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Oracle foreign key execution plan?

Consider the following (simplified) situation:

CREATE TABLE PARENT (
    PARENT_ID INT PRIMARY KEY
);

CREATE TABLE CHILD (
    CHILD_ID INT PRIMARY KEY,
    PARENT_ID INT NOT NULL,
    FOREIGN KEY (PARENT_ID) REFERENCES PARENT (PARENT_ID)
);

There is CHILD.PARENT_IDno index, so changing / deleting PARENTis expensive (Oracle must perform a full table scan on it CHILDto ensure referential integrity). However, the implementation plan for the next statement ...

DELETE FROM PARENT WHERE PARENT_ID = 1

... does not show a table scan (SYS_C0070229 is the index on PARENT.PARENT_ID):

query plan

I know that there are ways to see all non-indexed FOREIGN KEYs , but it would be even better if I could be “warned” about a potential problem in terms of query execution (BTW, MS SQL Server and, possibly, other databases do this) .

Is this possible in Oracle?

I am using Oracle 10.2 if that matters.

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SQL> alter table child disable table lock;

Table altered.

SQL> delete from parent where parent_id = 10;
delete from parent where parent_id = 10
            *
ERROR at line 1:
ORA-00069: cannot acquire lock -- table locks disabled for CHILD

, , sql SQL .

, SQL.

  1* alter session set SQL_TRACE = TRUE
SQL> /

Session altered.

SQL> delete from parent where parent_id = 10;

1 row deleted.

SQL> commit;

Commit complete.

SQL> alter session set SQL_TRACE=FALSe;

Session altered.

=====================
PARSING IN CURSOR #2 len=39 dep=0 uid=65 oct=7 lid=65 tim=763167901560 hv=3048246147 ad='3160891c'
delete from parent where parent_id = 10
END OF STMT
PARSE #2:c=0,e=61,p=0,cr=0,cu=0,mis=0,r=0,dep=0,og=1,tim=763167901555
=====================
PARSING IN CURSOR #1 len=48 dep=1 uid=0 oct=7 lid=0 tim=763167976106 hv=2120075951 ad='26722c20'
 delete from "RC"."CHILD" where "PARENT_ID" = :1
END OF STMT
PARSE #1:c=0,e=42,p=0,cr=0,cu=0,mis=0,r=0,dep=1,og=4,tim=763167976100
EXEC #1:c=0,e=291,p=0,cr=7,cu=7,mis=0,r=2,dep=1,og=4,tim=763168080347
EXEC #2:c=0,e=130968,p=0,cr=8,cu=14,mis=0,r=1,dep=0,og=1,tim=763168091605
STAT #2 id=1 cnt=1 pid=0 pos=1 obj=0 op='DELETE  PARENT (cr=8 pr=0 pw=0 time=130887 us)'
STAT #2 id=2 cnt=1 pid=1 pos=1 obj=58703 op='INDEX UNIQUE SCAN SYS_C006951 (cr=1 pr=0 pw=0 time=19 us)'
STAT #1 id=1 cnt=0 pid=0 pos=1 obj=0 op='DELETE  CHILD (cr=7 pr=0 pw=0 time=233 us)'
STAT #1 id=2 cnt=2 pid=1 pos=1 obj=58704 op='TABLE ACCESS FULL CHILD (cr=7 pr=0 pw=0 time=76 us)'

: http://www.oracle-base.com/articles/10g/SQLTrace10046TrcsessAndTkprof10g.php

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