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Re: BLOB performance test FYI

From: "Marin Dimitrov" <marin(dot)dimitrov(at)sirma(dot)bg>
To: "Barry Lind" <barry(at)xythos(dot)com>
Cc: <pgsql-jdbc(at)postgresql(dot)org>
Subject: Re: BLOB performance test FYI
Date: 2002-04-19 18:40:58
Message-ID: 000b01c1e7d1$bf5b3010$9b0e32d4@sirma.bg (view raw or flat)
Thread:
Lists: pgsql-jdbc
----- Original Message -----
From: "Barry Lind"

> > the Oracle driver demands that columns be read in left-to-right order
> too,
>  > without skipping a column
>
> This isn't true.  My code does not always read data in column order and
> it runs fine on Oracle.
>

does your code access LONG columns?

the docs say:

"If your query selects multiple columns and one of the columns contains a
data
stream, then the contents of the columns following the stream column are not
available until the stream has been read, and the stream column is no longer
available once any following column is read. Any attempt to read a column
beyond
a streaming column closes the streaming column."


and (there is an example code skipped):

"  - Call the stream column in SELECT-list order.

If your query selects multiple columns, the database sends each row as a set
of
bytes representing the columns in the SELECT order. If one of the columns
contains stream data, the database sends the entire data stream before
proceeding to the next column.
If you do not use the SELECT-list order to access data, then you can lose
the
stream data. That is, if you bypass the stream data column and access data
in a
column that follows it, the stream data will be lost. For example, if you
try to
access the data for the NUMBER column before reading the data from the
stream
data column, the JDBC driver first reads then discards the streaming data
automatically. This can be very inefficient if the LONG column contains a
large
amount of data."


    Marin

----
"...what you brought from your past, is of no use in your present. When
you must choose a new path, do not bring old experiences with you.
Those who strike out afresh, but who attempt to retain a little of the
old life, end up torn apart by their own memories. "




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