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drizzled/sql_select.cc
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  return cond;
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}
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/*
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  Try to extract and push the index condition
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  SYNOPSIS
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    push_index_cond()
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      tab            A join tab that has tab->table->file and its condition
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                     in tab->select_cond
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      keyno          Index for which extract and push the condition
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      other_tbls_ok  true <=> Fields of other non-const tables are allowed
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  DESCRIPTION
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    Try to extract and push the index condition down to table handler
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*/
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void push_index_cond(JoinTable *tab, uint32_t keyno, bool other_tbls_ok)
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{
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  Item *idx_cond;
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  if (tab->table->file->index_flags(keyno, 0, 1) & HA_DO_INDEX_COND_PUSHDOWN &&
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      tab->join->session->variables.engine_condition_pushdown)
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  {
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    idx_cond= make_cond_for_index(tab->select_cond, tab->table, keyno,
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                                  other_tbls_ok);
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    if (idx_cond)
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    {
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      tab->pre_idx_push_select_cond= tab->select_cond;
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      Item *idx_remainder_cond= tab->table->file->idx_cond_push(keyno, idx_cond);
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      /*
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        Disable eq_ref's "lookup cache" if we've pushed down an index
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        condition.
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        TODO: This check happens to work on current ICP implementations, but
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        there may exist a compliant implementation that will not work
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        correctly with it. Sort this out when we stabilize the condition
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        pushdown APIs.
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      */
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      if (idx_remainder_cond != idx_cond)
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        tab->ref.disable_cache= true;
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      Item *row_cond= make_cond_remainder(tab->select_cond, true);
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      if (row_cond)
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      {
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        if (!idx_remainder_cond)
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          tab->select_cond= row_cond;
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        else
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        {
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          tab->select_cond= new Item_cond_and(row_cond, idx_remainder_cond);
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          tab->select_cond->quick_fix_field();
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          ((Item_cond_and*)tab->select_cond)->used_tables_cache=
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            row_cond->used_tables() | idx_remainder_cond->used_tables();
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        }
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      }
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      else
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        tab->select_cond= idx_remainder_cond;
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      if (tab->select)
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      {
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        tab->select->cond= tab->select_cond;
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      }
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    }
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  }
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  return;
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}
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/**
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  cleanup JoinTable.
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*/
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   - If no index, create with filesort() an index file that can be used to
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     retrieve rows in order (should be done with 'read_record').
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     The sorted data is stored in tab->table and will be freed when calling
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     free_io_cache(tab->table).
 
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     tab->table->free_io_cache().
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  RETURN VALUES
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    0           ok
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        else if (tab->select && tab->select->quick)
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          keyno = tab->select->quick->index;
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        if (keyno != MAX_KEY && keyno == table->file->pushed_idx_cond_keyno &&
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            table->file->pushed_idx_cond)
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          extra.append(STRING_WITH_LEN("; Using index condition"));
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        if (quick_type == QUICK_SELECT_I::QS_TYPE_ROR_UNION ||
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            quick_type == QUICK_SELECT_I::QS_TYPE_ROR_INTERSECT ||
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            quick_type == QUICK_SELECT_I::QS_TYPE_INDEX_MERGE)
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          }
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          else if (tab->select->cond)
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          {
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            const COND *pushed_cond= tab->table->file->pushed_cond;
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            if (session->variables.engine_condition_pushdown && pushed_cond)
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            {
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              extra.append(STRING_WITH_LEN("; Using where with pushed "
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                                           "condition"));
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              if (session->lex->describe & DESCRIBE_EXTENDED)
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              {
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                extra.append(STRING_WITH_LEN(": "));
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                ((COND *)pushed_cond)->print(&extra, QT_ORDINARY);
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              }
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            }
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            else
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              extra.append(STRING_WITH_LEN("; Using where"));
 
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            extra.append(STRING_WITH_LEN("; Using where"));
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          }
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        }
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        if (key_read)