Question

I am experiencing an unclear sql server 2008 deadlock.

I have two tables:

T1: ID – bigint (PK), JOBID – bigint, X- bigint
T2: ID – bigint (PK), JOBID – bigint, X- bigint

The sql server error log describes the following:

Spid 233 is running this query: 
    SELECT TOP(500) FROM T1.X INNER JOIN T2 ON T1.X = T2.X WHERE T2.ID>-1 AND T2.ID<=10000
Spid 234 is running this query: 
    DELETE FROM T2 WHERE (X=1) OR (X=7) OR ( X=1233) OR X(=7878) OR (X=33) OR (X=776) OR (X=112)
Spid 233 is waiting for a Shared KEY lock on index t2.PK_T2.  (Spid 234 holds a conflicting X lock.)
Spid 234 is waiting for an eXclusive KEY lock on index t2.PK_T2.  (Spid 233 holds a conflicting S lock.)

PK_X is a Clustered ascending index on the identity column (ID which is auto increment column).
T2 also has another index which is a non clustered index on JOBID and X.

How come both processes are owners of a lock on the same object (T2.PK_T2)?

Please help,
Doron

Answer 1

How come both processes are owners of a lock on the same object (T2.PK_T2)?

The locks are not on the whole index. They are key locks and will be on different keys (rows) within the index.