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  • Committer: Andrew Hutchings
  • Date: 2011-02-07 17:20:59 UTC
  • mfrom: (2148 staging)
  • mto: (2148.2.3 build)
  • mto: This revision was merged to the branch mainline in revision 2149.
  • Revision ID: andrew@linuxjedi.co.uk-20110207172059-dyeahrgzrlincoe3
Merge with trunk

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drizzled/sql_select.cc
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  @param cond       condition whose multiple equalities are to be checked
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  @param table      constant table that has been read
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*/
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static void update_const_equal_items(COND *cond, JoinTable *tab)
 
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void update_const_equal_items(COND *cond, JoinTable *tab)
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{
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  if (!(cond->used_tables() & tab->table->map))
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    return;
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         position:
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          1. join->cur_embedding_map - bitmap of pairs of brackets (aka nested
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             joins) we've opened but didn't close.
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          2. {each nested_join_st structure not simplified away}->counter - number
 
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          2. {each NestedJoin class not simplified away}->counter - number
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             of this nested join's children that have already been added to to
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             the partial join order.
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  @endverbatim
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  return 0;
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}
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int join_read_const_table(JoinTable *tab, optimizer::Position *pos)
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{
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  int error;
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  Table *table=tab->table;
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  table->const_table=1;
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  table->null_row=0;
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  table->status=STATUS_NO_RECORD;
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  if (tab->type == AM_SYSTEM)
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  {
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    if ((error=join_read_system(tab)))
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    {                                           // Info for DESCRIBE
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      tab->info="const row not found";
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      /* Mark for EXPLAIN that the row was not found */
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      pos->setFanout(0.0);
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      pos->clearRefDependMap();
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      if (! table->maybe_null || error > 0)
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        return(error);
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    }
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  }
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  else
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  {
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    if (! table->key_read && 
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        table->covering_keys.test(tab->ref.key) && 
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        ! table->no_keyread &&
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        (int) table->reginfo.lock_type <= (int) TL_READ_WITH_SHARED_LOCKS)
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    {
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      table->key_read=1;
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      table->cursor->extra(HA_EXTRA_KEYREAD);
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      tab->index= tab->ref.key;
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    }
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    error=join_read_const(tab);
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    if (table->key_read)
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    {
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      table->key_read=0;
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      table->cursor->extra(HA_EXTRA_NO_KEYREAD);
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    }
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    if (error)
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    {
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      tab->info="unique row not found";
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      /* Mark for EXPLAIN that the row was not found */
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      pos->setFanout(0.0);
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      pos->clearRefDependMap();
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      if (!table->maybe_null || error > 0)
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        return(error);
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    }
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  }
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  if (*tab->on_expr_ref && !table->null_row)
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  {
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    if ((table->null_row= test((*tab->on_expr_ref)->val_int() == 0)))
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      table->mark_as_null_row();
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  }
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  if (!table->null_row)
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    table->maybe_null=0;
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  /* Check appearance of new constant items in Item_equal objects */
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  Join *join= tab->join;
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  if (join->conds)
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    update_const_equal_items(join->conds, tab);
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  TableList *tbl;
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  for (tbl= join->select_lex->leaf_tables; tbl; tbl= tbl->next_leaf)
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  {
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    TableList *embedded;
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    TableList *embedding= tbl;
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    do
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    {
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      embedded= embedding;
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      if (embedded->on_expr)
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         update_const_equal_items(embedded->on_expr, tab);
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      embedding= embedded->getEmbedding();
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    }
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    while (embedding &&
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           embedding->getNestedJoin()->join_list.head() == embedded);
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  }
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3445
 
  return(0);
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}
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int join_read_system(JoinTable *tab)
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{