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* vim:expandtab:shiftwidth=2:tabstop=2:smarttab:
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* Copyright (C) 2009 Sun Microsystems
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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 DRIZZLED_RECORDS_H
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#define DRIZZLED_RECORDS_H
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Initialize READ_RECORD structure to perform full index scan (in forward
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direction) using read_record.read_record() interface.
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This function has been added at late stage and is used only by
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UPDATE/DELETE. Other statements perform index scans using
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join_read_first/next functions.
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@param info READ_RECORD structure to initialize.
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@param session Thread handle
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@param table Table to be accessed
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@param print_error If true, call table->print_error() if an error
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occurs (except for end-of-records error)
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@param idx index to scan
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void init_read_record_idx(READ_RECORD *info,
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init_read_record is used to scan by using a number of different methods.
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Which method to use is set-up in this call so that later calls to
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the info->read_record will call the appropriate method using a function
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There are five methods that relate completely to the sort function
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filesort. The result of a filesort is retrieved using read_record
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calls. The other two methods are used for normal table access.
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The filesort will produce references to the records sorted, these
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references can be stored in memory or in a temporary cursor.
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The temporary cursor is normally used when the references doesn't fit into
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a properly sized memory buffer. For most small queries the references
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are stored in the memory buffer.
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The temporary cursor is also used when performing an update where a key is
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Methods used when ref's are in memory (using rr_from_pointers):
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rr_unpack_from_buffer:
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----------------------
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This method is used when table->sort.addon_field is allocated.
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This is allocated for most SELECT queries not involving any BLOB's.
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In this case the records are fetched from a memory buffer.
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Used when the above is not true, UPDATE, DELETE and so forth and
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SELECT's involving BLOB's. It is also used when the addon_field
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buffer is not allocated due to that its size was bigger than the
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session variable max_length_for_sort_data.
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In this case the record data is fetched from the handler using the
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saved reference using the rnd_pos handler call.
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Methods used when ref's are in a temporary cursor (using rr_from_tempfile)
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rr_unpack_from_tempfile:
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------------------------
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Same as rr_unpack_from_buffer except that references are fetched from
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temporary cursor. Should obviously not really happen other than in
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strange configurations.
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Same as rr_from_pointers except that references are fetched from
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temporary cursor instead of from
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This is a special variant of rr_from_tempfile that can be used for
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handlers that is not using the HA_FAST_KEY_READ table flag. Instead
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of reading the references one by one from the temporary cursor it reads
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a set of them, sorts them and reads all of them into a buffer which
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is then used for a number of subsequent calls to rr_from_cache.
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It is only used for SELECT queries and a number of other conditions
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All other accesses use either index access methods (rr_quick) or a full
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table scan (rr_sequential).
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rr_quick uses one of the QUICK_SELECT classes in optimizer/range.cc to
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perform an index scan. There are loads of functionality hidden
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in these quick classes. It handles all index scans of various kinds.
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This is the most basic access method of a table using rnd_init,
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rnd_next and rnd_end. No indexes are used.
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void init_read_record(READ_RECORD *info,
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drizzled::optimizer::SQL_SELECT *select,
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int use_record_cache,
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void end_read_record(READ_RECORD *info);
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#endif /* DRIZZLED_RECORDS_H */
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drizzled/records.h
