Is there a process to shrink "unused" space in specific tables

Products

• Management Platform (Formerly known as Notification Server)

Issue/Introduction

 

Resolution

Question

Customer has a report they run that shows table space usage. (See query blelow).

Some of these tables are using very little space but have many GBs of unused space . For example the SavedReport table is using 1480KB but has 16461624 of unused space. Is there a way to free up this unused space?

declare @id int      
declare @type character(2)      
declare @pages int      
declare @dbname sysname     
declare @dbsize dec(15,0)     
declare @bytesperpage dec(15,0)     
declare @pagesperMB dec(15,0)     
     
create table #spt_space     
(     
objid int null,     
rows int null,     
reserved dec(15) null,     
data dec(15) null,     
indexp dec(15) null,     
unused dec(15) null     
)     
     
set nocount on     
     
-- Create a cursor to loop through the user tables     
declare c_tables cursor for     
select id     
from sysobjects     
where xtype = 'U'     
     
open c_tables     
     
fetch next from c_tables     
into @id     
     
while @@fetch_status = 0     
begin     
     
/* Code from sp_spaceused */     
insert into #spt_space (objid, reserved)     
select objid = @id, sum(reserved)     
from sysindexes     
where indid in (0, 1, 255)     
and id = @id     
     
select @pages = sum(dpages)     
from sysindexes     
where indid < 2     
and id = @id     
select @pages = @pages + isnull(sum(used), 0)     
from sysindexes     
where indid = 255     
and id = @id     
update #spt_space     
set data = @pages     
where objid = @id     
     
     
/* index: sum(used) where indid in (0, 1, 255) - data */     
update #spt_space     
set indexp = (select sum(used)     
from sysindexes     
where indid in (0, 1, 255)     
and id = @id)     
- data     
where objid = @id     
     
/* unused: sum(reserved) - sum(used) where indid in (0, 1, 255) */     
update #spt_space     
set unused = reserved     
- (select sum(used)     
from sysindexes     
where indid in (0, 1, 255)     
and id = @id)     
where objid = @id     
     
update #spt_space     
set rows = i.rows     
from sysindexes i     
where i.indid < 2     
and i.id = @id     
and objid = @id     
     
fetch next from c_tables     
into @id     
end     
     
     
select top 50  
Table_Name = (select left(name,25) from sysobjects where id = objid),     
rows = convert(char(11), rows),     
reserved_KB = ltrim(str(reserved * d.low / 1024.,15,0)),     
data_KB = ltrim(str(data * d.low / 1024.,15,0)),     
index_size_KB = ltrim(str(indexp * d.low / 1024.,15,0)),     
unused_KB = ltrim(str(unused * d.low / 1024.,15,0))     
     
from #spt_space, master.dbo.spt_values d     
where d.number = 1     
and d.type = 'E'     
order by reserved desc   
     
drop table #spt_space     
close c_tables     
deallocate c_tables

 

Answer

 The “Rebuild Index Task” in a maintenance plan should shrink these tables automatically. However, if you have the “Keep index online while reindexing” checked in the Maintenace Plan, specific tables may NOT be reindexed due to locks. The recommendation is to make sure that “Keep index online while reindexing” is unchecked.

There isn’t a SQL Server shrink command to shrink just a table other than dbcc shrinkdatabase or dbcc shrinkfile which will shrink the entire database. However, dbcc  INDEXDEFRAG <tablename> should defrag and shrink the table.