Re: [BUGS] no way in LargeObject API to detect short read?

Peter,

Given the current implementation of size(), I don't think this is a good
solution to the problem at hand. Since size() is an expensive call
(especially on large files), using it in this way wouldn't be a
performant solution. Using size() also requires additional round trips
to the database to get this information. There needs to be a better
solution that doesn't require the additional overhead.

thanks,
--Barry

Peter T Mount wrote:
>
> Hmmm, what's the performance issues with this? Is there going to be a problem
> with very large LargeObject's?
>
> Quoting "Paul M. Aoki" <aoki(at)acm(dot)org>:
>
> > Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> > > Anyone able to fix this?
> >
> > here's a hack we've been using in-house (written by Jun Gabayan,
> > <jgabayan(at)pahv(dot)xerox(dot)com>).
> >
> > you may not like the style but it's a stab at a solution.
> > --
> > Paul M. Aoki / Xerox Palo Alto Research Center / 3333 Coyote Hill Road
> > aoki(at)acm(dot)org / Computer Science Laboratory / Palo Alto, CA
> > 94304-1314
> >
> > Index: LargeObject.java
> > ===================================================================
> > RCS file:
> > /project/placeless/cvsroot/placeless2/src/org/postgresql/largeobject/LargeObje
> ct.java,v
> > retrieving revision 1.1
> > retrieving revision 1.3
> > diff -r1.1 -r1.3
> > 64c64,67
> > <
> > ---
> > >
> > > private int pos = 0; //current position
> > > private int size = 0;
> > >
> > 85a89,90
> > > pos = tell();
> > > size = size();
> > 102a108
> > > if(fd == 0) return;
> > 105a112
> > > fd = 0;
> > 118a126,132
> > > // calculate available data to read to avoid reading pass the
> > end
> > > // to avoid an exception
> > > pos = tell();
> > > int avail = size - pos;
> > > if(avail == 0) return null;
> > > if(avail < len) len = avail;
> > > try {
> > 123c137,141
> > <
> > ---
> > > }catch(SQLException se) {
> > > System.out.println("***LargeObject.read: Caught
> > SQLException: " + se.getMessage());
> > > return null;
> > > }
> > >
> > 157c175
> > < public void read(byte buf[],int off,int len) throws SQLException
> > ---
> > > public int read(byte buf[],int off,int len) throws SQLException
> > 159c177,180
> > < System.arraycopy(read(len),0,buf,off,len);
> > ---
> > > byte mybuf[] = read(len);
> > > int sz = (mybuf != null) ? mybuf.length : -1; //must return -1 for
> > end of data
> > > if(sz > 0) System.arraycopy(mybuf,0,buf,off,sz);
> > > return sz;
> >
>
> --
> 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/