adding a new not null bit column with default 0
Is it only for reads? If you do not lock the table the "copy" and "rename" steps then if anyone modifies data in the source table during the process you could lose data when you drop the old table and rename the new one to take its place.The method Gail showed is your best bet for performance and protect against data loss unless you are OK with losing data or you know your table is truly only ever read
Adding Columns with Default Values and Not Null in Oracle 11g - Pythian - Data Experts Blog
In the pre-11g releases, adding a new not null column with a default value would have caused a massive update on the entire table, locking it for the operation and generating tons of undo and redo
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sql - Best way to populate a new column in a large table? - Database Administrators Stack Exchange
In my case though, it would have taken significantly more "Developer" work to use that solution and we had a 30 minute window of scheduled downtime that it could be accomplished in. Copy the whole table while letting the column default in the new table populate the new column - possibly ordering the rows in some favorable fashion while being at it
adding SERIAL to a table - PostgreSQL Database
DEFAULT because according to the SQL spec that implies doing the UPDATE to fill the column values immediately, and that's just a chunk of code no one's written yet
add one column
This appears to be because the ALTER TABLE uses a trigger, and probably one of the parameters to the trigger is (IS NOT NULL) which is the correct syntax for a stored procedure
It also demonstrates a pitfall of uncoordinated table design among developers: in our examples, the Book Town editions table already stores the publication date, so the column should not have been added to the books table. The owner has all rights that can be associated with a table, in addition to the ability to grant and revoke rights with the GRANT and REVOKE commands (for more information see Chapter 10)
This means that when there is no implicit or assignment cast from old to new type, ALTER TYPE might fail to convert the default even though a USING clause is supplied. Because of this flexibility, the USING expression is not applied to the column's default value (if any); the result might not be a constant expression as required for a default
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(You may also want to update the already existing rows to the new default value, using UPDATE.) If you want to mark the column non-null, use the SET NOT NULL form after you've entered non-null values for the column in all rows. Thus, dropping a column is quick but it will not immediately reduce the on-disk size of your table, as the space occupied by the dropped column is not reclaimed
(This requires superuser privilege if any of the triggers are internally generated constraint triggers such as those that are used to implement foreign key constraints or deferrable uniqueness and exclusion constraints.) USER Disable or enable all triggers belonging to the table except for internally generated constraint triggers such as those that are used to implement foreign key constraints or deferrable uniqueness and exclusion constraints. Because of this flexibility, the USING expression is not applied to the column's default value (if any); the result might not be a constant expression as required for a default
This -- Trying to add a NOT NULL column without a default ALTER TABLE DefaultTest ADD NotNull2 char(1) NOT NULL GO Returns an error of Msg 4901, Level 16, State 1, Line 1 ALTER TABLE only allows columns to be added that can contain nulls, or have a DEFAULT definition specified, or the column being added is an identity or timestamp column, or alternatively if none of the previous conditions are satisfied the table must be empty to allow addition of this column. Fill in your details below or click an icon to log in: Email (required) (Address never made public) Name (required) Website You are commenting using your WordPress.com account
This means that when there is no implicit or assignment cast from old to new type, ALTER TYPE might fail to convert the default even though a USING clause is supplied. Because of this flexibility, the USING expression is not applied to the column's default value (if any); the result might not be a constant expression as required for a default
Alter column position - PostgreSQL wiki
The current problem with implementing this lies in that currently postgres uses the same identifiers for both the logical and physical position within a table. The rest of this document is meant to explain the workarounds, and track the issues that must be dealt with should someone want to implement this functionality
PostgreSQL - hackers - Fast ALTER TABLE ... ADD COLUMN ... DEFAULT xxx?
I think users today often avoid the full table rewrite either make their application treat null as implicitly the default value or do a piecemeal rewrite using updates. It seems to me that these solutions would require everyone in the world to pay the overhead of a few to many bits in every tuple to optimize what appears to be a relatively rare circumstance after all
PostgreSQL NOT NULL constraint - w3resource
The reverse of NOT NULL constraint is NULL, but it is not necessary to mention NULL to create a table, the default is NULL, which does not mean that, the column must contain NULL, it means that the column might contain NULL value
Chris Kings-Lynne recently contributed code to support ALTER COLUMN SET NOT NULL and DROP NOT NULL, which will enable turning the built-in constraint on and off
PostgreSQL: Documentation: 8.1: ALTER TABLE
For example, to reclaim the space occupied by a dropped column immediately, the fastest way is ALTER TABLE table ALTER COLUMN anycol TYPE anytype; where anycol is any remaining table column and anytype is the same type that column already has. One may disable or enable a single trigger specified by name, or all triggers on the table, or only user triggers (this option excludes triggers that are used to implement foreign key constraints)
PostgreSQL: Documentation: 8.0: ALTER TABLE
For example, to reclaim the space occupied by a dropped column immediately, the fastest way is ALTER TABLE table ALTER COLUMN anycol TYPE anytype; where anycol is any remaining table column and anytype is the same type that column already has. Because of this flexibility, the USING expression is not applied to the column's default value (if any); the result might not be a constant expression as required for a default
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