Category Archives: SQL Server

How PostgreSQL stores the oversized or extended fields?

Recently I was loading the very large analytics data set to the PosgreSQL table and compare to the rows/tuples size, table has claimed the around 200X of the storage. Upon the investigation I found the issue related to toast bloating and have to reclaim the space. Let’s learn about the toast table in this article.

PostgreSQL loads and stores the data into pages. The page size is commonly 8KB. The page is used to store tuples, indexes etc. Even WAL files are written 8KB pages. Therefore it is not possible to store the very large field values directly to the page. To store the large filed values, PostgreSQL compresses the values and sliced into multiple rows. This technique is known as TOAST. TOAST the values (compressing and slicing) will also help handling large values in the memory.

Toast is enabled by default and all tables will have the toast table associated with it. You can check the toast table by querying the pg_class. Toast tables are resides in the PG_Toast schema.

select relname from pg_class where oid = (select reltoastrelid from pg_class where relname=’TABLE_NAME’)

or

select oid, relname,reltoastrelid, relkind from pg_class where relname = ‘table name’

select oid, relname, relkind from pg_class where oid = ‘reltoastrelid from above query’

In the next article we will check more information about the toast table bloating and how to reclaim the space from toast table.

T-SQL Script to get the Symantec NETBACKUP Version and Patch Information

You can execute below script to get Symantec NETBACKUP version and patch information.

set nocount on

CREATE TABLE #OUTPUT(
	[SQLInstanceName] [nvarchar](128) NULL,
	[WindowsServerName] [varchar](30) NULL,
	[NetBackupClientVersion] [varchar](255) NULL,
	[NetBackupPatchVersion] [varchar](255) NULL,
	[NetbackupStatusCheck] [varchar](28) NULL
) 

declare @regkeyval varchar(20), @value varchar(255), @rc int
exec @rc=master.dbo.xp_regread 
  @rootkey= 'HKEY_LOCAL_MACHINE',
  @key='SOFTWARE\Veritas\NetBackup\CurrentVersion\',
  @value_name='VERSION',
  @regkeyval=@value output

set @value =isnull(@value,'-')

declare @Pvalue varchar(255)
exec @rc=master.dbo.xp_regread 
  @rootkey= 'HKEY_LOCAL_MACHINE',
  @key='SOFTWARE\Veritas\Patches\NetBackup\',
  @value_name='PatchLevel',
  @regkeyval=@Pvalue output

set @Pvalue =isnull(@Pvalue,'-')

if @value <> '-'
insert into #OUTPUT(SQLInstanceName,WindowsServerName,NetBackupClientVersion,NetBackupPatchVersion,NetbackupStatusCheck)
select 
 @@servername as SQLInstanceName
,case serverproperty('IsClustered') when 1 then cast(serverproperty('computernamephysicalnetbios') as varchar)
 else cast(serverproperty('machinename') as varchar)
 end as WindowsServerName
,@value as NetBackupClientVersion 
,@Pvalue as NetBackupPatchVersion
,'NetBkup is installed' as NetbackupStatusCheck 
else
insert into #OUTPUT(SQLInstanceName,WindowsServerName,NetbackupStatusCheck,NetBackupClientVersion,NetBackupPatchVersion)
select 
 @@servername as SQLInstanceName
,case serverproperty('IsClustered') when 1 then cast(serverproperty('computernamephysicalnetbios') as varchar)
 else cast(serverproperty('machinename') as varchar)
 end as WindowsServerName
,'NetBkup nt installed' as NetbackupStatusCheck
,'0' as NetBackupClientVersion
,'0' as NetBackupPatchVersion 

select * from #OUTPUT

T-SQL Script to check Powershell Version

You can write $host command on powershell prompt to check powershell version or you can execute the below T-SQL script to check the powershell version.

declare @regkeyval varchar(20), @value varchar(255), @rc int
exec @rc=master.dbo.xp_regread 
  @rootkey= 'HKEY_LOCAL_MACHINE',
  @key='SOFTWARE\Microsoft\PowerShell\1\PowerShellEngine',
  @value_name='PowerShellVersion',
  @regkeyval=@value output


set @value =isnull(@value,'-') 

if @value <> '-'
select 
 @@servername as SQLInstanceName
,case serverproperty('IsClustered') when 1 then cast(serverproperty('computernamephysicalnetbios') as varchar)
 else cast(serverproperty('machinename') as varchar)
 end as WindowsServerName
,@value as PSClientVersion 
,'PS is installed' as PSStatusCheck 
else
insert into #OUTPUT(SQLInstanceName,WindowsServerName,PSStatusCheck)
select 
 @@servername as SQLInstanceName
,case serverproperty('IsClustered') when 1 then cast(serverproperty('computernamephysicalnetbios') as varchar)
 else cast(serverproperty('machinename') as varchar)
 end as WindowsServerName
,'PS nt installed' as PSStatusCheck 

Script to list out SQL Logins and Database User Mappings

You can use system stored procedure sp_msloginmappings to list out the SQL logins and database user mappings.

Syntax
sp_msloginmappings @Loginname , @Flags

@Loginname – Optional argument, in case if you not specify the Login name procedure will return the result for all the SQL Server logins
@Flags – You can specify value 0 or 1, 0 value will show user mapping to all databases and 1 will show the user mapping to current database only. Default value is 0

use master
go
exec sp_msloginmappings 'sa', 0

Image2

use master
go
exec sp_msloginmappings 'sa', 1

Image1

In case you want to run the sp_msloginmappings across multiple SQL Instance using either Central management server or powershell. You can use the below script.

 create table #loginmappings(  
  LoginName  nvarchar(128) NULL,  
  DBName     nvarchar(128) NULL,  
  UserName   nvarchar(128) NULL,  
  AliasName  nvarchar(128) NULL  
 )  
 
 insert into #loginmappings
 EXEC master..sp_msloginmappings
 
 select * from #loginmappings
 
 drop table #loginmappings