MDEV-16757 Memory leak after adding manually min/max statistical data

           for blob column

ANALYZE TABLE <table> does not collect statistical data on min/max values
for BLOB columns of <table>. However these values can be added into
mysql.column_stats manually by executing proper statements.
Unfortunately this led to a memory leak because the memory allocated
for these values was never freed.
This patch provides the server with a function to free memory allocated
for min/max statistical values of BLOB types.

1 files changed, 33 insertions, 0 deletions

diff --git a/sql/sql_statistics.cc b/sql/sql_statistics.cc
index be4547a69df..537ede91710 100644
--- a/sql/sql_statistics.cc
+++ b/sql/sql_statistics.cc
@@ -2917,6 +2917,39 @@ int read_statistics_for_table(THD *thd, TABLE *table, TABLE_LIST *stat_tables)
 
 
 /**
+  @breif
+  Cleanup of min/max statistical values for table share
+*/
+
+void delete_stat_values_for_table_share(TABLE_SHARE *table_share)
+{
+  TABLE_STATISTICS_CB *stats_cb= &table_share->stats_cb;
+  Table_statistics *table_stats= stats_cb->table_stats;
+  if (!table_stats)
+    return;
+  Column_statistics *column_stats= table_stats->column_stats;
+  if (!column_stats)
+    return;
+
+  for (Field **field_ptr= table_share->field;
+       *field_ptr;
+       field_ptr++, column_stats++)
+  {
+    if (column_stats->min_value)
+    {
+      delete column_stats->min_value;
+      column_stats->min_value= NULL;
+    }
+    if (column_stats->max_value)
+    {
+      delete column_stats->max_value;
+      column_stats->max_value= NULL;
+    }
+  }
+}
+
+
+/**
   @brief
   Check whether any statistics is to be read for tables from a table list