pbxt-discuss team mailing list archive

[Brian Aker <brian@xxxxxxxxxxx>]

Hi!

What are you using Table for? The table definition should have everything you need in it for defining the table. "Table" in drizzle is just a collection of caches used by a Cursor. TableShare, beyond its uses in locking, is just an interface to the information found in the table definition.

Cheers,
	-Brian

On May 14, 2010, at 12:38 AM, Paul McCullagh wrote:

> Hi Brian,
> 
> As far as I know, getTableDefinition() just returns the protobuf of the table.
> 
> What I need is a "class Table" (table.h) reference.
> 
> This structure is usually one per thread (i.e. some methods use instance variables).
> 
> However, I share one pointer between all threads, because I don't use any of the methods that address instance variables.
> 
> (Of course it would make more sense to move the methods that independent of instance variables to TableShare).
> 
> On May 11, 2010, at 2:43 AM, Brian Aker wrote:
> 
>> Hi!
>> 
>> If you know the table name you can do a getTableDefinition() for the table and get back the definition. Do you need anything beyond that?
>> 
>> Cheers,
>> 	-Brian
>> 
>> On May 10, 2010, at 1:20 AM, Paul McCullagh wrote:
>> 
>>> 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
>>> 
>>> 
>>> 
>> 
> 
> 
> 
> --
> Paul McCullagh
> PrimeBase Technologies
> www.primebase.org
> www.blobstreaming.org
> pbxt.blogspot.com
> 
> 
>