Re: #Personal#: Reg: Multiple queries in a transaction

From: Medhavi Mahansaria <medhavi(dot)mahansaria(at)tcs(dot)com>
To: Kevin Grittner <kgrittn(at)ymail(dot)com>
Cc: "pgsql-general(at)postgresql(dot)org" <pgsql-general(at)postgresql(dot)org>
Subject: Re: #Personal#: Reg: Multiple queries in a transaction
Date: 2015-02-19 05:41:59
Message-ID: OF71A79966.4D246CA6-ON65257DF1.001ED70D-65257DF1.001F4F75@tcs.com
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Hi Kevin,

Thanks!

But savepoint concept will not work for me as desired.

Is there any other way apart from SAVEPOINT that can be incorporated.

I am not using a script. I am writing a c++ program.

My problem is that I have 2 cases:

Case 1: When Q2 fails (we delete the error), i want to continue to Q3 and commit changes done by Q1 and Q3 once Q3 has executed successfully.

Case 2: When Q2 fails, I want it to throw an error. and rollback the changes made by Q1 and not proceed to Q3 at all.

Note: This is just a small example. I need a solution for an entire application which follows the same concept across multiple queries.

How can I incorporate this?

Thanks & Regards
Medhavi Mahansaria
Tata Consultancy Services Limited
Unit-VI, No.78, 79& 83,
L-Centre, EPIP Industrial Estate,
Whitefield
Bangalore - 560066,Karnataka
India
Ph:- +91 80 67253769
Cell:- +91 9620053040
Mailto: medhavi(dot)mahansaria(at)tcs(dot)com
Website: http://www.tcs.com
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-----Kevin Grittner <kgrittn(at)ymail(dot)com> wrote: -----
To: Medhavi Mahansaria <medhavi(dot)mahansaria(at)tcs(dot)com>, "pgsql-general(at)postgresql(dot)org" <pgsql-general(at)postgresql(dot)org>
From: Kevin Grittner <kgrittn(at)ymail(dot)com>
Date: 02/18/2015 09:40PM
Subject: Re: [GENERAL] #Personal#: Reg: Multiple queries in a transaction

Medhavi Mahansaria <medhavi(dot)mahansaria(at)tcs(dot)com> wrote:

> I need to execute a series of queries
> in a transaction, say Q1, Q2, Q3.
>
> Q1 -> success
> Q2 -> Failed
> Q3 -> Success
>
> My issue is that after Q2 fails all
> the queries that follow give error"ERROR: current transaction
> is aborted, commands ignored until end of transaction block"
>
> I want to move ahead in the transaction
> and execute Q3 also even though Q2 was a failure.
>
> Can you please suggest a way to do so
> in PostgreSQL 9.3.
>
> Is there a way to turn autocommit off?

The server does not support that, but if you're running a script
through psql you should look at using:

\set ON_ERROR_ROLLBACK on

Docs at:

http://www.postgresql.org/docs/9.3/interactive/app-psql.html

If you are not using psql you can use savepoints:

http://www.postgresql.org/docs/8.4/interactive/sql-savepoint.html

ROLLBACK TO SAVEPOINT if the statement fails.

--
Kevin Grittner
EDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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