SELECT ... FOR UPDATE locking trouble when applied on date range - mysql

Question

I'm having following table structure.
reservation: (InnoDB)
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id INT,
date DATE,
item_id INT,
slot VARCHAR(50);
PRIMARY KEY(id), UNIQUE KEY(item_id,date).
Now i'm trying to use SELECT.....FOR UPDATE on reservation table inside a transaction to lock specific rows within date range(eg:2012-06-15 to 2012-06-16) of a particular item_id.
SELECT availability FROM reservation WHERE item_id={$item_id} AND (date>='{$to_date}' AND date<='{$from_date}') FOR UPDATE
NOW when i use the above statement, it is blocking all the rows of particular item_id even beyond the date range.I'm also using this UNIQUE KEY(item_id,date).
How to lock only particular date range of a specific item_id?
regards,
ravi.
ADDED:
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=====================================
120615 20:14:13 INNODB MONITOR OUTPUT
=====================================
Per second averages calculated from the last 24 seconds
----------
SEMAPHORES
----------
OS WAIT ARRAY INFO: reservation count 12, signal count 12
Mutex spin waits 0, rounds 180, OS waits 4
RW-shared spins 10, OS waits 5; RW-excl spins 2, OS waits 2
------------
TRANSACTIONS
------------
Trx id counter 0 15147
Purge done for trx's n:o < 0 15136 undo n:o < 0 0
History list length 2
Total number of lock structs in row lock hash table 2
LIST OF TRANSACTIONS FOR EACH SESSION:
---TRANSACTION 0 0, not started, OS thread id 2940
MySQL thread id 76, query id 1487 localhost 127.0.0.1 root
SHOW innodb status
---TRANSACTION 0 15143, not started, OS thread id 2588
MySQL thread id 10, query id 578 localhost 127.0.0.1 root
---TRANSACTION 0 15144, ACTIVE 11526 sec, OS thread id 2740
3 lock struct(s), heap size 320
MySQL thread id 11, query id 577 localhost 127.0.0.1 root
--------
FILE I/O
--------
I/O thread 0 state: wait Windows aio (insert buffer thread)
I/O thread 1 state: wait Windows aio (log thread)
I/O thread 2 state: wait Windows aio (read thread)
I/O thread 3 state: wait Windows aio (write thread)
Pending normal aio reads: 0, aio writes: 0,
ibuf aio reads: 0, log i/o's: 0, sync i/o's: 0
Pending flushes (fsync) log: 0; buffer pool: 0
187 OS file reads, 75 OS file writes, 29 OS fsyncs
0.00 reads/s, 0 avg bytes/read, 0.00 writes/s, 0.00 fsyncs/s
-------------------------------------
INSERT BUFFER AND ADAPTIVE HASH INDEX
-------------------------------------
Ibuf: size 1, free list len 0, seg size 2,
0 inserts, 0 merged recs, 0 merges
Hash table size 62383, used cells 0, node heap has 1 buffer(s)
0.00 hash searches/s, 0.00 non-hash searches/s
---
LOG
---
Log sequence number 0 8287163
Log flushed up to 0 8287163
Last checkpoint at 0 8287163
0 pending log writes, 0 pending chkp writes
24 log i/o's done, 0.00 log i/o's/second
----------------------
BUFFER POOL AND MEMORY
----------------------
Total memory allocated 23277934; in additional pool allocated 1430400
Buffer pool size 960
Free buffers 895
Database pages 64
Modified db pages 0
Pending reads 0
Pending writes: LRU 0, flush list 0, single page 0
Pages read 64, created 0, written 51
0.00 reads/s, 0.00 creates/s, 0.00 writes/s
Buffer pool hit rate 1000 / 1000
--------------
ROW OPERATIONS
--------------
0 queries inside InnoDB, 0 queries in queue
1 read views open inside InnoDB
Main thread id 1544, state: waiting for server activity
Number of rows inserted 10, updated 0, deleted 0, read 66
0.00 inserts/s, 0.00 updates/s, 0.00 deletes/s, 0.00 reads/s
----------------------------
END OF INNODB MONITOR OUTPUT
============================
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