PostgreSQL 11 Administration Cookbook

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When an attribute is removed from a composite data type, the corresponding values will instantly disappear from all the values of that same type stored in any database table. What actually happens is that these values are still inside the tables, but they have become invisible because their attribute is now marked as deleted, and the space they occupy will be reclaimed only when the contents of the composite type are parsed again. This can be forced with a query such as the following:

UPDATE mytable SET mynode = mynode :: text :: node;

Here, mytable is a table that has a mynode column of the node type. This query converts the values into the text type, displaying only current attribute values, and then back to node. You may ...