mahara-contributors team mailing list archive

[Aaron Wells <1450676@xxxxxxxxxxxxxxxxxx>]

The current method programattically generates SQL statements, and then
executes them.

So the very first step on this, should be to determine exactly what SQL
statements it is generating. Then we can compare them with your raw SQL
and see why the performance is so much worse.

Cheers,
Aaron

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https://bugs.launchpad.net/bugs/1450676

Title:
  The way we add new columns to tables can cause db to lock up

Status in Mahara ePortfolio:
  Confirmed

Bug description:
  Currently when we want to add a column to an existing table we do
  something like this in lib/db/upgrade.php

  $table = new XMLDBTable('group');
  $field = new XMLDBField('allowarchives');
  $field->setAttributes(XMLDB_TYPE_INTEGER, 1, null, XMLDB_NOTNULL, null, null, null, 0);
  add_field($table, $field);

  The problem is if the database is big it can cause things to lock up

  Changing the above to a more direct:
  execute_sql('ALTER TABLE {group} ADD COLUMN allowarchives SMALLINT NOT NULL DEFAULT 0');

  seems to avoid this problem.

  So this bug is here so we can find out why the current way is so
  resource intensive and/or what dangers there are doing it the more
  direct way.

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