Improve update handler (long unique keys on blobs)

MDEV-21606 Improve update handler (long unique keys on blobs)
MDEV-21470 MyISAM and Aria start_bulk_insert doesn't work with long unique
MDEV-21606 Bug fix for previous version of this code
MDEV-21819 2 Assertion `inited == NONE || update_handler != this'

- Move update_handler from TABLE to handler
- Move out initialization of update handler from ha_write_row() to
  prepare_for_insert()
- Fixed that INSERT DELAYED works with update handler
- Give an error if using long unique with an autoincrement column
- Added handler function to check if table has long unique hash indexes
- Disable write cache in MyISAM and Aria when using update_handler as
  if cache is used, the row will not be inserted until end of statement
  and update_handler would not find conflicting rows.
- Removed not used handler argument from
  check_duplicate_long_entries_update()
- Syntax cleanups
  - Indentation fixes
  - Don't use single character indentifiers for arguments

1 files changed, 7 insertions, 0 deletions

diff --git a/sql/sql_delete.cc b/sql/sql_delete.cc
index bef77e1a2e9..da46a538a28 100644
--- a/sql/sql_delete.cc
+++ b/sql/sql_delete.cc
@@ -751,6 +751,10 @@ bool mysql_delete(THD *thd, TABLE_LIST *table_list, COND *conds,
           && !table->versioned()
           && table->file->has_transactions();
 
+  if (table->versioned(VERS_TIMESTAMP) ||
+      (table_list->has_period() && !portion_of_time_through_update))
+    table->file->prepare_for_insert(1);
+
   THD_STAGE_INFO(thd, stage_updating);
   while (likely(!(error=info.read_record())) && likely(!thd->killed) &&
          likely(!thd->is_error()))
@@ -1237,6 +1241,9 @@ multi_delete::initialize_tables(JOIN *join)
 	normal_tables= 1;
       tbl->prepare_triggers_for_delete_stmt_or_event();
       tbl->prepare_for_position();
+
+      if (tbl->versioned(VERS_TIMESTAMP))
+        tbl->file->prepare_for_insert(1);
     }
     else if ((tab->type != JT_SYSTEM && tab->type != JT_CONST) &&
              walk == delete_tables)