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Mention add_column_with_default in downtime guide 

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Yorick Peterse 2016-08-08 17:42:26 +02:00
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doc/development/what_requires_downtime.md
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@ -31,6 +31,14 @@ operation, even when using `ALGORITHM=INPLACE` and `LOCK=NONE`. This means
downtime _may_ be required when modifying large tables as otherwise the
operation could potentially take hours to complete.
Adding a column with a default value _can_ be done without requiring downtime
when using the migration helper method
`Gitlab::Database::MigrationHelpers#add_column_with_default`. This method works
similar to `add_column` except it updates existing rows in batches without
blocking access to the table being modified. See ["Adding Columns With Default
Values"](migration_style_guide.html#adding-columns-with-default-values) for more
information on how to use this method.
## Dropping Columns
On PostgreSQL you can safely remove an existing column without the need for