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/* -*- mode: c++; c-basic-offset: 2; indent-tabs-mode: nil; -*-
* vim:expandtab:shiftwidth=2:tabstop=2:smarttab:
*
* Copyright (C) 2009 Sun Microsystems
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; version 2 of the License.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#ifndef DRIZZLED_RECORDS_H
#define DRIZZLED_RECORDS_H
namespace drizzled
{
/**
Initialize READ_RECORD structure to perform full index scan (in forward
direction) using read_record.read_record() interface.
This function has been added at late stage and is used only by
UPDATE/DELETE. Other statements perform index scans using
join_read_first/next functions.
@param info READ_RECORD structure to initialize.
@param session Thread handle
@param table Table to be accessed
@param print_error If true, call table->print_error() if an error
occurs (except for end-of-records error)
@param idx index to scan
*/
void init_read_record_idx(READ_RECORD *info,
Session *session,
Table *table,
bool print_error,
uint32_t idx);
/*
init_read_record is used to scan by using a number of different methods.
Which method to use is set-up in this call so that later calls to
the info->read_record will call the appropriate method using a function
pointer.
There are five methods that relate completely to the sort function
filesort. The result of a filesort is retrieved using read_record
calls. The other two methods are used for normal table access.
The filesort will produce references to the records sorted, these
references can be stored in memory or in a temporary cursor.
The temporary cursor is normally used when the references doesn't fit into
a properly sized memory buffer. For most small queries the references
are stored in the memory buffer.
The temporary cursor is also used when performing an update where a key is
modified.
Methods used when ref's are in memory (using rr_from_pointers):
rr_unpack_from_buffer:
----------------------
This method is used when table->sort.addon_field is allocated.
This is allocated for most SELECT queries not involving any BLOB's.
In this case the records are fetched from a memory buffer.
rr_from_pointers:
-----------------
Used when the above is not true, UPDATE, DELETE and so forth and
SELECT's involving BLOB's. It is also used when the addon_field
buffer is not allocated due to that its size was bigger than the
session variable max_length_for_sort_data.
In this case the record data is fetched from the handler using the
saved reference using the rnd_pos handler call.
Methods used when ref's are in a temporary cursor (using rr_from_tempfile)
rr_unpack_from_tempfile:
------------------------
Same as rr_unpack_from_buffer except that references are fetched from
temporary cursor. Should obviously not really happen other than in
strange configurations.
rr_from_tempfile:
-----------------
Same as rr_from_pointers except that references are fetched from
temporary cursor instead of from
rr_from_cache:
--------------
This is a special variant of rr_from_tempfile that can be used for
handlers that is not using the HA_FAST_KEY_READ table flag. Instead
of reading the references one by one from the temporary cursor it reads
a set of them, sorts them and reads all of them into a buffer which
is then used for a number of subsequent calls to rr_from_cache.
It is only used for SELECT queries and a number of other conditions
on table size.
All other accesses use either index access methods (rr_quick) or a full
table scan (rr_sequential).
rr_quick:
---------
rr_quick uses one of the QUICK_SELECT classes in optimizer/range.cc to
perform an index scan. There are loads of functionality hidden
in these quick classes. It handles all index scans of various kinds.
rr_sequential:
--------------
This is the most basic access method of a table using rnd_init,
rnd_next and rnd_end. No indexes are used.
*/
void init_read_record(READ_RECORD *info,
Session *session,
Table *reg_form,
optimizer::SqlSelect *select,
int use_record_cache,
bool print_errors);
void end_read_record(READ_RECORD *info);
} /* namespace drizzled */
#endif /* DRIZZLED_RECORDS_H */
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