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https://issues.apache.org/jira/browse/DERBY-5111?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13006947#comment-13006947
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Knut Anders Hatlen commented on DERBY-5111:
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Another observation: If the primary key constraint is created before the unique
index on the same column, the NPE doesn't happen. But then there's a warning
when the unique index is created:
ij> CREATE UNIQUE INDEX UI1 ON T1 (t1_id);
0 rows inserted/updated/deleted
WARNING 01504: The new index is a duplicate of an existing index:
SQL110315145452330.
I think Derby doesn't create an index when it raises this warning.
CreateIndexConstantAction allows creation of duplicate indexes if the second
index is a constraint, but then it has one physical index and two logical
indexes. I'm wondering if it's these logical indexes that cause confusion in
the case that fails with NPE.
> NullPointerException on unique constraint violation with unique index
> ---------------------------------------------------------------------
>
> Key: DERBY-5111
> URL: https://issues.apache.org/jira/browse/DERBY-5111
> Project: Derby
> Issue Type: Bug
> Components: SQL
> Affects Versions: 10.6.1.0, 10.6.2.1, 10.7.1.1
> Reporter: Mark La Rue
>
> Given the below DDL, violations of the unique constraint (an example follows
> the DDL) specified on table t1 will result in a NullPointerException that
> terminates the active connection. The root cause appears to be related to
> the unique indexes; removing them results in the correct constraint violation.
> CREATE TABLE s.t0 (t0_id INTEGER NOT NULL, value VARCHAR(75) NOT NULL);
> ALTER TABLE s.t0 ADD CONSTRAINT pk_1 PRIMARY KEY (t0_id);
> CREATE TABLE s.t1 (t1_id INTEGER NOT NULL, t0_id INTEGER NOT NULL, value
> VARCHAR(75) NOT NULL);
> CREATE UNIQUE INDEX s.ui_1 ON s.t1 (t1_id);
> ALTER TABLE s.t1 ADD CONSTRAINT pk_2 PRIMARY KEY (t1_id);
> ALTER TABLE s.t1 ADD CONSTRAINT fk_1 FOREIGN KEY (t0_id) REFERENCES s.t0
> (t0_id) ON DELETE CASCADE;
> CREATE UNIQUE INDEX s.ui_2 ON s.t1 (t0_id, value);
> ALTER TABLE s.t1 ADD CONSTRAINT uc_1 UNIQUE (t0_id, value);
> Minimal DML to trigger the constraint violation:
> INSERT INTO s.t0 VALUES (0, 'foobar');
> INSERT INTO s.t1 VALUES(0, 0, 'Test');
> INSERT INTO s.t1 VALUES(1, 0, 'Test');
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