From: | Dann Corbit <DCorbit(at)connx(dot)com> |
---|---|
To: | 'Konstantin Izmailov' <pgfizm(at)gmail(dot)com>, "pgsql-general(at)postgresql(dot)org" <pgsql-general(at)postgresql(dot)org> |
Subject: | Re: Does Postgres support bookmarks (tuples ids)? |
Date: | 2010-12-01 06:13:35 |
Message-ID: | 87F42982BF2B434F831FCEF4C45FC33E4209AE91@EXCHANGE.corporate.connx.com |
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Lists: | pgsql-general |
Is your application by chance using OLEDB?
If that is the case, then just get a PostgreSQL OLEDB provider that supports bookmarks.
From: pgsql-general-owner(at)postgresql(dot)org [mailto:pgsql-general-owner(at)postgresql(dot)org] On Behalf Of Konstantin Izmailov
Sent: Tuesday, November 30, 2010 9:50 PM
To: pgsql-general(at)postgresql(dot)org
Subject: [GENERAL] Does Postgres support bookmarks (tuples ids)?
Dear experts,
I've noticed that commercial databases (e.g. SQLServer) and some open source databases (e.g. Cubrid) support so called "bookmarks".
As far as I understood, a bookmark allows quickly jump to a row for retrieval or modification.
Here is scenario that I'm trying to deal with:
A BI/ETL application is querying the Postgres database. The queries return lots of rows (36 mil), each is about 1KB or larger.
So I'm using DECLARE CURSOR/FETCH to read the rows into a buffer (size is 10000 rows, and I'm freeing memory for oldest rows).
The application may alter or re-read some previously read rows by the row index.
Problem is: if a row is not in the buffer (freed) the application cannot resolve row index into row itself.
I considered using a unique key to located the row, but unfortunately some queries do no allows determining the most unique key.
I'm thinking, is it possible to retrieve/alter row by its index after a Postgres Cursor have read the row?
The application allows a customer to define DB Schema as well as the queries, so my code does not have a prior knowledge about DB and queries.
It is supposed to provide a certain API with functions based on row indexes. The API was initially designed for SQLServer, so the goal is to migrate the application from SQLServer to Postgres.
Would you recommend a solution?
Thank you
Konstantin
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