MDEV-26519: Improved histograms: Better error reporting, test coverage

Also report JSON histogram load errors into error log, like it is already
done with other histogram/statistics load errors.

Add test coverage to see what happens if one upgrades but does NOT run
mysql_upgrade.

5 files changed, 107 insertions, 0 deletions

diff --git a/mysql-test/main/statistics_json.result b/mysql-test/main/statistics_json.result
index 43fd61b4203..7ad6827711b 100644
--- a/mysql-test/main/statistics_json.result
+++ b/mysql-test/main/statistics_json.result
@@ -4157,6 +4157,7 @@ set @@global.histogram_size=@save_histogram_size;
 drop table if exists t1;
 set @save_histogram_type=@@histogram_type;
 set @save_histogram_size=@@histogram_size;
+call mtr.add_suppression("Failed to parse histogram for table .*");
 create table ten(a int primary key);
 insert into ten values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
 set histogram_size=100;
diff --git a/mysql-test/main/statistics_json.test b/mysql-test/main/statistics_json.test
index e90df83f9c9..21d8ebc3829 100644
--- a/mysql-test/main/statistics_json.test
+++ b/mysql-test/main/statistics_json.test
@@ -16,6 +16,7 @@ drop table if exists t1;
 set @save_histogram_type=@@histogram_type;
 set @save_histogram_size=@@histogram_size;
 
+call mtr.add_suppression("Failed to parse histogram for table .*");
 create table ten(a int primary key);
 insert into ten values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
 
diff --git a/mysql-test/main/statistics_upgrade_not_done.result b/mysql-test/main/statistics_upgrade_not_done.result
new file mode 100644
index 00000000000..902bf25c242
--- /dev/null
+++ b/mysql-test/main/statistics_upgrade_not_done.result
@@ -0,0 +1,44 @@
+# Create the old-version of the table
+call mtr.add_suppression(".*Incorrect definition of table mysql.column_stats:.*");
+alter table mysql.column_stats rename test.t1;
+CREATE TABLE mysql.column_stats (
+`db_name` varchar(64) COLLATE utf8mb3_bin NOT NULL,
+`table_name` varchar(64) COLLATE utf8mb3_bin NOT NULL,
+`column_name` varchar(64) COLLATE utf8mb3_bin NOT NULL,
+`min_value` varbinary(255) DEFAULT NULL,
+`max_value` varbinary(255) DEFAULT NULL,
+`nulls_ratio` decimal(12,4) DEFAULT NULL,
+`avg_length` decimal(12,4) DEFAULT NULL,
+`avg_frequency` decimal(12,4) DEFAULT NULL,
+`hist_size` tinyint(3) unsigned DEFAULT NULL,
+`hist_type` enum('SINGLE_PREC_HB','DOUBLE_PREC_HB') COLLATE utf8mb3_bin DEFAULT NULL,
+`histogram` varbinary(255) DEFAULT NULL,
+PRIMARY KEY (`db_name`,`table_name`,`column_name`)
+) ENGINE=Aria DEFAULT CHARSET=utf8mb3 COLLATE=utf8mb3_bin PAGE_CHECKSUM=1 TRANSACTIONAL=0 COMMENT='Statistics on Columns';
+create table t0(a int);
+insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
+INSERT INTO mysql.column_stats VALUES
+('test','t0','a','0','9',0.0000,4.0000,1.0000,5,'DOUBLE_PREC_HB', x'5555AAAA00');
+flush tables;
+analyze select * from t0 where a<3;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	r_rows	filtered	r_filtered	Extra
+1	SIMPLE	t0	ALL	NULL	NULL	NULL	NULL	10	10.00	100.00	30.00	Using where
+# restart
+select hex(histogram) from mysql.column_stats where table_name='t0' and db_name='test';
+hex(histogram)
+5555AAAA00
+analyze select * from t0 where a<3;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	r_rows	filtered	r_filtered	Extra
+1	SIMPLE	t0	ALL	NULL	NULL	NULL	NULL	10	10.00	100.00	30.00	Using where
+create table t2 (a int);
+# This currently just pretends that the histogram was collected. 
+analyze table t2 persistent for all;
+Table	Op	Msg_type	Msg_text
+test.t2	analyze	status	Engine-independent statistics collected
+test.t2	analyze	status	Table is already up to date
+select * from mysql.column_stats where table_name='t2' and db_name='test';
+db_name	table_name	column_name	min_value	max_value	nulls_ratio	avg_length	avg_frequency	hist_size	hist_type	histogram
+analyze select * from t0 where a<3;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	r_rows	filtered	r_filtered	Extra
+1	SIMPLE	t0	ALL	NULL	NULL	NULL	NULL	10	10.00	33.33	30.00	Using where
+drop table t0, t1, t2;
diff --git a/mysql-test/main/statistics_upgrade_not_done.test b/mysql-test/main/statistics_upgrade_not_done.test
new file mode 100644
index 00000000000..a74a5f35d83
--- /dev/null
+++ b/mysql-test/main/statistics_upgrade_not_done.test
@@ -0,0 +1,57 @@
+--source include/not_embedded.inc
+--source include/mysql_upgrade_preparation.inc
+--source include/have_innodb.inc
+
+# 
+# This is like the upgrade test in statistics_upgrade.test, except that we also
+# check what happens if one doesn't do the upgrade and attempts to use the new
+# server with the old mysql.column_stats table
+#
+--echo # Create the old-version of the table
+
+call mtr.add_suppression(".*Incorrect definition of table mysql.column_stats:.*");
+
+alter table mysql.column_stats rename test.t1;
+
+CREATE TABLE mysql.column_stats (
+  `db_name` varchar(64) COLLATE utf8mb3_bin NOT NULL,
+  `table_name` varchar(64) COLLATE utf8mb3_bin NOT NULL,
+  `column_name` varchar(64) COLLATE utf8mb3_bin NOT NULL,
+  `min_value` varbinary(255) DEFAULT NULL,
+  `max_value` varbinary(255) DEFAULT NULL,
+  `nulls_ratio` decimal(12,4) DEFAULT NULL,
+  `avg_length` decimal(12,4) DEFAULT NULL,
+  `avg_frequency` decimal(12,4) DEFAULT NULL,
+  `hist_size` tinyint(3) unsigned DEFAULT NULL,
+  `hist_type` enum('SINGLE_PREC_HB','DOUBLE_PREC_HB') COLLATE utf8mb3_bin DEFAULT NULL,
+  `histogram` varbinary(255) DEFAULT NULL,
+  PRIMARY KEY (`db_name`,`table_name`,`column_name`)
+) ENGINE=Aria DEFAULT CHARSET=utf8mb3 COLLATE=utf8mb3_bin PAGE_CHECKSUM=1 TRANSACTIONAL=0 COMMENT='Statistics on Columns';
+
+create table t0(a int);
+insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
+INSERT INTO mysql.column_stats VALUES
+('test','t0','a','0','9',0.0000,4.0000,1.0000,5,'DOUBLE_PREC_HB', x'5555AAAA00');
+
+flush tables;
+analyze select * from t0 where a<3;
+
+# Restart the server
+
+--source include/restart_mysqld.inc
+
+select hex(histogram) from mysql.column_stats where table_name='t0' and db_name='test';
+analyze select * from t0 where a<3;
+
+create table t2 (a int);
+-- echo # This currently just pretends that the histogram was collected. 
+analyze table t2 persistent for all;
+select * from mysql.column_stats where table_name='t2' and db_name='test';
+
+--exec $MYSQL_UPGRADE --upgrade-system-tables  --force --silent 2>&1 
+let $MYSQLD_DATADIR= `select @@datadir`;
+--file_exists $MYSQLD_DATADIR/mysql_upgrade_info
+--remove_file $MYSQLD_DATADIR/mysql_upgrade_info
+
+analyze select * from t0 where a<3;
+drop table t0, t1, t2;
diff --git a/sql/opt_histogram_json.cc b/sql/opt_histogram_json.cc
index 8e04931b71c..faf5ec314ab 100644
--- a/sql/opt_histogram_json.cc
+++ b/sql/opt_histogram_json.cc
@@ -696,6 +696,10 @@ err:
                       ER_THD(thd, ER_JSON_HISTOGRAM_PARSE_FAILED),
                       db_name, table_name,
                       err, (je.s.c_str - (const uchar*)hist_data));
+  sql_print_error(ER_THD(thd, ER_JSON_HISTOGRAM_PARSE_FAILED),
+                  db_name, table_name, err,
+                  (je.s.c_str - (const uchar*)hist_data));
+
   DBUG_RETURN(true);
 }