD("prior", K_PRIOR, UNRESERVED_KEYWORD)
 	PG_KEYWORD("query", K_QUERY, UNRESERVED_KEYWORD)
 	PG_KEYWORD("relative", K_RELATIVE, UNRESERVED_KEYWORD)

src/pl/plpgsql/src/plpgsql.h

@@ -737,6 +737,8 @@ typedef struct PLpgSQL_function
 
 	PLpgSQL_resolve_option resolve_option;
 
+	bool		print_strict_params;
+
 	int			ndatums;
 	PLpgSQL_datum **datums;
 	PLpgSQL_stmt_block *action;
@@ -873,6 +875,8 @@ extern IdentifierLookup plpgsql_IdentifierLookup;
 
 extern int	plpgsql_variable_conflict;
 
+extern bool plpgsql_print_strict_params;
+
 extern bool plpgsql_check_syntax;
 extern bool plpgsql_DumpExecTree;