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Added read log caching and fixed a possible bug in write cacheing.

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This should cause fewer seeks when using replication.


Docs/manual.texi:
  Changelog
This commit is contained in:
unknown 2001-11-28 15:18:29 +02:00
commit 00d80ffff1
2 changed files with 25 additions and 6 deletions
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27
mysys/mf_iocache2.c
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@ -32,20 +32,35 @@
void my_b_seek(IO_CACHE *info,my_off_t pos)
{
my_off_t offset = (pos - info->pos_in_file);
DBUG_ENTER("my_b_seek");
DBUG_PRINT("enter",("pos: %lu", (ulong) pos));
if (info->type == READ_CACHE)
{
info->rc_pos=info->rc_end=info->buffer;
if ((ulonglong) offset < (ulonglong) (info->rc_end - info->buffer))
{
/* The read is in the current buffer; Reuse it */
info->rc_pos = info->buffer + offset;
DBUG_VOID_RETURN;
}
else
{
/* Force a new read on next my_b_read */
info->rc_pos=info->rc_end=info->buffer;
}
}
else if (info->type == WRITE_CACHE)
{
byte* try_rc_pos;
try_rc_pos = info->rc_pos + (pos - info->pos_in_file);
if (try_rc_pos >= info->buffer && try_rc_pos <= info->rc_end)
/* If write is in current buffer, reuse it */
if ((ulonglong) offset <
(ulonglong) (info->rc_end - info->buffer))
{
info->rc_pos = try_rc_pos;
return;
info->rc_pos = info->buffer + offset;
DBUG_VOID_RETURN;
}
flush_io_cache(info);
info->rc_end=(info->buffer+info->buffer_length-(pos & (IO_SIZE-1)));
}
info->pos_in_file=pos;
info->seek_not_done=1;