Improve how truncation is controlled within the ps_thread_trx_info function, by making the group_concat_max_len variable configurable via the sys_config table and a new ps_thread_trx_info.max_length variable. When truncation does happen, instead of returning NULL and ignoring the warnings, return an error JSON object instead.

Author: MarkLeith

README.md

@@ -79,9 +79,15 @@ Note, when functions check for configuration options, they first check whether a
 
 ##### Options included
 
-| Variable               | Default Value | Description                                                                    |
-| ---------------------- | ------------- | ------------------------------------------------------------------------------ |
-| statement_truncate_len | 64            | Sets the size to truncate statements to, for the `format_statement()` function |
+| Variable                             | Default Value | Description                                                                    |
+| ------------------------------------ | ------------- | ------------------------------------------------------------------------------ |
+| statement_truncate_len               | 64            | Sets the size to truncate statements to, for the `format_statement()` function. |
+| statement_performance_analyzer.limit | 100           | The maximum number of rows to include for the views that does not have a built-in limit (e.g. the 95th percentile view). If not set the limit is 100. |
+| statement_performance_analyzer.view  | NULL          | Used together with the 'custom' view. If the value contains a space, it is considered a query, otherwise it must be
+     an existing view querying the performance_schema.events_statements_summary_by_digest table. |
+| diagnostics.allow_i_s_tables         | OFF           | Specifies whether it is allowed to do table scan queries on information_schema.TABLES for the `diagnostics` procedure. |
+| diagnostics.include_raw              | OFF           | Set to 'ON' to include the raw data (e.g. the original output of "SELECT * FROM sys.metrics") for the `diagnostics` procedure.|
+| ps_thread_trx_info.max_length        | 65535         | Sets the maximum output length for JSON object output by the `ps_thread_trx_info()` function. |
 
 ### Views
 
@@ -3948,6 +3954,14 @@ thread_stack: {"rankdir": "LR","nodesep": "0.10","stack_created": "2014-02-19 13
 
 Returns a JSON object with info on the given thread's current transaction, and the statements it has already executed, derived from the `performance_schema.events_transactions_current` and `performance_schema.events_statements_history` tables (so the consumers for these also have to be enabled within Performance Schema to get full data in the object).
 
+When the output exceeds the default truncation length (65535), a JSON error object is returned, such as:
+
+`{ "error": "Trx info truncated: Row 6 was cut by GROUP_CONCAT()" }`
+
+Similar error objects are returned for other warnings/and exceptions raised when calling the function.
+
+The max length of the output of this function can be controlled with the `ps_thread_trx_info.max_length` variable set via `sys_config`, or the `@sys.ps_thread_trx_info.max_length` user variable, as appropriate.
+
 ##### Parameters
 
 * in_thread_id (BIGINT UNSIGNED): The id of the thread to return the transaction info for.

functions/ps_thread_trx_info.sql

@@ -31,6 +31,18 @@ CREATE DEFINER='root'@'localhost' FUNCTION ps_thread_trx_info (
              for these also have to be enabled within Performance Schema to get full
              data in the object).
 
+             When the output exceeds the default truncation length (65535), a JSON error
+             object is returned, such as:
+
+             { "error": "Trx info truncated: Row 6 was cut by GROUP_CONCAT()" }
+
+             Similar error objects are returned for other warnings/and exceptions raised
+             when calling the function.
+
+             The max length of the output of this function can be controlled with the
+             ps_thread_trx_info.max_length variable set via sys_config, or the
+             @sys.ps_thread_trx_info.max_length user variable, as appropriate.
+
              Parameters
              -----------
 
@@ -119,10 +131,39 @@ CREATE DEFINER='root'@'localhost' FUNCTION ps_thread_trx_info (
     NOT DETERMINISTIC
     READS SQL DATA
 BEGIN
-    DECLARE v_output TEXT;
+    DECLARE v_output LONGTEXT DEFAULT '{}';
+    DECLARE v_msg_text TEXT DEFAULT '';
+    DECLARE v_signal_msg TEXT DEFAULT '';
+    DECLARE v_mysql_errno INT;
+    DECLARE v_max_output_len BIGINT;
+    -- Capture warnings/errors such as group_concat truncation
+    -- and report as JSON error objects
+    DECLARE EXIT HANDLER FOR SQLWARNING, SQLEXCEPTION
+    BEGIN
+        GET DIAGNOSTICS CONDITION 1
+            v_msg_text = MESSAGE_TEXT,
+            v_mysql_errno = MYSQL_ERRNO;
+
+        IF v_mysql_errno = 1260 THEN
+            SET v_signal_msg = CONCAT('{ "error": "Trx info truncated: ', v_msg_text, '" }');
+        ELSE
+            SET v_signal_msg = CONCAT('{ "error": "', v_msg_text, '" }');
+        END IF;
+
+        RETURN v_signal_msg;
+    END;
+
+    -- Set configuration options
+    IF (@sys.ps_thread_trx_info.max_length IS NULL) THEN
+        SET @sys.ps_thread_trx_info.max_length = sys.sys_get_config('ps_thread_trx_info.max_length', 65535);
+    END IF;
 
-    SET @old_ground_concat_max_len = @@session.group_concat_max_len;
-    SET SESSION group_concat_max_len = 1000000000;
+    IF (@sys.ps_thread_trx_info.max_length != @@session.group_concat_max_len) THEN
+        SET @old_group_concat_max_len = @@session.group_concat_max_len;
+        -- Convert to int value for the SET, and give some surrounding space
+        SET v_max_output_len = (@sys.ps_thread_trx_info.max_length - 5);
+        SET SESSION group_concat_max_len = v_max_output_len;
+    END IF;
 
     SET v_output = (
         SELECT CONCAT('[', IFNULL(GROUP_CONCAT(trx_info ORDER BY event_id), ''), '\n]') AS trx_info
@@ -158,7 +199,7 @@ BEGIN
                                     GROUP_CONCAT(
                                       IFNULL(
                                         CONCAT('\n      {\n',
-                                               '        "sql_text": "', IFNULL(REPLACE(sql_text, '\\', '\\\\'), ''), '",\n',
+                                               '        "sql_text": "', IFNULL(sys.format_statement(REPLACE(sql_text, '\\', '\\\\')), ''), '",\n',
                                                '        "time": "', IFNULL(sys.format_time(timer_wait), ''), '",\n',
                                                '        "schema": "', IFNULL(current_schema, ''), '",\n',
                                                '        "rows_examined": ', IFNULL(rows_examined, ''), ',\n',
@@ -182,8 +223,9 @@ BEGIN
           GROUP BY thread_id
     );
 
-    SET @old_ground_concat_max_len = @@session.group_concat_max_len;
-    SET SESSION group_concat_max_len = 1000000000;
+    IF (@old_group_concat_max_len IS NOT NULL) THEN
+        SET SESSION group_concat_max_len = @old_group_concat_max_len;
+    END IF;
 
     RETURN v_output;
 END$$

mysql-test/suite/sysschema/include/sys_config_cleanup.inc

@@ -11,6 +11,7 @@ INSERT IGNORE INTO sys.sys_config (variable, value) VALUES
     ('statement_performance_analyzer.limit', 100),
     ('statement_performance_analyzer.view', NULL),
     ('diagnostics.allow_i_s_tables', 'OFF'),
-    ('diagnostics.include_raw', 'OFF');
+    ('diagnostics.include_raw', 'OFF'),
+    ('ps_thread_trx_info.max_length', 65535);
 
 SET @sys.ignore_sys_config_triggers := NULL;

mysql-test/suite/sysschema/r/fn_ps_thread_trx_info.result

@@ -3,7 +3,7 @@ sys.ps_thread_trx_info(234623462376)
 NULL
 SELECT JSON_VALID(sys.ps_thread_trx_info(sys.ps_thread_id(NULL)));
 JSON_VALID(sys.ps_thread_trx_info(sys.ps_thread_id(NULL)))
-NULL
+1
 CREATE DATABASE trx;
 CREATE TABLE trx.info (id INT PRIMARY KEY, info VARCHAR(20));
 USE trx;
@@ -77,4 +77,12 @@ JSON_CONTAINS(@json_doc, '0',                                      '$[0].stateme
 SELECT JSON_CONTAINS(@json_doc, '"COMMIT"', '$[0].statements_executed[1].sql_text');
 JSON_CONTAINS(@json_doc, '"COMMIT"', '$[0].statements_executed[1].sql_text')
 1
+SET @sys.ps_thread_trx_info.max_length = 100;
+SELECT sys.ps_thread_trx_info(@ps_thread_id);
+sys.ps_thread_trx_info(@ps_thread_id)
+{ "error": "Trx info truncated: Row 12 was cut by GROUP_CONCAT()" }
+SET @sys.ps_thread_trx_info.max_length = NULL;
+SELECT JSON_VALID(sys.ps_thread_trx_info(@ps_thread_id));
+JSON_VALID(sys.ps_thread_trx_info(@ps_thread_id))
+1
 DROP DATABASE trx;

mysql-test/suite/sysschema/t/fn_ps_thread_trx_info.test

@@ -67,6 +67,19 @@ SELECT JSON_CONTAINS(@json_doc, '0',                                      '$[0].
 # Second statement in transaction should be a COMMIT
 SELECT JSON_CONTAINS(@json_doc, '"COMMIT"', '$[0].statements_executed[1].sql_text');
 
-disconnect con1;
+# Simulate a truncated set of output by lowering the @sys.ps_thread_trx_info.max_length user variable
+# This also tests the user variable works appropriately, incidentally
+
+SET @sys.ps_thread_trx_info.max_length = 100;
+
+# Should return an error JSON object
+SELECT sys.ps_thread_trx_info(@ps_thread_id);
 
+# Setting the user variable back to NULL should reset to 65535 from sys_config, and no truncation
+SET @sys.ps_thread_trx_info.max_length = NULL;
+SELECT JSON_VALID(sys.ps_thread_trx_info(@ps_thread_id));
+
+# Clean up
+
+disconnect con1;
 DROP DATABASE trx;

sys_57.sql

@@ -16,7 +16,7 @@
 SOURCE ./before_setup.sql
 
 SOURCE ./tables/sys_config.sql
-SOURCE ./tables/sys_config_data.sql
+SOURCE ./tables/sys_config_data_57.sql
 
 SOURCE ./triggers/sys_config_insert_set_user.sql
 SOURCE ./triggers/sys_config_update_set_user.sql

tables/sys_config_data_57.sql

@@ -0,0 +1,24 @@
+-- Copyright (c) 2015 Oracle and/or its affiliates. All rights reserved.
+--
+-- This program is free software; you can redistribute it and/or modify
+-- it under the terms of the GNU General Public License as published by
+-- the Free Software Foundation; version 2 of the License.
+--
+-- This program is distributed in the hope that it will be useful,
+-- but WITHOUT ANY WARRANTY; without even the implied warranty of
+-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+-- GNU General Public License for more details.
+--
+-- You should have received a copy of the GNU General Public License
+-- along with this program; if not, write to the Free Software
+-- Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+
+-- NOTE: This needs to be replicated within the sys_config_clean.inc file
+
+INSERT IGNORE INTO sys.sys_config (variable, value) VALUES
+    ('statement_truncate_len', 64),
+    ('statement_performance_analyzer.limit', 100),
+    ('statement_performance_analyzer.view', NULL),
+    ('diagnostics.allow_i_s_tables', 'OFF'),
+    ('diagnostics.include_raw', 'OFF'),
+    ('ps_thread_trx_info.max_length', 65535);