pbxt-discuss team mailing list archive

[Paul McCullagh <paul.mccullagh@xxxxxxxxxxxxx>]

Yup, This is a C hack, so I agree it should be done differently for  
Drizzle.

my_close_table() is only used to close "tables" opened by  
my_open_table().

In my_open_table() we have:

	if (!(buffer = (char *) xt_malloc(self, size)))
		return NULL;
	table = (TABLE *) buffer;
	buffer += sizeof(TABLE);
	share = (TABLE_SHARE *) buffer;

So things have been setup so that:

 share == (TABLE_SHARE *) ((char *) table + sizeof(TABLE))

To get rid of this hack, we need to look at the purpose of this code:

PBXT requires a reference (or a copy of) the internal MySQL/Drizzle  
data dictionary (i.e. the structure that is created when a .frm file  
is loaded).

This is required for 2 purposes:

1. To determine the internal MySQL row and key structures.
2. PBXT uses reference to MySQL collation sequence based comparison  
routines.

MySQL/Drizzle supply this reference when opening a table handler.  
However, for PBXT this is not good enough, because there are  
background threads (like the recovery thread) that need the  
information as well.

Ideally Drizzle would supply a set of callback services. One of these  
would be to get a reference to Drizzle data dictionary for a table,  
and another would be a function to release the reference.

Then I could remove the hack for the Drizzle case entirely.

On May 9, 2010, at 1:24 AM, Brian Aker wrote:

> Hi!
>
> This code:
>
> static void my_close_table(TABLE *table)
> {
> #ifdef DRIZZLED
>        TABLE_SHARE     *share;
>
>        share = (TABLE_SHARE *) ((char *) table + sizeof(TABLE));
>        share->free_table_share();
> #else
>        delete_table(table, true);  // TODO: Q, why did Stewart  
> remove this?
> #endif
>        xt_free_ns(table);
> }
>
>
> This is not going to go well in Drizzle, since we the assumption  
> that the memory allocation will be aligned this way is wrong. In my  
> local tree I am going to drop the free_table_share().
>
> I'm not really sure what to do though. I believe what you will be  
> wanting to do is call delete on table->s, though if what you are  
> using is an TableInstance then it should clean up just fine on its  
> own.
>
> Is there something I can do to make this code a bit more  
> straightforward for you?
>
> Cheers,
> 	-Brian
>
>
>
>
>
>
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--
Paul McCullagh
PrimeBase Technologies
www.primebase.org
www.blobstreaming.org
pbxt.blogspot.com