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Re: Internal operations when the planner makes a hash join.

From: "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
To: "negora" <negora(at)negora(dot)com>
Cc: "pgsql-performance(at)postgresql(dot)org" <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Internal operations when the planner makes a hash join.
Date: 2010-02-23 23:03:23
Message-ID: 4B840A5B020000250002F599@gw.wicourts.gov (view raw or flat)
Thread:
Lists: pgsql-performance
>negora <negora(at)negora(dot)com> wrote: 
 
> I even might return the entire result to my external Java
> application
 
You are probably going to want to configure it to use a cursor, at
least if the result set is large (i.e., too big to cache the entire
result set in memory before you read the first row).  Read this over
carefully:
 
http://jdbc.postgresql.org/documentation/84/query.html#query-with-cursor
 
You don't have to use a Java cursor or do anything procedurally
there, but a PostgreSQL cursor is the only way to stream the data to
the application on demand (ResultSet.next), rather than pushing it
all there during the Statement.execute().
 
-Kevin

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