MDEV-17124: mariadb 10.1.34, views and prepared statements: ERROR 1615 (HY000): Prepared statement needs to be re-prepared

The problem is that if table definition cache (TDC) is full of real tables
which are in tables cache, view definition can not stay there so will be
removed by its own underlying tables.
In situation above old mechanism of detection matching definition in PS
and current version always require reprepare and so prevent executing
the PS.

One work around is to increase TDC, other - improve version check for
views/triggers (which is done here). Now in suspicious cases we check:
 - timestamp (microseconds) of the view to be sure that version really
   have changed;
 - time (microseconds) of creation of a trigger related to time
   (microseconds) of statement preparation.

1 files changed, 48 insertions, 18 deletions

diff --git a/sql/table.h b/sql/table.h
index 6036afd3750..1eb09f119ed 100644
--- a/sql/table.h
+++ b/sql/table.h
@@ -32,8 +32,18 @@
 #include "filesort_utils.h"
 #include "parse_file.h"
 
-/* buffer for timestamp (19+1) */
-#define VIEW_TIME_STAMP_BUFFER_SIZE (PARSE_FILE_TIMESTAMPLENGTH + 1)
+/*
+  Buffer for unix timestamp in microseconds:
+  9,223,372,036,854,775,807 (signed int64 maximal value)
+  1 234 567 890 123 456 789
+
+  Note: we can use unsigned for calculation, but practically they
+  are the same by probability to overflow them (signed int64 in
+  microseconds is enough for almost 3e5 years) and signed allow to
+  avoid increasing the buffer (the old buffer for human readable
+  date was 19+1).
+*/
+#define MICROSECOND_TIMESTAMP_BUFFER_SIZE (19 + 1)
 
 /* Structs that defines the TABLE */
 
@@ -1028,7 +1038,7 @@ struct TABLE_SHARE
    with a base table, a base table is replaced with a temporary
    table and so on.
 
-   @sa TABLE_LIST::is_table_ref_id_equal()
+   @sa TABLE_LIST::is_the_same_definition()
   */
   ulong get_table_ref_version() const
   {
@@ -2369,6 +2379,12 @@ struct TABLE_LIST
     to view with SQL SECURITY DEFINER)
   */
   Security_context *security_ctx;
+  uchar tabledef_version_buf[MY_UUID_SIZE >
+                               MICROSECOND_TIMESTAMP_BUFFER_SIZE-1 ?
+                             MY_UUID_SIZE + 1 :
+                             MICROSECOND_TIMESTAMP_BUFFER_SIZE];
+  LEX_CUSTRING tabledef_version;
+
   /*
     This view security context (non-zero only for views with
     SQL SECURITY DEFINER)
@@ -2382,7 +2398,7 @@ struct TABLE_LIST
   LEX_CSTRING	source;			/* source of CREATE VIEW */
   LEX_CSTRING	view_db;		/* saved view database */
   LEX_CSTRING	view_name;		/* saved view name */
-  LEX_STRING	timestamp;		/* GMT time stamp of last operation */
+  LEX_STRING	hr_timestamp;           /* time stamp of last operation */
   LEX_USER      definer;                /* definer of view */
   ulonglong	file_version;		/* version of file's field set */
   ulonglong	mariadb_version;	/* version of server on creation */
@@ -2465,7 +2481,7 @@ struct TABLE_LIST
   /* TABLE_TYPE_UNKNOWN if any type is acceptable */
   Table_type    required_type;
   handlerton	*db_type;		/* table_type for handler */
-  char		timestamp_buffer[VIEW_TIME_STAMP_BUFFER_SIZE];
+  char		timestamp_buffer[MICROSECOND_TIMESTAMP_BUFFER_SIZE];
   /*
     This TABLE_LIST object is just placeholder for prelocking, it will be
     used for implicit LOCK TABLES only and won't be used in real statement.
@@ -2657,19 +2673,7 @@ struct TABLE_LIST
   */
   bool process_index_hints(TABLE *table);
 
-  /**
-    Compare the version of metadata from the previous execution
-    (if any) with values obtained from the current table
-    definition cache element.
-
-    @sa check_and_update_table_version()
-  */
-  inline bool is_table_ref_id_equal(TABLE_SHARE *s) const
-  {
-    return (m_table_ref_type == s->get_table_ref_type() &&
-            m_table_ref_version == s->get_table_ref_version());
-  }
-
+  bool is_the_same_definition(THD *thd, TABLE_SHARE *s);
   /**
     Record the value of metadata version of the corresponding
     table definition cache element in this parse tree node.
@@ -2686,6 +2690,26 @@ struct TABLE_LIST
     m_table_ref_version= table_ref_version_arg;
   }
 
+  void set_table_id(TABLE_SHARE *s)
+  {
+    set_table_ref_id(s);
+    set_tabledef_version(s);
+  }
+
+  void set_tabledef_version(TABLE_SHARE *s)
+  {
+    if (!tabledef_version.length && s->tabledef_version.length)
+    {
+      DBUG_ASSERT(s->tabledef_version.length <
+                  sizeof(tabledef_version_buf));
+      tabledef_version.str= tabledef_version_buf;
+      memcpy(tabledef_version_buf, s->tabledef_version.str,
+             (tabledef_version.length= s->tabledef_version.length));
+      // safety
+      tabledef_version_buf[tabledef_version.length]= 0;
+    }
+  }
+
   /* Set of functions returning/setting state of a derived table/view. */
   inline bool is_non_derived()
   {
@@ -2814,6 +2838,12 @@ struct TABLE_LIST
     }
   }
 
+  inline void set_view_def_version(LEX_STRING *version)
+  {
+    m_table_ref_type= TABLE_REF_VIEW;
+    tabledef_version.str= (const uchar *) version->str;
+    tabledef_version.length= version->length;
+  }
 private:
   bool prep_check_option(THD *thd, uint8 check_opt_type);
   bool prep_where(THD *thd, Item **conds, bool no_where_clause);