Gateforum Test Series: Databases - Indexing

Question

suppose that in a file organization record size(R)=150 bytes , block size (B)=512 bytes. there are totally 30000 records. the data field on which indexing is done is 9 bytes and block pointer size is 7 bytes how many block access will be needed to access a data item in case of single level primary indexing?

Comments

is it 10?

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The answer should be 10.

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yes I too got 10 but in the answer key they have given 9 , just wanted to confirm.

Thanks :)

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Shivam Kasat

The answer will be 9 when we have access the Block only. If you want to access the data of that particular Block then the answer will be 10.

==> Here asking for the Data items. So, the answer will be 10.

Answer 1

10 is right .

Comments

thanks...concept got clear

Answer 2

No. of blocks in disk = (30000x150)/512 = 8789.

In primary indexing , one entry for each block is there , so number of blocks in index = (8789 x 16)/512 = 274.65 = 275.

Now , we can apply binary search for primary indexing .

ceil(log(275)) = 9

In worst case , it'll take 9 block transfers to locate the exact block and 1 extra transfer for getting that block.

Therefore total number of transfers = 10.