README.longs.txt

lib/DBD/Oracle/Troubleshooting.pm

@@ -129,6 +129,79 @@ SQL scripts to get at V$ info.
   my $dbh = DBI->connect("dbi:Oracle:$dbname", $dbuser, $dbpass)
              || die "Unable to connect to $dbname: $DBI::errstr\n";
 
+=head1 LONGS
+
+Some examples related to the use of LONG types.
+
+For complete working code, take a look at the t/long.t file.
+
+You must fetch the row before you can fetch the longs associated with
+that row.  In other words, use the following algorithm...
+
+   1) login
+   2) prepare( select ... )
+   3) execute
+   4) while rows to fetch do
+   5)    fetch row
+   6)    repeat
+   7)        fetch chunk of long
+   8)    until have all of it
+   9) done
+
+If your select selects more than one row the need for step 4 may
+become a bit clearer... the blob_read always applies to the row
+that was last fetched.
+
+=head2 Example for reading LONG fields via blob_read
+ 
+	$dbh->{RaiseError} = 1;
+	$dbh->{LongTruncOk} = 1; # truncation on initial fetch is ok
+	$sth = $dbh->prepare("SELECT key, long_field FROM table_name");
+	$sth->execute;
+	while ( ($key) = $sth->fetchrow_array) {
+		my $offset = 0;
+		my $lump = 4096; # use benchmarks to get best value for you
+		my @frags;
+		while (1) {
+			my $frag = $sth->blob_read(1, $offset, $lump);
+			last unless defined $frag;
+			my $len = length $frag;
+			last unless $len;
+			push @frags, $frag;
+			$offset += $len;
+		}
+		my $blob = join "", @frags;
+		print "$key: $blob\n";
+	}
+
+=head2 Example for inserting LONGS
+
+    # Assuming the existence of @row and an associative array (%clauses) containing the 
+    # column names and placeholders, and an array @types containing column types ...
+
+	$ih = $db->prepare("INSERT INTO $table ($clauses{names})
+				 VALUES ($clauses{places})")
+			|| die "prepare insert into $table: " . $db->errstr;		  
+
+	$attrib{'ora_type'} = $longrawtype;  # $longrawtype == 24
+
+	##-- bind the parameter for each of the columns
+	for ($i = 0; $i < @types; $i++) {
+
+		##-- long raw values must have their type attribute explicitly specified
+		if ($types[$i] == $longrawtype) {
+			$ih->bind_param($i+1, $row[$i], \%attrib)
+				|| die "binding placeholder for LONG RAW " . $db->errstr;
+		}
+		##-- other values work OK with the default attributes
+		else {
+			$ih->bind_param($i+1, $row[$i])
+				|| die "binding placeholder" . $db->errstr;
+		}
+	}
+
+	$ih->execute || die "execute INSERT into $table: " . $db->errstr;
+
 =head1 LINUX
 
 =head2 Installing with Instantclient .rpm files.