Received: from malur.postgresql.org ([217.196.149.56]) by arkaria.postgresql.org with esmtp (Exim 4.84_2) (envelope-from ) id 1eE9Dn-0003nr-Gv for pgsql-sql@arkaria.postgresql.org; Mon, 13 Nov 2017 07:31:55 +0000 Received: from localhost ([127.0.0.1] helo=postgresql.org) by malur.postgresql.org with smtp (Exim 4.84_2) (envelope-from ) id 1eE9Dm-0004oB-Qn for pgsql-sql@arkaria.postgresql.org; Mon, 13 Nov 2017 07:31:54 +0000 Received: from magus.postgresql.org ([2a02:c0:301:0:ffff::29]) by malur.postgresql.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA384:256) (Exim 4.84_2) (envelope-from ) id 1eE9Dl-0004nA-NP for pgsql-sql@postgresql.org; Mon, 13 Nov 2017 07:31:53 +0000 Received: from mail.inqbus.de ([2a00:b6c0:1108::1c8c]) by magus.postgresql.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.89) (envelope-from ) id 1eE9Dd-0002gB-Ji for pgsql-sql@postgresql.org; Mon, 13 Nov 2017 07:31:53 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=stb-datenservice.de; s=20160215; h=Content-Type:In-Reply-To:MIME-Version: Date:Message-ID:From:References:To:Subject:Sender:Reply-To:Cc: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=Css38rkv2hwIpNUfg0grm4Ya70PAc12+ke1pbJZpf/4=; b=mIeWDYOB8BbIbgjuD5RHzUs+p 7FqV2w+v5kMfYH+29P0cX2gxXZm59/GF4iIIZDSlzR8l9ex5PSUIU6bWZadeubGfWGFC0VyYBe1DY qEQacfrf6/Jt66ZtiOlC6yJxNA/Or+YZzEPH4PconT+pPsKFs2EG/An9OAEAKNIK5PYqg=; Received: from ip9234fcfc.dynamic.kabel-deutschland.de ([146.52.252.252]:61763 helo=[192.168.178.254]) by mail.inqbus.de with esmtpa (Exim 4.88) (envelope-from ) id 1eE9DZ-0002EM-Bk for pgsql-sql@postgresql.org; Mon, 13 Nov 2017 08:31:42 +0100 Subject: Re: md5 checksum of a previous row To: pgsql-sql@postgresql.org References: From: "MS (direkt)" Message-ID: <95a944da-e4f2-2500-b917-6aa825a28f03@stb-datenservice.de> Date: Mon, 13 Nov 2017 08:31:40 +0100 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: multipart/alternative; boundary="------------31DB56C069E94193EA2102F3" Content-Language: de List-Archive: List-Help: List-ID: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: X-Mailing-List: pgsql-sql Precedence: bulk Sender: pgsql-sql-owner@postgresql.org This is a multi-part message in MIME format. --------------31DB56C069E94193EA2102F3 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Hi, you can easily join the preceeding row, e.g. select sub.id, sub.created_at, preceedingid, m2.* from ( select m.id, m.created_at, lag(m.id) over(order by m.created_at) as preceedingid from test m order by m.created_at) as sub left join test m2 on m2.id=sub.preceedingid order by sub.created_at; Regards, Martin Am 13.11.2017 um 07:15 schrieb Iaam Onkara: > Hi, > > I have a requirement to create an tamper proof chain of records for > audit purposes. The pseudo code is as follows > > before_insert: > 1. compute checksum of previous row (or conditionally selected row) > 2. insert the computed checksum in the current row > 3. using on-update or on-delete trigger raise error to prevent > update/delete of any row. > > Here are the different options that I have tried using lag and md5 > functions > > http://www.sqlfiddle.com/#!17/69843/2 > > > CREATE TABLE test >     ("id" uuid DEFAULT uuid_generate_v4() NOT NULL, >      "value" decimal(5,2) NOT NULL, >      "delta" decimal(5,2), >      "created_at" timestamp default current_timestamp, >      "words" text, >      CONSTRAINT pid PRIMARY KEY (id) >     ) > ; > > INSERT INTO test >     (value, words) > VALUES >     (51.0, 'A'), >     (52.0, 'B'), >     (54.0, 'C'), >     (57.0, 'D') > ; > > select >   created_at, value, >   value - lag(value, 1, 0.0) over(order by created_at) as delta, >   md5(lag(words,1,words) over(order by created_at)) as the_word, >   md5(textin(record_out(test))) as Hash > FROM test >   ORDER BY created_at; > > But how do I use lag function or something like lag to read the > previous record as whole. > > Thanks, > Onkara > PS: This was earlier posted in 'pgsql-in-general' mailing list, but I > think this is a more appropriate list, if I am wrong I am sorry -- Widdersdorfer Str. 415, 50933 Köln; Tel. +49 / 221 / 9544 010 HRB Köln HRB 75439, Geschäftsführer: S. Böhland, S. Rosenbauer --------------31DB56C069E94193EA2102F3 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: 8bit Hi,

you can easily join the preceeding row, e.g.

select sub.id, sub.created_at, preceedingid, m2.* from (
select m.id, m.created_at, lag(m.id) over(order by m.created_at) as preceedingid from test m
order by m.created_at) as sub
left join test m2 on m2.id=sub.preceedingid order by sub.created_at;

Regards, Martin

Am 13.11.2017 um 07:15 schrieb Iaam Onkara:
Hi,

I have a requirement to create an tamper proof chain of records for audit purposes. The pseudo code is as follows

before_insert:
1. compute checksum of previous row (or conditionally selected row)
2. insert the computed checksum in the current row
3. using on-update or on-delete trigger raise error to prevent update/delete of any row.

Here are the different options that I have tried using lag and md5 functions

http://www.sqlfiddle.com/#!17/69843/2

CREATE TABLE test
    ("id" uuid DEFAULT uuid_generate_v4() NOT NULL,
     "value" decimal(5,2) NOT NULL,
     "delta" decimal(5,2),
     "created_at" timestamp default current_timestamp,
     "words" text,
     CONSTRAINT pid PRIMARY KEY (id)
    )
;
   
INSERT INTO test
    (value, words)
VALUES
    (51.0, 'A'),
    (52.0, 'B'),
    (54.0, 'C'),
    (57.0, 'D')
;

select
  created_at, value,
  value - lag(value, 1, 0.0) over(order by created_at) as delta,
  md5(lag(words,1,words) over(order by created_at)) as the_word,
  md5(textin(record_out(test))) as Hash
FROM test
  ORDER BY created_at;

But how do I use lag function or something like lag to read the previous record as whole.

Thanks,
Onkara
PS: This was earlier posted in 'pgsql-in-general' mailing list, but I think this is a more appropriate list, if I am wrong I am sorry

-- 
Widdersdorfer Str. 415, 50933 Köln; Tel. +49 / 221 / 9544 010
HRB Köln HRB 75439, Geschäftsführer: S. Böhland, S. Rosenbauer
--------------31DB56C069E94193EA2102F3--