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Implement MySQL framework to support consistent read views in

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cursors. This should fix Bug#11813 when InnoDB part is in 
(tested with a draft patch).
The idea of the patch is that if a storage engine supports
consistent read views, we open one when open a cursor,
set is as the active view when fetch from the cursor, and close
together with cursor close.
This commit is contained in:
konstantin@mysql.com
2005-07-20 20:02:36 +04:00
parent 4570ace8fb
commit 21957c423e
15 changed files with 151 additions and 95 deletions
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30
sql/sql_select.cc
View File

@ -1712,12 +1712,14 @@ Cursor::Cursor(THD *thd)
/* We will overwrite it at open anyway. */
init_sql_alloc(&main_mem_root, ALLOC_ROOT_MIN_BLOCK_SIZE, 0);
thr_lock_owner_init(&lock_id, &thd->lock_info);
bzero((void*) ht_info, sizeof(ht_info));
}
void
Cursor::init_from_thd(THD *thd)
{
Engine_info *info;
/*
We need to save and reset thd->mem_root, otherwise it'll be freed
later in mysql_parse.
@ -1749,15 +1751,16 @@ Cursor::init_from_thd(THD *thd)
thd->lock_info.n_cursors++;
close_at_commit= FALSE; /* reset in case we're reusing the cursor */
for (TABLE *table= open_tables; table; table= table->next)
info= &ht_info[0];
for (handlerton **pht= thd->transaction.stmt.ht; *pht; pht++)
{
const handlerton *ht= table->file->ht;
if (ht)
close_at_commit|= (ht->flags & HTON_CLOSE_CURSORS_AT_COMMIT);
else
const handlerton *ht= *pht;
close_at_commit|= (ht->flags & HTON_CLOSE_CURSORS_AT_COMMIT);
if (ht->create_cursor_read_view)
{
close_at_commit= TRUE; /* handler status is unknown */
break;
info->ht= ht;
info->read_view= (ht->create_cursor_read_view)();
++info;
}
}
/*
@ -1853,6 +1856,9 @@ Cursor::fetch(ulong num_rows)
/* save references to memory, allocated during fetch */
thd->set_n_backup_item_arena(this, &backup_arena);
for (Engine_info *info= ht_info; info->read_view ; info++)
(info->ht->set_cursor_read_view)(info->read_view);
join->fetch_limit+= num_rows;
error= sub_select(join, join_tab, 0);
@ -1869,6 +1875,9 @@ Cursor::fetch(ulong num_rows)
/* Grab free_list here to correctly free it in close */
thd->restore_backup_item_arena(this, &backup_arena);
for (Engine_info *info= ht_info; info->read_view; info++)
(info->ht->set_cursor_read_view)(0);
if (error == NESTED_LOOP_CURSOR_LIMIT)
{
/* Fetch limit worked, possibly more rows are there */
@ -1909,6 +1918,13 @@ Cursor::close(bool is_active)
else
(void) join->select_lex->cleanup();
for (Engine_info *info= ht_info; info->read_view; info++)
{
(info->ht->close_cursor_read_view)(info->read_view);
info->read_view= 0;
info->ht= 0;
}
if (is_active)
close_thread_tables(thd);
else