ENABLE NOVALIDATE behaviour bug

  • From: Mark Richard <mrichard@xxxxxxxxxxxxxxxxx>
  • To: oracle-l@xxxxxxxxxxxxx
  • Date: Tue, 29 Jun 2004 16:09:22 +1000




Hi List,

I regularly have to change the structure of some fairly large tables (~200m
rows).  Often we use the opportunity to do a full table rebuild if we want
to change other settings (such as index locations) but other times we would
prefer to modify the existing table.

I currently have the scenario where I need to add a single CHAR(1) column
to a 250m row table and populate it with a constant value (new records may
have a different value).  The approach I am considering is:

1) alter table blah add (mycol char(1));
2) update blah set mycol = 'F';     {perhaps include a parallel hint on
this statement}
3) alter table blah modify mycol not null enable novalidate;

I was hoping to use "enable novalidate" to avoid a verification of all
records when I know they will be populated.  However I noticed that a
describe on the table produces unexpected results.  Here is a demo:

SQL> desc blah
 Name                                            Null?    Type
 ----------------------------------------------- --------
--------------------------------
 FIRSTCOL                                                 NUMBER

SQL> alter table blah add (mycol char(1));

Table altered.

Elapsed: 00:00:00.04
SQL> desc blah;
 Name                                            Null?    Type
 ----------------------------------------------- --------
--------------------------------
 FIRSTCOL                                                 NUMBER
 MYCOL                                                    CHAR(1)

SQL> alter table blah modify mycol not null enable novalidate;

Table altered.

Elapsed: 00:00:00.04
SQL> desc blah;
 Name                                            Null?    Type
 ----------------------------------------------- --------
--------------------------------
 FIRSTCOL                                                 NUMBER
 MYCOL                                                    CHAR(1)

SQL> insert into blah (firstcol) values (1);
insert into blah (firstcol) values (1)
            *
ERROR at line 1:
ORA-01400: cannot insert NULL into ("SPARKY"."BLAH"."MYCOL")
SQL> alter table blah modify mycol null;

Table altered.

Elapsed: 00:00:00.04
SQL> alter table blah modify mycol not null;

Table altered.

Elapsed: 00:00:00.06
SQL> desc blah;
 Name                                            Null?    Type
 ----------------------------------------------- --------
--------------------------------
 FIRSTCOL                                                 NUMBER
 MYCOL                                           NOT NULL CHAR(1)


This is happening on Oracle 8.1.7.4 (running on Solaris) and is repeatable.
Whenever "enable novalidate" is used the constraint doesn't appear.  Trying
to insert null data shows the constraint is actually there, just not
appearing in describe.

Any ideas?  Any workarounds?  Fixed in Oracle 9 (although we are bound to 8
due to applications that connect)?

Thanks in advance,

Mark.



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