09-30-2009
Hi.
Sorry, I'm not so familiar with mySQL, but as you didn't get an answer yet!
This is based on Oracle, but the same ideas should relate.
Firstly it's safe to update a table with however many rows. The worst that could happen is that the update fails and the uncommitted changes are rolled back.
You could:
- split the updates in to smaller batches
- add commit statements every few hundred / thousand statements
- instruct your sql client to commit every few hundred / thousand statements
- add more redo / undo logs or make your existing ones larger, or both
- switch off logging on the table (alter table .. nologging if mySQL supports that) to reduce redo / undo (in most cases)
- disable referential / unique constraint indexes (more for performance)
Last edited by Scott; 09-30-2009 at 07:48 PM..
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LEARN ABOUT DEBIAN
alzabo::runtime::joincursor
Alzabo::Runtime::JoinCursor(3pm) User Contributed Perl Documentation Alzabo::Runtime::JoinCursor(3pm)
NAME
Alzabo::Runtime::JoinCursor - Cursor that returns arrays of "Alzabo::Runtime::Row" objects
SYNOPSIS
use Alzabo::Runtime::JoinCursor;
my $cursor = $schema->join( tables => [ $foo, $bar ],
where => [ $foo->column('foo_id'), '=', 1 ] );
while ( my @rows = $cursor->next )
{
print $rows[0]->select('foo'), "
";
print $rows[1]->select('bar'), "
";
}
DESCRIPTION
Objects in this class are used to return arrays of Alzabo::Runtime::Row objects when requested. The cursor does not preload objects but
rather creates them on demand, which is much more efficient. For more details on the rational please see the RATIONALE FOR CURSORS section
in Alzabo::Design.
INHERITS FROM
"Alzabo::Runtime::Cursor"
METHODS
next
Returns the next array of "Alzabo::Runtime::Row" objects or an empty list if no more are available.
If an individual row could not be fetched, then the array may contain some "undef" values. For outer joins, this is normal behavior, but
for regular joins, this probably indicates a data error.
all_rows
This method fetches all the rows available from the current point onwards. This means that if there are five set of rows that will be
returned when the object is created and you call "next()" twice, calling "all_rows()" after it will only return three sets.
The return value is an array of array references. Each of these references represents a single set of rows as they would be returned from
the "next" method.
reset
Resets the cursor so that the next "next()" call will return the first row of the set.
count
Returns the number of rowsets returned by the cursor so far.
next_as_hash
Returns the next rows in a hash, where the hash keys are the table names and the hash values are the row object. If a table has been
included in the join via an outer join, then it is only included in the hash if there is a row for that table.
AUTHOR
Dave Rolsky, <autarch@urth.org>
perl v5.8.8 2007-12-23 Alzabo::Runtime::JoinCursor(3pm)