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Re: Number of rows in a ResultSet ?

From: Peter T Mount <peter(at)retep(dot)org(dot)uk>
To: Michael Stephenson <mstephenson(at)tirin(dot)openworld(dot)co(dot)uk>
Cc: pgsql-interfaces(at)postgresql(dot)org
Subject: Re: Number of rows in a ResultSet ?
Date: 2001-01-18 15:23:07
Message-ID: 979831387.3a670a5b6ed23@webmail.retep.org.uk (view raw or flat)
Thread:
Lists: pgsql-interfaces
Quoting Michael Stephenson <mstephenson(at)tirin(dot)openworld(dot)co(dot)uk>:

> > I need to know how many rows exist in a ResultSet. I've tried to use
> > getFetchSize() method of ResultSet interface, but a message was
> > displayed "this method is not yet implemented".
> >
> > Anyone can help me ?
> 
> You could use:
>   ResultSet.last();
>   int numberOfRows = ResultSet.getRow();
> 
> Now, my understanding of this area is a but sketchy, but I think that
> most implementations of ResultSet do not get all of the results in one
> go
> (like the PostgreSQL JDBC driver does), so getFetchSize() is not a safe
> way of determining the number of results returned.

Until about 30 minutes ago getFetchSize() threw an SQLException as it wasn't 
implemented ;-)

For normal ResultSet's in 7.1 getFetchSize() will return the number of rows, 
but I'd advise you use Michael's suggestion as it's probably the safest bet for 
TYPE_SCROLL_INSENSITIVE & TYPE_SCROLL_SENSITIVE ResultSets (remember 
technically TYPE_FORWARD_ONLY ResultSet's should not allow you to go back after 
the .last() call).

Peter
> 
> Or, you could do another query with count() in your sql..
> 
> Or (and I wouldn't do this without carefully looking at the jdbc spec),
> you could just alter the getFetchSize() method
> org.postgresql.jdbc2.ResultSet driver to look like:
> 
>     public int getFetchSize() throws SQLException
>     {
> 	return rows.size();
>     }
> 
> The choice is yours..
> 
> Michael Stephenson      mstephenson(at)openworld(dot)co(dot)uk
> Developer   -    Web Applications    -   Open World
> Tel: +44 1225 444 950         Fax: +44 1225 336 738
> 
> 



-- 
Peter Mount peter(at)retep(dot)org(dot)uk
PostgreSQL JDBC Driver: http://www.retep.org.uk/postgres/
RetepPDF PDF library for Java: http://www.retep.org.uk/pdf/

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