SQL Server mystery: Hekaton tables and Hekaton Procedures
Skrivet den 12 juni 2012 i T-SQL, SQL Server 2008, SQL Server 2008R2, SQL Server 2012, Level 500, SQL Server maintenance, Steinar Andersen, sv, en
Have you ever heard of Hekaton Tables and Hekaton Procedures in SQL Server? Neither had I until recently. And it seems neither have Google. I happened to stumble upon the mention of these mysterious object, and tried to find out more, but had no luck. But I wanted to share what I have seen of is so far, and ask you, the readers of our blog, if you might have some light to shed on this? If so, please comment on this blogpost.
To find the mention of Hekaton on your own SQL Server instance, run the following code:
select * from syscomments where text like '%hekaton%'
That should generate an output that indicates that sp_updatestats, sp_createstats and sp_recompile contains the word Hekaton.
The relevant lines of code are as follows:
from "sp_helptext sp_createstats":
-- filter out local temp tables, Hekaton tables, and tables for which current user has no permissions
-- Note that OBJECTPROPERTY returns NULL on type="IT" tables, thus we only call it on type='U' tables
if (
(@@fetch_status <> -2) and
(substring(@tablename, 1, 1) <> '#') and -- temp tables
((@table_type<>'U') or (0 = OBJECTPROPERTY(@table_id, 'TableIsInMemory'))) and -- Hekaton table
from "sp_helptext sp_updatestats"
-- filter out local temp tables and Hekaton tables
-- Note that OBJECTPROPERTY returns NULL on type="IT" tables, thus we only call it on type='U' tables
if ((@@fetch_status <> -2) and
(substring(@table_name, 1, 1) <> '#') and -- temp tables
((@table_type<>'U') or (0 = OBJECTPROPERTY(@table_id, 'TableIsInMemory')))) -- Hekaton tables
from "sp_helptext sp_recompile"
-- Hekaton procedure cannot be recompiled
-- Make them go through schema version bumping branch, which will fail
ObjectProperty(@objid, 'ExecIsCompiledProc') = 0)
None of that really tells us exactly what Hekaton tables and Hekaton procedures are, but might give some clues. The undocumented OBJECTPROPERTY(@table_id, 'TableIsInMemory') call (another mystery...) seems to indicate that it could possibly be connected to memory, caching or even the old and removed feature of DBCC PINTABLE? That would be a real surprise in that case.
The comments tells us the following: Hekaton Procedures cannot be recompiled using sp_recompile Hekaton tables can not update or create stats using sp_updatestats and sp_createstats
I know that this is not much, but if you have more information about this little mystery, please comment it on this blogpost or mail me at firstname.lastname@sqlservice.se