261 lines
7.1 KiB
C++
261 lines
7.1 KiB
C++
/* Copyright (c) 2016, 2019, Oracle and/or its affiliates. All rights reserved.
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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, version 2.0,
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as published by the Free Software Foundation.
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This program is also distributed with certain software (including
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but not limited to OpenSSL) that is licensed under separate terms,
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as designated in a particular file or component or in included license
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documentation. The authors of MySQL hereby grant you an additional
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permission to link the program and your derivative works with the
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separately licensed software that they have included with MySQL.
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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, version 2.0, for more details.
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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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#ifndef SQL_DD_SHOW_QUERY_BUILDER_H
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#define SQL_DD_SHOW_QUERY_BUILDER_H
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#include "lex_string.h"
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#include "sql/mem_root_array.h"
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class Item;
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class PT_derived_table;
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class PT_order_list;
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class PT_select_item_list;
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class PT_table_reference;
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class SELECT_LEX;
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class String;
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class THD;
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struct YYLTYPE;
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typedef YYLTYPE POS;
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namespace dd {
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namespace info_schema {
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/**
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This class provide framework to build a SELECT_LEX using ParseTree
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nodes.
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Note that this class is designed to help build queries that are
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required to implement SHOW commands over data dictionary tables. It
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does not provide complete framework, e.g., you cannot add a GROUP BY
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node for now, mainly because that is not needed to implement SHOW
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command.
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This class is used by implementation of SHOW command in
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sql/dd/show.cc. The class enables code re-usability.
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One can build SELECT_LEX that represents following,
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...
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SELECT star_select_item, select_item1, select_item2, ...
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FROM from_item OR FROM PT_derived_table
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WHERE condition AND condition AND ...
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ORDER BY order_by_field1, order_by_field2 , ...
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...
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Where as, a 'condition' can be one of,
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field_name = "value"
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field_name LIKE "value%"
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One can think of enhancing this framework on need basis.
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Note to server general team: This framework can be used by
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sql/sql_show_status.* implementation. For now, this file is kept
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inside sql/dd, but we can think of moving it out to sql/.
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The memory used while building the this Parse Tree is thd->mem_root.
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*/
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class Select_lex_builder {
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public:
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Select_lex_builder(const POS *pc, THD *thd);
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/**
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Add item representing star in "SELECT '*' ...".
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@return false on success.
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true on failure.
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*/
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bool add_star_select_item();
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/**
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Add item representing a column as,
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"SELECT <field_name> AS <alias>, ...".
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The item will be appended to existing list of select items
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for this query.
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@return false on success.
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true on failure.
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*/
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bool add_select_item(const LEX_CSTRING &field_name, const LEX_CSTRING &alias);
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/**
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Add expression as an item tree, with an alias to name the resulting column.
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The item will be appended to existing list of select items
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for this query block.
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@return false on success.
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true on failure.
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*/
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bool add_select_expr(Item *select_list_item, const LEX_CSTRING &alias);
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/**
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Add item representing a FROM clause table as,
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"SELECT ... FROM <schema_name>.<table_name> ...".
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Only single table can be added. We cannot build a query with
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JOIN clause for now.
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@return false on success.
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true on failure.
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*/
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bool add_from_item(const LEX_CSTRING &schema_name,
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const LEX_CSTRING &table_name);
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/**
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Add item representing a FROM clause table as,
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"SELECT ... FROM <sub query or derived table> ...".
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Only single table can be added. We cannot build a query with
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JOIN clause for now.
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@return false on success.
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true on failure.
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*/
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bool add_from_item(PT_derived_table *dt);
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/**
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Prepare item representing a LIKE condition,
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"SELECT ... WHERE <field_name> LIKE <value%> ... "
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This item should be intern added to Select_lex_builder using
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add_condition() method.
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@return pointer to Item* on success.
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nullptr on failure.
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*/
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Item *prepare_like_item(const LEX_CSTRING &field_name, const String *wild);
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/**
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Prepare item representing a equal to comparision condition,
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"SELECT ... WHERE <field_name> = <value> ... "
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This item should be intern added to Select_lex_builder using
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add_condition() method.
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@return pointer to Item* on success.
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nullptr on failure.
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*/
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Item *prepare_equal_item(const LEX_CSTRING &field_name,
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const LEX_CSTRING &value);
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/**
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Add a WHERE clause condition to Select_lex_builder.
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"SELECT ... WHERE ... AND <condition> ... "
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If there are existing conditions, then the new condition is
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append to the WHERE clause conditions with a 'AND' condition.
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@return false on success.
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true on failure.
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*/
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bool add_condition(Item *a);
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/**
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Add a ORDER BY clause field to Select_lex_builder.
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"SELECT ... ORDER BY <field_name>, ... "
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If there are existing ORDER BY field, then we append a new
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field to the ORDER BY clause. All the fields are added to be
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order in ascending order.
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@return false on success.
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true on failure.
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*/
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bool add_order_by(const LEX_CSTRING &field_name);
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/**
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This function build ParseTree node that represents this
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Select_lex_builder as sub-query. This enables us to build a
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SELECT_LEX containing a sub-query in its FROM clause. This
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sub-query is represented by ParseTree node PT_derived_table.
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"SELECT ... FROM <PT_dervied_table>, ... "
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@return pointer to PT_derived_table on success.
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nullptr on failure.
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*/
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PT_derived_table *prepare_derived_table(const LEX_CSTRING &table_alias);
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/**
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Prepare a SELECT_LEX using all the information information
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added to this Select_lex_builder.
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@return pointer to SELECT_LEX* on success.
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nullptr on failure.
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*/
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SELECT_LEX *prepare_select_lex();
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private:
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/**
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Prepare a list of expression used to build select items for
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the query being built.
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@return false on success.
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true on failure.
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*/
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bool add_to_select_item_list(Item *expr);
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private:
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// Parser current position represented by YYLTYPE
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const POS *m_pos;
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// Current thread
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THD *m_thd;
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// List of select_items for the query.
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PT_select_item_list *m_select_item_list;
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// Table reference in FROM clause for the query.
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Mem_root_array_YY<PT_table_reference *> m_table_reference_list;
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// Expression representing a WHERE clause.
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Item *m_where_clause;
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// List of order by clause elements.
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PT_order_list *m_order_by_list;
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};
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} // namespace info_schema
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} // namespace dd
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#endif /* SQL_DD_SHOW_QUERY_BUILDER_H */
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