WL#5928: Most statements should clear the diagnostic area

Previously, the errors/warnings list was only cleared when
a statement accessed tables. This was non-standard. We now
clear the DA for every procedure statement (mostly anything
that is executed and is not a diagnostics statement like
GET DIAGNOSTICS or SHOW WARNINGS).

This changes both code and behaviour for
- direct invocation
- stored procedures/functions
- prepared statements
- query cache

GET DIAGNOSTICS and the old SHOW WARNINGS, SHOW ERRORS,
SHOW COUNT(*) WARNINGS, SHOW COUNT(*) ERRORS are diagnostics
statements. They do not clear the diagnostics area even
when issued repeatedly.

@@error_count and @@warning_count are "diagnostics variables"
and will appear in non-diagnostics statements like SELECT.
For backward compatibility, they will contain the correct
values describing the previous statement when queried
immediately after execution of the previous statement:
DROP TABLE does_not_exist;
SELECT @@error_count;      # renders 1 (result of DROP)
SELECT @@error_count;      # renders 0 (result of SELECT)
This is discouraged; use GET DIAGNOSTICS instead.

Likewise, SHOW WARNINGS could be used as the first
statement of a HANDLER (or preceeded only by other
diagnostics statements), but this is discouraged --
use GET [STACKED] DIAGNOSTICS instead.

Errors during parsing correctly set the DA; any
errors thrown there replace the previous command's
diagnostics, even if it was a diagnostics statement
the user failed at issuing.

The SQL standard requires the diagnostics statement
(GET DIAGNOSTICS) not to be preparable; likewise,
SHOW WARNINGS, SHOW ERRORS, and statements containing
@@error_count or @@warning_count must not be used in
prepared statements.

Code:
DA resetting was sprinkled all over the code, sometimes
in the form of a "maybe" (opt_reset_condition_info()).
All occurences of the latter were removed.
Care was taken to reduce the number of occurences of the
former, usually to one central point for each subsystem
(parsing, SP, PS, QC, signaling, logging).
Self-printing of SP instructions was slightly extended
and refactored.

Tests:
wl5928.test tests and documents the new expected behaviour.
Various other tests were adapted to provided similarly
expressive results as they used to under the previous
circumstances.

Author: Tatjana Azundris Nuernberg

mysql-test/include/sp-vars.inc

@@ -34,6 +34,8 @@ BEGIN
   DECLARE v19 DECIMAL(64, 2) DEFAULT 11 + 1;
   DECLARE v20 DECIMAL(64, 2) DEFAULT 12 + 0.123;
 
+  SHOW WARNINGS;
+
   SELECT v1, v1u, v2, v2u, v3, v3u, v4, v4u;
   SELECT v5, v5u, v6, v6u;
   SELECT v7, v8, v9, v10, v11, v12, v13, v14, v15, v16;
@@ -80,12 +82,16 @@ BEGIN
   SET d2 = 1234.12;
   SET d3 = 1234.1234;
 
+  SHOW WARNINGS;
+
   SELECT d1, d2, d3;
 
   SET d1 = 12 * 100 + 34;
   SET d2 = 12 * 100 + 34 + 0.12;
   SET d3 = 12 * 100 + 34 + 0.1234;
 
+  SHOW WARNINGS;
+
   SELECT d1, d2, d3;
 END|
 

mysql-test/r/get_diagnostics.result

@@ -251,7 +251,6 @@ SET @cond = "invalid";
 GET DIAGNOSTICS CONDITION @cond @var1 = CLASS_ORIGIN;
 Warnings:
 Error	1758	Invalid condition number
-Error	1758	Invalid condition number
 SELECT COUNT(max_questions) INTO @var FROM mysql.user;
 CREATE PROCEDURE p1()
 BEGIN
@@ -267,6 +266,8 @@ DECLARE var INT;
 GET DIAGNOSTICS CONDITION cond var = CLASS_ORIGIN;
 END|
 CALL p1();
+Warnings:
+Error	1758	Invalid condition number
 DROP PROCEDURE p1;
 #
 # Test GET DIAGNOSTICS runtime
@@ -467,10 +468,6 @@ cursor_name
 message_text	Truncated incorrect DECIMAL value: ''
 mysql_errno	1292
 returned_sqlstate	22007
-Warnings:
-Level	Warning
-Code	1292
-Message	Truncated incorrect DECIMAL value: ''
 DROP PROCEDURE p1;
 CREATE PROCEDURE p1()
 BEGIN
@@ -490,13 +487,6 @@ errno1	1292
 msg1	Truncated incorrect DECIMAL value: ''
 errno2	1758
 msg2	Invalid condition number
-Warnings:
-Level	Warning
-Code	1292
-Message	Truncated incorrect DECIMAL value: ''
-Level	Error
-Code	1758
-Message	Invalid condition number
 DROP PROCEDURE p1;
 
 # Interaction with SIGNAL
@@ -607,7 +597,7 @@ SELECT var, @var;
 END|
 CALL p1();
 var	@var
-1	1
+0	0
 DROP PROCEDURE p1;
 
 # Setting TABLE_NAME is currently not implemented.
@@ -638,8 +628,6 @@ CREATE TABLE t1 (a INT);
 CALL p1();
 v
 T
-Warnings:
-Note	1050	Table 't1' already exists
 DROP TABLE t1;
 DROP PROCEDURE p1;
 
@@ -678,13 +666,13 @@ SIGNAL SQLSTATE '01002';
 GET CURRENT DIAGNOSTICS CONDITION 1 @y = RETURNED_SQLSTATE;
 END;
 SIGNAL SQLSTATE '01001';
-SELECT @x, @y;
 END|
 CALL p1();
-@x	@y
-01001	01002
 Warnings:
 Warning	1642	Unhandled user-defined warning condition
+SELECT @x, @y;
+@x	@y
+01001	01002
 DROP PROCEDURE p1;
 
 # Using OUT and INOUT parameters as the target variables.
@@ -854,35 +842,29 @@ 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;
+GET CURRENT DIAGNOSTICS CONDITION 1 @msg1 = MESSAGE_TEXT, @errno1 = MYSQL_ERRNO;
+GET STACKED DIAGNOSTICS CONDITION 1 @msg2 = MESSAGE_TEXT, @errno2 = MYSQL_ERRNO;
+SELECT @msg1, @errno1;
+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;
+GET STACKED DIAGNOSTICS CONDITION 1 @msg4 = MESSAGE_TEXT, @errno4 = MYSQL_ERRNO;
+SELECT @msg4, @errno4;
 END;
 DROP TABLE non_existent;
 END|
 CALL p1();
-msg1	errno1
+@msg1	@errno1
 Unknown table 'test.non_existent'	1051
-msg2	errno2
+@msg2	@errno2
 Unknown table 'test.non_existent'	1051
 a
 @cno
 0
-msg4	errno4
+@msg4	@errno4
 Unknown table 'test.non_existent'	1051
 DROP PROCEDURE p1;
 DROP TABLE t1;
@@ -893,39 +875,32 @@ 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;
+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;
+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;
+RESIGNAL SET MYSQL_ERRNO= 9999, MESSAGE_TEXT= 'Changed by resignal, for caller';
 END;
 SELECT 10 + 'a';
 END|
 CALL p1();
 10 + 'a'
 10
-msg1	errno1
+@msg1	@errno1
 Truncated incorrect DOUBLE value: 'a'	1292
-msg2	errno2
+@msg2	@errno2
 Truncated incorrect DOUBLE value: 'a'	1292
-msg3	errno3
+@msg3	@errno3
 Changed by resignal	9999
-msg4	errno4
+@msg4	@errno4
 Changed by resignal	9999
 Warnings:
-Warning	9999	Changed by resignal
+Warning	9999	Changed by resignal, for caller
 DROP PROCEDURE p1;

mysql-test/r/partition.result

@@ -1543,11 +1543,7 @@ ROLLBACK to savepoint t1_save;
 COMMIT;
 END|
 CALL test.p1(12);
-Warnings:
-Warning	1196	Some non-transactional changed tables couldn't be rolled back
 CALL test.p1(13);
-Warnings:
-Warning	1196	Some non-transactional changed tables couldn't be rolled back
 drop table t1;
 drop procedure test.p1;
 CREATE TABLE t1 (a int not null)

mysql-test/r/ps.result

@@ -2761,7 +2761,7 @@ drop procedure proc_1;
 create function func_1() returns int begin show errors; return 1; end|
 ERROR 0A000: Not allowed to return a result set from a function
 prepare abc from "show errors";
-deallocate prepare abc;
+ERROR HY000: This command is not supported in the prepared statement protocol yet
 drop table if exists t1;
 drop table if exists t2;
 create procedure proc_1() show warnings;
@@ -2770,46 +2770,22 @@ Warnings:
 Note	1051	Unknown table 'test.t1'
 call proc_1();
 Level	Code	Message
-Note	1051	Unknown table 'test.t1'
 drop table if exists t2;
 Warnings:
 Note	1051	Unknown table 'test.t2'
 call proc_1();
 Level	Code	Message
-Note	1051	Unknown table 'test.t2'
 drop table if exists t1, t2;
 Warnings:
 Note	1051	Unknown table 'test.t1'
 Note	1051	Unknown table 'test.t2'
 call proc_1();
 Level	Code	Message
-Note	1051	Unknown table 'test.t1'
-Note	1051	Unknown table 'test.t2'
 drop procedure proc_1;
 create function func_1() returns int begin show warnings; return 1; end|
 ERROR 0A000: Not allowed to return a result set from a function
 prepare abc from "show warnings";
-drop table if exists t1;
-Warnings:
-Note	1051	Unknown table 'test.t1'
-execute abc;
-Level	Code	Message
-Note	1051	Unknown table 'test.t1'
-drop table if exists t2;
-Warnings:
-Note	1051	Unknown table 'test.t2'
-execute abc;
-Level	Code	Message
-Note	1051	Unknown table 'test.t2'
-drop table if exists t1, t2;
-Warnings:
-Note	1051	Unknown table 'test.t1'
-Note	1051	Unknown table 'test.t2'
-execute abc;
-Level	Code	Message
-Note	1051	Unknown table 'test.t1'
-Note	1051	Unknown table 'test.t2'
-deallocate prepare abc;
+ERROR HY000: This command is not supported in the prepared statement protocol yet
 set @my_password="password";
 set @my_data="clear text to encode";
 prepare stmt1 from 'select decode(encode(?, ?), ?)';

mysql-test/r/ps_1general.result

@@ -319,7 +319,9 @@ prepare stmt4 from ' show master status ';
 prepare stmt4 from ' show master logs ';
 prepare stmt4 from ' show slave status ';
 prepare stmt4 from ' show warnings limit 20 ';
+ERROR HY000: This command is not supported in the prepared statement protocol yet
 prepare stmt4 from ' show errors limit 20 ';
+ERROR HY000: This command is not supported in the prepared statement protocol yet
 prepare stmt4 from ' show storage engines ';
 execute stmt4;
 drop table if exists t5;

mysql-test/r/query_cache.result

@@ -1777,3 +1777,36 @@ COUNT(*)
 DROP TABLE t1;
 SET GLOBAL query_cache_size= @qc;
 #
+
+# WL5928: Most statements should clear the diagnostic area
+#         Show this also works when we serve from query-cache!
+#
+SELECT @@session.query_cache_type INTO @qc_type;
+SET SESSION query_cache_type=2;
+CREATE TABLE t1 (f1 VARCHAR(16));
+INSERT INTO t1 VALUES ("cat"),("dog"),("wombat"),("elephant");
+
+DROP TABLE no_such_table;
+ERROR 42S02: Unknown table 'test.no_such_table'
+SELECT SQL_CACHE * FROM t1;
+f1
+cat
+dog
+wombat
+elephant
+SHOW WARNINGS;
+Level	Code	Message
+
+DROP TABLE no_such_table;
+ERROR 42S02: Unknown table 'test.no_such_table'
+SELECT SQL_CACHE * FROM t1;
+f1
+cat
+dog
+wombat
+elephant
+SHOW WARNINGS;
+Level	Code	Message
+
+DROP TABLE t1;
+SET SESSION query_cache_type=@qc_type;

mysql-test/r/rollback.result

@@ -6,24 +6,21 @@ insert into t1 values (5);
 rollback;
 Warnings:
 Warning	1196	Some non-transactional changed tables couldn't be rolled back
-select @@warning_count;
-@@warning_count
-1
-select @@error_count;
-@@error_count
-0
 show warnings;
 Level	Code	Message
 Warning	1196	Some non-transactional changed tables couldn't be rolled back
 show errors;
 Level	Code	Message
+select @@warning_count,@@error_count;
+@@warning_count	@@error_count
+1	0
 select * from t1;
 n
 4
 5
+show warnings;
+Level	Code	Message
 select @@warning_count;
 @@warning_count
 0
-show warnings;
-Level	Code	Message
 drop table t1;