May 2018
Intermediate to advanced
576 pages
30h 25m
English
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 like 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 to the text type, displaying only current attribute values, and then back to node. You may have ...