Implement MySQL framework to support consistent read views in

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.


sql/examples/ha_archive.cc:
  - extend handlerton with cursors methods; fix coding style
sql/examples/ha_example.cc:
  - extend handlerton with cursors methods; fix coding style
sql/examples/ha_tina.cc:
  - extend handlerton with cursors methods; fix coding style
sql/ha_berkeley.cc:
  - extend handlerton with cursors methods
sql/ha_blackhole.cc:
  - extend handlerton with cursors methods; fix coding style
sql/ha_federated.cc:
  - extend handlerton with cursors methods; fix coding style
sql/ha_heap.cc:
  - extend handlerton with cursors methods; fix coding style
sql/ha_innodb.cc:
  - extend handlerton with cursors methods
sql/ha_myisam.cc:
  - extend handlerton with cursors methods; fix coding style
sql/ha_myisammrg.cc:
  - extend handlerton with cursors methods; fix coding style
sql/ha_ndbcluster.cc:
  - extend handlerton with cursors methods
sql/handler.h:
  - extend handlerton with cursors methods
sql/sql_select.cc:
  - create a consistent read view when we open a cursor,
    set it for a fetch, and free when we closing the cursor.
sql/sql_select.h:
  - add Cursor::ht_info to remember read views used in a cursor.
tests/mysql_client_test.c:
  Disable an assert that will be no longer valid when consistent
  read views in InnoDB are used.

sql/examples/ha_archive.cc

@@ -140,16 +140,19 @@ static handlerton archive_hton = {
   "archive",
   0,       /* slot */
   0,       /* savepoint size. */
-  0,       /* close_connection */
-  0,       /* savepoint */
-  0,       /* rollback to savepoint */
-  0,       /* releas savepoint */
-  0,       /* commit */
-  0,       /* rollback */
-  0,       /* prepare */
-  0,       /* recover */
-  0,       /* commit_by_xid */
-  0,       /* rollback_by_xid */
+  NULL,    /* close_connection */
+  NULL,    /* savepoint */
+  NULL,    /* rollback to savepoint */
+  NULL,    /* releas savepoint */
+  NULL,    /* commit */
+  NULL,    /* rollback */
+  NULL,    /* prepare */
+  NULL,    /* recover */
+  NULL,    /* commit_by_xid */
+  NULL,    /* rollback_by_xid */
+  NULL,    /* create_cursor_read_view */
+  NULL,    /* set_cursor_read_view */
+  NULL,    /* close_cursor_read_view */
   HTON_NO_FLAGS
 };
 

sql/examples/ha_example.cc

@@ -77,16 +77,19 @@ static handlerton example_hton= {
   "CSV",
   0,       /* slot */
   0,       /* savepoint size. */
-  0,       /* close_connection */
-  0,       /* savepoint */
-  0,       /* rollback to savepoint */
-  0,       /* release savepoint */
-  0,       /* commit */
-  0,       /* rollback */
-  0,       /* prepare */
-  0,       /* recover */
-  0,       /* commit_by_xid */
-  0,       /* rollback_by_xid */
+  NULL,    /* close_connection */
+  NULL,    /* savepoint */
+  NULL,    /* rollback to savepoint */
+  NULL,    /* release savepoint */
+  NULL,    /* commit */
+  NULL,    /* rollback */
+  NULL,    /* prepare */
+  NULL,    /* recover */
+  NULL,    /* commit_by_xid */
+  NULL,    /* rollback_by_xid */
+  NULL,    /* create_cursor_read_view */
+  NULL,    /* set_cursor_read_view */
+  NULL,    /* close_cursor_read_view */
   HTON_NO_FLAGS
 };
 

sql/examples/ha_tina.cc

@@ -58,16 +58,19 @@ static handlerton tina_hton= {
   "CSV",
   0,       /* slot */
   0,       /* savepoint size. */
-  0,       /* close_connection */
-  0,       /* savepoint */
-  0,       /* rollback to savepoint */
-  0,       /* release savepoint */
-  0,       /* commit */
-  0,       /* rollback */
-  0,       /* prepare */
-  0,       /* recover */
-  0,       /* commit_by_xid */
-  0,       /* rollback_by_xid */
+  NULL,    /* close_connection */
+  NULL,    /* savepoint */
+  NULL,    /* rollback to savepoint */
+  NULL,    /* release savepoint */
+  NULL,    /* commit */
+  NULL,    /* rollback */
+  NULL,    /* prepare */
+  NULL,    /* recover */
+  NULL,    /* commit_by_xid */
+  NULL,    /* rollback_by_xid */
+  NULL,    /* create_cursor_read_view */
+  NULL,    /* set_cursor_read_view */
+  NULL,    /* close_cursor_read_view */
   HTON_NO_FLAGS
 };
 

sql/ha_berkeley.cc

@@ -121,6 +121,9 @@ static handlerton berkeley_hton = {
   NULL, /* recover */
   NULL, /* commit_by_xid */
   NULL, /* rollback_by_xid */
+  NULL, /* create_cursor_read_view */
+  NULL, /* set_cursor_read_view */
+  NULL, /* close_cursor_read_view */
   HTON_CLOSE_CURSORS_AT_COMMIT
 };
 

sql/ha_blackhole.cc

@@ -30,16 +30,19 @@ static handlerton blackhole_hton= {
   "BLACKHOLE",
   0,       /* slot */
   0,       /* savepoint size. */
-  0,       /* close_connection */
-  0,       /* savepoint */
-  0,       /* rollback to savepoint */
-  0,       /* release savepoint */
-  0,       /* commit */
-  0,       /* rollback */
-  0,       /* prepare */
-  0,       /* recover */
-  0,       /* commit_by_xid */
-  0,       /* rollback_by_xid */
+  NULL,    /* close_connection */
+  NULL,    /* savepoint */
+  NULL,    /* rollback to savepoint */
+  NULL,    /* release savepoint */
+  NULL,    /* commit */
+  NULL,    /* rollback */
+  NULL,    /* prepare */
+  NULL,    /* recover */
+  NULL,    /* commit_by_xid */
+  NULL,    /* rollback_by_xid */
+  NULL,    /* create_cursor_read_view */
+  NULL,    /* set_cursor_read_view */
+  NULL,    /* close_cursor_read_view */
   HTON_NO_FLAGS
 };
 

sql/ha_federated.cc

@@ -685,16 +685,19 @@ static handlerton federated_hton= {
   "FEDERATED",
   0,       /* slot */
   0,       /* savepoint size. */
-  0,       /* close_connection */
-  0,       /* savepoint */
-  0,       /* rollback to savepoint */
-  0,       /* release savepoint */
-  0,       /* commit */
-  0,       /* rollback */
-  0,       /* prepare */
-  0,       /* recover */
-  0,       /* commit_by_xid */
-  0,       /* rollback_by_xid */
+  NULL,    /* close_connection */
+  NULL,    /* savepoint */
+  NULL,    /* rollback to savepoint */
+  NULL,    /* release savepoint */
+  NULL,    /* commit */
+  NULL,    /* rollback */
+  NULL,    /* prepare */
+  NULL,    /* recover */
+  NULL,    /* commit_by_xid */
+  NULL,    /* rollback_by_xid */
+  NULL,    /* create_cursor_read_view */
+  NULL,    /* set_cursor_read_view */
+  NULL,    /* close_cursor_read_view */
   HTON_NO_FLAGS
 };
 

sql/ha_heap.cc

@@ -27,16 +27,19 @@ static handlerton heap_hton= {
   "MEMORY",
   0,       /* slot */
   0,       /* savepoint size. */
-  0,       /* close_connection */
-  0,       /* savepoint */
-  0,       /* rollback to savepoint */
-  0,       /* release savepoint */
-  0,       /* commit */
-  0,       /* rollback */
-  0,       /* prepare */
-  0,       /* recover */
-  0,       /* commit_by_xid */
-  0,       /* rollback_by_xid */
+  NULL,    /* close_connection */
+  NULL,    /* savepoint */
+  NULL,    /* rollback to savepoint */
+  NULL,    /* release savepoint */
+  NULL,    /* commit */
+  NULL,    /* rollback */
+  NULL,    /* prepare */
+  NULL,    /* recover */
+  NULL,    /* commit_by_xid */
+  NULL,    /* rollback_by_xid */
+  NULL,    /* create_cursor_read_view */
+  NULL,    /* set_cursor_read_view */
+  NULL,    /* close_cursor_read_view */
   HTON_NO_FLAGS
 };
 

sql/ha_innodb.cc

@@ -216,12 +216,9 @@ static handlerton innobase_hton = {
   innobase_xa_recover,		/* recover */
   innobase_commit_by_xid,	/* commit_by_xid */
   innobase_rollback_by_xid,     /* rollback_by_xid */
-  /*
-    For now when one opens a cursor, MySQL does not create an own
-    InnoDB consistent read view for it, and uses the view of the
-    currently active transaction. Therefore, cursors can not
-    survive COMMIT or ROLLBACK statements, which free this view.
-  */
+  NULL,
+  NULL,
+  NULL,
   HTON_CLOSE_CURSORS_AT_COMMIT
 };
 

sql/ha_myisam.cc

@@ -50,16 +50,19 @@ static handlerton myisam_hton= {
   "MyISAM",
   0,       /* slot */
   0,       /* savepoint size. */
-  0,       /* close_connection */
-  0,       /* savepoint */
-  0,       /* rollback to savepoint */
-  0,       /* release savepoint */
-  0,       /* commit */
-  0,       /* rollback */
-  0,       /* prepare */
-  0,       /* recover */
-  0,       /* commit_by_xid */
-  0,       /* rollback_by_xid */
+  NULL,    /* close_connection */
+  NULL,    /* savepoint */
+  NULL,    /* rollback to savepoint */
+  NULL,    /* release savepoint */
+  NULL,    /* commit */
+  NULL,    /* rollback */
+  NULL,    /* prepare */
+  NULL,    /* recover */
+  NULL,    /* commit_by_xid */
+  NULL,    /* rollback_by_xid */
+  NULL,    /* create_cursor_read_view */
+  NULL,    /* set_cursor_read_view */
+  NULL,    /* close_cursor_read_view */
   /*
     MyISAM doesn't support transactions and doesn't have
     transaction-dependent context: cursors can survive a commit.

sql/ha_myisammrg.cc

@@ -38,16 +38,19 @@ static handlerton myisammrg_hton= {
   "MRG_MyISAM",
   0,       /* slot */
   0,       /* savepoint size. */
-  0,       /* close_connection */
-  0,       /* savepoint */
-  0,       /* rollback to savepoint */
-  0,       /* release savepoint */
-  0,       /* commit */
-  0,       /* rollback */
-  0,       /* prepare */
-  0,       /* recover */
-  0,       /* commit_by_xid */
-  0,       /* rollback_by_xid */
+  NULL,    /* close_connection */
+  NULL,    /* savepoint */
+  NULL,    /* rollback to savepoint */
+  NULL,    /* release savepoint */
+  NULL,    /* commit */
+  NULL,    /* rollback */
+  NULL,    /* prepare */
+  NULL,    /* recover */
+  NULL,    /* commit_by_xid */
+  NULL,    /* rollback_by_xid */
+  NULL,    /* create_cursor_read_view */
+  NULL,    /* set_cursor_read_view */
+  NULL,    /* close_cursor_read_view */
   HTON_NO_FLAGS
 };
 

sql/ha_ndbcluster.cc

@@ -63,6 +63,9 @@ static handlerton ndbcluster_hton = {
   NULL, /* recover */
   NULL, /* commit_by_xid */
   NULL, /* rollback_by_xid */
+  NULL, /* create_cursor_read_view */
+  NULL, /* set_cursor_read_view */
+  NULL, /* close_cursor_read_view */
   HTON_NO_FLAGS
 };
 

sql/handler.h

@@ -106,9 +106,11 @@
 
 /*
   Note: the following includes binlog and closing 0.
-  so: innodb+bdb+ndb+binlog+0
+  so: innodb + bdb + ndb + binlog + myisam + myisammrg + archive +
+      example + csv + heap + blackhole + federated + 0
+  (yes, the sum is deliberately inaccurate)
 */
-#define MAX_HA 6
+#define MAX_HA 14
 
 /*
   Bits in index_ddl_flags(KEY *wanted_index)
@@ -349,6 +351,9 @@ typedef struct
    int  (*recover)(XID *xid_list, uint len);
    int  (*commit_by_xid)(XID *xid);
    int  (*rollback_by_xid)(XID *xid);
+   void *(*create_cursor_read_view)();
+   void (*set_cursor_read_view)(void *);
+   void (*close_cursor_read_view)(void *);
    uint32 flags;                                /* global handler flags */
 } handlerton;
 

sql/sql_select.cc

@@ -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)
+    const handlerton *ht= *pht;
     close_at_commit|= (ht->flags & HTON_CLOSE_CURSORS_AT_COMMIT);
-    else
+    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

sql/sql_select.h

@@ -389,6 +389,12 @@ class Cursor: public Sql_alloc, public Query_arena
   TABLE *derived_tables;
   /* List of items created during execution */
   query_id_t query_id;
+  struct Engine_info
+  {
+    const handlerton *ht;
+    void *read_view;
+  };
+  Engine_info ht_info[MAX_HA];
 public:
   Item_change_list change_list;
   select_send result;

tests/mysql_client_test.c

@@ -13874,10 +13874,12 @@ static void test_bug10760()
       printf("Fetched row %s\n", id_buf);
     rc= mysql_rollback(mysql);                  /* should close the cursor */
     myquery(rc);
+#if 0
     rc= mysql_stmt_fetch(stmt);
     DIE_UNLESS(rc);
     if (!opt_silent)
       printf("Got error (as expected): %s\n", mysql_error(mysql));
+#endif
   }
 
   mysql_stmt_close(stmt);