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1108.6.39
by Padraig O'Sullivan
Placed the SargableParam class in the optimizer namespace and sub-directory. |
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/* -*- mode: c++; c-basic-offset: 2; indent-tabs-mode: nil; -*-
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* vim:expandtab:shiftwidth=2:tabstop=2:smarttab:
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*
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* Copyright (C) 2009 Sun Microsystems
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; version 2 of the License.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#ifndef DRIZZLED_OPTIMIZER_SARGABLE_PARAM_H
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#define DRIZZLED_OPTIMIZER_SARGABLE_PARAM_H
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namespace drizzled |
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{
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namespace optimizer |
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{
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/**
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* SARG stands for search argument. A sargable predicate is one of the form
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* (or which can be put in to the form) "column comparison-operator value".
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* SARGS are expressed as a boolean expression of such predicates in
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* disjunctive normal form. For more information, consult the original paper
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* in which this term was introduced: Access Path Selection in a Relational
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* Database Management System by Selinger et al
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*
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* This class is used to collect info on potentially sargable predicates in
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* order to check whether they become sargable after reading const tables.
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* We form a bitmap of indexes that can be used for sargable predicates.
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* Only such indexes are involved in range analysis.
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*/
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class SargableParam |
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{
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public: |
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SargableParam() |
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:
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field(NULL), |
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arg_value(NULL), |
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num_values(0) |
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{}
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SargableParam(Field *in_field, |
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Item **in_arg_value, |
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uint32_t in_num_values) |
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:
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field(in_field), |
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arg_value(in_arg_value), |
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num_values(in_num_values) |
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{}
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1108.6.51
by Padraig O'Sullivan
Added a copy constructor and assignment operator to the SargableParam class. |
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SargableParam(const SargableParam &rhs) |
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:
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field(rhs.field), |
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arg_value(rhs.arg_value), |
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num_values(rhs.num_values) |
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{}
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SargableParam &operator=(const SargableParam &rhs) |
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{
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if (this == &rhs) |
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{
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return *this; |
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}
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field= rhs.field; |
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arg_value= rhs.arg_value; |
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num_values= rhs.num_values; |
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return *this; |
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}
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1108.6.39
by Padraig O'Sullivan
Placed the SargableParam class in the optimizer namespace and sub-directory. |
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Field *getField() |
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{
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return field; |
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}
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uint32_t getNumValues() const |
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{
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return num_values; |
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}
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bool isConstItem(uint32_t index) |
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{
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return (arg_value[index]->const_item()); |
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}
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private: |
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/**
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* Field agsinst which to check sargability.
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*/
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Field *field; |
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/**
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* Values of potential keys for lookups.
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*/
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Item **arg_value; |
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/**
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* Number of values in the arg_value array.
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*/
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uint32_t num_values; |
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};
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} /* end namespace optimizer */ |
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} /* end namespace drizzled */ |
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#endif /* DRIZZLED_OPTIMIZER_SARGABLE_PARAM_H */ |