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4.0 repository of mydev. When mydev does a push these changes will
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ChangeSet
1.2184 06/06/30 22:05:01 ingo@stripped +1 -0
Bug#20719 - Reading dynamic records with write buffer could fail
Not to be pushed.
Fixed a possible problem with reading of dynamic records
when a write cache is active. The cache must be flushed
whenever a part of the file in the write cache is to be
read.
Added a read optimization to _mi_read_dynamic_record().
No test case. This was a hypothetical but existing problem.
myisam/mi_dynrec.c
1.35 06/06/30 22:04:59 ingo@stripped +64 -26
Bug#20719 - Reading dynamic records with write buffer could fail
Fixed a possible problem with reading of dynamic records
when a write cache is active. The cache must be flushed
whenever a part of the file in the write cache is to be
read. This must be done before the header read and the
rest block read.
Renamed the 'flag' and 'skipp_deleted_blocks' variables.
Added a read optimization to _mi_read_dynamic_record()
that was present in _mi_read_rnd_dynamic_record() already.
After _mi_get_block_info() we have some bytes of the record
in the header buffer already. No need to read them again.
# This is a BitKeeper patch. What follows are the unified diffs for the
# set of deltas contained in the patch. The rest of the patch, the part
# that BitKeeper cares about, is below these diffs.
# User: ingo
# Host: chilla.local
# Root: /home/mydev/mysql-4.0-bug20719
--- 1.34/myisam/mi_dynrec.c 2004-05-06 22:55:28 +02:00
+++ 1.35/myisam/mi_dynrec.c 2006-06-30 22:04:59 +02:00
@@ -1100,7 +1100,7 @@ void _my_store_blob_length(byte *pos,uin
int _mi_read_dynamic_record(MI_INFO *info, my_off_t filepos, byte *buf)
{
- int flag;
+ int block_of_record;
uint b_type,left_length;
byte *to;
MI_BLOCK_INFO block_info;
@@ -1112,17 +1112,16 @@ int _mi_read_dynamic_record(MI_INFO *inf
LINT_INIT(to);
LINT_INIT(left_length);
file=info->dfile;
- block_info.next_filepos=filepos; /* for easyer loop */
- flag=block_info.second_read=0;
+ block_of_record= 0; /* First block of record is numbered as zero. */
+ block_info.second_read= 0;
do
{
if (info->opt_flag & WRITE_CACHE_USED &&
- info->rec_cache.pos_in_file <= block_info.next_filepos &&
+ info->rec_cache.pos_in_file < filepos + MI_BLOCK_INFO_HEADER_LENGTH &&
flush_io_cache(&info->rec_cache))
goto err;
info->rec_cache.seek_not_done=1;
- if ((b_type=_mi_get_block_info(&block_info,file,
- block_info.next_filepos))
+ if ((b_type= _mi_get_block_info(&block_info, file, filepos))
& (BLOCK_DELETED | BLOCK_ERROR | BLOCK_SYNC_ERROR |
BLOCK_FATAL_ERROR))
{
@@ -1130,9 +1129,8 @@ int _mi_read_dynamic_record(MI_INFO *inf
my_errno=HA_ERR_RECORD_DELETED;
goto err;
}
- if (flag == 0) /* First block */
+ if (block_of_record++ == 0) /* First block */
{
- flag=1;
if (block_info.rec_len > (uint) info->s->base.max_pack_length)
goto panic;
if (info->s->base.blobs)
@@ -1147,11 +1145,35 @@ int _mi_read_dynamic_record(MI_INFO *inf
}
if (left_length < block_info.data_len || ! block_info.data_len)
goto panic; /* Wrong linked record */
- if (my_pread(file,(byte*) to,block_info.data_len,block_info.filepos,
- MYF(MY_NABP)))
- goto panic;
- left_length-=block_info.data_len;
- to+=block_info.data_len;
+ /* copy information that is already read */
+ {
+ uint offset= (uint) (block_info.filepos - filepos);
+ uint prefetch_len= (sizeof(block_info.header) - offset);
+ filepos+= sizeof(block_info.header);
+
+ if (prefetch_len > block_info.data_len)
+ prefetch_len= block_info.data_len;
+ if (prefetch_len)
+ {
+ memcpy((byte*) to, block_info.header + offset, prefetch_len);
+ block_info.data_len-= prefetch_len;
+ left_length-= prefetch_len;
+ to+= prefetch_len;
+ }
+ }
+ /* read rest of record from file */
+ if (block_info.data_len)
+ {
+ if (info->opt_flag & WRITE_CACHE_USED &&
+ info->rec_cache.pos_in_file < filepos + block_info.data_len &&
+ flush_io_cache(&info->rec_cache))
+ goto err;
+ if (my_read(file, (byte*) to, block_info.data_len, MYF(MY_NABP)))
+ goto panic;
+ left_length-=block_info.data_len;
+ to+=block_info.data_len;
+ }
+ filepos= block_info.next_filepos;
} while (left_length);
info->update|= HA_STATE_AKTIV; /* We have a aktive record */
@@ -1310,9 +1332,9 @@ err:
int _mi_read_rnd_dynamic_record(MI_INFO *info, byte *buf,
register my_off_t filepos,
- my_bool skipp_deleted_blocks)
+ my_bool skip_deleted_blocks)
{
- int flag,info_read,save_errno;
+ int block_of_record, info_read, save_errno;
uint left_len,b_type;
byte *to;
MI_BLOCK_INFO block_info;
@@ -1338,7 +1360,8 @@ int _mi_read_rnd_dynamic_record(MI_INFO
else
info_read=1; /* memory-keyinfoblock is ok */
- flag=block_info.second_read=0;
+ block_of_record= 0; /* First block of record is numbered as zero. */
+ block_info.second_read= 0;
left_len=1;
do
{
@@ -1361,15 +1384,15 @@ int _mi_read_rnd_dynamic_record(MI_INFO
{
if (_mi_read_cache(&info->rec_cache,(byte*) block_info.header,filepos,
sizeof(block_info.header),
- (!flag && skipp_deleted_blocks ? READING_NEXT : 0) |
- READING_HEADER))
+ (!block_of_record && skip_deleted_blocks ?
+ READING_NEXT : 0) | READING_HEADER))
goto panic;
b_type=_mi_get_block_info(&block_info,-1,filepos);
}
else
{
if (info->opt_flag & WRITE_CACHE_USED &&
- info->rec_cache.pos_in_file <= filepos &&
+ info->rec_cache.pos_in_file < filepos + MI_BLOCK_INFO_HEADER_LENGTH &&
flush_io_cache(&info->rec_cache))
DBUG_RETURN(my_errno);
info->rec_cache.seek_not_done=1;
@@ -1380,7 +1403,7 @@ int _mi_read_rnd_dynamic_record(MI_INFO
BLOCK_FATAL_ERROR))
{
if ((b_type & (BLOCK_DELETED | BLOCK_SYNC_ERROR))
- && skipp_deleted_blocks)
+ && skip_deleted_blocks)
{
filepos=block_info.filepos+block_info.block_len;
block_info.second_read=0;
@@ -1394,7 +1417,7 @@ int _mi_read_rnd_dynamic_record(MI_INFO
}
goto err;
}
- if (flag == 0) /* First block */
+ if (block_of_record == 0) /* First block */
{
if (block_info.rec_len > (uint) share->base.max_pack_length)
goto panic;
@@ -1427,7 +1450,7 @@ int _mi_read_rnd_dynamic_record(MI_INFO
left_len-=tmp_length;
to+=tmp_length;
filepos+=tmp_length;
- }
+ }
}
/* read rest of record from file */
if (block_info.data_len)
@@ -1436,11 +1459,17 @@ int _mi_read_rnd_dynamic_record(MI_INFO
{
if (_mi_read_cache(&info->rec_cache,(byte*) to,filepos,
block_info.data_len,
- (!flag && skipp_deleted_blocks) ? READING_NEXT :0))
+ (!block_of_record && skip_deleted_blocks) ?
+ READING_NEXT : 0))
goto panic;
}
else
{
+ if (info->opt_flag & WRITE_CACHE_USED &&
+ info->rec_cache.pos_in_file <
+ block_info.filepos + block_info.data_len &&
+ flush_io_cache(&info->rec_cache))
+ goto err;
/* VOID(my_seek(info->dfile,filepos,MY_SEEK_SET,MYF(0))); */
if (my_read(info->dfile,(byte*) to,block_info.data_len,MYF(MY_NABP)))
{
@@ -1450,10 +1479,14 @@ int _mi_read_rnd_dynamic_record(MI_INFO
}
}
}
- if (flag++ == 0)
+ /*
+ Increment block-of-record counter. If it was the first block,
+ remember the position behind the block for the next call.
+ */
+ if (block_of_record++ == 0)
{
- info->nextpos=block_info.filepos+block_info.block_len;
- skipp_deleted_blocks=0;
+ info->nextpos= block_info.filepos + block_info.block_len;
+ skip_deleted_blocks= 0;
}
left_len-=block_info.data_len;
to+=block_info.data_len;
@@ -1485,6 +1518,11 @@ uint _mi_get_block_info(MI_BLOCK_INFO *i
if (file >= 0)
{
+ /*
+ We do not use my_pread() here because we want to have the file
+ pointer set to the end of the header after this function.
+ my_pread() may leave the file pointer untouched.
+ */
VOID(my_seek(file,filepos,MY_SEEK_SET,MYF(0)));
if (my_read(file,(char*) header,sizeof(info->header),MYF(0)) !=
sizeof(info->header))
| Thread |
|---|
| • bk commit into 4.0 tree (ingo:1.2184) BUG#20719 | ingo | 30 Jun |
