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mariadb/sql/records.cc
Davi Arnaut a10ae35328 Bug#34043: Server loops excessively in _checkchunk() when safemalloc is enabled 
Essentially, the problem is that safemalloc is excruciatingly
slow as it checks all allocated blocks for overrun at each
memory management primitive, yielding a almost exponential
slowdown for the memory management functions (malloc, realloc,
free). The overrun check basically consists of verifying some
bytes of a block for certain magic keys, which catches some
simple forms of overrun. Another minor problem is violation
of aliasing rules and that its own internal list of blocks
is prone to corruption.

Another issue with safemalloc is rather the maintenance cost
as the tool has a significant impact on the server code.
Given the magnitude of memory debuggers available nowadays,
especially those that are provided with the platform malloc
implementation, maintenance of a in-house and largely obsolete
memory debugger becomes a burden that is not worth the effort
due to its slowness and lack of support for detecting more
common forms of heap corruption.

Since there are third-party tools that can provide the same
functionality at a lower or comparable performance cost, the
solution is to simply remove safemalloc. Third-party tools
can provide the same functionality at a lower or comparable
performance cost. 

The removal of safemalloc also allows a simplification of the
malloc wrappers, removing quite a bit of kludge: redefinition
of my_malloc, my_free and the removal of the unused second
argument of my_free. Since free() always check whether the
supplied pointer is null, redudant checks are also removed.

Also, this patch adds unit testing for my_malloc and moves
my_realloc implementation into the same file as the other
memory allocation primitives.
2010-07-08 18:20:08 -03:00

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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 */
#ifdef USE_PRAGMA_INTERFACE
#pragma implementation /* gcc class implementation */
#endif
/**
@file
@brief
Functions for easy reading of records, possible through a cache
*/
#include "records.h"
#include "sql_priv.h"
#include "records.h"
#include "filesort.h" // filesort_free_buffers
#include "opt_range.h" // SQL_SELECT
#include "sql_class.h" // THD
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_last(READ_RECORD *info);
static int rr_index(READ_RECORD *info);
static int rr_index_desc(READ_RECORD *info);
/**
Initialize READ_RECORD structure to perform full index scan in desired
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 thd Thread handle
@param table Table to be accessed
@param print_error If true, call table->file->print_error() if an error
occurs (except for end-of-records error)
@param idx index to scan
@param reverse Scan in the reverse direction
*/
void init_read_record_idx(READ_RECORD *info, THD *thd, TABLE *table,
bool print_error, uint idx, bool reverse)
{
empty_record(table);
bzero((char*) info,sizeof(*info));
info->thd= thd;
info->table= table;
info->file= table->file;
info->record= table->record[0];
info->print_error= print_error;
info->unlock_row= rr_unlock_row;
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= reverse ? rr_index_last : 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.
SYNOPSIS
init_read_record()
info OUT read structure
thd Thread handle
table Table the data [originally] comes from.
select SQL_SELECT structure. We may select->quick or
select->file as data source
use_record_cache Call file->extra_opt(HA_EXTRA_CACHE,...)
if we're going to do sequential read and some
additional conditions are satisfied.
print_error Copy this to info->print_error
disable_rr_cache Don't use rr_from_cache (used by sort-union
index-merge which produces rowid sequences that
are already ordered)
DESCRIPTION
This function sets up reading data via one of the methods:
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,
bool disable_rr_cache)
{
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
{
empty_record(table);
info->record= table->record[0];
info->ref_length= table->file->ref_length;
}
info->select=select;
info->print_error=print_error;
info->unlock_row= rr_unlock_row;
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 (!disable_rr_cache &&
!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.optimizer_switch &
OPTIMIZER_SWITCH_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(info->cache);
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 (info->thd->killed)
{
info->thd->send_kill_message();
return 1;
}
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 || (tmp != HA_ERR_RECORD_DELETED))
{
tmp= rr_handle_error(info, tmp);
break;
}
}
return tmp;
}
/**
Reads first row in an index scan.
@param info Scan info
@retval
0 Ok
@retval
-1 End of records
@retval
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 last row in an index scan.
@param info Scan info
@retval
0 Ok
@retval
-1 End of records
@retval
1 Error
*/
static int rr_index_last(READ_RECORD *info)
{
int tmp= info->file->index_last(info->record);
info->read_record= rr_index_desc;
if (tmp)
tmp= rr_handle_error(info, tmp);
return tmp;
}
/**
Reads index sequentially after first row.
Read the next index record (in forward direction) and translate return
value.
@param info Scan info
@retval
0 Ok
@retval
-1 End of records
@retval
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;
}
/**
Reads index sequentially from the last row to the first.
Read the prev index record (in backward direction) and translate return
value.
@param info Scan info
@retval
0 Ok
@retval
-1 End of records
@retval
1 Error
*/
static int rr_index_desc(READ_RECORD *info)
{
int tmp= info->file->index_prev(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)))
{
/*
rnd_next can return RECORD_DELETED for MyISAM when one thread is
reading and another deleting without locks.
*/
if (info->thd->killed || (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.
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.
@param info Reference to the context including record descriptors
@retval
0 Record successfully read.
@retval
-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.
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.
@param info Reference to the context including record descriptors
@retval
0 Record successfully read.
@retval
-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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