Re: [BUGS] no way in LargeObject API to detect short read?
От | Peter Mount |
---|---|
Тема | Re: [BUGS] no way in LargeObject API to detect short read? |
Дата | |
Msg-id | 5.0.2.1.0.20010127165622.009e6110@mail.retep.org.uk обсуждение исходный текст |
Ответ на | Re: [BUGS] no way in LargeObject API to detect short read? (Barry Lind <barry@xythos.com>) |
Список | pgsql-jdbc |
At 15:37 26/01/01 -0800, Barry Lind wrote: >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. That's exactly what I was thinking of. Most of the largeobject API is based on libpq hence where this came from. I don't think there is anything available elsewhere for getting the size. Yes, there needs to be a better way. Peter >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@acm.org>: > > > > > Bruce Momjian <pgman@candle.pha.pa.us> writes: > > > > Anyone able to fix this? > > > > > > here's a hack we've been using in-house (written by Jun Gabayan, > > > <jgabayan@pahv.xerox.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@acm.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@retep.org.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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