Field Level Auditing using Change Data Capture – Part 2

  • David Balthrop

    SSC Veteran

    Points: 212

    Comments posted to this topic are about the item Field Level Auditing using Change Data Capture – Part 2

  • TheSpyder

    SSC Enthusiast

    Points: 163

    What could be better you ask. How about doing it all in the database and leaving out he SSIS stuff. I had an occasion in the old 2000 days when I needed to move to a new server. The database was no problem but we had loads of DTS jobs to maintain the Disaster Recovery and Data Warehouse. That was a nightmare. Since then, I've tried to do everything with stored procedures and SQL Agent jobs which makes moving from one server to another a doddle.

    Perhaps SSIS is easier to move than DTS? I have yet to get my fingers dirty with it. I'd be interested in your comments.

  • David Balthrop

    SSC Veteran

    Points: 212

    Unless the database table structures are changing, switching an SSIS job from one server to another is pretty straight forward. The configuration information for the database connections should be stored either in a config file or in a database, simiply change that connection information to point at the new server.

    If the table structures are changing, CDC does not handle that automagically. See the posts on Part 1 article on example of how to update CDC with DDL changes.

    CDC does have it's draw backs, to track who is making the changes you have to add user information to your tables and change the data access to save that data. Some people may not need that level of control. But if you are working on aa application that shullfes billions of dollars a year, it is pretty important to be able to answer "who made that change"?

    But beyond auditing, there are other uses for CDC like ETL processing for delta updates, load use reports, etc. Still say it's cool.

  • tutupouet

    SSCommitted

    Points: 1512

    There is an error in [CDCDemo].[dbo].[spgGetCDCContract]

    replace

    SET @from_lsn = sys.fn_cdc_map_time_to_lsn('largest greater than', @FromLSNDate);

    by

    SET @from_lsn = sys.fn_cdc_map_time_to_lsn('smallest greater than', @FromLSNDate);

  • e.t.anicet

    SSC Enthusiast

    Points: 151

    Hi David

    I did try several times your demonstration but I couldn't get the stagingCdcContract Table populate with data.

    When I run the stored procedure "Exec [dbo].[sPgGetCDCContract] @FromLSNDate=?, @ToLSNDate=?" I get an empty table in return, So I don't know whether I have done something wrong or the stored procedure has an mistake.

    Here is the [sPgGetCDCContract] code:

    USE [CDCDemo]

    GO

    /****** Object: StoredProcedure [dbo].[sPgGetCDCContract] Script Date: 11/12/2011 15:43:18 ******/

    SET ANSI_NULLS ON

    GO

    SET QUOTED_IDENTIFIER ON

    GO

    CREATE PROCEDURE [dbo].[sPgGetCDCContract]

    @FromLSNDate as datetime,

    @ToLSNDate as datetime

    AS

    begin

    SET NOCOUNT ON

    SET ROWCOUNT 0

    declare @from_lsn binary(10)

    declare @to_lsn binary(10)

    SET @from_lsn = sys.fn_cdc_map_time_to_lsn('smallest greater than', @FromLSNDate);

    SET @to_lsn = sys.fn_cdc_map_time_to_lsn('largest less than or equal', @ToLSNDate);

    if (@from_lsn is not null and @to_lsn is not null and @from_lsn < @to_lsn)

    begin

    DECLARE @name_ordinal int

    DECLARE @year_ordinal int

    DECLARE @length_ordinal int

    DECLARE @type_ordinal int

    DECLARE @amount_ordinal int

    DECLARE @last_change_id_ordinal int

    SET @name_ordinal = sys.fn_cdc_get_column_ordinal('dbo_contract','name')

    SET @year_ordinal = sys.fn_cdc_get_column_ordinal('dbo_contract','year')

    SET @length_ordinal = sys.fn_cdc_get_column_ordinal('dbo_contract','length')

    SET @type_ordinal = sys.fn_cdc_get_column_ordinal('dbo_contract','type')

    SET @amount_ordinal = sys.fn_cdc_get_column_ordinal('dbo_contract','amount')

    SET @last_change_id_ordinal = sys.fn_cdc_get_column_ordinal('dbo_contract','last_change_id')

    SELECT cdc.fn_cdc_get_all_changes_dbo_contract.*,

    sys.fn_cdc_map_lsn_to_time(__$start_lsn) as 'last_change_date',

    cast(isnull(user_name, '') as varchar(100)) as 'last_change_name',

    sys.fn_cdc_is_bit_set(@name_ordinal,__$update_mask) as 'IsNameUpdated',

    sys.fn_cdc_is_bit_set(@year_ordinal,__$update_mask) as 'IsYearUpdated',

    sys.fn_cdc_is_bit_set(@length_ordinal,__$update_mask) as 'IsLengthUpdated',

    sys.fn_cdc_is_bit_set(@type_ordinal,__$update_mask) as 'IsTypeUpdated',

    sys.fn_cdc_is_bit_set(@amount_ordinal,__$update_mask) as 'IsAmountUpdated',

    sys.fn_cdc_is_bit_set(@last_change_id_ordinal,__$update_mask) as 'IsLastChangeIdUpdated'

    FROM cdc.fn_cdc_get_all_changes_dbo_contract( @from_lsn, @to_lsn, 'all')

    left join Users

    on Users.user_id = fn_cdc_get_all_changes_dbo_contract.last_change_id

    end

    else

    begin

    -- return empty row

    select cdc.dbo_contract_CT.*,

    getdate() as 'last_change_date',

    '' as 'last_change_name',

    cast(0 as bit) as 'IsNameUpdated',

    cast(0 as bit) as 'IsYearUpdated',

    cast(0 as bit) as 'IsLengthUpdated',

    cast(0 as bit) as 'IsTypeUpdated',

    cast(0 as bit) as 'IsAmountUpdated',

    cast(0 as bit) as 'IsLastChangeIdUpdated'

    from cdc.dbo_contract_CT

    where __$start_lsn = 0x00000000000000000000

    end

    end

    GO

    Thanks

  • David Balthrop

    SSC Veteran

    Points: 212

    Am gussing it has something to do with the From or To LSN values, do you get any data back if you run this query directly against the CDCDemo database, this should verify that the change table is returning data:

    DECLARE @from_lsn binary(10), @to_lsn binary(10)

    SET @from_lsn =

    sys.fn_cdc_get_min_lsn('dbo_contract')

    SET @to_lsn = sys.fn_cdc_get_max_lsn()

    SELECT * FROM cdc.fn_cdc_get_all_changes_dbo_contract( @from_lsn, @to_lsn, 'all')

    GO

  • e.t.anicet

    SSC Enthusiast

    Points: 151

    Hi David,

    Thanks to reply, yes I get data back when I run this last query against CDCDemo database:

    DECLARE @from_lsn binary(10), @to_lsn binary(10)

    SET @from_lsn =

    sys.fn_cdc_get_min_lsn('dbo_contract')

    SET @to_lsn = sys.fn_cdc_get_max_lsn()

    SELECT * FROM cdc.fn_cdc_get_all_changes_dbo_contract( @from_lsn, @to_lsn, 'all')

    GO

  • David Balthrop

    SSC Veteran

    Points: 212

    ok, that's good. Let's try this next to see if the stored procedure can be run by itself.

    -- get the @FromLSNDate date

    use [CDCDW]

    go

    exec [spgGetCDCHistoryLastLSNDate] @cdcTable='dbo_contract'

    go

    -- get the @ToLSNDate date

    use [CDCDemo]

    go

    exec [spgGetCDCMaxLSNDate]

    go

    -- substitute the dates returned above here and see if this returns results

    exec [spgGetCDCContract] @FromLSNDate='2011-09-01 14:08:45.000', @ToLSNDate='2011-10-17 15:46:02.013'

  • e.t.anicet

    SSC Enthusiast

    Points: 151

    When I try this:

    -- get the @FromLSNDate date

    use [CDCDW]

    go

    exec [spgGetCDCHistoryLastLSNDate] @cdcTable='dbo_contract'

    go

    -- get the @ToLSNDate date

    use [CDCDemo]

    go

    exec [spgGetCDCMaxLSNDate]

    go

    -- substitute the dates returned above here and see if this returns results

    exec [spgGetCDCContract] @FromLSNDate='2011-11-15 09:18:39.000', @ToLSNDate='2011-11-15 09:23:40.700'

    I still get no data back!

  • e.t.anicet

    SSC Enthusiast

    Points: 151

    Hi David,

    have you still investigate in that stored procedure: "spgGetCDCContract", why I could not get data back when I try what you asked me to do?

    Thanks

  • David Balthrop

    SSC Veteran

    Points: 212

    Sorry for the delay, think the problem may be in the history table timestamp, I've had trouble getting that to initialize correctly.

    But before changing that, try this to make sure the stored procedure is working. This should use the min LSN date from the change table that worked before instead of the history date:

    declare @from_lsn binary(10)

    declare @from_date as datetime

    SET @from_lsn = sys.fn_cdc_get_min_lsn('dbo_contract');

    set @from_date = sys.fn_cdc_map_lsn_to_time(@from_lsn);

    exec [spgGetCDCContract] @FromLSNDate=@from_date, @ToLSNDate='2011-11-15 09:23:40.700'

    If that works, then change the cdcHistory table initial timestamp to the change table min LSN date:

    delete from cdcHistory

    go

    declare @from_lsn binary(10)

    declare @from_date as datetime

    SET @from_lsn = sys.fn_cdc_get_min_lsn('dbo_contract');

    set @from_date = sys.fn_cdc_map_lsn_to_time(@from_lsn);

    insert into [cdcHistory]

    values ('dbo_contract', @from_date)

    go

  • e.t.anicet

    SSC Enthusiast

    Points: 151

    Hi,

    There is someone who can also check this stored procedure : "spgGetCDCContract" ?

    Thanks

  • jjarboe

    Newbie

    Points: 6

    If you look at the comment just above your first entry saying you get no data, SSC Rookie has the fix. I did something similar by using this:

    SET @from_lsn = isnull(sys.fn_cdc_map_time_to_lsn('largest less than', @FromLSNDate),sys.fn_cdc_get_min_lsn('dbo_Contract'));

    The problem is that there is nothing 'largest less than' your date in the cdc.lsn_time_mapping table.

  • jjarboe

    Newbie

    Points: 6

    See SSC Rookie's fix and you will get data.

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