Question: What can
I do to increase the performance of an "alter table xxx add
column yyy default value 'zzz';? I understand that
this will invoke a full table scan. Can this alter
table default value be done in parallel with Oracle parallel
query?
Answer: The behavior of the "alter
table add column default value" behavior has changed between
versions of Oracle. You use a command like this:
alter table
fred
add column
new_col
default value
'hello'
not null';
Before Oracle 11gr2 this was a very time-consuming
command that required parallel DDL;
Beginning with
Oracle 11g release 2, Oracle introduced a great optimization
for the "alter column add column default value".
Oracle behaves differently in 11gr2 and 12c.
It
stores the default value only in data dictionary instead of
updating each physical row.
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