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mariadb/sql/records.cc
kaa@polly.(none) 97226f1027 Merge polly.(none):/home/kaa/src/maint/mysql-5.0-maint 
into  polly.(none):/home/kaa/src/maint/mysql-5.1-maint
2007-10-18 14:32:43 +04:00

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/* Copyright (C) 2000-2006 MySQL AB
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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
/* Functions for easy reading of records, possible through a cache */
#include "mysql_priv.h"
static int rr_quick(READ_RECORD *info);
int rr_sequential(READ_RECORD *info);
static int rr_from_tempfile(READ_RECORD *info);
static int rr_unpack_from_tempfile(READ_RECORD *info);
static int rr_unpack_from_buffer(READ_RECORD *info);
static int rr_from_pointers(READ_RECORD *info);
static int rr_from_cache(READ_RECORD *info);
static int init_rr_cache(THD *thd, READ_RECORD *info);
static int rr_cmp(uchar *a,uchar *b);
static int rr_index_first(READ_RECORD *info);
static int rr_index(READ_RECORD *info);
/*
Initialize READ_RECORD structure to perform full index scan
SYNOPSIS
init_read_record_idx()
info READ_RECORD structure to initialize.
thd Thread handle
table Table to be accessed
print_error If true, call table->file->print_error() if an error
occurs (except for end-of-records error)
idx index to scan
DESCRIPTION
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.
*/
void init_read_record_idx(READ_RECORD *info, THD *thd, TABLE *table,
bool print_error, uint idx)
{
bzero((char*) info,sizeof(*info));
info->table= table;
info->file= table->file;
info->record= table->record[0];
info->print_error= print_error;
table->status=0; /* And it's always found */
if (!table->file->inited)
table->file->ha_index_init(idx, 1);
/* read_record will be changed to rr_index in rr_index_first */
info->read_record= rr_index_first;
}
/*
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 file.
The temporary file 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 file 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 file (using rr_from_tempfile)
rr_unpack_from_tempfile:
------------------------
Same as rr_unpack_from_buffer except that references are fetched from
temporary file. 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 file 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 file 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 opt_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,THD *thd, TABLE *table,
SQL_SELECT *select,
int use_record_cache, bool print_error)
{
IO_CACHE *tempfile;
DBUG_ENTER("init_read_record");
bzero((char*) info,sizeof(*info));
info->thd=thd;
info->table=table;
info->file= table->file;
info->forms= &info->table; /* Only one table */
if (table->s->tmp_table == NON_TRANSACTIONAL_TMP_TABLE &&
!table->sort.addon_field)
VOID(table->file->extra(HA_EXTRA_MMAP));
if (table->sort.addon_field)
{
info->rec_buf= table->sort.addon_buf;
info->ref_length= table->sort.addon_length;
}
else
{
info->record= table->record[0];
info->ref_length= table->file->ref_length;
}
info->select=select;
info->print_error=print_error;
info->ignore_not_found_rows= 0;
table->status=0; /* And it's always found */
if (select && my_b_inited(&select->file))
tempfile= &select->file;
else
tempfile= table->sort.io_cache;
if (tempfile && my_b_inited(tempfile)) // Test if ref-records was used
{
DBUG_PRINT("info",("using rr_from_tempfile"));
info->read_record= (table->sort.addon_field ?
rr_unpack_from_tempfile : rr_from_tempfile);
info->io_cache=tempfile;
reinit_io_cache(info->io_cache,READ_CACHE,0L,0,0);
info->ref_pos=table->file->ref;
if (!table->file->inited)
table->file->ha_rnd_init(0);
/*
table->sort.addon_field is checked because if we use addon fields,
it doesn't make sense to use cache - we don't read from the table
and table->sort.io_cache is read sequentially
*/
if (!table->sort.addon_field &&
! (specialflag & SPECIAL_SAFE_MODE) &&
thd->variables.read_rnd_buff_size &&
!(table->file->ha_table_flags() & HA_FAST_KEY_READ) &&
(table->db_stat & HA_READ_ONLY ||
table->reginfo.lock_type <= TL_READ_NO_INSERT) &&
(ulonglong) table->s->reclength* (table->file->stats.records+
table->file->stats.deleted) >
(ulonglong) MIN_FILE_LENGTH_TO_USE_ROW_CACHE &&
info->io_cache->end_of_file/info->ref_length * table->s->reclength >
(my_off_t) MIN_ROWS_TO_USE_TABLE_CACHE &&
!table->s->blob_fields &&
info->ref_length <= MAX_REFLENGTH)
{
if (! init_rr_cache(thd, info))
{
DBUG_PRINT("info",("using rr_from_cache"));
info->read_record=rr_from_cache;
}
}
}
else if (select && select->quick)
{
DBUG_PRINT("info",("using rr_quick"));
info->read_record=rr_quick;
}
else if (table->sort.record_pointers)
{
DBUG_PRINT("info",("using record_pointers"));
table->file->ha_rnd_init(0);
info->cache_pos=table->sort.record_pointers;
info->cache_end=info->cache_pos+
table->sort.found_records*info->ref_length;
info->read_record= (table->sort.addon_field ?
rr_unpack_from_buffer : rr_from_pointers);
}
else
{
DBUG_PRINT("info",("using rr_sequential"));
info->read_record=rr_sequential;
table->file->ha_rnd_init(1);
/* We can use record cache if we don't update dynamic length tables */
if (!table->no_cache &&
(use_record_cache > 0 ||
(int) table->reginfo.lock_type <= (int) TL_READ_HIGH_PRIORITY ||
!(table->s->db_options_in_use & HA_OPTION_PACK_RECORD) ||
(use_record_cache < 0 &&
!(table->file->ha_table_flags() & HA_NOT_DELETE_WITH_CACHE))))
VOID(table->file->extra_opt(HA_EXTRA_CACHE,
thd->variables.read_buff_size));
}
/* Condition pushdown to storage engine */
if (thd->variables.engine_condition_pushdown &&
select && select->cond &&
(select->cond->used_tables() & table->map) &&
!table->file->pushed_cond)
table->file->cond_push(select->cond);
DBUG_VOID_RETURN;
} /* init_read_record */
void end_read_record(READ_RECORD *info)
{ /* free cache if used */
if (info->cache)
{
my_free_lock((char*) info->cache,MYF(0));
info->cache=0;
}
if (info->table)
{
filesort_free_buffers(info->table,0);
(void) info->file->extra(HA_EXTRA_NO_CACHE);
if (info->read_record != rr_quick) // otherwise quick_range does it
(void) info->file->ha_index_or_rnd_end();
info->table=0;
}
}
static int rr_handle_error(READ_RECORD *info, int error)
{
if (error == HA_ERR_END_OF_FILE)
error= -1;
else
{
if (info->print_error)
info->table->file->print_error(error, MYF(0));
if (error < 0) // Fix negative BDB errno
error= 1;
}
return error;
}
/* Read a record from head-database */
static int rr_quick(READ_RECORD *info)
{
int tmp;
while ((tmp= info->select->quick->get_next()))
{
if (info->thd->killed)
{
my_error(ER_SERVER_SHUTDOWN, MYF(0));
return 1;
}
if (tmp != HA_ERR_RECORD_DELETED)
{
tmp= rr_handle_error(info, tmp);
break;
}
}
return tmp;
}
/*
Reads first row in an index scan
SYNOPSIS
rr_index_first()
info Scan info
RETURN
0 Ok
-1 End of records
1 Error
*/
static int rr_index_first(READ_RECORD *info)
{
int tmp= info->file->index_first(info->record);
info->read_record= rr_index;
if (tmp)
tmp= rr_handle_error(info, tmp);
return tmp;
}
/*
Reads index sequentially after first row
SYNOPSIS
rr_index()
info Scan info
DESCRIPTION
Read the next index record (in forward direction) and translate return
value.
RETURN
0 Ok
-1 End of records
1 Error
*/
static int rr_index(READ_RECORD *info)
{
int tmp= info->file->index_next(info->record);
if (tmp)
tmp= rr_handle_error(info, tmp);
return tmp;
}
int rr_sequential(READ_RECORD *info)
{
int tmp;
while ((tmp=info->file->rnd_next(info->record)))
{
if (info->thd->killed)
{
info->thd->send_kill_message();
return 1;
}
/*
rnd_next can return RECORD_DELETED for MyISAM when one thread is
reading and another deleting without locks.
*/
if (tmp != HA_ERR_RECORD_DELETED)
{
tmp= rr_handle_error(info, tmp);
break;
}
}
return tmp;
}
static int rr_from_tempfile(READ_RECORD *info)
{
int tmp;
for (;;)
{
if (my_b_read(info->io_cache,info->ref_pos,info->ref_length))
return -1; /* End of file */
if (!(tmp=info->file->rnd_pos(info->record,info->ref_pos)))
break;
/* The following is extremely unlikely to happen */
if (tmp == HA_ERR_RECORD_DELETED ||
(tmp == HA_ERR_KEY_NOT_FOUND && info->ignore_not_found_rows))
continue;
tmp= rr_handle_error(info, tmp);
break;
}
return tmp;
} /* rr_from_tempfile */
/*
Read a result set record from a temporary file after sorting
SYNOPSIS
rr_unpack_from_tempfile()
info Reference to the context including record descriptors
DESCRIPTION
The function first reads the next sorted record from the temporary file.
into a buffer. If a success it calls a callback function that unpacks
the fields values use in the result set from this buffer into their
positions in the regular record buffer.
RETURN
0 - Record successfully read.
-1 - There is no record to be read anymore.
*/
static int rr_unpack_from_tempfile(READ_RECORD *info)
{
if (my_b_read(info->io_cache, info->rec_buf, info->ref_length))
return -1;
TABLE *table= info->table;
(*table->sort.unpack)(table->sort.addon_field, info->rec_buf);
return 0;
}
static int rr_from_pointers(READ_RECORD *info)
{
int tmp;
uchar *cache_pos;
for (;;)
{
if (info->cache_pos == info->cache_end)
return -1; /* End of file */
cache_pos= info->cache_pos;
info->cache_pos+= info->ref_length;
if (!(tmp=info->file->rnd_pos(info->record,cache_pos)))
break;
/* The following is extremely unlikely to happen */
if (tmp == HA_ERR_RECORD_DELETED ||
(tmp == HA_ERR_KEY_NOT_FOUND && info->ignore_not_found_rows))
continue;
tmp= rr_handle_error(info, tmp);
break;
}
return tmp;
}
/*
Read a result set record from a buffer after sorting
SYNOPSIS
rr_unpack_from_buffer()
info Reference to the context including record descriptors
DESCRIPTION
The function first reads the next sorted record from the sort buffer.
If a success it calls a callback function that unpacks
the fields values use in the result set from this buffer into their
positions in the regular record buffer.
RETURN
0 - Record successfully read.
-1 - There is no record to be read anymore.
*/
static int rr_unpack_from_buffer(READ_RECORD *info)
{
if (info->cache_pos == info->cache_end)
return -1; /* End of buffer */
TABLE *table= info->table;
(*table->sort.unpack)(table->sort.addon_field, info->cache_pos);
info->cache_pos+= info->ref_length;
return 0;
}
/* cacheing of records from a database */
static int init_rr_cache(THD *thd, READ_RECORD *info)
{
uint rec_cache_size;
DBUG_ENTER("init_rr_cache");
info->struct_length= 3+MAX_REFLENGTH;
info->reclength= ALIGN_SIZE(info->table->s->reclength+1);
if (info->reclength < info->struct_length)
info->reclength= ALIGN_SIZE(info->struct_length);
info->error_offset= info->table->s->reclength;
info->cache_records= (thd->variables.read_rnd_buff_size /
(info->reclength+info->struct_length));
rec_cache_size= info->cache_records*info->reclength;
info->rec_cache_size= info->cache_records*info->ref_length;
// We have to allocate one more byte to use uint3korr (see comments for it)
if (info->cache_records <= 2 ||
!(info->cache=(uchar*) my_malloc_lock(rec_cache_size+info->cache_records*
info->struct_length+1,
MYF(0))))
DBUG_RETURN(1);
#ifdef HAVE_purify
// Avoid warnings in qsort
bzero(info->cache,rec_cache_size+info->cache_records* info->struct_length+1);
#endif
DBUG_PRINT("info",("Allocated buffert for %d records",info->cache_records));
info->read_positions=info->cache+rec_cache_size;
info->cache_pos=info->cache_end=info->cache;
DBUG_RETURN(0);
} /* init_rr_cache */
static int rr_from_cache(READ_RECORD *info)
{
reg1 uint i;
ulong length;
my_off_t rest_of_file;
int16 error;
uchar *position,*ref_position,*record_pos;
ulong record;
for (;;)
{
if (info->cache_pos != info->cache_end)
{
if (info->cache_pos[info->error_offset])
{
shortget(error,info->cache_pos);
if (info->print_error)
info->table->file->print_error(error,MYF(0));
}
else
{
error=0;
memcpy(info->record,info->cache_pos,
(size_t) info->table->s->reclength);
}
info->cache_pos+=info->reclength;
return ((int) error);
}
length=info->rec_cache_size;
rest_of_file=info->io_cache->end_of_file - my_b_tell(info->io_cache);
if ((my_off_t) length > rest_of_file)
length= (ulong) rest_of_file;
if (!length || my_b_read(info->io_cache,info->cache,length))
{
DBUG_PRINT("info",("Found end of file"));
return -1; /* End of file */
}
length/=info->ref_length;
position=info->cache;
ref_position=info->read_positions;
for (i=0 ; i < length ; i++,position+=info->ref_length)
{
memcpy(ref_position,position,(size_t) info->ref_length);
ref_position+=MAX_REFLENGTH;
int3store(ref_position,(long) i);
ref_position+=3;
}
my_qsort(info->read_positions, length, info->struct_length,
(qsort_cmp) rr_cmp);
position=info->read_positions;
for (i=0 ; i < length ; i++)
{
memcpy(info->ref_pos,position,(size_t) info->ref_length);
position+=MAX_REFLENGTH;
record=uint3korr(position);
position+=3;
record_pos=info->cache+record*info->reclength;
if ((error=(int16) info->file->rnd_pos(record_pos,info->ref_pos)))
{
record_pos[info->error_offset]=1;
shortstore(record_pos,error);
DBUG_PRINT("error",("Got error: %d:%d when reading row",
my_errno, error));
}
else
record_pos[info->error_offset]=0;
}
info->cache_end=(info->cache_pos=info->cache)+length*info->reclength;
}
} /* rr_from_cache */
static int rr_cmp(uchar *a,uchar *b)
{
if (a[0] != b[0])
return (int) a[0] - (int) b[0];
if (a[1] != b[1])
return (int) a[1] - (int) b[1];
if (a[2] != b[2])
return (int) a[2] - (int) b[2];
#if MAX_REFLENGTH == 4
return (int) a[3] - (int) b[3];
#else
if (a[3] != b[3])
return (int) a[3] - (int) b[3];
if (a[4] != b[4])
return (int) a[4] - (int) b[4];
if (a[5] != b[5])
return (int) a[1] - (int) b[5];
if (a[6] != b[6])
return (int) a[6] - (int) b[6];
return (int) a[7] - (int) b[7];
#endif
}
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