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Pushing down statements to FederatedX engine is implemented by printing either SELECT_LEX or SELECT_LEX_UNIT into a string and sending that string to the engine. In the case of pushing down a single SELECT having a CTE (WITH clause) there was a problem, because normally single SELECTs were printed using SELECT_LEX::print(). But CTEs are stored in the upper unit of the SELECT_LEX - SELECT_LEX_UNIT, so they were not unfolded in the string produced. The solution is to invoke SELECT_LEX_UNIT::print() when pushing down single SELECT statements (but not those which are parts of units), so the possible CTEs are unfolded and printed. Reviewed by Sergei Petrunia (sergey@mariadb.com)
119 lines
3.3 KiB
Objective-C
119 lines
3.3 KiB
Objective-C
/*
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Copyright (c) 2018, 2019 MariaDB
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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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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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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 SELECT_HANDLER_INCLUDED
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#define SELECT_HANDLER_INCLUDED
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#include "mariadb.h"
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#include "sql_priv.h"
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enum class select_pushdown_type {
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SINGLE_SELECT,
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PART_OF_UNIT,
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WHOLE_UNIT
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};
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/**
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@class select_handler
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This interface class is to be used for execution of select queries
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by foreign engines
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*/
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class select_handler
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{
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public:
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// Constructor for a single SELECT_LEX (not a part of a unit)
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select_handler(THD *thd_arg, handlerton *ht_arg, SELECT_LEX *sel_lex);
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// Constructor for a unit (UNION/EXCEPT/INTERSECT)
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select_handler(THD *thd_arg, handlerton *ht_arg, SELECT_LEX_UNIT *sel_unit);
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/*
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Constructor for a SELECT_LEX which is a part of a unit
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(partial pushdown). Both SELECT_LEX and SELECT_LEX_UNIT are passed
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*/
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select_handler(THD *thd_arg, handlerton *ht_arg, SELECT_LEX *sel_lex,
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SELECT_LEX_UNIT *sel_unit);
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virtual ~select_handler();
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int execute();
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virtual bool prepare();
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/*
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Select_handler processes these cases:
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- single SELECT
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- whole unit (multiple SELECTs combined with UNION/EXCEPT/INTERSECT)
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- single SELECT that is part of a unit (partial pushdown)
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In the case of single SELECT select_lex is initialized and lex_unit==NULL,
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in the case of whole UNIT select_lex == NULL and lex_unit is initialized,
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in the case of partial pushdown both select_lex and lex_unit
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are initialized
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*/
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SELECT_LEX *select_lex; // Single select/part of a unit to be executed
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SELECT_LEX_UNIT *lex_unit; // Unit to be executed
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/*
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Temporary table where all results should be stored in record[0]
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The table has a field for every item from the select_lex::item_list.
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The table is actually never filled. Only its record buffer is used.
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*/
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TABLE *table;
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protected:
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/*
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Functions to scan the select result set.
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All these returns 0 if ok, error code in case of error.
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*/
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/* Initialize the process of producing rows of result set */
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virtual int init_scan() = 0;
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/*
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Put the next produced row of the result set in table->record[0]
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and return 0. Return HA_ERR_END_OF_FILE if there are no more rows,
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return other error number in case of fatal error.
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*/
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virtual int next_row() = 0;
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/* Finish scanning */
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virtual int end_scan() = 0;
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/* Report errors */
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virtual void print_error(int error, myf errflag);
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bool send_result_set_metadata();
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bool send_data();
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bool send_eof();
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TABLE *create_tmp_table(THD *thd);
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select_pushdown_type get_pushdown_type();
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THD *thd;
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handlerton *ht;
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select_result *result; // Object receiving the retrieved data
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List<Item> result_columns;
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bool is_analyze;
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};
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#endif /* SELECT_HANDLER_INCLUDED */
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