WL#6406 Stacked diagnostic areas

This worklog implements support for stacked diagnostic areas and the
GET STACKED DIAGNOSTICS statement.

Each connection has it's own stack of diagnostic areas. The diagnostic area on
top of the stack is called the first diagnostic area. The diagnostic area just
below is the second diagnostic area. There can be more than just two diagnostic
areas, but only the top two are accessible.

Normally all interaction happens with the first diagnostic area. This is where
conditions (errors, warnings, notes) that are raised, are entered. The contents
of the first diagnostic area can be queried by the existing GET [CURRENT]
DIAGNOSTICS statement, while the contents of the second diagnostic area can be
queried by the new GET STACKED DIAGNOSTICS statement.

A new diagnostic area is pushed to the diagnostic area stack when a stored
routine handler is activated. Initially, this new area contains a copy of the
contents of the second diagnostic area (i.e. the first diagnostic area before
the push). This allows GET STACKED DIAGNOSTICS to be used throughout the handler
to inspect the conditions that triggered the handler, regardless of what happens
with the first diagnostic area.

This worklog also fixes
Bug#14342913 SP HANDLER DOES NOT PRESERVE CURRENT DIAGNOSTICS AREA 
If a stored routine handler exits with RESIGNAL, the first diagnostic area now
contains all conditions present when the handler was activated + the condition
added by RESIGNAL. Before this fix, only the first condition present at handler
activation was preserved.

The worklog also contains serveral refactorings of the error handling API.

Author: jhauglid

Diff for: libmysqld/emb_qcache.cc

@@ -487,7 +487,7 @@ int emb_load_querycache_result(THD *thd, Querycache_stream *src)
   data->embedded_info->prev_ptr= prev_row;
 return_ok:
   net_send_eof(thd, thd->server_status,
-               thd->get_stmt_da()->current_statement_warn_count());
+               thd->get_stmt_da()->current_statement_cond_count());
   DBUG_RETURN(0);
 err:
   DBUG_RETURN(1);

Diff for: libmysqld/lib_sql.cc

@@ -246,7 +246,7 @@ static my_bool emb_read_prepare_result(MYSQL *mysql, MYSQL_STMT *stmt)
   stmt->stmt_id= thd->client_stmt_id;
   stmt->param_count= thd->client_param_count;
   stmt->field_count= 0;
-  mysql->warning_count= thd->get_stmt_da()->current_statement_warn_count();
+  mysql->warning_count= thd->get_stmt_da()->current_statement_cond_count();
 
   if (thd->first_data)
   {
@@ -437,7 +437,7 @@ static void emb_free_embedded_thd(MYSQL *mysql)
 static const char * emb_read_statistics(MYSQL *mysql)
 {
   THD *thd= (THD*)mysql->thd;
-  return thd->is_error() ? thd->get_stmt_da()->message() : "";
+  return thd->is_error() ? thd->get_stmt_da()->message_text() : "";
 }
 
 
@@ -1140,7 +1140,7 @@ bool Protocol::send_result_set_metadata(List<Item> *list, uint flags)
 
   if (flags & SEND_EOF)
     write_eof_packet(thd, thd->server_status,
-                     thd->get_stmt_da()->current_statement_warn_count());
+                     thd->get_stmt_da()->current_statement_cond_count());
 
   DBUG_RETURN(prepare_for_send(list->elements));
  err:

Diff for: mysql-test/r/get_diagnostics.result

@@ -800,3 +800,132 @@ GET DIAGNOSTICS @var1 = NUMBER;
 SHOW STATUS LIKE 'Com%get_diagnostics';
 Variable_name	Value
 Com_get_diagnostics	1
+#
+# WL#6406 Stacked diagnostic areas
+#
+#
+# Test non-reserved keywords: STACKED
+CREATE TABLE t1 (stacked INT);
+INSERT INTO t1 (stacked) values (1);
+SELECT stacked FROM t1 WHERE stacked = 1;
+stacked
+1
+SELECT `stacked` FROM t1 WHERE `stacked` = 1;
+stacked
+1
+DROP TABLE t1;
+CREATE PROCEDURE p1()
+BEGIN
+DECLARE stacked INT DEFAULT 1;
+SELECT stacked;
+END|
+CALL p1();
+stacked
+1
+DROP PROCEDURE p1;
+#
+# Test GET STACKED DIAGNOSTICS syntax
+GET STACKED;
+ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '' at line 1
+GET STACKED DIAGNOSTICS;
+ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '' at line 1
+#
+# Error if used without active HANDLER
+GET STACKED DIAGNOSTICS @var1 = NUMBER;
+ERROR 0Z002: GET STACKED DIAGNOSTICS when handler not active
+CREATE PROCEDURE p1() GET STACKED DIAGNOSTICS @var1 = NUMBER;
+CALL p1();
+ERROR 0Z002: GET STACKED DIAGNOSTICS when handler not active
+DROP PROCEDURE p1;
+CREATE FUNCTION f1() RETURNS INT
+BEGIN
+GET STACKED DIAGNOSTICS @var1 = NUMBER;
+RETURN 1;
+END|
+SELECT f1();
+ERROR 0Z002: GET STACKED DIAGNOSTICS when handler not active
+DROP FUNCTION f1;
+#
+# GET CURRENT DIAGNOSTICS = GET STACKED DIAGNOSTICS
+# when handler is first activated
+# GET STACKED DIAGNOSTICS doesn't change during handler
+CREATE TABLE t1(a INT);
+CREATE PROCEDURE p1()
+BEGIN
+DECLARE EXIT HANDLER FOR SQLEXCEPTION
+BEGIN
+DECLARE msg1 TEXT;
+DECLARE errno1 INT;
+DECLARE msg2 TEXT;
+DECLARE errno2 INT;
+DECLARE msg4 TEXT;
+DECLARE errno4 INT;
+# Should be identical
+GET CURRENT DIAGNOSTICS CONDITION 1 msg1 = MESSAGE_TEXT, errno1 = MYSQL_ERRNO;
+SELECT msg1, errno1;
+GET STACKED DIAGNOSTICS CONDITION 1 msg2 = MESSAGE_TEXT, errno2 = MYSQL_ERRNO;
+SELECT msg2, errno2;
+SELECT * FROM t1;   # Clear first diagnostics area
+# CURRENT should be empty, STACKED unchanged
+GET CURRENT DIAGNOSTICS @cno = NUMBER;
+SELECT @cno;
+GET STACKED DIAGNOSTICS CONDITION 1 msg4 = MESSAGE_TEXT, errno4 = MYSQL_ERRNO;
+SELECT msg4, errno4;
+END;
+DROP TABLE non_existent;
+END|
+CALL p1();
+msg1	errno1
+Unknown table 'test.non_existent'	1051
+msg2	errno2
+Unknown table 'test.non_existent'	1051
+a
+@cno
+0
+msg4	errno4
+Unknown table 'test.non_existent'	1051
+DROP PROCEDURE p1;
+DROP TABLE t1;
+#
+# RESIGNAL of a warning should modify the warning both in first and
+# second diagnostics area.
+CREATE PROCEDURE p1()
+BEGIN
+DECLARE CONTINUE HANDLER FOR SQLWARNING
+BEGIN
+DECLARE msg1 TEXT;
+DECLARE errno1 INT;
+DECLARE msg2 TEXT;
+DECLARE errno2 INT;
+DECLARE msg3 TEXT;
+DECLARE errno3 INT;
+DECLARE msg4 TEXT;
+DECLARE errno4 INT;
+# Should be identical
+GET CURRENT DIAGNOSTICS CONDITION 1 msg1 = MESSAGE_TEXT, errno1 = MYSQL_ERRNO;
+SELECT msg1, errno1;
+GET STACKED DIAGNOSTICS CONDITION 1 msg2 = MESSAGE_TEXT, errno2 = MYSQL_ERRNO;
+SELECT msg2, errno2;
+RESIGNAL SET MYSQL_ERRNO= 9999, MESSAGE_TEXT= 'Changed by resignal';
+# Should be changed, but still identical
+GET CURRENT DIAGNOSTICS CONDITION 1 msg3 = MESSAGE_TEXT, errno3 = MYSQL_ERRNO;
+SELECT msg3, errno3;
+GET STACKED DIAGNOSTICS CONDITION 1 msg4 = MESSAGE_TEXT, errno4 = MYSQL_ERRNO;
+SELECT msg4, errno4;
+END;
+SELECT 10 + 'a';
+END|
+CALL p1();
+10 + 'a'
+10
+msg1	errno1
+Truncated incorrect DOUBLE value: 'a'	1292
+msg2	errno2
+Truncated incorrect DOUBLE value: 'a'	1292
+msg3	errno3
+Changed by resignal	9999
+msg4	errno4
+Changed by resignal	9999
+Warnings:
+Warning	9999	Changed by resignal
+DROP PROCEDURE p1;