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Top Forums Web Development Mysql question: Best way to update a column containing 8 million rows Post 302357837 by Scott on Wednesday 30th of September 2009 06:37:36 PM
Old 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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Table(3)						User Contributed Perl Documentation						  Table(3)

NAME
Tk::Table - Scrollable 2 dimensional table of Tk widgets SYNOPSIS
use Tk::Table; $table = $parent->Table(-rows => number, -columns => number, -scrollbars => anchor, -fixedrows => number, -fixedcolumns => number, -takefocus => boolean); $widget = $table->Button(...); $old = $table->put($row,$col,$widget); $old = $table->put($row,$col,"Text"); # simple Label $widget = $table->get($row,$col); $cols = $table->totalColumns; $rows = $table->totalRows; $table->see($widget); $table->see($row,$col); ($row,$col) = $table->Posn($widget); DESCRIPTION
Tk::Table is an all-perl widget/geometry manager which allows a two dimensional table of arbitary perl/Tk widgets to be displayed. Entries in the Table are simply ordinary perl/Tk widgets. They should be created with the Table as their parent. Widgets are positioned in the table using: $table->put($row,$col,$widget) If $widget is not a reference it is treated as a string, and a Lable widget is created with the string as its text. All the widgets in each column are set to the same width - the requested width of the widest widget in the column. Likewise, all the widgets in each row are set to the same height - the requested height of the tallest widget in the column. A number of rows and/or columns can be marked as 'fixed' - and so can serve as 'headings' for the remainder the rows which are scrollable. The requested size of the table as a whole is such that the number of rows specified by -rows (default 10), and number of columns specified by -columns (default 10) can be displayed. If the Table is told it can take the keyboard focus then cursor and scroll keys scroll the displayed widgets. The Table will create and manage its own scrollbars if requested via -scrollbars. The table can be emptied using $table->clear the widgets which were in the table are destroyed. The Tk::Table widget is derived from a Tk::Frame, so inherits all its configure options. BUGS
/ Snags / Possible enhancements o Very large Tables consume a lot of X windows. o No equivalent of pack's -anchor/-pad etc. options SEE ALSO
Tk::grid, Tk::HList, Tk::TableMatrix, Tk::MListbox, Tk::Columns perl v5.12.1 2007-11-08 Table(3)
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